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Bass management -- the trick of putting absorbers at a front null

Very interesting discussion with Anthony Grimani. He advocates both traps and multiple subs and goes through the basics and tactics of bass management.

What's of interest to me is a "trick" he mentions -- putting an absorber panel at null between the listening position and the front wall. This, he says, can help even out the bass and take the place of the brute (and impractical) physics of trying to absorb the standing wave with absurdly thick absorbers.

He mentions it very soon after this point (which provides some context): https://youtu.be/QYpAbv7gKrs?t=1853

Has anyone tried this? Any details or outcomes you can share will be welcome.

P.S. He mentions Todd Welti, who did a Ph.D. thesis on using multiple subs. He's now with Harman. There is a paper by Welti, here: "Low-Frequency Optimization Using Multiple Subwoofers" https://www.semanticscholar.org/paper/Low-Frequency-Optimization-Using-Multiple-Welti-Devantier/00da...

This looks interesting, too: "How Many Subwoofers are Enough"
https://www.semanticscholar.org/paper/How-Many-Subwoofers-are-Enough-Welti/96b772af4ea937d8028c2f845...
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Showing 7 responses by hilde45

hilde45's avatar
hilde45 OP
4,838 posts
 
He explains what he means in the clip or perhaps shortly before. Thanks for the link to your post. I'll take a look. 

hilde45's avatar
hilde45 OP
4,838 posts
 
Thanks, Erik. Since I last posted about traps, etc. I was able to find someone locally who was literally giving away their traps to any local audiophile who was interested. I scored 14 traps in all, including stuff from GIK. I'm just not quite making a dent yet in some peaks and nulls, so I'm interested in additional tricks. 
hilde45's avatar
hilde45 OP
4,838 posts
 
Thanks, Erik -- good to have that reality check -- "a combination of traps, placement of sub and listener AND EQ."

I've figured out placement of listener and speakers, and am trying to dial the room in now with traps and, to a degree, a single sub. I have a second sub in the house, but it was too complicated initially (because I was figuring out the other things). I hope to have a couple more good traps to work with, soon, and will try to work those in as best I can and then see how the addition of subs can help. Then, I'll move to EQ. I hope that process sounds logical.
hilde45's avatar
hilde45 OP
4,838 posts
 
Thanks, Erik. I'll take a look, but the problem is that my room's irregular shape and non-hermetic situation makes it impossible to put into these room simulators. I use REW a lot but it's as much a systematic try-and-see and try-and-listen approach.
hilde45's avatar
hilde45 OP
4,838 posts
 
Thanks, Rego. I will message you if I am buried under traps! When you say, "The idea is that a frictional absorber necessarily is placed away from a wall ... not always very practical."

I know that frictional absorbers are placed away from walls -- to gain the extra absorption from a distance to the wall roughly equal to the width of the traps, if I remember right. 

But Grimani is suggesting something different than this. He is suggesting placing them very very far from the wall in order to capitalize on a null endemic to the room's modes. That is an application utilizing a different phenomenon, no?
hilde45's avatar
hilde45 OP
4,838 posts
 
@oldhvymec If you watch a bit more of the video, you'll see he's not suggesting such a simplistic solution. He's pointing to a fact about acoustics which, combine with a variety of other techniques -- in some rooms, not all -- can help mitigate problems, and not just at 50hz. So, your off the cuff response while amusing kind of turns him into a simpleton. Not really fair, but hey, this is a just a forum so I guess mere joking is kosher!
hilde45's avatar
hilde45 OP
4,838 posts
 
@oldhvymec  I understand better now, thanks. I found it easy to follow the first time, so I was unclear about what you meant. Apologies and regards.
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