I was recently playing with hornresp with the motivation to design a front loaded horn with a modern driver. I was guiding myself on the rough dimension and information one has from the EM Acoustics Quake and VOID psycho subs for example. 

I will post the hornresp data in following. Driver is B&C 18DS115. Graphs show input mask, single sub, four subs. Without making any folding or detailed drawing yet, my question is: 

How do you get 110 db (4x Quake) or even 112 db (4x Psycho if that value is reliable) from a pack of 4 speakers? 

Best Regards,  

With a custom pointed dust cap when I looked in a quake.

I absolutely agree, these modern high power drivers are to some degree the difference of what I would have choosen for a horn a few years ago but the strong BL and low QTS on some of the new B&C/18sound drivers motivated me to start a project with them. 

The design might be not yet fully optimized at all, too. I justed wanted to check if my hornresp simulations goes somewhere close to the reported sensitivity of Quake/Psycho.

I also simulated with the 1850/2 and its sucessors. The horn is kept similar for comparisson. Please see the attached screenshots. Actually with the same horn path, the drivers are pretty exchangeable.

Also I put the screenshots of MAX SPL at the rated Power and Xmax. Due to the capabilities of the 18DS115, this looks kind of heavy.

PD1850/2 input 

PD1850/2 single

PD1850/2 pack of four 

MAX SPL plots 

B&C 18DS115

MAX SPL PD1850/2

Sensitivity of PD1850 is still below 110db... Did one of you guys attempted a similar design? 

When I compare to a few of these guys' design, the sensitivity looks like in range: 

https://soundagency.fr/docs/hessbh-le-sbh-killer/

Cheers 

Fabian 

This should allow greater loading which, in turn, should offer greater sensitivity. 

Best Regards, 

Best Regards, 

When you are simulating the multiple cabinets you are using 2 series 2 parallel. So overall each driver is only getting 1/4 of the power. So when you run a sim like this you will see the increased bandwith from 4 times the size - but no increase in SPL as you are still only running with 1 watt nominal total power (2.7V -8 ohm). Are you comparing these to sims run with 4 parallel - each driver getting 2.7V which would give about 6db extra ?

What does 'greater loading' mean? In layman's terms? 

Higher air pressure build-up in the compression chamber. 

Best Regards,

Ahh got it. Thank you. I've seen this used in kick part of a fk1 speaker that has blown. 

Also, drivers sensitivity has nothing to do with the result od the driver+box combination. 

Lab12 used in the Labsubs has only 88db sensitivity. 

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 

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...

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!

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.

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):

 

Though your design does claim to outperform it by quite some margin. Nevermind, I realised I was looking at the 4x HessBH graph :P They definitely seem to be doing quite some magic here to get such a respose in a 530L enclosure.

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?). 

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? 

Out of curiosity, I also modelled a B&C 18DS115. I was able to achieve a roughly 2db sensitivity improvement from 35 to 80hz, but there are a few caveats:

The idea is effectively to have two horns, the main one from the front of the driver as normal, and a smaller separate horn originating from the back of the chamber.

Throwing some quick numbers together I was able to come up with http://https://imgur.com/a/HvXqngO - this. Black line = CH, grey line is my previous FLH design. Sensitivity is 1w/1m in half space (2Pi). This is using the same B&C 18DS115 driver. You can see f0 is about 4hz higher (37 vs 33), however sensitivity is vastly improved ~4dB, and this enclosure is around 110L smaller (670L vs 780L); so the f0 could likely be dropped to match in a comparably sized enclosure. The compression ratio is also a much more reasonable 3.13:1, versus 5:1 in the FLH design.

One caveat is you can see there is a sharp dip at 70hz, I assume this is some form of cancellation from the two horn paths. There is also a bit more of a "sag" between 43-50hz than I'd like (most dnb basslines sit around 43hz), however this does smooth out http://https://imgur.com/a/BGxIm4q - once you scale up to 4 boxes. In a stack of 4 the f0 point also drops to around 35hz with f3 around 31. 

The other thing is I'm not at all sure how this type of enclosure sounds. The main reason I am a big fan of sealed FLH (and less of a fan of TH) is they have a very "tight" but aggressive sound (I assume this stems from the fact that the driver sits in a sealed chamber). On the other hand, I find TH to have a less punchy/more "loose" sound -- I'm not sure if this compound horn design would suffer the same issue. With that said, power handling can potentially be increased, as there would be some airflow into the driver chamber - sealed FLH tent to get preeeeety toasty. 

Does anyone know of any designs based around this CH principle? I saw some early stuff from the paraflex guys, but nothing concrete, and it seems those sketches don't use a flared horn.

I dropped a little the B&C 18DS115 since the max SPL is anyway limited by the excursion. Because of large excursions, I decided to continue with the BMS 18N862 but also the RCF 18N405 as in the HESSBH seems to work nicely with almost no modifications. As psychotea wrote, I don't really see the described low frequency enhancement from the HESSBH design in hornresp. Maybe I am not getting it, but anyway, with the classical design I can see 30Hz now. I want to stay below 700l in volume. Following just a documentation of the recent hornresp output. 

The max SPL is wideband above 150dB (1xpi, 4 speakers) and is higher compared to the older PD 1850 mainly due to higher excursion as seems to be possible with the BMS driver. 

Please correct me if I am wrong. 

 

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In practise such loading keeps travel in check, and you will run out of thermal capabilities before excursion. There is a video on yt with the DSL BC218 which shows it.

Besides all that, I doubt the 862 cone would survive such loading. Its most suited for BR or CB purposes normally. 

In practise such

Why Sims in 1 x Pi Do you have a massive wall that you will be using directly behind the stack? If just on the ground 2 X Pi then you are simulating the equivalent of 8 cabinets which is helping the LF extension somewhat with a FLH design.

The red line on your Sim, being a displacement limit I guess, suggests a lack of a High Pass filter?

Maybe a good idea to look at SBH, Invader, WSX, and refine one of them.

Would think WSX is pretty much perfect, apart from compression being too high.

Hopefully this post doesn't violate the forum rules regarding commercial designs. If so I'd be happy to remove it. This is purely for hypothetic research purposes with regards to designing something new & improved. To be very clear, all the information is gleamed from freely available sources online, combined with a bit of brainpower to extract some data.

I came across a rough sketch online which outlines the folding of a Quake. Using this alongside the measurements EM Acoustics provide, I was able to trace over this in SketchUp and create what I think is quite an accurate representation of the horn path:

(My sketch is actually about 40mm too wide, but I realised this too late)

I unfolded the horn into a straight line, and was able to make it accurate to within <1sqcm:

I split the first segment of the horn into two parts, a 11.6L throat, and a 31.39cm horn segment. I'm not sure exactly the best way to model this in Hornresp, since the throat still appears to be flared (as if its part of the horn), but with the driver entering on the side, rather than at S0 which Hornresp assumes. I don't know if there's an option to specify the driver entering between S1 & S2.

Hornresp inputs:

Using PD1850/2, the box sims really well:

As a single unit we see an f3 point of 35hz, which matches EM's claimed specs.

The response in a stack of 4x also looks great, with f3 around 33hz. The thing I don't get is EM claims 27hz here, which just doesn't add up. The 2-3hz drop is about what I'd expect from horn loading, so I don't understand how they are claiming 8hz lower. Their frequency response graph is also much flatter down to 30hz, with a slight bump at 30 (https://emacoustics.co.uk/wp-content/uploads/2021/12/MSE-118_gb_2015.pdf)

If anyone knows what they might be doing here to get this result, I'm all ears. My first guess would be the driver/throat/S1 & S2 entry sim.

Just for fun, 4 boxes @ 80v (800w). A nice 140dB @ 40hz:

HTH, 

David.