radulescu_paul_mircea Posted December 28, 2016 Report Share Posted December 28, 2016 Hi all!, Could somebody enlighten me about how this works? http://www.vueaudio.com/active-compliance-management-acm/ I know it's a Band-pass design, but why to use that delay between the drivers in the same enclosure? Link to comment Share on other sites More sharing options...
Ricci Posted December 28, 2016 Report Share Posted December 28, 2016 Thanks for linking that. You keep up with all of the latest don't you? As far as the enclosure goes I believe that type of thing has been tried before. You basically have a 6th order bandpass for one woofer and a vented cab for the other. How they interact in the common vented chamber is more complex but my gut says it shouldn't make much difference in the low end down near the vented cab tuning. That's the low end output there and the air volume and port will dominate and dictate the driver behavior. The bandpass upper section in front of the one woofer is small with a large vent so the tuning is going to be rather high probably in the 65-90Hz range. It should modify that drivers behavior over that range but not much down low near the vented section tuning. I'm not sure how much it would have effect on the vented driver over the same upper range. If anything I'd say all of the sauce is in the dsp. I'm not sure what actual gains over a traditional design would be there though. Doesn't make a lot of sense to me at first glance. The bandpass and vented drivers sections should have large differences in the phase and delay over the range where the upper BP chamber overlaps the direct radiating driver. It would likely be not so pretty if looking at the attack and decay characteristics. Perhaps they are fixing that in the dsp but it seems like that would be a moving target as the output level increases. Unless they are using dsp trickery to somehow operate each driver harder where efficiency is highest and limit excursion I don't see how they would get significantly more output than with a conventional system with both drivers in a 6th order or vented rather than half and half. Their chart comparing to a dual vented 21 is highly dubious IMO. They imply that their hybrid is +10dB or more on a dual 21 vented at 30Hz but clearly that's a response graph not a max output graph and the response shape of the "typical" dual 21 vented looks like nothing I've seen. We all know a smaller cab which is what they claim, producing +10db at the low corner with the same driver compliment and similar vent area is not happening. I could probably model the enclosure in Akabak but the dsp section who knows. I think that's where the important bits are if there are any. I could be completely wrong and they are really on to something here but I'm skeptical. Would be a good system to test for DB to find out. Got a link to patents? Link to comment Share on other sites More sharing options...
SME Posted December 29, 2016 Report Share Posted December 29, 2016 Interesting concept. Yes, it does look like the smaller chamber and shorter pipe are boosting HF output. Presumably the DSP ensures they operate in phase with the direct radiating "outer" driver. As frequency drops, the smaller chamber/port effectively unloads and output from it drops rapidly. At that point, the larger chamber and port starts to contribute. Where things get interesting is that the inner driver is still active and controlled independently by the DSP while being essentially unloaded at the front end. The claim appears to be that moving the drivers asynchronously effectively creates a ported system with significantly less box air spring compliance for a given volume and thus substantially more extension for the size without giving up vent output. If it actually works, it would be a real breakthrough for getting more low frequency output from a smaller box. But does it actually work as advertised? Edit: Does anyone know if the two drivers are identical? Link to comment Share on other sites More sharing options...
Ricci Posted December 29, 2016 Report Share Posted December 29, 2016 Interesting concept. Yes, it does look like the smaller chamber and shorter pipe are boosting HF output. Presumably the DSP ensures they operate in phase with the direct radiating "outer" driver. As frequency drops, the smaller chamber/port effectively unloads and output from it drops rapidly. At that point, the larger chamber and port starts to contribute. Where things get interesting is that the inner driver is still active and controlled independently by the DSP while being essentially unloaded at the front end. The claim appears to be that moving the drivers asynchronously effectively creates a ported system with significantly less box air spring compliance for a given volume and thus substantially more extension for the size without giving up vent output. If it actually works, it would be a real breakthrough for getting more low frequency output from a smaller box. But does it actually work as advertised? Edit: Does anyone know if the two drivers are identical? It appears that the drivers are identical but that is speculation. I wouldn't say that the front of the inner driver becomes unloaded. It is loaded by the rear vented chamber as the front one loses loading and will become the dominant output through the port same as with the direct radiating driver as the driver output slowly hands off to the vent as the frequency drops and nears the vent tuning. I'm not sure how this idea of delayed or asynchronous driver operation in a common chamber would help with output headroom, sensitivity, efficiency, etc. If we think about it as reproduction of the input signal this would have to smear the time response, add additional ringing, etc. Say it is tuned to 35Hz and a 35Hz sine wave is input, would what comes out look like the sine wave on a scope? If it doesn't what does that mean for the signal coming out and the sound of it? They show in their animation the drivers being basically 180deg out of phase. That won't work clearly since the drivers would cancel each other out and you would lose almost all of your output headroom. That leads me to believe the drivers would be fed a signal that is 90deg out of phase or less. They may be doing something very complicated in the dsp but any obvious advantages just aren't hitting me yet. I'm interested now so I'll try to dig around. If anything it seems like perhaps they are able to delay one driver by a certain amount and trick each driver into seeing a larger air volume than it's actually in and that results in a bit better efficiency or extension. That's not going to increase the headroom though. That'll still be driver displacement and vent air speeds limits at low frequencies. That doesn't really explain why the odd half and half common enclosure though. Link to comment Share on other sites More sharing options...
radulescu_paul_mircea Posted December 29, 2016 Author Report Share Posted December 29, 2016 Hi, I am glad this caught your attention as it did to me. I try to stay as well informed as I can, but it is easy for me because I have lots of time to do it and all I do is in the same field: work, study, personal development. So I spend 8-12 hours a day,everyday thinking of audio and acoustics. I am also very eager to find out how that combination works. Probably both drivers are the same but the one in the bandpass is affected by the air in the chamber and the port even under the Fs. There is some mass and some friction over there. Also, at the port frequency there will be some phase shifts and excursion differences between the drivers so that would be necessary to correct via allpass filters. The developer is a guy that used to work for EAW so he's no slouch. He has a patent but not for this. I couldn't find anything about this except in that link and a PDF file on Google. Link to comment Share on other sites More sharing options...
3ll3d00d Posted December 29, 2016 Report Share Posted December 29, 2016 seems like https://www.google.co.uk/patents/US20130322656is the referenced patent. I only skimmed through it but it seems rather vague to me. Link to comment Share on other sites More sharing options...
radulescu_paul_mircea Posted December 29, 2016 Author Report Share Posted December 29, 2016 The same esoteric sense I get when I look at the passive cardioid subs from Fulcrum Acoustics http://www.fulcrum-acoustic.com/products/cardioid-subwoofers/ 3ll3d00d , could you please find that patent also please? I searched it for a while then I gave up and now my interest is on again on that tech also. Thinking about how many new things we could develop using digital sound processing to avoid the general problems we encounter. also the fact that we can get our hands on super powerful and efficient amplifiers like the M-drive or the SpeakerPower modules, using drivers with large excursions like the Ipal or the T3 19 , many of the old limits could be easily be crossed. Like the ideea LowerFE had of using FIR filters to change the behavior of the driver at the Helmholz resonance to decrease the rolloff slope. My ideea was using a passive radiator that got active under Fs, effectively becoming stiff or something like the think these guys from VUE are saying , to create a slight delay that would virtualy change the enclosure volume. Coupled with an acoustic pressure sensor feedback, that could lead to an extremely complicated fun and cool project... Link to comment Share on other sites More sharing options...
3ll3d00d Posted December 29, 2016 Report Share Posted December 29, 2016 nothing obvious listed under David W. Gunness or Loud Technologies (who seem to be the actual owner) the description says it's just a rear firing resistive port though (e.g. a bit like http://www.google.co.uk/patents/US8428284) Link to comment Share on other sites More sharing options...
radulescu_paul_mircea Posted December 30, 2016 Author Report Share Posted December 30, 2016 http://www.google.co.uk/patents/US8428284)The link is not working Link to comment Share on other sites More sharing options...
3ll3d00d Posted December 30, 2016 Report Share Posted December 30, 2016 The link is not working try now, there was an extra ) on the end (this forum software seems to do this to me regularly) Link to comment Share on other sites More sharing options...
radulescu_paul_mircea Posted December 30, 2016 Author Report Share Posted December 30, 2016 I've read it. Nice design ! Link to comment Share on other sites More sharing options...
Ricci Posted December 30, 2016 Report Share Posted December 30, 2016 You know...The most important bit of information from the patent was the impedance curves for the two drivers. They may actually have something. It reminds me of an old 3 chamber ABC style box but with drivers loaded into two different points. I may have to try simulating this after all. Sucks that my Akabak access is on an old junk laptop I only keep around for that. Link to comment Share on other sites More sharing options...
3ll3d00d Posted December 30, 2016 Report Share Posted December 30, 2016 You know...The most important bit of information from the patent was the impedance curves for the two drivers. They may actually have something. It reminds me of an old 3 chamber ABC style box but with drivers loaded into two different points. I may have to try simulating this after all. Sucks that my Akabak access is on an old junk laptop I only keep around for that. fwiw I have akabak running on a modern version of Windows in an XP VM using VirtualBox, I could clone that and put it somewhere for you to download if you want to run it on a modern machine Link to comment Share on other sites More sharing options...
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