Asymmetrical Room Treatment

I guess if the glass window was several inches thick then maybe the bass waves will reflect off it . . . The size of a low freq wave is huge in comparison to a thin pane of glass so as I said before it will easily pass right through it. You need only to listen to the boom-boom of car subwoofers a block away despite their windows being rolled up. Smaller freq wavelenghts will "see" the glass as a hard reflective surface and but bass won't - it's physics.

You have a nice small listening room so I might imagine that with your seat so close to the back wall and hence close to your back wall corners that absorption in the back corners - on top of all the other absorption you have in place - will reduce the reflections further and prevent any kind of envelopment which is not soundstage. Soundstage width is side wall dependant, depth is front wall dependant and height is well ceiling dependnat. Make sense? Maybe we're defining 'soundstage' differently . . .

Kevin.

I've often wondered about soundstage depth and width.
Since it all happens at the ear, how does the width of a room and depth of a room affect what happens at your ear ?

I can hear or perhaps preceive that a kettle drum is thirty feet behind my speakers when in fact, the wall is only three feet behind my speakers.

Is it the illusion of depth from reverberation in the mixing of the music ?

I have some Mapleshade CD's that doesn't go through the mixer, but goes from the mike strait to two track and the depth goes well beyond my wall.

If you can explain this to me it would help me understand the three dim. soundstage much better.

John

John,
Great question you ask. What’s happening at the ear is the sum of direct and indirect reflections which are attenuated and delayed versions of the original direct reflections – in other words reflections of reflections. The reason sound reproduction sounds better in a room than outside is due to the reflections from the room’s surfaces. The surfaces of your room are in their own right sound sources, not of direct sound but of indirect reflected sound. The variables that come into play include reflection strength, direction, and time delays from the direct sound source.
As your mind assimilates direct and reflected sounds, the direction, intensity and time lag from which the reflection is coming helps tell the brain how wide, high, or deep a room is. Think about how music sounds in a large cathedral verses a small residential room – with your eyes closed you can tell if you’re listening in a large or small room. It’s the indirect reflections that provide the mind with the answer.
Reflections from the first reflection points between the speakers and your listening position (side walls, ceiling, floor) tend to pull the perceived sound towards the adjacent surface as your ear hears both the direct sound and reflected but delayed and attenuated versions of itself. Apparent source width, image broadening, impressions of height and depth are the result of reflections occurring at delays of less than 80ms and include the reflections that are included within the recordings.
The sound reflections from the recorded venue which makes up its natural reverb, or electronic reverb introduced into the mix, is what you’re hearing when your kettle drums appear far away.
Hope this helps . . .

Hey everyone, thanks for the responses; they've been very helpful! At the moment I have treated the front wall behind the right speaker pretty heavily, and just with this I can tell that there is a pretty large improvement in imaging detail; instruments seem more defined into specific spatial locations. I will experiment with treating or not treating the rear corners and see what results I get.

On a related note- I currently have two, 4' tall (4" thick) bass traps in the front, right corner (one on top of the other). My ceiling is only about 7'8" tall, so the bottom trap is at a pretty tilted angle, which at the bottom floor/wall/wall corner leaves a substantial airspace, probably about 2' at the furthest point. While I know that having a decent amount of airspace between a trap and wall is beneficial, is there an upper limit on this? My guess would be that about 1 or 2 times the thickness of the trap would be ideal, but I am just guessing here.

Chrisar wrote:
"While I know that having a decent amount of airspace between a trap and wall is beneficial, is there an upper limit on this? My guess would be that about 1 or 2 times the thickness of the trap would be ideal, but I am just guessing here"

If you're using fiberglass filled absorbers (which you are) then you simple change the frequency at which the absorber maximizes its effectiveness at by changing the air space distance. I don't believe there is anything intrincically good or bad about how far you pull the trap out, it's a matter of using that flexibility to your advance to attenuate a problem frequency. Remember that the absorber works best when the particle air speed is fastest which is at the 25% mark of a frequency's wavelength. It's easy enough to calculate what that is as follows using a 440Hz frequency for example:

Speed of sound 1130 / 440Hz *12inches = 30.8" then multiply that by 25% and you get 7.7" which is the airspace needed to max the absorber placement.

I would think other practical issues like asthetics or not having the absorber blocking a walking path through the room etc might factor into it too.