Importance of wall behind listener?

My sweetspot backs up to the rear wall. This is paramount for good bass slam and visceral impact. Move the seating position further into the room and bass starts to lean out. Even a few inches further into the room makes a difference. You can see my setup in system pics...

I have a nearly identical room with essentially no back wall and sloped ceiling. I have experimented with various acoustic treatments behind the listening postion. Absorbers kill the openness, and even diffusors sound less open than just leaving that space alone. One thing that will help is diffusors on the ceiling, I use RPG Skylines and Doublebusters. You may also want to try diffusors behind the speakers. I get a very nice enveloping and palpable soundstage with these treatments!

I agree with Sns on this.

You may also want to try diffusers behind the speakers. I get a very nice enveloping and palpable soundstage with these treatments!

I tried damping panels, Polyester batting, tube traps (alone), diffusion by way of artificial plants and even carpet.

In the end, RPG QRD 734 diffusers directly behind the speakers worked the best. I disguised mine with acoustically transparent cloth (good wife acceptance factor) and wound up preferring the sound over the uncovered version.

Thanks guys...

SNS, do you have any pics that you can email me? I'm interested to see what it looks like (WAF!). And thanks for the tip on the QRD 734, Albert. I will look into it.

I should also add that I have a 55" RP TV between the speakers, a foot or two behind the front plane of the speakers. I cover it up completely with 3" foam pyramid diffuser panels to reduce reflection.

1markr, you can look at my system here at Audiogon for the WAF images :^).

http://forum.audiogon.com/cgi-bin/fr.pl?vaslt&1022712214&view

Here is a photo of my QRD 734 during construction, built into the back wall.
http://cgim.audiogon.com/i/vs/i/f/1111001394.jpg

Click on room views to see the acoustical cloth wrapped around the room obscuring RPG's and damping panels.

1mrkr, I should have made it more clear that I do use diffusion behind my listening position, only on the ceiling. I use a combination of skylines and doublebusters spread from just behind 1st reflection point on ceiling to behind listening postion. Sitting diffusors on floor stands behind listening postion has not worked as well as the natural ambience of no diffusors.
On WAF, that is difficult for me to know, I have a dedicated listening room so it doesn't matter. I actually like the esthetics of a fully treated room, I'm not so sure others do.

In my room, the wall behind me is 20 ft. away, and I use no diffusors or absorbers. The sound stage is wide, high and deep.

"1markr, I should have made it more clear that I do use diffusion behind my listening position, only on the ceiling. I use a combination of skylines and doublebusters spread from just behind 1st reflection point on ceiling to behind listening postion"

Scott, I think you meant "do NOT use diffusion behind listening position"....

Perfectionist

I have experienced exactly the same results you describe and have therefore always backed my listening chair as close as possible to the rear wall.

I always assumed that the "lean" sound you described might have been inherent to my favorite Magneplanars, but I notice you are not using planar speakers.

For me, in any case, close to the rear wall is a rule of thumb for basic placement, and I only move the position forward into the room to counteract any boominess.

(Nice system and room, by the way.)

1markr

If this is not possible for you, I hope you are still able to achieve happy results.

I cannot comment more specifically on rear wall treatments, but I have had everything from fireplaces to big windows and never thought that was a critical element.

I would think first reflections, closer to the speakers and especially on side walls should be more carefully controlled.

I would also think a lively rear wall might yield acceptable results for ambience and later reflections.

But I am not an expert so hopefully we will hear from others.

It is interesting to hear the different opinions on this subject. But in the end it all comes down to the room your hi-fi is located in, the orientation of hi-fi in said room, and how much money one is willing and able to spend on acoustic treatments. I actually put my 8'x11' rugs on my walls when I was still mid-fi. It was a relatively inexpensive way to aesthetically and acoustically treat a room with 10' flat ceiling's and a lot of wall space. Also, the room my hi-fi is located in was the best choice in my home, as I have a 9' pool table in my other large room. When my house was being built, I even took into consideration which of my two large rooms I would use for my hi-fi in regards to ambient noise levels outside my home during late night loud/listening sessions. My gear had to be orientated in this room a certain way due to a door in the room that leads out to the backyard. Hence, IMR (in my room), I really have no choice but to put the listening position against the rear wall. But, in playing with that seating position both fore and aft a few inches, I've noticed that it profoundly affects bass slam. I will say that there is a more enveloping soundstage with the seating postion pulled out from the rear wall, but at the expense of bass slam. And I'll admit, I'm a bit of a (tight) bass junkie. I wish I would have been into high-end when the house was being built-there are so many things that could have been done in preperation for a proper musical experience (i.e., many dedicated circuits, insulation, wallboard, etc). All that being said, and as deep as I am into high-end now, I would completely design my next (if there is a next) home around my hi-fi. ;-)

I also have a similar configuration, but with a 9" flat ceiling a 12'rear opening in the center of the rear wall (an entry/foyer followed by a 12' hallway). I found that a Janis 15" Subwoofer placed in the rear corner added a significant demensional improvement.
This unit is upward fired, and has a variable output. But once you have it set it blends very well.I have no experience with diffusion or other sound treatments. Other responces are very positve, but I am concerned cosmetics.

A few random ramblings and this is an issue I have wondered about for along time. I think it is interesting that so many live performances have the best seats in the front third and, in larger venues, the back is very open. In all the indoor orchestral concert halls this is the case. Bass is reinforced by a sealed room, but that also makes it harder to control. How many of us have openings to the rooms our equipment is in? I have found that I can compensate for the bass with large subwoofer. My next purchase will be for a second sub to even out the bass frequencies. The high and mid range is usually quite good without a back wall, since there is no concern about reflections from the back. The responses so far are interesting!

I had a similar problem in a large unbounded space and resolved it to my satisfaction without consulting Rives or purchasing acoustic treatments. After some experimentation, the extended space behind the listen has become irrelevant. There is now a deep convincing soundstage and wonderful bass performance, in balance with the rest of the spectrum.

I got this result by covering the stud wall behind the speakers with 3/4" plywood. I believe this helped rigidify the wall and boost the bass energy. It also seems to reflect the sound toward the listener which in this situation is favorable. You can experiment for yourself by leaning some sheets of finish plywood against the speaker wall. When I did that I could hear the difference immediately, so I mounted them to the wall. If it doesn't work for you, try the plywood somewhere else, or use it for some other project.

You could also try experimenting with a partial room divider, shelving, or piece of furniture at various distances behind your listening position. My hunch is you'd want something more absorptive than reflective in this position. Don't spend any money on treatments until you've gotten some direction from mockup arrangements of items you already have. Go by ear and have fun figuring it out.

In my experience, there is a trade off between placement for bass performance & soundstage. Usually, if you place the speakers nearer the front wall or sit near the back wall, you get better bass but the soundstage suffers.

I would suggest that a better way is to chose speakers with the bass performance for the size of room even when it is placed in the optimum position for the best soundstage.
In my room, the rear of my speakers are 4 feet from the front wall and I sit 5 feet in front of the back wall and on the better recorded CDs, I can hear an all enveloping soundstage which extends to ambience & echos coming from behind my listening position. In a friend's place, where his back wall is further back still, the effect is even better and you really get the illusion of sitting in a concert hall.

Hope this helps.