Using sub woofers destructively?

[Purité Audio]

ASRers I want to experiment using subwoofers not to extend bass response but destructively to smooth response.
I have looked at Todd Welti’s research using multiple subs over a multi seat position.
I am interested in two channl for a limited number of seats.
I would like to know , your thoughts on placement, phase, delay generally a ‘how to’ guide , if you have read some pertinent research any links would be most appreciated.
Thanks in advance,
Keith

 

[DonH56]

Ping @andyc56 for his multi-sub program (long thread on AVS). You have already seen the white paper on the Harman site. REW also has a simulator mode for sub placement, and there are numerous internet room mode calculators and such.

Using multiple subs involves constructive and destructive combinations... Using subs destructively sounds to me like bringing the house down (literally) by shaking it to death...

Tuned absorbers are also a good approach, albeit expensive and somewhat narrowband, to solving room modes. They essentially act like resonant absorbers so at modal frequencies they make the room "look bigger" to the sound waves...

HTH - Don

 

[Soniclife]

Have you ever tried the automatic version of this I think done by PSI? You do there stuff don't you?

 

[labdoc]

Dallasjustice describes his "cascaded sub" arrangement here https://www.audiosciencereview.com/...m2-audiolense-digital-crossovers-w-subs.2369/ and talks about this and another arrangement in comments following this article by Mitchco https://www.computeraudiophile.com/ca/ca-academy/ integrating-subwoofers-with-stereo-mains-using-audiolense-r712/

 

[Purité Audio]

Thanks chaps, Don is the white paper on Harman, Todd Weltis?
I will check it out, I am going to experiment with the 8Cs their sub software should be implemented soon, I don’t think I need to add subs to extend bass because they have more than enough to begin with but the idea of implementing a sub/subs to smooth response is appealing.
I already use tuned Modex traps and they’ve do work but you need a huge area of them.
Absorbing low bass with foam is useless for a domestic environment hence the destructive sub enquiry.
Keith

 

[andyc56]

ASRers I want to experiment using subwoofers not to extend bass response but destructively to smooth response.
I have looked at Todd Welti’s research using multiple subs over a multi seat position.
I am interested in two channl for a limited number of seats.
I would like to know , your thoughts on placement, phase, delay generally a ‘how to’ guide , if you have read some pertinent research any links would be most appreciated.
Thanks in advance,
Keith

There's a thorough treatment of this subject in the Ph.D thesis of Adrian Celestinos, describing a system called CABS. Here is the PDF file. CABS is similar to the Double Bass Array (DBA), but unfortunately the main paper describing the DBA is in German.

The idea for both of these systems is to approximate a plane wave from front to back in a rectangular room. There are subs on the front and back walls, and the back-wall subs are in opposite polarity to the front-wall ones. They are also delayed with respect to the front-wall subs such that the delay is equal to the "time of flight" of the wave from front to back. As such, they are designed to act as active absorbers.

 

[Purité Audio]

Andy thank goodness you shoe]wed up because this lot were frankly useless!
I will read thoroughly and be back with some no doubt inane questions.
Thanks again,
Keith

 

[DonH56]

Sorry to be useless, Keith, had not checked back and been busy. Yes, the Harman paper is by Todd Welti: https://www.harman.com/sites/default/files/white-paper/12/11/2015 - 06:12/files/multsubs.pdf -- there is also a spreadsheeet around to help with the calculations. I used that and a few other sources in optimizing sub placement and EQ in my room. My long-range plan is to use a miniDSP with Andy's program but Life and Work keep intervening.

 

[Purité Audio]

You are not useless at all done Don , my weak attempt at humour.
BW Keith

 

[mansr]

I was hoping this thread would be about using subwoofers for some kind of demolition work. Now I'm disappointed.

 

[mitchco]

user notnyt on AVSForum has a system capable of some demolition work of his own listening room:

I have the same JBL 4722 mains, but my subs certainly are not at this level.... but I do like them time aligned... Makes a difference to my ears.

 

[hvbias]

Keith it seems like Acourate or Audiolense would be right up your ally, have you thought about using either?

I also think @mitchco 's awesome book on DSP is worth reading.

 

[andreasmaaan]

Sorry to be useless, Keith, had not checked back and been busy. Yes, the Harman paper is by Todd Welti: https://www.harman.com/sites/default/files/white-paper/12/11/2015 - 06:12/files/multsubs.pdf -- there is also a spreadsheeet around to help with the calculations. I used that and a few other sources in optimizing sub placement and EQ in my room. My long-range plan is to use a miniDSP with Andy's program but Life and Work keep intervening.

Excellent paper, which I hadn't been aware of. Thanks Don.