Asymmetrical Room Treatment

Chrisar - I feel your pain. ;)

I would tend to agree with your thinking; as the door way behind your left speaker is for all intents and purposes a very effective and broadband absorber then so too must the wall behind the right speaker to match. How far out from the front wall is your speakers? Using a resistive-type trap with OC fiberglass means you will need to make it very thick and should have a decent air space (e.g. 6") so as to allow absorption down to 100Hz (or below?).

I think that even with a very thick broadband absorber behind your right speaker you will never get it to match the left as glancing reflections off the absorbers won't get absorbed so you will / should always hear a tad more indirect reflections coming from the right side which may pull the image rightwards a tad. But I suspect you already know this . . .

Can you add an exterior door behind the left speaker?

The reflections on the back wall can be just as damaging so have you treated the back wall yet? Back wall treatment may pay more sonic dividends as you usually sit closer to the back wall than the front wall. Try thick bass traps in the floor-to-wall corners and diffusion (2Dimensional like a Skyline Diffuser due to the close sitting proximity) in the centre of your back wall.

good luck! We'll keep our fingers, toes, and eyes crossed for 'ya. ;-)

Hi Kevinzoe, thanks for the response! I'll try and address your points to provide a bit more info:

"How far out from the front wall is your speakers?"

The speakers are about 45" out from the front wall measured from the woofer (or 30" from the back of the speaker). I do have some leeway here and could move them out a bit more- the main reason I have them where they are is to allow enough distance to my seating position, as per Thiel recommendations to allow the drivers to integrate.
As a side note, my ears in the seating position are about 5' out from the back wall, which I have found seems to avoid a heavy mid-bass peak which occurs when I sit closer to the rear wall. This position also gives me just about 8' from the midpoint between the speakers.

"Using a resistive-type trap with OC fiberglass means you will need to make it very thick and should have a decent air space (e.g. 6")"

The traps I just made are 4" thick 2'x4' OC-703. One of them that is across the diagonal corner has about 9" airspace from the corner, and the other that is sitting right next to it on the front wall has about 7" airspace at the bottom, but it is learning against the wall (not mounted- sitting on the floor), so the airspace decreases across the 4' height of the trap. This is definitely a place I could improve on I think, and just double-up each of these traps to make their thickness' 8". Only issue would be the traps would be getting pretty close to the back of the speaker, though this may not be a problem.

"Can you add an exterior door behind the left speaker?"

This is something I had considered (in theory at least!). I can't add a door (one of the many downside of renting...can't add doors or drill holes in walls to mount my traps...not to mention one of the walls is cinderblock!), but I did think about having some sort of removable partition that I could just place when listening, and set aside otherwise. I would assume it would need to cover most of the opening, from floor to ceiling? And also be fairly thick? Perhaps I could find some sort of big wooden board and then mount a bass trap onto that, then put that in place behind the left speaker during listening?

"The reflections on the back wall can be just as damaging so have you treated the back wall yet? "

Unfortunately my back wall has a large window centered in the middle of it, so essentially the whole thing is glass aside from near the top/bottom and left/right sides. I did recently put up some drapes to help with high and mid-frequency reflections, but I am not sure if it would be feasible to treat any additional way. I did consider also having some sort of removable partition with treatment on it that I could place over the window in the area behind my head, but I am not sure how this would work... I do like your idea for diffusion back there though- I've heard this can make a big difference in a small/medium room, I've just never tried one in here.

So I am thinking now that the best option may be a combination of more broadband absorbers behind the right speaker, and maybe some sort of partition to block the opening behind the left speaker. One of the pro's of being single and living alone: aesthetics are not a huge concern, especially if I keep things removable when I have guests over :). Thanks again!

The drapes will only dampen the very high frequencies at best. (20khz+)
Get some absorbers behind you and infront of the window.
I would also pull the bass trap out of the corner thats behind you.

You may not realize it because you don't have your first reflections dampened in the room. But trapping the rear corners will kill the soundstage of a room.
I would take the rear bass trap and put it in the same corner behind the right speaker with the other bass trap and that will kill any bass node that is behind your speakers.

The open wall to the left is allowing the bass to be dampened by escaping the room.

This will help in the bass department, but the imaging and soundstage will only be good with treatments in at least the first reflection points through out the room.
It's only then that you will be able to realize the potentual of your soundstage and imaging and ballance out the system.

My best freind has the same problem as you.
He's treated the room on the sides and behind his seating position and the soundstage is very ballanced.

Hope this helps.
John

Hi John. Thanks for the feedback! I actually do have hi/mid absorbers (foam, not 703) at my first reflection points on the side walls. I will move out the bass trap I have in the rear-right corner and place it with the others in the front behind the right speaker. This will mean I will have my 3 bass traps all in the front right, and the corners in the back will be untreated.

I have 2 additional foam absorbers along with the ones at the side-wall first reflection points, which I currently have against the front wall in the center and near the opening. Perhaps it would be good to use these against the back wall in front of the window? Or better yet, I guess I should probably just get another broadband absorber if not a diffusor, as suggested by Kevin, for back there. Good to know about drapes- I had assumed they would be effective a little further down, but I suppose it makes sense that they would only tame the very high frequencies...

Chisar, while the foam based devices/absorbers are not as "good", assuming they have a shaped face, you may find the following somewhat helpful for the wall behind you.

Glue a strip of very thin plywood (even just a veneer board) to the top of the foam's back. Get a suction cup clamp with hook (ie. Lowes, HD, Michaels) and stick this to the top of the window behind you. Since the foam is so light, even with the strip of wood, you can hang it directly on the window. Easy to remove when guests come over. I do this as my side window is a 1st reflection point and it is much more productive than just drapes (but not as good as a full fledged absorber).

While there is limited absorbption in doing so, assuming again that it has pyramids or something on its face, it will also act as a diffusor.

Another thing to consider for the open doorway is to use a tension based curtain/shower rod and install drapes in the doorway. With the right material and lots of folds in it even in the closed position, this will provide some support to what you are seeking to balance the two sides.

I recognize that there are better solutions, but based on limitations of renting, higher costs, etc. . . mine are only intended to offer easily changeable, relatively cheap and not to require drilling - as opposed to being the perfect solution that allows us to ignore these restrictions.