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FLH design Sensitivity compared to Quake, Psycho . |
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MarjanM 
Old Croc 
Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7745 |
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 Posted: 28 July 2022 at 5:17pm |
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Change from 2.0 pi to 0.5pi and simulate one box. That gives more relistic 4 box responce then 2+2.
Also, drivers sensitivity has nothing to do with the result od the driver+box combination. Lab12 used in the Labsubs has only 88db sensitivity.
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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toastyghost
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Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10894 |
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Posted: 29 July 2022 at 9:06am |
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Technically there’s no throat chamber in the Andrews-style BPH |
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coolboarder
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Joined: 23 June 2010 Location: Germany Status: Offline Points: 29 |
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Posted: 29 July 2022 at 5:44pm |
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Thanks a lot for all the input.
I am not using any equations. I am just playing with the parameters.  Do you have any literature on hand? And thanks for the suggestion in the input voltage. When I am giving the stack of 4 an input voltage of 4V and configure them 2x2, so 8 Ohms, I get a little above 110 dB. When I give 2,83V (=1W at 8Ohm) for 1 box in 0.5 pi, I get similar response as with 4 boxes but even the 3db more in sensitivity so 113db which makes sense to me. So looks like sensitivity wise I am in "range". Current state of the simulations (I added a little the throat adapter that gave a smoother response):   Thanks a lot Fabian |
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fatfreddiescat
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Joined: 15 October 2010 Location: N.E.Wales Status: Offline Points: 1060 |
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Posted: 29 July 2022 at 9:19pm |
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Looks like your throat is 6:1 compression ratio which is generally considered very high, around 2.5:1 is considered to be towards the upper limit for a bass horn, it may work but...
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VECTORDJ
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Posted: 31 July 2022 at 3:49pm |
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Is the Quake out of Production????
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psychotea
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Posted: 31 July 2022 at 10:58pm |
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Funny timing, I was working on an FLH design based on the B&C 18S115 a few months ago. As you mentioned, I figured with the modern driver technologies a much better DIY FLH design should be possible than what is currently out there; demonstrated by what Quakes and Psyco X's are able to achieve.
Here's a couple of measurements from my sims. I've modelled sensitivity the same as you for comparison (4v, 2S2P), and max SPL is 1700w @ 8ohm in a stack of 4. Both measurements in 2Pi. I'm happy to upload some more data if you're interested. See here: https://imgur.com/a/aXUDQM0 I aimed to get down into the low 30's with this design, F0 is roughly 32hz (109.2dB), with F3 around 28hz (in a stack of 4). (I have great visions about running small, intimate dance music events with great sound quality and heavy infrabass content music) Sensitivity is within about 1dB of your design, and max SPL is also within ±0.5dB, but as I mentioned dropping ~8hz lower. There are two kickers: - This is big cabinet, about 780L (100~ larger than your latest revision). Granted, not as big as some (cough p*raflex), but still bigger than SBH, WSX, Psyco X, etc. The price you pay for LF extension, hey! - Compression ratio is 5:1. As @fatfreddiescat mentioned, this is much higher than the typical advice of 2.5:1. However, from my sim'ing it seems that a higher compression ratio greatly helps with SPL. I've never been able to find a solid answer on where that 2.5:1 rule is derived from, and whether newer drivers (ie. carbon cones) will be able to hold up (any input is appreciated here) - Bonus kicker: I have no idea how to go about folding this thing :P Also, thanks for linking the HessBH design; it seems reassuring that what we're trying to achieve is indeed possible. Do you know anyone who has built any of those cabs? I wasn't able to find any further information online outside of that website. Their specs appear to match up with the design I've put together (granted mine is 160L larger, and using the more powerful 1700w B&C driver, allowing for the +4-5dB gain in max SPL response). It makes me quite tempted to put one of these HessBH boxes together, considering the more reasonable size and much cheaper driver (around £200). Cheers!
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coolboarder
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Joined: 23 June 2010 Location: Germany Status: Offline Points: 29 |
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Posted: 09 August 2022 at 5:03pm |
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Hi @psychotea,
thanks a lot for joining the discussion. Indeed, compression is high and as said, I am just fiddling around with hornresp without making neither knowing too much theory around it. My horn path is around 3.1m, therefore I was surprised that my f0 is rather high at ~40Hz rather then 30Hz. What' the route to lower f0 here apart from longer horn path if I may ask. The HessSBH I just found (I think on inst**ram) and the other designs of that collective. I have no more info on that.
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snowflake
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Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3096 |
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Posted: 09 August 2022 at 6:44pm |
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your rear volume is too large. not reactance annulled (search for Kolbrek in the forum). you need more than four boxes that size to hit 30Hz. Le is probably high enough you need to double click the 'Le' to engage lossy inductance model. what's the throat adapter doing for you?
maybe try the system design with driver for a two driver box in 0.5Pi space. you can then split it in half to get a sensible sized single driver horn. use the hyperbolic horn approximator to turn it into a horn of four sections and you can start tweaking the throat. |
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Nakwa
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Joined: 26 October 2022 Location: France Status: Offline Points: 1 |
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Posted: 26 October 2022 at 11:03pm |
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Hi !
I'm the hessBH designer, randomly finding this topic. All its specs and plans are avaliable at soundagency.fr (in public projects). This design isn't a pure flh horn, it has the driver offseted in a Transmission Line which excites some harmonics that helps the low end ;) Some people built them in France/Belgium and the calibrated measurements with the LF18X401 fits for 1/3/6U, you can find superposition of my sims/measurements on my Facebook post about this design.
Edited by Nakwa - 26 October 2022 at 11:05pm |
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psychotea
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Posted: 18 November 2022 at 1:01am |
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Hey! Thanks for joining us :-) And sharing your HessBH plan with the world.
I had a look through the Facebook page, but I wasn't able to find a copy of the measurements you mentioned. Would you be able to share a link? Also, would you be able to share the hornresp inputs? Call me lazy, the plans are public I know :P I would be interested in experimenting with raising the tuning frequency from ~32hz -> ~37hz to see if there are any gains to be had in sensitivity in that area. Similar to the tuning of the JTR Obrital Pro (credit @totallyghost):  I was also a bit unsure about the +6dB claim on your website (which doesn't seem to be working, by the way). The +3dB sensitivity gain I understand, but I'm unsure where the other +3dB power increase is coming from? While the driver you recommend (RCF LF18N405) is 1500w power handling, which equates to a ~1dB increase versus the 1200w SBH (RCF LF18N401), you mention on your website that only 1200w RMS should be used (I assume due to power compression / overheating?).
Edited by psychotea - 18 November 2022 at 4:00am |
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psychotea
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Posted: 18 November 2022 at 1:06am |
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And on the general topic of aiming for 105dB sensitivity á la EM Quake, Psyco X, @Nakwa has a very good article on their website http://https://agency.fr/docs/le-processing-a-outrance-void-stasys-x/ - here (assuming it's working again) discussing how these figures can easily be manipulated. So while I agree that ~105dB should be achievable with modern driver technology, I think we shouldn't hold these figures in too much regard.
The JTR Orbit Shifter Pro claims 103dB sensitivity, and in a stroke of madness, this actually matches up with the real-world measurement! Kudos for that. |
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psychotea
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Posted: 18 November 2022 at 1:19am |
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Also, what was your reason for going for the RCF LF18N405 verus a driver like the B&C 18DS115? Obviously cost is one consideration, is power handling/compression is the other?
Edited by psychotea - 18 November 2022 at 4:01am |
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