Can Subs also act as AVAAs?

[voodooless]

Hmm, there may be hope yet, see here from ADAU1701:

ADC group delay on 1701/1702 - Q&A - SigmaDSP Processors & SigmaStudio Dev. Tool - EngineerZone

Hi, does anyone know the group delay of ADCs (audio and auxiliary) and DACs on ADAU1701/1702 SigmaDSPs? And how long does one sample need through the whole DSP

ez.analog.com

I really didn’t do except it to be that low. You need to be careful with the processing steps though.

You can get a board for about $€£ 20. You’ll need a few components to hook up a mic, and a programmer for about $€£ 35, but the you should be good to go with a bit of SigmaStudio

 

[dasdoing]

Wanted: Proof of multiple subs and sub EQ

"Through PSI Audio’s patented technology, it will transform acoustic pressure into acoustic velocity and absorb it over a large range of frequencies." I can try :). When a sound wave hits the wall, by definition the velocity of the air molecules drops to zero. Inversely, pressure becomes...

www.audiosciencereview.com

 

[-Matt-]

So the microphone will need to be quite high dynamic range, because the sound from the sub will be loud compared to the ambient noise.

Calibration will probably be needed to adjust the relative magnitude of the intended sub signal and the mic measurement in the calculation.

Any other considerations that spring to mind?

 

[Don Hills]

Noise canceling headphones work because the mic is on the outside where it picks-up noise to be canceled without picking-up sound from the headphone itself (on the inside) that you don't want canceled.

Most on/over ear ANC headphones have the canceling microphone on the inside, as close as possible to the ear canal. They compare the signal from the microphone with the incoming audio signal. Any difference generates a compensating signal to the earphone driver. Negative feedback... Some headphones such as Bose QC 25/35 have additional external microphones to allow some environmental sounds such as speech through.

I have seen some ANC IEMs with microphones on the outside, there's simply no room on the inside and the microphone is close enough to the ear canal to be effective. The closer it is, the lower the delay (phase shift) between microphone and eardrum and thus the higher the maximum frequency range that can be canceled.

 

[Don Hills]

I see a problem using the same subs for both sound generation and resonance cancelling. The ideal position for a "music" sub is where it minimises excitation of resonances. The ideal position for an active cancellation sub is where it maximises excitation of resonances and thus is most effective at cancelling resonances excited by the "music" subs.

 

[-Matt-]

I see a problem using the same subs for both sound generation and resonance cancelling. The ideal position for a "music" sub is where it minimises excitation of resonances. The ideal position for an active cancellation sub is where it maximises excitation of resonances and thus is most effective at cancelling resonances excited by the "music" subs.

That is probably true.

As it happens I pretty much have my subs in the room corners. I guess this the "optimal for resonance excitation" case. And yet, to some extent MSO is then able to use the multiple subs to smooth out the response. So in this case the subs should be in an ok position to act as AVAAs?

As usual in audio, everything is a compromise!

 

[-Matt-]

Thinking on this a bit further...

Could the proposed system effectively be described as a servo driven subwoofer, except with the feedback signal being derived from a microphone?

Anyone know of any existing speakers systems (perhaps historical ones) that use such a mechanism?

Edit: Answering my own question...
Post 6 in this thread mentions that Meyer sound already did servo feedback with a microphone. (I like the way they mounted it). Although it seems that their aim was more on improving woofer linearity rather than on on cancellation of unwanted bass reverberations.