Room acoustics question... reflections !

[Mooly]

I wonder if any room acoustic experts would know what might be gained by adding soft damping to the rear wall such as curtaining etc. All the walls/ceiling are hard surfaces (embossed paper on plaster/brick). Overall the sound is very good but I notice imaging improves as I lean forward a little away from the rear wall. Also I have noticed in the past when various pure tones are played (from memory around the 2 to 5khz region) it is possible to almost totally null the sound out by moving around the room... reflections !
The listening position is the seat by the door which is in the centre line of the room.

The pics give some idea and the dimensions are in the drawing.

Speakers are B&W 703's with the port unplugged.

How much of an issue do you feel that hard rear wall is ? and what do you feel would be the effect of deadning the wall ?

This is a subject I feel I know very little about in a practical sense although it's just as important as all the electronics.

The small white heater showing in the pics doesn't normally live here

[Keriwena]

The short of it is, "short" reflections are bad.

For this reason, the drapes behind your speakers are good.

I'd lose the mirror and hang a shag rug over the couch.

[Ron E]

Sound is so subjective I think the best thing is to try it, get a big moving blanket and put it on the wall.

I think your sound will improve dramatically by doing one thing - get a rolling or portable listening chair and put it a lot closer to your speakers.

[Pano]

Yes, try it.
My taste is for heavy absorption behind me. As little sound coming off that back wall as possible. I've heard this done in many rooms of different shapes and sizes and always liked it.

But there are those who don't like it at all!

Also not that your leather sofa has a rather high back, so it's blocking a lot of the sound from the rear wall, and creating its own reflections.

[Top Shelf]

JBL had a paper in their archives that I have not found in a while that dealt with absorptive materials and their aplications in relation to room treatment . It had to do with type /thickness of material and actual distance it was draped from the "problem" wall ,( distance relating to frequency?/ reflection to be attenuated) this may be of help if you can find it.
You're most likely getting some jagged off axis reponse variations from the stereo stand and cupboard seeing as they have hard multi faceted fronts and are at level with the drivers.

[Mooly]

Thanks for sharing your thoughts folks...

Going to have to experiment I guess in the first instance and see what kind of differences come to light just trying something draped as you suggest. Of course domestic acceptability has to figure heavily too. I'm sure your right on the moveable listening chair Ron E, but that sofa is just so comfy

Your right Pano, that's something else I had noticed, that the sofa does seem to alter the soundstage in it's own unique way, well I'm assuming it's that, in that as you settle back the image blurs slightly with a very slight left of centre bias. Sit forward and it snaps back into focus again. That's the kind of thing that really bugs me. I know we are only talking matters of degrees here but even so, it's the little things that add up to make it all come together.

It's a subject that in its own way is just as complex as tweaking the electronics. So much to read when you start researching it. Hmmm....

[dewardh]

Originally Posted by Pano

My taste is for heavy absorption behind me. As little sound coming off that back wall as possible.

+1

And with dipoles a diffusive front wall (behind the speakers) gives a more "natural" sense of spaciousness without compromising imaging. Conventional "box" speakers, which present a different front wall reflection above and below baffle step pose a problem (with which, fortunately, I don't have to deal . . .).

[Pano]

Yep, that wall behind the speakers makes a big difference.
When I visited JBSpeakerman up in his Sierra mountain hide-away, his listening room was his garage. The front wall was the double garage door. First listen was to a pair of OBs. Wow! That sounded live. Harry James and his trumpet were out there in the driveway. Great image, great dynamics. Very real.

Push of a button, close the "wall". Big difference. Not so live sounding any more, Mr. James is not so far back. Image not as real. But it sure did fill out the midbass. Not all that bass energy going out into the wild.

Being able to remove or replace the wall at the push of a button was very cool. It made a difference to box speakers, but not as much as it did to the OBs. It really did reinforce my belief that good diffusion is the way to go behind the speakers. Scatter the direct reflections so that you don't "hear" them, but keep the energy that the wall contains in the room.

Mooly - you have that typical English bay window space behind his speakers. Not random diffusion, but not the reflections off a flat wall, either. That should help. BTW, my leather sofa tilts the image slightly left, too.

[steviedon]

If it were me i'd exile the piano to the bay window (depending on whether the cabinet currently there will fit in the lower left corner of your diagram), and move the speakers to that wall, swap couches, treat the wall behind.....done. You will see some benefit from damping the rear wall in the current configuration however, I'd guess more pertinent are the undesireable reflections likely coming from all the gear flanking each side. You could try crossing the image a couple feet in front of you, opposed to directly at the listening position as it may achieve what you're describing when moving slightly forward.

[Paul W]

You are getting good advise. Escape both the wall and the leather sofa. I've had each of them at one time or another...both were terrible for listening. Both at the same time...yikes!

Try a comfy lo/mid back rolling chair (or one with an exceptionally small headrest).