[mfsoa]

I've been poking my head into various places along my walls while bass-heavy music is playing, trying to hear (or sense, at low freqs) where there is the most bass, figuring that that would be the best place for a bass trap.

My understanding was that the tri-corners, either floor or ceiling, were where the worst of the bass build-up would be. But this is just not so in my room - I sense much more bass energy mid-corner (where side and front walls meet, 1/2 way between floor and ceiling). In the tri-corners, the overall balance is not too much different from out in the room, but mid-corner, wow, severely skewed toward the low end. Boomy. Ugly. Bad.

My theory is that brontosaurusus are thin at one end, much much thicker...- ooops - sorry - start again.

My theory is that for the long wavelengths we are concerned with, they don't "see" an individual tri-corner as a room feature - The feature is just too small relative to the wavelength. Kinda like the way (I think) that electomagnetic radiation works - Really small wavelengths go right through large "pore" satelite dishes, yet you can capture a long wavelength w/ a large, relatively porous dish. Anyway, I think that the long wavelength sound waves see an upper tri-corner, the mid-wall, and the lower tri-corner as a single, 8-12' room feature and want to play with it, resulting in build-up mid-corner.

This theory is probably shockingly wrong to those who actually know this stuff, but what can explain what I hear and feel?

1) That what I hear and feel actually doesn't correlate to the areas that will result in the most efective bass-trapping?
2) It's peculiar to my, or any room. My room is funny in that it has no rear corners - They are both open (imagine removing the outer 3' of the rear wall on both sides) into other rooms, so maybe I'm not getting the opposite-corner bass loading.

Maybe question 1 is the big take-home question - Can you predict, based on bass quantity, the best areas to treat?

Thank you all, and curse you all, for making me run acoustic simulations in my head all the time!
(Here's a good one - walk down the towel aisle at a Target etc. store - Totally different acoustics and "feel" there!)

[jqp]

Well it is obviously somewhat non-intuitive  

I haven't had to deal with these issue too much since I don't have my subs yet. Yet my speakers put out plenty of bass. I hear a " bass effect" in the bathroom in the corner of my downstairs area. I think it is an issue of where the bass waves can cause problem resonances, which can be radically different in each room.

My sound system is like a giant fish...

[brj]

Don't forget that any particular room feature may cause a null in once place, but a gain in another.  Your corner could very well cause a null near the corner itself, but still cause a gain (or another null) at your listening position.

[Ethan Winer]

I've been poking my head into various places along my walls while bass-heavy music is playing, trying to hear (or sense, at low freqs) where there is the most bass, figuring that that would be the best place for a bass trap.

This is exactly the right way to do it. If you'd like a slightly more scientific approach, download the filtered pink noise file from THIS page on my company's site.

(I hope nobody minds the commercial link, but it's exactly what he needs.)

--Ethan

[woodsyi]

I've been poking my head into various places along my walls while bass-heavy music is playing, trying to hear (or sense, at low freqs) where there is the most bass, figuring that that would be the best place for a bass trap.

My understanding was that the tri-corners, either floor or ceiling, were where the worst of the bass build-up would be. But this is just not so in my room - I sense much more bass energy mid-corner (where side and front walls meet, 1/2 way between floor and ceiling). In the tri-corners, the overall balance is not too much different from out in the room, but mid-corner, wow, severely skewed toward the low end. Boomy. Ugly. Bad.

My theory is that brontosaurusus are thin at one end, much much thicker...- ooops - sorry - start again.

My theory is that for the long wavelengths we are concerned with, they don't "see" an individual tri-corner as a room feature - The feature is just too small relative to the wavelength. Kinda like the way (I think) that electomagnetic radiation works - Really small wavelengths go right through large "pore" satelite dishes, yet you can capture a long wavelength w/ a large, relatively porous dish. Anyway, I think that the long wavelength sound waves see an upper tri-corner, the mid-wall, and the lower tri-corner as a single, 8-12' room feature and want to play with it, resulting in build-up mid-corner.

This theory is probably shockingly wrong to those who actually know this stuff, but what can explain what I hear and feel?

1) That what I hear and feel actually doesn't correlate to the areas that will result in the most efective bass-trapping?
2) It's peculiar to my, or any room. My room is funny in that it has no rear corners - They are both open (imagine removing the outer 3' of the rear wall on both sides) into other rooms, so maybe I'm not getting the opposite-corner bass loading.

Maybe question 1 is the big take-home question - Can you predict, based on bass quantity, the best areas to treat?

Thank you all, and curse you all, for making me run acoustic simulations in my head all the time!
(Here's a good one - walk down the towel aisle at a Target etc. store - Totally different acoustics and "feel" there!)

Please shut up!  If you don't shut up, I shall have to shoot you!   

My theory on room acoustics is as follows. 
It begins now.
My theory, which I own, is that by absorbing here and diffusing there all will be well, which you must admit hits the nail on the head.

[ctviggen]

This is exactly the right way to do it. If you'd like a slightly more scientific approach, download the filtered pink noise file from THIS page on my company's site.

(I hope nobody minds the commercial link, but it's exactly what he needs.)

--Ethan

I think Ethan's link will help.  The problem with playing "bass heavy" music is that you're limited to whatever frequency range is in the music.  Therefore, you might reach a different conclusion if you used a different frequency band.  Another interesting thing to try would be to find the strongest bass response, then have someone else move your speakers/subs.  You would then try to find the speaker/sub location that minimized the bass response (taking into account reality -- i.e., you have a sitting location and speakers "aimed" at that location).