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FLH design Sensitivity compared to Quake, Psycho . |
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coolboarder 
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 Topic: FLH design Sensitivity compared to Quake, Psycho .Posted: 25 July 2022 at 12:15pm |
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Hi Guys,
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? In my simulation, I didn't restrict myself too much, just that the hornpath does not get longer ~3m but only get 107 db sensitivity. Is there any hidden porting or so to the commercial designs? hornresp input data:    Edited by coolboarder - 25 July 2022 at 12:17pm |
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Peter Jan
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Joined: 16 December 2008 Location: Belgium Status: Offline Points: 1014 |
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Posted: 25 July 2022 at 7:43pm |
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The 18DS115 is probably not as sensitivity as the speaker types used in the cabs you compare it with. The datasheets says 98dB/1W/1m, but the respons curve draws another (more realistic) picture, more like 92dB/1W/1m, which is good/normal for a driver of that caliber (heavy cone/big voicecoil/high power capable and all).
I have no idea what speakers are used in EM Quake or the Void, but take for instance older speakers like JBL 2241/E155 or Beyma 18GT200/18G400 and you get ~6dB more sensitivity just like that (or "only" 1/4th of the power needed to get the same SPL as the 92dB/1W/1m driver). Most modern drivers are designed for BR/BP these days and while it is possible to get a few dB more out of them as compared to not so modern drivers, it takes BIG power to get there. That's the trade-off. Sensitivity is one thing, but in the end it will boil down to how much dB SPL you squeeze out of your design within the mechanical and electrical capabilities of the driver and also the power you have available to feed the combo with. Maybe it makes more sense to use a less power capable (probably less expensive), but more sensititive driver, maybe not, it all depends on the combination driver/cab design. |
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Elliot Thompson
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Posted: 26 July 2022 at 4:43am |
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I recall the EM Acoustics representative mentioning the Quake uses Precision Devices PD 1850.
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Elliot Thompson
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KDW32
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Posted: 26 July 2022 at 9:01am |
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With a custom pointed dust cap when I looked in a quake.
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coolboarder
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Posted: 26 July 2022 at 12:00pm |
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Thanks a lot for your thoughts.
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 Edited by coolboarder - 26 July 2022 at 12:07pm |
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Elliot Thompson
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Posted: 26 July 2022 at 12:21pm |
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This should allow greater loading which, in turn, should offer greater sensitivity. Best Regards, |
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Elliot Thompson
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Elliot Thompson
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Posted: 26 July 2022 at 12:28pm |
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Horn Response is a simulator. As with all simulators, they can only offer estimates and, will not take into account various things such as distortion. It is always best to build and measure to find the true response than relying solely on simulators.
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Elliot Thompson
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Xoc1
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Posted: 26 July 2022 at 10:08pm |
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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 ?
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KDW32
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Posted: 27 July 2022 at 2:52am |
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What does 'greater loading' mean? In layman's terms?
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toastyghost
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Posted: 27 July 2022 at 12:23pm |
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You might also want to check your expansion type. Currently, all sections are using conical flare, which offers the least loading to the transducer.
I’m not sure where your horn’s segment cross-sectional areas are derived from either. Are you using the Salmon hyperbolic-exponential equation to derive a horn from target parameters, or alternatively for a specific transducer? The MSE-118 spec sheet is available here: https://emacoustics.co.uk/wp-content/uploads/2021/12/MSE-118_gb_2015.pdf with magnitude response plot for four boxes. Pay attention to the footnotes with the measurement method for the sensitivity metrics. I’m pretty sure the 4W is a typo, and they mean 4V  Edited by toastyghost - 27 July 2022 at 1:08pm |
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Elliot Thompson
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Posted: 28 July 2022 at 12:52pm |
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Higher air pressure build-up in the compression chamber. Best Regards,
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Elliot Thompson
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KDW32
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Posted: 28 July 2022 at 4:53pm |
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Ahh got it. Thank you. I've seen this used in kick part of a fk1 speaker that has blown.
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Elliot Thompson wrote: