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I was reading an old stereophile article, and the reviewer was talking about installing echo busters, bass busters, etc in his room. But he was talking about trying to get rid of peaks and such in the room itself, not just at the listening position.
Why would I care if, say, in a corner my bass is up 10 db at 80 hz? Isn't it the listening position that counts?
Just curious. I always thought room treatments were about getting the sound at the listening position right.
Follow Ups:
undesired responses at the listening position are in some cases functions of the room response as a whole, like too much bass energy in the form of standing waves etc. I always understood things like first-reflection points, that makes very clear sense, but now I think I got this better. Thanks again )
Standing sound waves in the room store energy. It takes significant time to build up and dissipate the energy unless there are dissipative objects like traps in the room. An under-damped room can make the bass muddy.
Standing waves have peaks and nulls in different locations. The dissipative traps work best if located where most of the waves have peaks. This is in the corners.
> I always thought room treatments were about getting the sound at the listening position right.
Yes, but the room corners is where the problems emanate from, so that's why bass trap are usually put in corners. If that reviewer said his goal was to improve the response when listening / measuring at the corners, then he does not know very much about acoustics. So just listen to David because he understand this stuff fully. You might also find this short article useful:
Acoustic Basics
--Ethan
Sure, it's the listening position that counts.
But, peaks and dips in the bass frequencies are reflection phenomena which you reduce by absorption and the best place to put the absorbers so that they work most effectively at those frequencies is in the room corners. Sure, their effect is room wide but there's no way with physical treatments to fix just the listening area and leave the rest of the room "untouched". Any physical room treatment is going to have an effect across the whole room.
You can use electronic room correction to correct some things like frequency response for just the listening area, and a lot of HT gear now has that technology built in. The problem is that electronic correction doesn't correct other aspects of sound in the room which cause problems and physical treatments can correct for those aspects. Where you place the physical treatments to correct some of those other problems (if, for example, you're treating first reflections) will vary depending on where you put the speakers and listening position in the room and the placement of those treatments will have maximum benefit at the listening position as a result.
It's just that, because of the way sound behaves in a room, the best place to put bass traps in order to smooth frequency response at bass frequencies is at the junction of 2 or, even better 3, room surfaces and as a matter of fact in most rooms, the best place to do that is vertically in the 4 room corners. That's not the case for some other issues as I noted above, but it is for bass response.
David Aiken
yeah, but this reviewer was talking about trying to correct peaks *in* the corners. I understand room treatments to smooth out stuff at the listening position, but this reviewer (Brian Damkroger, 2003 article) was applying treatments as if he was trying to smooth out the room itself. Which sounds like monkey business to me.
Here:
http://stereophile.com/roomtreatments/931/
Bass waves are huge- they fill your entire room, corners and listening position. What you want to hear is the sound of the speakers but not the sound of the bass waves reflecting off of your walls and corners. These reflections combine with the speakers' direct sound at your listening position, adding and subtracting bass at different frequencies. So the best place to stop these bass waves from reflecting towards your chair, is in the corners, where they tend to build up, before reflecting back in to the room. In other words, the corners act like extra speakers, reflecting sound back in to the room. You don't want that, so you "trap" the bass in the corners, where they tend to be the strongest.
"I see sound waves"
Not monkey business.
As I said, bass peaks and troughs are a reflection problem. Reduce the reflections by using absorption and the peaks and troughs reduce in scale across the whole room.
There are various points in the room where the peaks and troughs will be biggest, including in the corners but also at various points in the room. Reduce the scale of the peaks and troughs in the corners and their scale elsewhere will reduce also. You probably can't eliminate modal variation completely, but you can certainly reduce it very significantly and if you do that with physical treatments the benefit will be realised across the whole room.
David Aiken
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