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Skram vs. C2E - Subwoofers info research

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Printed Date: 01 July 2022 at 2:39am
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Topic: Skram vs. C2E - Subwoofers info research
Posted By: sushi
Subject: Skram vs. C2E - Subwoofers info research
Date Posted: 17 January 2022 at 10:12am
Hello! Lately i've been doing some research for sub designs, looking for a single driver/ high efficiency/ loud and deep sounding cab to build in the future.. two designs fashinated me the most: Ricci's Skram (a ported horn with 21' woofer) and HOQWS's C2E (a Paraflex, kind of compound horn with a high tuned resonator combined with a low tuned folded path) which has 18' and 21' versions available.. Sinai had the 21s built recently.
Both the designs seem to be really loud and clear sounding, in the words of the builders/owners, and it seems they can go fairly low.
I've been looking around for graphs and measurements but since they are both recent designs, not so many people built them yet and fewer measured or even compared them.
Can anyone here give some direct feedback on these 2 subs? Some real life outdoor measuraments would be nice to see too
I would like to be sure before i pick one, and spend money on drivers and plywood. I'd like to get more output than my ESW1018 give, a deeper bass (let's say 30hz f6, f3 if possible), all-around versatile and possibly suitable to music as well to outdoor cinema.. demanding a lot, i admit.
If somebody has heard, tested, or measured, one of these 2 designs and would like to share his knowledge, i would be grateful!

Cheers!



Replies:
Posted By: sushi
Date Posted: 18 January 2022 at 6:04pm
I managed to get some info on HOQWS fb page: aparently, somebody did test all these subs, but measurements were unfortunately taken in different locations.. for what i've been told, 18' C2E golden formula was taken in free field, 21'C2E silver formula was in a backyard (no specification about significant boundaries around), and Skram was taken indoors at Motion Lab, Berlin (no obstacles in a 5m radius). This is quite invalidating for the comparison between them imho.. anyway, here's the graph i've been provided

Edit: basic data i forgot to mention! C2E gf was loaded with B&C 18DS115-4, C2E sf was loaded with 21NWL9001, Skram had SAN215.30 in them.


Posted By: bob4
Date Posted: 18 January 2022 at 7:02pm
Originally posted by sushi sushi wrote:


I've been looking around for graphs and measurements but since they are both recent designs, not so many people built them yet and fewer measured or even compared them.
Can anyone here give some direct feedback on these 2 subs? Some real life outdoor measuraments would be nice to see too

The SKRAM was published almost three years ago, and there is active discussion going on. Many successful builds and feedback there. why don't you ask the designer himself?  He seems very accommodating.......

https://data-bass.ipbhost.com/topic/742-riccis-skram-subwoofer-files/page/36/" rel="nofollow - https://data-bass.ipbhost.com/topic/742-riccis-skram-subwoofer-files/page/36/


Posted By: toastyghost
Date Posted: 18 January 2022 at 7:56pm
I take it there’s also no information regarding the stimulus level, calibration process, mic distance, and atmospheric parameters with those REW plots? Have they been calculated back to a common distance?

I doubt the first one is truly done in free field conditions unless someone shoved it 10 metres up on a crane...

If the sweeps are not taken in the far-field of the cabinet, then the data can’t be trusted even if they’ve measured and documented the amp output with a TrueRMS voltmeter and 50 Hz sine. Up close, the radiation versus frequency will be inconsistent and won’t necessarily obey inverse distance law.

This is worth a read - you can do ultra near-field and scale the IR by a/2r for low frequency measurements, but you also have to merge the ultra near-field data from all radiating surfaces, ports and the like first. https://www.artalabs.hr/AppNotes/AN4-FreeField-Rev03eng.pdf" rel="nofollow - https://www.artalabs.hr/AppNotes/AN4-FreeField-Rev03eng.pdf

That said, the overall plots look as I'd expect from listening to and simulating a few Paraflex cabinets in Akabak BEM. You've got some 20+ dB of gain above 60 Hz relative to the low corner around 30 Hz. Since this design type is a variation on a tapped horn and similar quarter-wave air column resonators, you can't expect the same 'flattening' of response that results as multiples of FLH designs with compromised mouth areas are stacked together.

Judging by that, I'd personally much prefer the SKRAM's more linear response.


Posted By: sushi
Date Posted: 19 January 2022 at 2:54pm
Thanks for the answers!
Bob, i've red that topic months ago but it looked like most links and pics were unavailable.. opened it today on my laptop and they work, so probably my phone was the problem then..
Defo reading it once again, thanks!
Toastyghost, the only other info given to me was they were all 1w/1m measurements, can't assure if mic had been freshly calibrated or if a truerms multimeter was used to set power.. i just don't know, and wouldn't even ask again since the test wasn't really a fair comparison between the 3 cabs. Testing one of the subs indoors makes no sense to me in the first place, moreover no info was given about room's size, shape, impulse response, so.. kinda worthless!
Like you said, me too think the Skram would have a more linear response than the C2E which is also tuned a bit higher (35 vs. 30, iirc) and drops rapidly below fs, while Skram seems to drop more gradually.
I admit the Skram seems to me a really versatile cab: even response, wide usable band, compact size, multiple tunings available.. Wins for now!


Posted By: snowflake
Date Posted: 19 January 2022 at 6:01pm
it's amazing how many paraflex seem to have been built without anyone doing a proper measurement.


Posted By: bee
Date Posted: 31 January 2022 at 9:10pm
first post in many years, Plenty of Rta measurments of the paraflex cabs have been done. Any that have been published with the plans, were taken 1w at 1m out doors. set a 1khz. All the guys on the design team working in the back ground all measure to the same standards, so we can compare data ect. The free field was measured in a field. the back yard was done outside his workshop, there was walls on both sides near by. 

-------------
https://www.elements-audio.com


Posted By: toastyghost
Date Posted: 01 February 2022 at 9:20am
It’s a shame that measuring a sub like that doesn’t produce valid data. You need to be in the acoustic far-field and should be using a much lower frequency for calibration of voltage to accommodate for the limited range of validity on cheaper DMMs. Typically, 50 Hz or 60 Hz allows the use of cheap multimeters, and 2.83 V is easy to get a stable result for.

Measuring in the near field produces much higher sound pressure levels and a response curve that is not representative of real listening, as the radiation conditions do not follow the inverse distance rule.

Ideally, ten metres is the best position for subs as it is easy to calculate back. Using 28.3 V is also a more realistic drive level, which is a benefit. Otherwise, if you’re not able to get that far out, at least 4 times the diagonal dimension of the mouth area is the rule of thumb. Just reduce the voltage, or calculate back by reducing the measured by the factor difference until you’re at 1 metre.

You should also document the electrical impedance versus frequency, so that the data can be properly scaled for comparison to other boxes. Easily done with REW, and a known resistor value. Using the driver’s free air nominal value isn’t really good enough. You’re in the same boat as most manufacturers in that, though.

While you’re at it, seems it would be good to do the CEA 2010 test built into REW, or do the M-Noise Linear LPeak test?

Unfortunately the poor or complete lack of labeling and documentation of test conditions, and all of the data I’ve seen needs to be taken with a large pinch of salt. I’m afraid that goes for your own massive design too.


Posted By: Sinai Sound
Date Posted: 01 February 2022 at 1:22pm
Originally posted by toastyghost toastyghost wrote:

It’s a shame that measuring a sub like that doesn’t produce valid data. You need to be in the acoustic far-field and should be using a much lower frequency for calibration of voltage to accommodate for the limited range of validity on cheaper DMMs. Typically, 50 Hz or 60 Hz allows the use of cheap multimeters, and 2.83 V is easy to get a stable result for.

Measuring in the near field produces much higher sound pressure levels and a response curve that is not representative of real listening, as the radiation conditions do not follow the inverse distance rule.

Ideally, ten metres is the best position for subs as it is easy to calculate back. Using 28.3 V is also a more realistic drive level, which is a benefit. Otherwise, if you’re not able to get that far out, at least 4 times the diagonal dimension of the mouth area is the rule of thumb. Just reduce the voltage, or calculate back by reducing the measured by the factor difference until you’re at 1 metre.

You should also document the electrical impedance versus frequency, so that the data can be properly scaled for comparison to other boxes. Easily done with REW, and a known resistor value. Using the driver’s free air nominal value isn’t really good enough. You’re in the same boat as most manufacturers in that, though.

While you’re at it, seems it would be good to do the CEA 2010 test built into REW, or do the M-Noise Linear LPeak test?

Unfortunately the poor or complete lack of labeling and documentation of test conditions, and all of the data I’ve seen needs to be taken with a large pinch of salt. I’m afraid that goes for your own massive design too.

How much to just live in your brain for a bit please


Posted By: smitske96
Date Posted: 01 February 2022 at 1:39pm
@toasty

I once opted for CE2010 tests in the paraflex fb group, and most where not fond of it. While it is one of the methods to see what is going on at higher levels and show the absolute limits compared to other designs. Just saying it is loud would not do it for me, because that observation can be influenced by several factors. 

It is the only thing I sometimes dislike about the group, it is seen as the 'holy grail', with that its own following. Sure, it is a nice relatively new innovation in DIY etc, but its not the one go-to solution for all your needs.


Posted By: toastyghost
Date Posted: 01 February 2022 at 2:55pm
That's a shame, since the point of the CEA-2010 process is to find the distortion-limited max output. That’s far more useful than a calculated value, even if you use the newer B variant of the test process which is supposed to be more psychoacoustically informed.

Of course to do it properly, you need to use a calibration measurement of a known sealed cabinet, even in most outdoor locations. Plus you have to also consider how to stay within the distortion limits of their microphone or audio interface, while maintaining sufficient signal to noise ratio for the data to be valid.

The CEA 2010 process is also more useful for comparing impulsive signals like a kick drum or an explosion sound effect for home theatre, and this can be easier for some boxes or designs than playing music content constantly.

The M-Noise process is a little more friendly to most practitioners, while also being more representative of long term signal drive levels. Your neighbours might not appreciate the noise running for the typical test lengths, though...

Both tests are very valid, especially for DIY boxes, and can be done at home by folk with a garden or access to a car park at their warehouse. It seems odd to be dismissive of them, since these procedures can easily highlight where a DIY design succeeds or fall short when compared to the 'industry standard' or professional cabinets.


Posted By: toastyghost
Date Posted: 01 February 2022 at 5:03pm
Pictures tell a thousand words and all that... plus this has been floating about on my hard drive for a couple of months, so might as well share.



This is a coupled lumped element and boundary element model of the Paraflex C2A Golden 21" cabinet in AKABAK3. This is the largest and most performant design as I understand it, a no-compromise version of the loading with outer dimensions of 1.2 metres by 1.2 metres by 0.6 metres.

The PDF plans don't indicate what driver was used, but I believe it was the Eighteen Sound NLW9601-4, so my model uses that as well. The shared traces from CLIO Pocket on the first page are sadly super compressed as part of a single image. I did the best I could with curve tracing tools, to get comparison data.

The base CAD model was drawn by myself from the plans shared on the HOQWS group, using quarter-symmetry on the XY plane. Eight subdomains are used, with the interfaces between each subdomain being meshed at twice the element count of the subdomains on either side. The CAD model has been manually meshed using the Frontal-Delauney algorithm in Gmsh, using frequency-swept element length parameters based on the internal geometry - in particular, channel dimensions were considered versus the element size, to ensure there was no overlap between integration points across the boundaries.

Stuffing was modelled in the corner pieces of the driver's rear chamber, using a measured absorption coefficient curve for a densely compressed piece of dacron.

There are 4,319 elements per quadrant, and an Infinite Baffle plane is used to create half-space (2pi) radiation conditions.

The recommended 21NLW9601-4 driver was modelled via the AKABAK voice coil model of complex, frequency-dependent inductance, using the driver-identification tool in the accompanying VACS software. For those who aren't familiar with this model, it uses exponential functions for resistance and reactance:
Zvc = Re(f) + j·Xe(f)
where
Re(f) = Re·(1 + f/fre)ExpoRe
and
Xe = (ω·Le)r
with
r = (1 + ExpoLe·q2)/(1 + q2)
q = ω·Le/Re

It is still a linear model overall, but this method produces a non-linear behaviour of Z(Le) as frequency increases.

Frequencies from 20 Hz to 250 Hz at 24 points per octave were calculated, for a total of 111 data points on each complex curve. Additionally, a 3-metre x 3-metre field across the ground plane was generated, with a resolution of 4 elements every 0.07 metres.

2V RMS driving level was used, based on the nominal impedance in pass-band being approximately 4 Ohm. This is equivalent to 1 Watt @ 1 metre distance, and matches the reported method on the plans.

Of interest to most people is the axial SPL, and electrical impedance, which I've shown compared to the measured data for qualification.


The electrical impedance tracks well, although it appears there is a slight shift down in tuning. Also, the upper response is reduced compared to measurement - this is likely caused by the lack of absorption from stuffing in the initial chambers of the model, and also the linear modelling method not including higher-order harmonic distortion components.

Another possible cause is that AKABAK3 is a BEM model in the physical domain, so does include effects of diffraction and wavefront distortion around bends and the like.

There's also a chance that the CLIO Pocket mic used for the original measurements was distorting, with the 3 dB crest factor of the log chirp (swept sine wave) stimulus and the CLIO Pocket mic's stated max peak SPL capability of 130 dB linear SPL at 1 kHz. The small plastic electret condensers typically perform worse at low frequencies, and I recently saw some strange behaviour at high signal levels when comparing two 'full-fat' CLIO mics to my own mics in a hemi-anechoic chamber.

If this wasn't just a 'bit of fun', and I had the cabinets to hand to experiment, I'd investigate further to determine what causes this discrepancy. As it is, close enough...


You can see that the electrical impedance dips to just under 3 Ohms at a couple of points between 30 Hz and 120 Hz, even in the measured data. As these are both small-signal data, it indicates that a 2 Ohm capable amplifier with one cabinet per channel would be a good idea for this box.

More importantly, you can see the problem of measuring at 1 metre. The light blue SPL trace tracks the 1-metre measurement very well, but the near-field condition provides an apparent +3 dB boost below 50 Hz when compared to a measurement taken in the far-field (green trace) and scaled back to 1 metre (purple trace). I don't know about you, but on my gigs and installs, only a tiny percentage of the punters are anywhere close to 1 metre away from the mouth of the boxes.


While we're here, one thing that is modelled well regardless of SPL discrepancies is cabinet diffraction. That is the primary effect on directivity, for low frequency enclosures. Since I've heard it said that Paraflex are supposedly very directional, that's worth a look at:


This is a broadband sum of all frequencies from 25 Hz to 125 Hz, looking from above the box at the 'ground'. The same pattern can be observed in the normalised horizontal polar plot - this is normalised relative to the axial response, so removes the SPL discrepancy between model and measurement from the equation:



It looks like there's little to no rear rejection - at least for a single cabinet - but there is a significant edge diffraction toward the lateral directions of +/-90 degrees, toward the rear cabinet corners.

One final bit of fun; stepping through the pressure response pattern from 10 Hz to 250 Hz, across that 3m x 3m plane. The meshing resolution of the observation field isn't high enough to show the entire internal path, so the 'gaps' are just where the cabinet walls are, but you can see the development of the pressure wavefront. That includes frequencies where the rearward radiation from the diaphragm is not in phase with that coming from the series resonant chambers.





Thanks for coming to my TED Talk


Posted By: Ricci
Date Posted: 01 February 2022 at 8:43pm
I was informed of this GTG at Motion Labs a few weeks before it took place. I was told there was going to be a comparison of a few subs with measurements and someone would be building a Skram and was asked if the 21NTLW5000 was a match. It's not ideal for the Skram due to slightly lower motor force than the cab was designed to work with (NSW6021, etc...) and I said as much, but told them it would be serviceable. As far as I was aware all of the other subs were the paraflex type that suddenly seems to be the popular flavor in DIY subs. Unfortunately I never saw any good measurements or data come from this meeting and the only thing I was told is that the Skram was placed differently, built very quickly and barely listened to at all at the gathering because it wasn't as "exciting" as the much larger, I believe pairs of paraflex subs. Not very confidence inspiring for a fair or scientific comparison. I'm not sure what driver, amp, settings were used for the subs and I don't think it was level matched. 

The Skram is a 30Hz tuned 450L net cabinet with a lot of effort put into balancing: Smooth linear response, output capability, low distortion, tuning flexibility to work in multiple applications and manageable size / weight. Scaling the system with multiple cabs to fulfill the output requirements of the app is intended. I intentionally choose not to tune any higher than about 30Hz on any of my subs. I know this gives up some loudness to achieve this type of extension. It'd be easy to tune it to 35 or even 40Hz and gain some sensitivity and loudness in the 40-100Hz bandwidth but it's a tradeoff that I choose to make for being able to really hit that 25-30Hz content when it does show up. I design for the top tier drivers because the extra xmax and power handling can help make up some of the deficit from tuning lower and/or being smaller than a lot of other subs. It's not a philosophy that fits or is cost effective for everyone and that's ok. There are a lot of ways to skin the cat. 

The 21" paraflex appears to be 2X the size at 900L net and with a higher 35Hz corner. 
900L is a huge cabinet. My Skhorn 2x 21" is quite a bit smaller at 680L net.  As we all know bass efficiency is all about air volume / size balanced against extension. Is a 21" paraflex going to be more sensitive and louder than a Skram that is half the size and tuned lower? Yes.
I'd be very interested to see a fair comparison with 2 Skrams since the dual cabs take up the same volume as the 21" paraflex. With equally good amplification, proper level matching, processing, etc... 

+1 on pretty much everything TG has posted in here. We need data!

I'm a hard data kind of guy. Hence my website...
It's crucial to understanding the behavior of a system and understanding the causes of the difference in sound between designs. Part of the qualification / improvement process if you will. I don't put much value on subjective reviews/opinion especially from people who have built the cabinet they are evaluating. 

 I'll eventually get around to testing Skram and Ckram subs. I should've done it long ago but I took a hiatus from DB testing. I'd really like to see an equivalent ground-plane measurement workup on a few of the paraflex designs considered to be the most refined. I'd like to see some popular scoops done as well. Impedance and 1w sensitivity measurements are a start but the interesting bits are what happens with compression, thermal shifting of output and distortion at war volume. CEA style short term SPL capability. Etc. Most designs look great at a few volts. What happens at 50 volts? 100? I want to see where things start to degrade and fall apart. 


Posted By: Ricci
Date Posted: 01 February 2022 at 9:04pm
Toasty,

Hell of a post you made there. Thanks for the Ted Talk. LOL
I can tell you put a fair amount of time into looking at that. 

A couple short observations if I may...
You are dead on that the low end response will droop by a couple of dB when measuring a front firing sub of this size at 1m vs 10m. These are big subs with a very large frontal area. At minimum a 4m ground-plane measurement would be advisable if 10m isn't possible. Or use the 10m measurement for a cal file on the shorter distance. 

I suspect that the response differences between your sim and the provided measurement are primarily due to a different driver being used in the measurement. Perhaps a 21NTLW5000. I could be wrong but that'd be my quick guess. Also some of the extra upper end response in the measurement would be from cab diffraction. That's a good sized frontal area. You may have taken this into account already and I missed it, 3dB extra gain by 100Hz already wouldn't be out of the question. Combine those 2 possibilities and it may close the gap between the measurement and sim considerably. 


Edit to add a Skram FR measurement. This was taken by a user Jay Michael outdoors at 1m GP in his backyard. Driver is the B&C 21SW152-4. This is the most trustworthy FR measurement of one I've seen yet. I don't trust the SPL calibration of the measurement but the overall FR shape should be close. 





Posted By: citizensc
Date Posted: 02 February 2022 at 6:37am
Originally posted by Ricci Ricci wrote:

I'd be very interested to see a fair comparison with 2 Skrams since the dual cabs take up the same volume as the 21" paraflex. 


A 900L volume and 800 euro driver budget opens up a lot of options. To be honest, I would like to see it compared to a couple of simple 21 inch reflex with something like the 21PW1400Fe.

-------------
https://www.facebook.com/voyager.system

@voyager_soundsystem


Posted By: kipman725
Date Posted: 02 February 2022 at 2:10pm
Thanks for doing all that sim work Kyle, I had suspected all the talk about rear rejection was incorrect as I couldn't think of a physical mechanism beyond the frontal area.  The HOQWs in general is lacking in test data, its disappointing that ASFIK the only people doing proper testing are data-bass and production partner.


Posted By: sushi
Date Posted: 02 February 2022 at 2:26pm
Gentlemen, thank you all for you answers and for the data provided. I may not perfectly understand some of those, being me a newbie for what regards audio measurements, but this is for me a big motivation to learn more and achieve a deeper understanding of this matter.
Ricci, thanks for showing up, as well for sharing your good work! I'm currently re-reading the Skram topic on data-bass, couldn't see pics the first time i read it.. that measurement taken by Jay might not be good for a proper and complete review of your sub, but it shows a smooth and even response which is really promising.. i definitely could be building a pair of Skrams in the future, as they seem to well fit my requirements for now.
As regards the paraflex subs, i really like they are "free" plans and get constantly improved through shared knowledge, but i find nowadays some people are kinda taking them for "the best subs ever - period" and contribute to fuel a hype that could illude some non-expert users (like me) that they are just as good as one could dream a sub to sound. A badass look makes things worse..
Pay attention! I'm not saying C2E are not good! I believe they must sound loud and clear since lots of people are happy with them, and i'm really looking forward to hear one personally. But if the outdoor measurements are correct, then 30hz 15db down from 60hz seems no such dream performance for a sub, also that big.. it has a powerful overall bass response indeed, but the graph also suggests the low end is not so loud. It could maybe get better with some eq lowering that large peak around 65hz but, again.. we don't know cause no detailed eq setting are posted with the plans on the fb page, neither real life measuraments, sometimes not even simulations.. I understand many just want to build and play, but that doesn't work for me. I think it would work better if common half-space test setting standards had been given to the builders, and the resultant measurements and eq tips had been posted with the designs. This way it would really be society work, as people could give something back while sharing their own experience. That said, i reckon admins and designers are quite helpful when asked.


Posted By: toastyghost
Date Posted: 02 February 2022 at 3:07pm
I actually wanted to do one of the C2E since the size is way more practical for most people, but I was quite put off by the fact that the pinned post on the group had 3 ‘drawings’, all with different dimensions, and the lack of any apparent measurements for comparison or validation.

One thing to consider for anyone interested in measuring subwoofers is that you can actually get useful data even if you’re stuck indoors. Using the principle of superposition, if the sub’s mouth is placed at the very centre of a room, then putting the mic’s capsule right into one of the corners where the walls meet the floor gives you the fewest reflections possible in that space.

It does of course produce a massive boost to the overall response since you’re in 1/8th space, so you have to manually adjust the measured response down by approximately 9 dB for that, as well as adjusting for the distance offset.

The room still has to be quite large, and ideally square, and have solid, dense walls on all sides to ensure that there’s an even distribution of reflections and a relatively easy calculation of the modal response. However, if you can get a distance of >8 metres from the sub’s mouth to the nearest boundary, then you should push the reflection down to well below 30 Hz. Any peaks in the data can be compared to the calculated modes, to see if they can be ignored.

You can also make a simple sealed subwoofer, and measure this to create an inverse calibration curve including the modal response. That can then be applied to any future measurements in that space.

I'm pretty sure most folk have access to a reasonably sized warehouse or barn. You could also try this outdoors, if your nearest car park or yard isn't massive...

The same principle applies when looking for the best subwoofer placement in your house or a venue too. Stick the speaker where you'd normally have your ears, and move the mic to the various positions where you could reasonably put the speaker. Far less effort than shifting the heavy box around!

It is however essential that the charts are labelled properly, and are accompanied by photos or text explaining what you did, what kit was used, how cold and humid it was, etc etc. The boring part where you document the method is as important as the actual process of gathering the data for any acoustical measurement - and a foundation of scientific process, regardless of field.

Funnily enough, this sort of thing is documented as part of the CEA 2010 process


Posted By: snowflake
Date Posted: 02 February 2022 at 5:03pm
any measurements or model of second and third harmonic distortion in paraflex? this could account for perceived loudness and directivity...


Posted By: Ricci
Date Posted: 02 February 2022 at 8:49pm
It would be great to have a few more outlets of in depth performance evaluation style testing of "pro"  subs and speakers, but I can understand why there are not. It is tedious, time consuming and requires a healthy dose of grunt work. It's really only the last 15 years that has seen this type of measurements enter into the mainstream. I find it slightly amusing that the home audio segment appears to be adopting objective data like spinorama and CEA-2010 testing more rapidly than the professional market. 



Posted By: toastyghost
Date Posted: 02 February 2022 at 9:48pm
Originally posted by snowflake snowflake wrote:

any measurements or model of second and third harmonic distortion in paraflex? this could account for perceived loudness and directivity...


Unfortunately, if the measurement process isn’t correct for magnitude, the harmonic data produced from the Farina sweep method is also questionable. Especially at low drive levels.

In modeling terms, it is possible to derive an estimation of the lower order linear harmonic distortion components from FEA or BEM models, but you need to integrate over a lot of finely spaced data points along a line from the driver to the far field.

There are also time-dependent solvers which can be used to simulate nonlinear acoustics in the newer versions of COMSOL, but I tried to run the example model of a simple, axisymmetric horn ( https://www.comsol.com/blogs/simulating-nonlinear-sound-propagation-in-an-acoustic-horn/" rel="nofollow - https://www.comsol.com/blogs/simulating-nonlinear-sound-propagation-in-an-acoustic-horn/ ) and I don't think my desktop PC has forgiven me since.

It is a shame there's not more quantified, repeatable data shared publicly in the pro audio world. My cynical side says that's at least partly intentional, but then I also see the variety of standards and understand a little why practitioners are less likely to pick up a book or paper, let alone a microphone. The folk in the actual engineering jobs seem to understand this stuff pretty well, though.

The upcoming AES standardisation of the M-Noise process should go some way to knocking s few of those barriers down, at least in practical terms.


Posted By: bee
Date Posted: 07 February 2022 at 6:38pm
Wow some very good detail in that response. The driver tested was the 18 sound 21 9601c (carbon). The rear projection in all sims is on par with your findings, but in real would we are getting a massive 6 to 9 db drop off, behind, I would love to post why, in truth I have no idea.. a positive gain yes but why... I see your point re 10m distance readings. This can be done. Soon as weather gets a bit nicer, I'll get them back outside and measureLile alot of things, some of the designs are or where done by a few people all over the world, with different measuring kit ECT. The c2a golden was designed and prototyped in the UK, by my self and Mathew's assistance via video links ECT. The plotts need to be updated on the plan, as I did do a revised set, this included a few updates to the tuning of the front chamber. Plans show updates. I could possibly arrange to get some boxes to you, if you would like a play. 

-------------
https://www.elements-audio.com


Posted By: T Willy
Date Posted: 07 February 2022 at 10:51pm
The reasoning behind the lack of data is due to the DIY nature of it. Some don't have the means or proper knowledge to take measurements. Some don't have the space to do it. Some don't have a working sample built to test. Everyone is at varying stages of knowledge, capabilities, and ability.
Granted there is always someone who has more knowledge and i would be glad to test anything with some guidance of the guru's.
For now, attached is the REW response taken at 1m/2.83v of the Paraflex C-2E Silver Formula loaded with SB Audience Nero 18SW1100d driver. UMIK1 was used as measurement mic. Overlay is the Hornresp model for same enclosure/driver combo using actual T/S parameters pulled from one of my nero drivers using DATS.
Take this data as you wish. Is it perfect or "uniform" test? No, but some of us are working on a knowledge and ability limited circumstance here.

https://www.facebook.com/photo.php?fbid=10220100161723166&set=p.10220100161723166&=3

If the link does not work, please reply. I can find another way to satisfy the archaic means of photo sharing here.


Posted By: Jay michali
Date Posted: 08 February 2022 at 6:19am
Great conversations happening here, thanks everyone. I've built both Skram's as well as some smaller 15" Type A paraflex cabinets. They are both great sounding cabinets and honestly as far as sound character goes they are more similar than they are different in my opinion. I wont go any deeper with comparisons at this time as they aren't anywhere similar in size, tuning, or in driver used.

The Skram measurement Josh posted above is mine. I was very much a measurement noob at the time and I definitely didn't db calibrate my mic so take that with a grain of salt. The response shape however is truthful to more recent measurements I've taken. I have learned a lot about measurements since, and intend to do more complete and accurate measurements of both cabinets once the snow melts up here in Canada.

To the original poster. The Skram is a fantastic sounding cabinet when powered properly with the 21sw152, and I would imagine it would be even better with the new Eminence 21. With casters, or on a dolly, I can load them in and out of venues and my trailer with no issues on my own. I previously used some Othorns, and found them way more challenging to move around even though they are just slightly larger. I think the Skram hits a perfect balance of size, weight, output and low extension. A bank of 6 of them is really impressive, they really can haul ass all the way down to the mid 20's. We love them so much, there is going to be another 4 or 6 coming to our city real soon.

If you can tolerate larger cabinets, then that may change the game and other options might be more suitable for your purposes. If its just output you're looking for, you could just built more as Josh mentioned.

On the Type A's, for the size they are also really impressive. For a relatively small cabinet and a 15" driver they punch way above their weight. They excel with kick drum oriented music, and offer a cleaner and more dynamic sound than most subs I've heard. I like playing the track Invincible by Tool during sound checks with these subs, I've never heard a studio recording of a band sound as impressive through PA style subs, there really is some magic sauce happening with the design. My particular versions are tuned to 35hz, they can do a reasonably good job of deeper bass music but they are better suited for house and techno for sure. I haven't heard any larger paraflex's before so my opinion is limited to the type A's I've built.

Lastly to Toasty. Thanks for the Ted talk, lots of good pointers in regards to measurements, I've taken some notes. On the rear rejection topic I'd like to add something to the conversation. These type A's have a noticeable reduction in output behind them. I don't know anything about the software you are using to simulate with, but in my experience the rear cancellation is a real phenomenon. I will add this to my measurement to-do list and report back in a month or two when I can get back outside again. I made this measurement last summer, and again note that I was very much in measurement noob territory at the time. Perhaps it offers a glimpse into whats happening. Disregard the 2.83v@1meter, I believe it was at 6 feet, measured with a tape measure from the mouth, and from the back wall of the cabinet. The mic was not db calibrated at the time.

https://imgur.com/a/dlMY3kp" rel="nofollow - https://imgur.com/a/dlMY3kp







Posted By: T Willy
Date Posted: 08 February 2022 at 1:22pm
Originally posted by Jay michali Jay michali wrote:

Lastly to Toasty. Thanks for the Ted talk, lots of good pointers in regards to measurements, I've taken some notes. On the rear rejection topic I'd like to add something to the conversation. These type A's have a noticeable reduction in output behind them. I don't know anything about the software you are using to simulate with, but in my experience the rear cancellation is a real phenomenon. I will add this to my measurement to-do list and report back in a month or two when I can get back outside again. I made this measurement last summer, and again note that I was very much in measurement noob territory at the time. Perhaps it offers a glimpse into whats happening. Disregard the 2.83v@1meter, I believe it was at 6 feet, measured with a tape measure from the mouth, and from the back wall of the cabinet. The mic was not db calibrated at the time.


Agreed. I have noticed a large amount of rear rejection with the C-2E as well. Funny thing is that it seems to be more prominent above a certain frequency. An educated guess i would say above 50 hz. Id like to test this some time with 360 deg of measurements at 8 points around the subwoofer. Chosen distance and calibrated mic. Would be interesting to find out what it is actually doing per response to level.


Posted By: toastyghost
Date Posted: 08 February 2022 at 6:27pm
Measuring rear rejection has to be done properly, and that’s a problem if you’re in the near field where cabinet shadowing will be occurring.

The first thing is to ensure that the rear position is equi-temporal with the front one. And that also means finding the acoustic centre, if you want to check near field rejection. Then you have to go a decent distance from that, at least a few metres, in both directions. You’ll find that any box of a dual 18” size has 3-5 dB near field rear rejection like this thanks to the cabinet’s shadowing. That's also present on a TH118XL and is what I see in the last imgur link too, but it isn't particularly exceptional.

I think confusion maybe stems from people not realising that most of the larger manufacturers refer to far field data, as this is where the vast majority of listeners to PA systems are going to be.

Anyone who has setup a wall of horn subs will notice this too, but while impressive up close it isn’t often very useful in real life once you get to distance.

The best thing is still to measure in the far field, where it matters. 10 metres (which is what the polar maps are generated at in my model) is a good indicator for real, useful rejection. The model uses the boundary element method, which solves the wave equation in 3D as a partial differential equation called the Helmholtz-Kirchhoff integral - so all cabinet geometry effects are included, unlike an isophase lumped element model like Hornresp.

You’ll see on the animated heat map of output that close to the cabinet there is a drop of 3-5 dB in the colour allocation, but this disappears in the far field. This effect is also created primarily by the cabinet’s size and shape, including the size of the radiating area on the front, regardless of internal layout. I spent 7 months researching this last year, with real-world measurements to qualify plenty of models. There’s always plenty of room for more investigation, but I the only thing I can see about the Paraflex alignment which could cause rear rejection is the fact that a lot of the low and upper corner response has phase offsets created by the stacked series resonant pipes. You can see a similar but less exaggerated effect in the response ripple of a straight transmission line, and those are modelled very well by a BEM model of sufficient mesh resolution.

Cardioid system designs such as gradient or end-fire have to be made with consideration as to whether you want a ‘clean stage’ or to avoid upsetting the neighbours many miles away. It is a case of ‘pick one’ usually, and only physical acoustic circuits like the Fulcrum patent or the Danley BC achieve both.


As an aside, I appreciate you guys popping out of the FB group to share the data. I genuinely think a lot of these concerns stem from the somewhat insular nature of the community and the use of Facebook for it. Sometimes the fast-moving chat and flood of cabinet drawings on the HOQS can come across like some magic bullet has been found, even if that isn't the intention. Plus, the data on there isn't yours and isn't easily shareable outside. What would you do if the group gets Zucc'd?!

We've all been excited and inexperienced at gathering worthwhile data, but learning happens a lot faster if things a presented more as questions and discussion across a broader range of communities.


Posted By: Ricci
Date Posted: 08 February 2022 at 9:23pm
Originally posted by Jay michali Jay michali wrote:

Great conversations happening here, thanks everyone.

Hey Jay...Fancy meeting you here. Thanks for posting since you have some experience with cabs of both types. 

It's too bad we aren't closer. I'd talk you into letting me borrow a few cabs for a full workup over the summer. I wonder if there are any C2E cabs near me in the US...Perhaps something worth looking into as I'm planning to get back at it this year. 

I don't really see any more attenuation to the rear than expected in the measurement. There will be some up close to the cabs simply due to the size of the cabinet and pathlength differences from the radiation point around the physical boundaries of the cab. Measurements from a larger distance such as 10m mitigate these and other issues. I don't see anything about the generic cab design that would explain greatly increased attenuation to the rear vs other similar size /shape cabs. Then again you and others are reporting something going on. It makes me wonder. Measurements should be able to show it if it's there and identify a cause if so. 


Posted By: Jay michali
Date Posted: 08 February 2022 at 11:07pm
Originally posted by Ricci Ricci wrote:

Originally posted by Jay michali Jay michali wrote:

Great conversations happening here, thanks everyone.

It's too bad we aren't closer. I'd talk you into letting me borrow a few cabs for a full workup over the summer. I wonder if there are any C2E cabs near me in the US...Perhaps something worth looking into as I'm planning to get back at it this year. 




Hey Josh, good to hear from you as well. Remind me where you are located again? Ill ask around, perhaps there is someone in your area who would donate a cabinet to get the proper data-bass treatment.

Would be nice  to see the Skram get measured up properly as well, I keep hearing of more and more getting build up here in Canada. From my knowledge there are at least 16 of them in western Canada at the moment with another 6 in the planning process. 


Posted By: Jay michali
Date Posted: 08 February 2022 at 11:12pm
Originally posted by toastyghost toastyghost wrote:



The best thing is still to measure in the far field, where it matters. 10 metres (which is what the polar maps are generated at in my model) is a good indicator for real, useful rejection. The model uses the boundary element method, which solves the wave equation in 3D as a partial differential equation called the Helmholtz-Kirchhoff integral - so all cabinet geometry effects are included, unlike an isophase lumped element model like Hornresp.


Thanks again for the great info Toasty. I do have access to a large paved parking lot at our studio, 10 meter measurements would be easy to pull off. I will try to make this happen, snow usually clears up around here in later march or early April. Super appreciate the detailed response, super helpful information



Posted By: JBK
Date Posted: 09 February 2022 at 10:36am
I have nothing to contribute but wanted to thanks everyone for your input, that's a brilliant thread.


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https://www.facebook.com/rootikalvibeshifi

http://jbkaudio.fr

https://www.youtube.com/playlist?list=PLKB8xPHqsVywM2EgtOaMjdgfIUf_-kFdV


Posted By: Ricci
Date Posted: 10 February 2022 at 8:22pm
Originally posted by Jay michali Jay michali wrote:

Hey Josh, good to hear from you as well. Remind me where you are located again? Ill ask around, perhaps there is someone in your area who would donate a cabinet to get the proper data-bass treatment.

Would be nice  to see the Skram get measured up properly as well

Louisville KY, USA is where I'm based. Really far away from Canada, or Europe!

I'm working on that 2nd part. Need to do a Ckram too. 


Posted By: MMJ of HOQS
Date Posted: 11 February 2022 at 9:21am
 Hello everyone! Smile  

  Considering how the topic of some rear-rejection or a directional effect as observed with the HOQS Paraflex subwoofers has become a focus of this discussion it is helpful for us to have more real world data for us to work with, so with that in mind here (below) are some contributions from our friend Patrick Sander in Munster Germany ... 

 These are multiple outdoor measurements taken at distances ranging from 1m to 10m.... 
 The subject is a single Paraflex Golden Formula C-2E 1x18 subwoofer in a field .....Fundamental tuning of this cabinet is 35hz... This cabinet's outer dimensions are 24" x 48" x 36" ..

 At each distance he first measured with this cabinet facing the microphone on-axis, and then without changing the position of the mic (or measurement settings) a second measurement was taken after turning the cabinet around (facing away from the microphone) while keeping our cabinet located in the very same place ...  

First at 1 meter:



Then at 2 meters:




Here we are at 4 meters:





At 6 meters, still looking great here:



 Then finally at 10 meters (almost 33 feet) :

 



   As you can see this amount of rear-rejection which we have in these charts coincide fairly well with what we see in the chart at the link which Jay Michali shared in this discussion earlier .......

 Jay's Paraflex subwoofer is of a different design being a Type "A" layout based Paraflex as opposed to the GF C-2E Paraflex which Patrick has,  so you can see that the dip & bump features are in different locations but the amount of rear rejection is very similar . .

In case anyone missed it earlier here is the chart which Jay had kindly provided:

 

So the effect has been measured out to 10 meters, and is still pronounced at 10 meters .. .
  
 We cannot yet say for sure if it diminishes beyond that point but nevertheless 10 meters is almost 33 feet and many stages aren't even 33 feet deep, so this is in fact a useful feature of HOQS Paraflex subwoofers, and it is one which has already been used to a practical advantage during shows & events, even by some who have responded in this discussion .. .     

A few examples of reports include a happily acceptable amount of bass energy on stage despite the array of Paraflex subwoofers being located directly in front of that stage, and another report included avoidance of noise complaints from a certain direction (as opposed to other more conventional cabinets which had previously been used in that particular challenging event space generating more complaints from neighbors without producing any more SPL on the dance floor ..)... 

 A combination of consistent measured data & consistent reports from experienced people whom we trust is extremely valuable to us...   After all these fellows are in the trenches with our boxes..... They come from various backgrounds & other forums (some are from Speakerplans apparently and are still members) ..... They have various levels of experience but some of them are seasoned industry veterans who have worked with many more PA cabinets in the field than I ever did, so contrary to whatever perceptions there may or may not be this community is quite the opposite of "insular" (if that word was used in the derogatory sense, but of course not, since there is no place for that sort of thing in a technical forum) .... In other words what they have to say holds a lot of weight, and is much preferred over conjecture from afar .. 

  We do encounter skepticism all of the time and I can totally understand why...... I would probably be skeptical too if coming from an outside perspective ......   Of course it doesn't help that Akabak is not predicting the sort of passive-cardioid or rear-rejection effect that we are measuring, and it was one of our own developers by the name of Tom Armitage-Giles (also of The UK) who was the first to point this out to us a while back when the predicted pattern in his Akabak simulation of a Paraflex subwoofer did not even remotely resemble the reports .......  Not sure if anyone ever figured out why that is (note: it was inconclusive and probably never even hit the public feed for that reason),  however, Tom is fully brilliant so I don't doubt his Akabak skills.....  

Toasty, if you don't know Tom already you two should connect,  he is a good guy, highly recommended Thumbs Up  



Yes, the Facebook group is fast paced which can often be fun but posts do get buried quickly and we also realize that it is not always easy to navigate and find what you want, unless you know exactly how to go about it and even then is a little tricky at times ........ Yes, being Zucc'd would be terrible, and that is always a risk with Facebook so we definitely don't want to "have all of our eggs in one basket" so to speak    ........... We do love our Facebook group while also staying aware of the issues and have taken some measures, but ultimately a new platform would be best and that will take time (work on it has already begun) .. 





Posted By: toastyghost
Date Posted: 11 February 2022 at 9:47am
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

 
 These are multiple outdoor measurements taken at distances ranging from 1m to 10m.... 
 The subject is a single Paraflex Golden Formula C-2E 1x18 subwoofer in a field .....Fundamental tuning of this cabinet is 35hz... This cabinet’s outer dimensions are 24" x 48" x 36" ..

 At each distance he first measured with this cabinet facing the microphone on-axis, and then without changing the position of the mic (or measurement settings) a second measurement was taken after turning the cabinet around (facing away from the microphone) while keeping our cabinet located in the very same place


Thanks for posting these. I don’t suppose these folk are also making an electrical impedance sweep? If not, please recommend that is done as part of a measurement process. It only needs a resistor and a crocodile clip or two and is as much a part of validating sims or models (and checking general box alignment and health) as pressure measurements. It would be nice to see phase and raw IR, but REW doesn’t make that easy.

Is there any photo or record of the environmental setup? Temperature, nearest boundary, etc.?

One thing to note is there’s a rather large physical offset if you do it this way of spinning the box around because the ‘rear’ data is taken with the back of the cabinet as the zero point. Am I assuming the mouth edge of the cabinet was set as the initial zero?

This is a common mistake, and why I mentioned that these sorts of measurements have to be ‘equi-temporal’ or, in simpler terms, the peak energy arrival has to be at the same position in the impulse response.

That is the equivalent of measuring from the acoustic centre of the cabinet, which is against the grille for upper bass notes, but quite far out in front of the box even for reflex cabinets. Finding it empirically is often easier than deriving it from theory and cabinet measurements, but it will vary with frequency. There’s a section in the ARTA manual on that and many other things related to making good measurements.

If that’s compensated for, it looks like you’re back to the same sort of rear rejection which is present in tapped horns. Taking the 1-metre measurement, you’ve got to boost the lower trace by 6 dB for a cabinet of 36” depth. That takes the 10 dB broadband rejection to 4 dB. A ‘good’ cardioid bass array typically aims to achieve >16 dB rear rejection, with some getting over 25 dB broadband, but again the issue of ‘near field’ or ‘far field’ targets comes into play and that is where any acoustical circuit that creates a rear cancellation becomes of serious interest.

This is somewhat expected and likely created by the physical mouth being relatively small compared to the cabinet’s baffle. Note how the gap closes at the lower corner? For example that’s what you observe with a BC sub (although there’s other stuff going on there).

As ever, measurements are only good if they’ve correlated to what you already expect to see. The analyser is a tool to confirm your idea, and if the physics don’t make sense, it’s time to analyse deeper.

I’m not aware of your buddy Tom, but always happy to chat about Akabak3 stuff. After literally 10 hours a day for six months using it, I feel I know the limits of what it can and can’t do, but there’s always something you can learn. Feel free to share my email with him; toastyghost@gmail.com works (and I don't care if bots spam it)

It’s healthy to be sceptical, regardless of circumstance - and please don’t take offence if people are trying to understand ‘the hype’ and what’s going on. There are few mysteries in this world of sound, and most of them end up coming back to perception and psychoacoustics. Modelling and quantifying the behaviour of a single box is the first step to understanding the behaviour of a cluster. Then perhaps any qualified benefit can be used more confidently to derive newer designs or market the concept.

I’ve been kindly shared a C2E CAD file from Huw Sinai’s builder, so at some point, I’ll try to model it in COMSOL instead. FEA for the internal domain might help figure some of this stuff out because then you can generate isoline plots of phase and the like across the entire air volume. Don’t expect that any time soon, though although now the weather is nicer, perhaps one of the many Paraflex in Sheffield might be dragged outside for me to measure with multiple mics.

All communities of passionate nerds are ‘insular’, don’t worry! Ever tried to speak to car enthusiasts or people really into chocolate?! As for Facebook, unfortunately, my life is infinitely better without an account in many ways, so I’m afraid I can’t see the general info unless it’s on a publicly accessible platform.


Posted By: toastyghost
Date Posted: 11 February 2022 at 10:27am
Here's some comparative data, since talk is cheap. I forgot my own rule of pictures = thousand words!

DAS EVENT-218A ported subwoofer, at 3-metre distance in a very large hall with Schroeder frequency of approximately 30 Hz. Traces taken with separate matched mics front and rear, impulse matched to acoustic centre:


Vertical stack of 3x Danley TH118XL tapped horn in landscape orientation, 4-metre distance outdoors. Separate mics again, front and rear, distance matched to the acoustic centre:


Note the overlapping phase traces at front and rear positions, in both sets of data? If the ‘delay locator’ or acoustic timing reference is kept the same between measurements (turn off the automatic ‘set offset to IR peak’ in REW) then this is an easy way to make sure you know the physical distance offset is from the acoustic centre of the cabinet. Just move the mic or box back and forth, until the phase overlaps. You might be surprised where the mic ends up!

Also, here's an example of a tuned cardioid system, same location as the other TH118XL trace but with an extra rear-facing sub added and tuned for maximum rejection in the far-field at the lowest notes, which were causing issues off-site and at other stages:


Posted By: Sinai Sound
Date Posted: 11 February 2022 at 11:30am
Talking in depth about speakers!

On speakerplans!

What dark magic is this!!!

When it's freezing cold, and dark at 7pm at night, I'm taking one of these into an open space somewhere with Kyle 


Posted By: toastyghost
Date Posted: 11 February 2022 at 1:19pm
Originally posted by Sinai Sound Sinai Sound wrote:

Talking in depth about speakers!

On speakerplans!

What dark magic is this!!!

When it's freezing cold, and dark at 7pm at night, I'm taking one of these into an open space somewhere with Kyle 



I know, right?! it’s a shame our demo stock of battery-powered 4x 1000W DC amplifiers won’t arrive til mid March, because that opens up a lot of outdoor space well away from boundaries. Generators aren’t the one as the noise contaminates the data.

Also, I just updated my last post to clarify that you have to keep the timing reference consistent between measurements. By default, REW will automatically shift that on each new trace.


Posted By: sushi
Date Posted: 17 February 2022 at 1:58pm
Thanks to all for showing up, and providing data and feedback i requested.. and much more! I really hope other people would benefit from this!

Jay, it's good to hear from you. I loved following your building/tuning progress on data-bass and i totally agree with you about the Skram being a good compromise between size, low extension, and output.. i'm looking forward to build my first pair, just waiting for birchply prices to come down a bit (+100% on last year prices, what the hell)
MMJ, good to see you here too! Happy to hear a new online platform is coming! Fb group is connecting a lot of people and spreading the designs around the globe, but i fear fb itself has lots of negative sides and many we still have to see. Protect the community work and keep it clear, i say!
Toasty, i'm having some days off and i would like to study.. is there an official paper for CEA2010 standards, i can download? I found a couple pdf's online but i don't know which one is the one.
I have a trustable and professional contact who could help me learn Smaart, is there any reason i should better use Rew instead?
Big thanks, again!
Cheers!


Posted By: toastyghost
Date Posted: 17 February 2022 at 3:11pm
You might be struggling a bit because they rebranded from CEA to CTA a few years back.

Smaart isn't the correct tool for CTA-2010 tests, nor speaker design really. It's possible, but the software and interface is focused around quickly getting two-channel transfer functions for relative source EQ and phase alignment, or tracking SPL data over time periods at events.

REW generates more useful frequency-time plots such as CSD, Wavelet, and separated nonlinear harmonic distortion magnitude for loudspeaker design and testing. It's also got an automated CTA-2010 test method built in. Plus you know, it's £700 less than a Smaart license

As for the method, the standard itself is $60 here: https://www.techstreet.com/standards/cta-2010-b?product_id=1888053

But Brent Butterworth has a good 'plain English' guide with illustrations. Use this:
https://brentbutterworth.com/cta-2010-manual

Make sure you've got a calibrator, and make a new SPL calibration at the test location each time you do the test. I think the UMIK mics are pre-calibrated, but it's best practice to do it fresh. You can get accurate enough calibrators for DIY purposes from about £70. Make sure you keep the audio interface mic pre at its lowest gain, to give maximum SPL headroom. Even then, you wanna go farther out and calculate back to 1 metre values, as most cheaper mics are only rated at 1 kHz. 120 dB max at the capsule is a good guideline before electret mics distort - even the CLIO ones.

If you want to be bang on, log the temperature and humidity too, and take a photo of your setup. A tape measure helps more than you'd think, as does some way to mark locations on the floor - neon gaffa tape, or some cheap pitch markers for sports.

You'll benefit a lot from making a simple sealed box of known volume, to get a calibration measurement in your measurement space - even if it's outdoors in the typical garden or car park environments available to most of us. Doesn't have to be anything super special, just six bits of wood and a half-decent driver. Borrow one from your other subs if you haven't got a spare.

Oh, and having a voltmeter hooked up at the amp terminals to log the output voltage for each given SPL is also important.

Check Ricci's data-bass reviews of subs for examples of how to format the data.


Posted By: T6ss
Date Posted: 20 February 2022 at 5:45pm
Having built and tested 6 golden 21s, and having heard them in anger at a gig you can do all the simulations and testing you like, it is a very flawed cab, they are not impressive at all, at the 21 sub test it was said to be the loudest cab, just, however Ben had a 4ohm driver in his golden 21 where as everyone else had 8s, not a proper test at all, last night Method 24 had 6 21 goldens out, alternatives wsx bins were far superior in every way. If you ever go on the Paraflex FB page and make a solitary negative remark you are treated as some sort of idiot, like the guy who complained that adding 3db at 50hz caused he drivers to become very hot, who wants a sub you can't eq ? At rumble in the jungle Revolt had their paraflex bins out, modified by them to be better, I honestly think Tomo's old Flair bins are much better, on that night RC1 were in the main room and in my honest opinion two of those would destroy a stack of paraflex with ease, I hope all the people who have spent a fortune on having huge Paraflex bins built and loaded with very expensive drivers aren't to upset, we've had two years of not being able to play out, that time is over and the Paraflex boys will be tested against lots of proven systems, good luck you are seriously going to need it.


Posted By: al_x
Date Posted: 20 February 2022 at 8:07pm
T6ss sounds like you have a chip on your shoulder more than anything.


Posted By: T6ss
Date Posted: 20 February 2022 at 8:41pm
Originally posted by al_x al_x wrote:

T6ss sounds like you have a chip on your shoulder more than anything.
 Wow, so after hearing them first hand and giving an honest assessment I have a chip on my shoulder, exactly the response I expected, perfect lol.


Posted By: al_x
Date Posted: 20 February 2022 at 8:47pm
Mate the language you have used throughout your opinion piece is just angry and arrogant. It’s unnecessary tbh Big smile
Especially the closing statement. 



Posted By: T6ss
Date Posted: 20 February 2022 at 8:54pm
Originally posted by al_x al_x wrote:

Mate the language you have used throughout your opinion piece is just angry and arrogant. It’s unnecessary tbh Big smile
Especially the closing statement. 


Not in any way, it's an honest assessment, plenty of cheaper to build and load plans are much better, so the Paraflex guys will luck, however take it how you want, your opinion of my language has no bearing on the performance of these cabs, please tell me your experience with Paraflex, have you stood in front of multiple systems with them included ?


Posted By: MMJ of HOQS
Date Posted: 20 February 2022 at 11:17pm
Toasty , 

I asked Patrick about it and he says he only takes measurements on days when there is no wind or rain .....  ..     As far as temperature is concerned he didn't note it but figure whatever the average temperature would be in October, mid-day, in Munster Germany ... 

In Patrick's words "it is the delta that matters here" .. .

 Patrick is pretty busy with the forums he is involved in but who knows, he may pop on here to join in ... .  That would be nice .... Patrick is great Star


Posted By: MMJ of HOQS
Date Posted: 20 February 2022 at 11:36pm
T6ss ,

 Who are You really?     What you are saying doesn't add up in the slightest .. 


   The Golden Formula C-2A 1x21 isn't lacking by any means  .... .. A single is impressive and a group is even more so ..   The Sinai show with Method Twenty Four which you reference above was not even remotely falling short on sound ... 

Are you someone who had cabinets among one of the subwoofer shootouts where Ben obliterated everything he went up against? These were friendly gatherings from what I understand....  Ben's GF C-2A sub had an audibly strong margin ahead of the others (not just a barely audible 3db) when all were run near their safe limits, so your complaint about his 4 ohm driver doesn't stand ...   




Posted By: T6ss
Date Posted: 21 February 2022 at 4:43am
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

T6ss ,

 Who are You really?     What you are saying doesn't add up in the slightest .. 


   The Golden Formula C-2A 1x21 isn't lacking by any means  .... .. A single is impressive and a group is even more so ..   The Sinai show with Method Twenty Four which you reference above was not even remotely falling short on sound ... 

Are you someone who had cabinets among one of the subwoofer shootouts where Ben obliterated everything he went up against? These were friendly gatherings from what I understand....  Ben's GF C-2A sub had an audibly strong margin ahead of the others (not just a barely audible 3db) when all were run near their safe limits, so your complaint about his 4 ohm driver doesn't stand ...   



I am not referencing Electric London, Method 24 were out in Bristol, no I did not have a 21 sub in a shoot out, what I'm saying certainly does add up, many at Bristol said the gf c2a sounded pants, were you there Matt ? Were you at Electric London Matt ? And here is the big issue Matt, you are assuming I am some bitter 21 cab owner when I'm not, you say Electric London did not lack bass when you were not there, you were not at the 21 shoot out, you were not in Bristol, on  you FB page you were asked a question  by someone that you failed to answer, so I will ask the same, have you personally built and tested a Paraflex 21, or any for that matter. When designs are being recommended to the public as awesome then generally the person doing the recommending has at least built and tested one and as far as I'm  aware you have not



Posted By: T6ss
Date Posted: 21 February 2022 at 5:05am
Matt  sorry to bang on but I just re read you post, Ben Obliterated everything there, you see the problem yet Matt, you were not there but you are sounding like you were, Obliterated is a very big word, no one was Obliterated by it, stop over exaggerating things that you were not even present  for, people are spending a small fortune because of your words, someone who was not at the 21 shout out and as far as I'm aware not built and tested the cab in question, generally when I buy a new car I speak to people who have actually driven one.


Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 5:27am
T6ss , I don't live in The UK   ...  Again I ask who are You? 

Are you a cabinet builder in The UK?  The reason I ask is because there is one builder in particular (in The UK) who builds other sorts of cabinets and has been stirring up trouble lately because he feels threatened or insecure or whatever .... Probably freaking out because people keep asking him to build Paraflex cabinets Clap

 Anyway, You are just talking a bunch of trash with the passion of someone who has an agenda while hiding behind some vague internet handle , so you can understand my curiosity..

 Your account has "new member" status , created on the 16th of February which is just a few days ago .... So did you create this fake name account just the purpose of jumping in on this discussion to spout off your garbage in here?   Did you really go through all of that trouble just to shoot us down?  

  We are trying to have a civil discussion here about technical matters  ....  Your nastiness isn't called for .... 


Posted By: T6ss
Date Posted: 21 February 2022 at 5:51am
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

T6ss , I don't live in The UK   ...  Again I ask who are You? 

Are you a cabinet builder in The UK?  The reason I ask is because there is one builder in particular (in The UK) who builds other sorts of cabinets and has been stirring up trouble lately because he feels threatened or insecure or whatever .... Probably freaking out because people keep asking him to build Paraflex cabinets Clap

 Anyway, You are just talking a bunch of trash with the passion of someone who has an agenda while hiding behind some vague internet handle , so you can understand my curiosity..

 Your account has "new member" status , created on the 16th of February which is just a few days ago .... So did you create this fake name account just the purpose of jumping in on this discussion to spout off your garbage in here?   Did you really go through all of that trouble just to shoot us down?  

  We are trying to have a civil discussion here about technical matters  ....  Your nastiness isn't called for .... 

So shall I take it that you have not built your own design, my account has new status because I've only just joined, I came on here to tell.my honest opinion of what I've seen and heard, you on the other hand are talking about things you have not seen and heard, no I am not a threatened or insecure cab builder, I have asked you to clarify  a few points and you have not, what you have done is start a personal attack just like I said happens in my first post, so what I first said is now adding up.


Posted By: T6ss
Date Posted: 21 February 2022 at 5:55am
Matt, your member status says new member joined on the 10th of Feb.


Posted By: T6ss
Date Posted: 21 February 2022 at 6:09am
We are trying to have a civil discussion here about technical matters  ....  Your nastiness isn't called for ...


Asking if you have built your own design is not being nasty, saying I am not impressed is not being nasty, asking you if you were at certain events is not being nasty, saying there are better and cheaper plans is not being nasty, if giving an honest assessment of what I have seen and heard is nasty then the world is in trouble.


Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 6:15am
 Tss ,      I didn't join to troll anonymously  .... Big difference  .. 


Posted By: T6ss
Date Posted: 21 February 2022 at 6:16am
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

 Tss ,      I didn't join to troll anonymously  .... Big difference  .. 

Can you please answer the questions


Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 6:28am
You won't even bother to identify yourself but you know who I am ...  I don't have time for anonymous internet trolls hiding behind a vague alias ..    The internet is maggoty with such creeps . .   You aren't entitled to anything from me .. 


  I will say that You apparently also don't have a clue about how our process works, I am only the first step, but I do interact with other parts of the process where I can help  , and I receive constant reports & feedback ....  I pretty much eat, sleep, and live this and have for some years now without much of a break and momentum just continues to build for us , and that is for good reason  ....    

People enjoy what we make. .   


Posted By: T6ss
Date Posted: 21 February 2022 at 6:38am
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

You won't even bother to identify yourself ...  I don't have time for anonymous internet trolls hiding behind a vague alias ..    The internet is maggoty with such creeps . .   You aren't entitled to anything from me .. 


  I will say that You apparently also don't have a clue about how our process works, I am only the first step, but I do interact with other parts of the process where I can help  , and I receive constant reports & feedback ....  I pretty much eat, sleep, and live this and have for some years now without much of a break and momentum just continues to build for us , and that is for good reason  ....    

People enjoy what we make. .   

Maggoty creep, OK I will leave it there, I'm sure most intelligent people will understand why you have not answered a few simple questions and I'm sure they will see how any factual. criticism of a Paraflex design gets a proper personal attack, thanks for clarifying what I originally wrote 👍


Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 7:12am
You misunderstood...   I said the internet is maggoty (with such creeps)......  The word maggoty just means covered with many of something and or filled with many of something ....  I didn't call you maggoty .....   

I called you a creep which is a fitting term for an anonymous troll with an agenda who signed up to make an account specifically for this discussion just to talk trash about things he doesn't have a clue about, to known people (yet won't identify and expects to be taken seriously?)   .... ......    Welcome to The Internet right?    Oh well ...

Take care "T6ss" ..

I was just here on Speakerplans tonight for the purpose of making a nice response to Sushi , and I will get back to that now . .


Posted By: al_x
Date Posted: 21 February 2022 at 8:33am
T6ss
Yeh I didn’t read that as him calling you a maggoty creep. 
I guess from your profile details you are someone called Colin from Hillbilly Acoustics.
Your first opinion piece could have been ok but it was just angry and arrogant, especially the closing statement….

  I hope all the people who have spent a fortune on having huge Paraflex bins built and loaded with very expensive drivers aren't to upset, we've had two years of not being able to play out, that time is over and the Paraflex boys will be tested against lots of proven systems, good luck you are seriously going to need it.”

You just sound like a dick. 



Posted By: al_x
Date Posted: 21 February 2022 at 8:40am
I’ve been here on and off since 2005 and haven’t seen this much beef for years. 


Posted By: fat_brstd
Date Posted: 21 February 2022 at 9:17am
The paraflex boxes have a lot of hype behind them and very little data that can be used to compare to other designs in any sort of meaningful way. I have not seen any direct comparisons between a paraflex box and other designs.

It seems that a lot of the crews who are building paraflex designs are very new to Sound System and do not have a lot of real world experience with a variety of designs (especially down here in Aus/NZ). The people building them do seem to be very happy with their performance but I was over the moon with the performance of the 12" scoops that were my first steps into the world of Sound System and I can now say with the benefit of hindsight and experience that those boxes were inefficient rubbish and I had no idea what a proper speaker box was capable of at that time.

I would be very interested in knowing if someone has actually heard multiple paraflex boxes loaded with different drivers and driven off different front ends and particularly if they have had a chance to hear them in the same space as another sound system. A good example of this would have been Sinai & Channel One at the Steel Yard back in December or Sinai & Iration in Leeds where they put the 21" paraflex up against the Iration double 21" subs which I believe are a Bandpass design. We all know that Huw/Sinai is a clever bloke and uses technology to get the absolute maximum he can out of his boxes but are they really miles ahead of every other type of box out there? Did Sinai thrash Iration on bottom end with half the number of sub drivers? Only someone who was present can say but somehow I don't think that is what happened at that dance.

If you take the best of the best drivers and put mountains of power up them by using the biggest amps available with the most advanced limiting that exists then they should be very very impressive, that is the whole point of using the absolute best of the best gear.

I would love to have the opportunity to hear some paraflex boxes but no-one around me has managed to build one that works. The only guy I know who has built one (a small 15" box, I think designed for kick, I do not know the exact plan he used) had his driver fail within 10 mins of turning it on. The cone/surround ripped from too much pressure on the driver but it was an old driver (around 20 years old) and probably not played with a suitable highpass filter so not unsurprising.

I regards to the OP the best way to decide on what sort of box to build is to go out and listen to as many different types of boxes as you possibly can. I must have heard 30 different sub designs before I decided on what I was going to build and what I wanted from my sound may not be what they want from their sound. As always sound is subjective and opinion often accounts for far more than raw undisputed scientific data. Personally I would never spend the amount of money that it costs to build a decent box on something that I hadn't already heard with my own ears as the worry about it not performing to spec would be too great for me to risk.

Finally can we stick to people reporting real world events that they were present at. If you are not present at an event where boxes are compared then do not make statements about what happened as 2nd hand information presented as being accurate is no use to anyone and creates false ideas of a design (be that positive or negative). This happened heaps with the scoop shootouts that I went to over 10 years ago when people who were not there tried to imply that one design was way louder than another even though the SPL measurements for all boxes were within 1dB of each other. Yes, there were variations in tone between the boxes but for raw SPL they all put out essentially the same level which was not surprising given that all the boxes had the same driver and were being driven off the same amp to the same clip point.

-------------
Adrians Wall Sound System
Melbournes Rootical Warrior
Roots - Dub - Steppers

http://www.facebook.com/adrians.wall" rel="nofollow - facebook page


Posted By: Sypa
Date Posted: 21 February 2022 at 9:21am
I dont think he sounds like a dick , didnt go that far . The man just gave his assesment and experience with the cabs . Yeah the last sentence is a bit harsh but so what , when did we become so sensitive ?
With all the hype around paraflex like its the best thing since sliced bread pretty much guarantees they will fall short a bit in the real world.



Posted By: al_x
Date Posted: 21 February 2022 at 9:56am
Originally posted by Sypa Sypa wrote:

I dont think he sounds like a dick , didnt go that far . The man just gave his assesment and experience with the cabs . Yeah the last sentence is a bit harsh but so what , when did we become so sensitive ?
With all the hype around paraflex like its the best thing since sliced bread pretty much guarantees they will fall short a bit in the real world.


It did sound very antagonistic, as if he has a sub he wants to compete in the same category. 
I agree there has been a lot of hype but I think that’s driven from people just being bored of the same old reflex/band pass/folded horn options when it comes to bass and the various paraflex designs provide a decent alternative. Not better or worse necessarily, just an alternative. I and alot of people are very impressed with the sound and performance, and no it’s not because I have only heard a 12” scoop before Big smile



Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 12:54pm
Sushi, 

In response to your most recent comment I would like to say thanks! 
 I am glad to be here!   Big smile

Beer 

Yes,  the Facebook group has been great for building community and making the designs available and also makes for rapid & convenient communication while developing etc, and we are fully grateful for all of it, thank You Facebook!  However that service definitely also has it's drawbacks and things to be concerned about ..... People are wary of Facebook, and or reluctant about it, and that is all for good reason.... Congrats to the people who have freed themselves of it ...

We hope to always have a presence on Facebook but when the time comes we plan to make our primary home on another platform Smile..  

 Now to reach back further, in response to your Original Post I have to say that it isn't an easy question for me to answer because there are several designs in the C-2E series of cabinets which are all a little different but I can speak in generalizations about the series....   The Skram is another matter since I am really not familiar with the Skram other than what a few people in our circles have said to me after listening to them in relation to Paraflex cabinets, so I personally don't feel that I am qualified to speak on the Skram in any detail but I will just say that based upon what I have been told the C-2E subs and the Skram are two very different animals .....    It is an apples to oranges sort of comparison and what is best for someone will depend on what sort of sound they prefer or the characteristics they need for their application.......    In fact one of the guys in Germany who owns both a Skram and some 35hz tuned Paraflex GF C-2E subs has stated that he has an upcoming performance involving deep subbass synth sounds (the sort of stuff that revolves around the vicinity of 30hz) and plans to use the Skram for that because he knows the Skram will really shine in this situation ... 

We do have a 28hz tuned Paraflex C-2E 1x21 subwoofer which has recently been fully updated by one of our very talented digital artists Declan O'Regan (now includes the Damped (stuffed) Angle-Brace feature) .... This cabinet may very well reach deep like the Skram but won't sound the same as a Skram ...  They will each have their own sonic personality ..  

So as promised I will speak generally of the Paraflex C-2E series and say that like most Paraflex subwoofers intended for PA work they do have a rising response as a single and their sound can be described as lively & energetic, exciting, dynamic and detailed, musical and a bunch of other subjective terms but those are just words and none of that really matters as much as what YOU think of their sound, and that means getting out there and hearing some for yourself (as others have suggested) ..  ....  I recommend reaching out to people who own Paraflex cabinets and talk to them about their experiences (especially as compared to other types of subwoofer cabinets) and then make plans to meet up with them for a demonstration if they are close enough, or show up at one of their events to have a listen (even a remote demo is better than nothing) ...   The HOQS folks are typically pleasant, friendly & helpful (we have worked hard every day to nurture that culture in the Facebook group) so please don't be shy, feel free to connect with them ...  


As Jay had pointed out there is something special going on in the way a Paraflex subwoofer reproduces the low frequencies in music and it is appealing to most but it is hard to describe, you just need to hear it for yourself and then you will understand what we are talking about ..... This isn't something a person can so easily assume (at least not correctly) just by looking at our drawings (though people do try, those guys can be disregardedTongue).. .....It must be experienced......   There are some good reasons why the Paraflex cabinets have increasing popularity in recent years, it wasn't just random, and isn't just hype ...

  
As more and more of the HOQS cabinets are being built around the world it will become easier to get out there and hear some, or even measure some, so there is less need to assume anything ..  

 Also important to mention that it the HOQS is a very mixed crowd community but some who are involved with us are highly experienced and have been in the industry for a while, more than long enough to have worked with all sorts of different subwoofers, so to dismiss the entirety of us as a bunch of noobs who don't know any better simply isn't accurate ...      

  


Sushi,  about CEA 2010 , there an HOQS member who goes by the name of "Plippie Plop" on Facebook or USRFobiwan on DIYaudio and he has performed the CEA 2010 tests on some Paraflex C-2E 1x15 subwoofer cabinets which he built (he has made many of them and uses them arrayed for festival sound in The Netherlands) .. ..   Like other distortion measurements which he has taken of HOQS Paraflex cabinets he was very happy with the results (and I remember him showing me the charts from it) but if i recall correctly he found the method to be impractical, and so yes, he was not fond of CEA 2010 but he did indeed perform the tests ..... He can explain it all so much better than I can (not my department) so if you want more details he can be contacted on Facebook .......... I do know of the Facebook post which Stef "Smitzke96" is referring to , it is from January 8th,  and for the sake of clearing up any misunderstanding about what happened Plippie Plop actually did take the time to respond to him about it .... 

  Plippie's response is as follows:          

"
I did many CEA2010 tests, but the bursts are just too damn loud for any 'realistic scenarios' of PA cabinet performances. With realistic I mean I never let cabinets go to the max and into distortion, I just add more cabinets. It doesn't make any sense.
Also the CEA2010 have an A and B variant, where B got a higher distortion tolerance at the lower scale and adds more frequencies to the type A list (20, 25,
31.5 and 40, 50, 63 Hz frequencies) which to me means the whole method is flawed and try to compensate. Also note that the CEA2010 test was primarily made for "powered subwoofers", read as in Consumer level sub cabinets. Basically it's a marketing tool. It literally says so in the papers...
The CEA2010 measurements I did on the 63hz burst of the tc2e115 alone was over 135db at 4m before any signs of distortion, in fact the mic would distort much sooner than the cabinet itself. Unless you are living in the middle of nowhere and can do tests all day and can setup you mic far enough away so it doesn't distort first, I say go for it.
Here you can find all the info you need to setup a test in REW:
http://www.roomeqwizard.com/betahelp/help_en-GB//siggen.?fbclid=IwAR1sfbpYboghvErEI6o_sqvXj0hqD8edXL-bWSYhIKlV7jdF-sf7mM8QpAU#cea2010 - http://www.roomeqwizard.com/.../help.../html/siggen.html...
And here you can find a extended technical paper:
https://www.klippel.de/admin/klippel/Bilder/Our_Products/R-D_System/PDF/S44_TBM_Tone_Burst_Measurement.pdf?fbclid=IwAR04bUlWYmBmV6T0otCPosp_tpjmMfcAR6Ump4cNgGl0FMt9_aYZL4UY1os - https://www.klippel.de/.../S44_TBM_Tone_Burst_Measurement...
2006 paper (see page 17):
https://l.facebook.com/l.php?u=https%3A%2F%2Fwww.x3mhc.no%2Fdokumenter%2Fstarobin_CEA2010.pdf%3Ffbclid%3DIwAR2c8EMcof1QAA_Oe2HEAqieyGSn1Msax-ARdGrmfAr0NO9dlyBAWNH25qM&h=AT1OhfyXPL4dvHDBKks7M_F8VhRABGG0Ae1EIFbPzCYDZMOcfFhobAHjhjcMprABLtjyoZuLg3FamD1PxcV3AbrdlEgeJLh5zd2NjVx4unpuvAD0dTTl9Ivtm1iV11GOsuvE&__tn__=R%5d-R&c%5b0%5d=AT284MFcvkwyt01v3UHYSs5xxah_ry9RpOfIZIupnXhYOg3sdSZzW-9R96qnjdWbLxAz3QGiqUEVfeK8YQ5aoKX27ljIsIbIKfF9d4A0eLzpP-1Bt5-yebzR_oo2GBmTubmMUGegdvClY4QCNxRz5VZZ14cx - https://www.x3mhc.no/dokumenter/starobin_CEA2010.pdf
"  

I hope that helps Smile






Posted By: MMJ of HOQS
Date Posted: 21 February 2022 at 1:11pm
Al_x ,  

Is "T6ss" really Hillbilly from Hillbilly Acoustics?    If so then thank You for figuring that out ...  He is a commercial builder (of other cabinets) in The UK   .. 

I suspected it might be something along those lines..




Posted By: sushi
Date Posted: 21 February 2022 at 6:48pm
Originally posted by MMJ of HOQS MMJ of HOQS wrote:

<span style=": rgb251, 251, 253;">Sushi, </span>

<span style=": rgb251, 251, 253;">In response to your most recent comment I would like to say thanks! </span>
<span style=": rgb251, 251, 253;"> I am glad to be here!   </span>Big smile

Beer<span style=": rgb251, 251, 253;"> </span>

<span style=": rgb251, 251, 253;">Yes,  the Facebook group has been great for building community and making the designs available and also makes for rapid & convenient communication while developing etc, and we are fully grateful for all of it, thank You Facebook!  However that service definitely also has it's drawbacks and things to be concerned about ..... People are wary of Facebook, and or reluctant about it, and that is all for good reason.... Congrats to the people who have freed themselves of it ...</span>

<span style=": rgb251, 251, 253;">We hope to always have a presence on Facebook but when the time comes we plan to make our primary home on another platform </span>Smile<span style=": rgb251, 251, 253;">..  

</span><span style=": rgb251, 251, 253;"> Now to reach back further, in response to your Original Post I have to say that it isn't an easy question for me to answer because there are several designs in the C-2E series of cabinets which are all a little different but I can speak in generalizations about the series....   The Skram is another matter since I am really not familiar with the Skram other than what a few people in our circles have said to me after listening to them in relation to Paraflex cabinets, so I personally don't feel that I am qualified to speak on the Skram in any detail but I will just say that based upon what I have been told the C-2E subs and the Skram are two very different animals .....    It is an apples to oranges sort of comparison and what is best for someone will depend on what sort of sound they prefer or the characteristics they need for their application.......    In fact one of the guys in Germany who owns both a Skram and some 35hz tuned Paraflex GF C-2E subs has stated that he has an upcoming performance involving deep subbass synth sounds (the sort of stuff that revolves around the vicinity of 30hz) and plans to use the Skram for that because he knows the Skram will really shine in this situation ... 

We do have a 28hz tuned Paraflex C-2E 1x21 subwoofer which has recently been fully updated by one of our very talented digital artists Declan O'Regan (now includes the Damped (stuffed) Angle-Brace feature) .... This cabinet may very well reach deep like the Skram but won't sound the same as a Skram ...  They will each have their own sonic personality ..  

So as promised I will speak generally of the Paraflex C-2E series and say that like most Paraflex subwoofers intended for PA work they do have a rising response as a single and their sound can be described as lively & energetic, exciting, dynamic and detailed, musical and a bunch of other subjective terms but those are just words and none of that really matters as much as what YOU think of their sound, and that means getting out there and hearing some for yourself (as others have suggested) ..  ....  I recommend reaching out to people who own Paraflex cabinets and talk to them about their experiences (especially as compared to other types of subwoofer cabinets) and then make plans to meet up with them for a demonstration if they are close enough, or show up at one of their events to have a listen (even a remote demo is better than nothing) ...   The HOQS folks are typically pleasant, friendly & helpful (we have worked hard every day to nurture that culture in the Facebook group) so please don't be shy, feel free to connect with them ...  


As Jay had pointed out there is something special going on in the way a Paraflex subwoofer reproduces the low frequencies in music and it is appealing to most but it is hard to describe, you just need to hear it for yourself and then you will understand what we are talking about ..... This isn't something a person can so easily assume (at least not correctly) just by looking at our drawings (though people do try, those guys can be disregardedTongue).. .....It must be experienced......   There are some good reasons why the Paraflex cabinets have increasing popularity in recent years, it wasn't just random, and isn't just hype
</span>


I'm quite on your side on fb pros and cons. Hype is the term i did use and i believe in this case it is totally depended on algorithms matters. You clearly didn't want some sort of fame, but just to design loudspeaker cabs, as we all would love to i guess.. I trust that you and the other developers are skilled techs with some serious background, and besides putting out good plans for the DIYers you are also quite helpful on the page when people need it.
I actually did asked for paraflex owners around me and i found out a guy is building a 12" type A less than 100km from me, we'll meet right after he complete his work. It's a 50hz tuned cab (not exactly what i was looking for) but it's a start and i would manage to hear a Paraflex myself.. Unluckily, in my country the last two years have been almost dead for a lot of public events organizers, show companies and indipendent crews.. many are selling used but valuable stuff to stay above water, so i guess less people is now willing to spend time and money building new cabs instead of buying a cheaper branded pa. I'm probably the only fool looking for new subs to build
Skrams and Paraflex subs are clearly different beasts, it was just my personal taste and interest in these different designs that drove me here asking for opinions and data, and you kindly gave me both.
Is the C2A (which i didn't really see when i first watched the plans in the guides) any better than the C2E for what regards deep sub performance?


Posted By: Ricci
Date Posted: 21 February 2022 at 6:52pm
MMJ,

Let's just say that I disagree completely about CEA-2010's usefulness. (1/3rd octave, shaped burst, distortion limited, output testing). Is it perfect? No. Is it the entire picture when objectively evaluating the performance of a bass system? No. As a yardstick for comparing headroom, extension and distortion and evaluating what might be enough rig for the gig, it does pretty well. Especially when so much of bass bins comparisons are subjective opinions of how hard they hit, how low they drop, or how clean they sound, often in entirely different environments with different gear and processing. 

It honestly baffles me that a lot of home audio companies are putting out more hard data such as internal CEA2010 and spinorama results than pro audio outfits. 

If you could pick one PF cab/driver combo to get a full measurement workup which one would it be?


Posted By: KaphaSound
Date Posted: 23 February 2022 at 1:07am
Would Discord be a better option than FB MMJ?

Also I may have missed these since the FB group is quite fast paced but by chance are there any calculated excursion plots with filters applied? I’m assuming this would likely depend a lot on the driver used?


Posted By: T Willy
Date Posted: 23 February 2022 at 7:58pm
Originally posted by KaphaSound KaphaSound wrote:


Also I may have missed these since the FB group is quite fast paced but by chance are there any calculated excursion plots with filters applied? I’m assuming this would likely depend a lot on the driver used?


When using one of the recommended drivers, this will never be of concern. Thermal limits will be reached long before the mechanical limits due to the cone control exhibited in these enclosures.


Posted By: MMJ of HOQS
Date Posted: 26 February 2022 at 3:45am
Hello Josh! Smile 

 CEA-2010 isn't my topic,  I was just attempting to clear something up about a post in the Facebook group from earlier this year and CEA-2010 happens to be the subject of that post .. .
I was quoting a response from one of our developers in the Facebook group who had responded to that post  ....  

Personally I have no thoughts on CEA-2010 itself since I never gave it a try, but I do know Plippie Plop well and if he said that it is unrealistic or inconvenient then I believe him ......  
I have worked with Plippie (USRFobiwan on DIYaudio) for many years now, he is one of our most prolific & helpful developers.. He can be very direct and I appreciate that about him ......  If anyone wants to reach out to Plippie for a friendly discussion about CEA-2010 then please feel free to do so, he is signed up in the group as a mentor and he is available for chat  ........  It is not my debate . . 

 Next, about the last part of your reply;   If i could pick one PF cab/driver combo to get a full measurement workup ... Hmmmm.... That is a really good question! .... I would have to think about that .....     Are you offering?  That would be an honor!   Beer






Posted By: MMJ of HOQS
Date Posted: 26 February 2022 at 4:13am
Kapha,

  I don't really know, I am not familiar with Discord yet .... 

We have a few HOQS friends who are very talented when it comes to coding things for the internet (it is what they do when they aren't working with speakers) and they have volunteered to put something together for us ... The project is already underway .. 

Kapha,  I model excursion plots in Hornresp and then utilize it's Filter Wizard utility so I can determine where a High-Pass filter should be set in order to protect a driver from mechanical damage .. A BW24 filter works well for this purpose (I find it to be a good compromise).....   This Filter Wizard method may not be perfect but it gives me an approximation which I can recommend, and it gives people a good place to start with their filter setting (some like to go a few hertz higher with it, and others don't, a few have gone lower like Mr T Willy)    ... 



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