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FLH design Sensitivity compared to Quake, Psycho .

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psychotea View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psychotea Quote  Post ReplyReply Direct Link To This Post Posted: 18 November 2022 at 3:56am
Ok, so I spent some time building a rough simulation of the HessBH in hornresp. @Nakwa I'd be curious to see how far out I was in the end!
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 compression ratio is quite high at 3.75 (vs 1.8 in the original model) -- again I'm not sure if this is acceptable for modern drivers. The loading on the driver should be fairly even considering the throat chamber (S1-S3) is rectangular. With that said 1.8 is relatively low (I think?) so there might be some room for improvement there in the original design(?)
- Volume is increased by ~25L -- but this isn't a big deal at ~4%
- Cost: the B&C driver is about 50% more expensive (£525GBP) - but whether this is worth it is up to the builder :P

I've attached all the hornresp data here: https://imgur.com/a/vTuKA1F

Would love to know everyone's thoughts :-) 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 18 November 2022 at 10:38pm
Smile

Edited by VECTORDJ - 01 December 2022 at 4:25am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psychotea Quote  Post ReplyReply Direct Link To This Post Posted: 30 November 2022 at 2:16pm
Played around a bit with the "Compound Horn" design type in hornresp. Using an offset driver in a classical horn I wasn't really able to see the improved low end extension (it was there, just very very minimal), however the CH poses some interesting gains. 

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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 30 November 2022 at 2:22pm
Playing around with FLH design, using 15" driver, seems bit of a nom starter to me.

Most 18" FLH designs struggle to get below 50hz (in reality, not a sim), with a single cab.

WSX being the best exception, I know.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote coolboarder Quote  Post ReplyReply Direct Link To This Post Posted: 08 June 2023 at 11:33am
I continued on the FLH design. 
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. 


 







Edited by coolboarder - 08 June 2023 at 11:36am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 09 June 2023 at 11:20am
While the BMS has a high xmax on the spec sheet. That does not mean it is in any form linear to that point. If you have lower BL to begin with, you end up with less control during the end of travel, compared to a higher BL driver.
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 09 June 2023 at 6:39pm
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?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2023 at 3:00pm
Good point there..

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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote psychotea Quote  Post ReplyReply Direct Link To This Post Posted: 04 October 2023 at 2:06pm
EM Quake

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:




Edited by psychotea - 04 October 2023 at 2:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 04 October 2023 at 3:53pm
Re your splitting the throat, you can handle this in Hornresp by double clicking on the Nd field and changing it to OD (offset driver). That then models it with S1 at the very end of the horn and S2 at the driver entry point. However for a low frequency horn like this where wavelengths are much longer than the throat dimensions, it will probably only make a subtle difference assuming you got the total volume right in the first place.
HTH, 
David. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 04 October 2023 at 11:20pm
BMS 18N862 is not horn load subwoofer material. Forget about it.
Marjan Milosevic
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https://www.facebook.com/pages/MM-Acoustics/608901282527713
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