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New idea: Rear speakers, small room with couch against back wall. Will it work?

post #1 of 7
Thread Starter 
I had a new idea for incorporating a rear channel in a small room. Hoping some experts can chime in to let me know if the idea has merit.

I'm yet another poor soul who is stuck with a 5.1 setup in a small room (11x11). No, the couch can not be moved from the back wall.

I understand conventional 6.1 and 7.1 speaker placement was not designed to work in this scenario. Here are the classic blunders for small room rear channels:

1. Rear channel in-wall speakers: too close to listening area. Too easy to localize, ruins the surround sound effect.

2. Rear channel mounted on ceiling: sounds like it's coming from overhead instead of behind, ruins the surround sound effect.

Here's my concept, not sure if anyone has though of this before:

Mount the rear speaker(s) on the ceiling in the center of the room, firing down and angled slightly against the wall to create reflection.

Next, hang a 2'x4' 2" thick Owens Corning acoustic panel vertically against the wall, covering the speaker.

My hypothisis: Most of the sound waves traveling strait down will be absorbed and diffused, since they are passing through the length of the panel.

Reflected sound bouncing off the back wall might be easier to hear, since waves would pass through panel at a different angle.

Hoping the reflected sound would have the most presence, and make it seem as if the sound is coming from behind.


The layout:

I'm thinking about hanging three acoustic panels above my couch. This should also make my room sound quite a bit better. I'm planing to space each panel apart about 6" ... Wondering if reflected sound will pass through the gaps.

In my case, I'm consitering a 6.1 setup, using a polk cs1 as a rear channel in the center of the room. I guess a 7.1 setup would work too, but I'm not sure there's a need to cram all of these speakers in a small room.

Ok Brainiacs... is this worth testing? I understand I won't know how it sounds until I try it... just looking to see if anyone wants to shoot me down before I exert the effort.

If this is in fact a new idea that works... I'm dubbing it the BRADLEY technique!

Thanks guys, -Bradley
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post #2 of 7
I would not waste the time, money or effort. 5.1 is the way to go.
post #3 of 7
Have you looked at the Energy CR-10s? You might find that kind of bipole/dipole design interesting given your situation.
post #4 of 7
Quote:
Originally Posted by cel4145 View Post

Have you looked at the Energy CR-10s? You might find that kind of bipole/dipole design interesting given your situation.

That would work with a 5.1 system in that room. Not 7.1
post #5 of 7
Quote:
Originally Posted by saladtown View Post

I had a new idea for incorporating a rear channel in a small room. Hoping some experts can chime in to let me know if the idea has merit.

Putting sound absorbers on the rear wall is a good idea in general. If you are slamming your listening position up against the wall, its an even better idea if the sound absorbers are effective. And that's the rub - 2" sound absorbers are only efficient down to fairly high frequencies, usually 200 Hz or so.

Long story short my mix position at church has problems with massive bass build up due to the expected and observed standing wave along the back wall immediately behind me. We installed a 4" thick sound absorber about 6' tall and running the width of the church (45') right above my seat, on the front of the balcony. This worked very well down to 100 Hz or so, but it stopped being effective all the way down as soon as I installed a subwoofer for the sound system that goes down to about 32 Hz. The sonic effect is actually kinda neat - a lot of tight gutsy bass. But, I don't hear anything like what's going on for the audience seating area, particularly the middle of the room.

I see a strong similarity between my experience and what you are proposing to do.

First off, your smaller 2" absorbers are going to clean up a lot of problems well above 200 Hz, but right below 200 Hz is the 100 Hz area which is known as the region of boom and doom. You are in a thickness versus area war. If you increased your absorbers to 4" then you'd kill not only the upper frequency reflections but also a lot of the boom. If you simply covered the whole wall, the absorbers wouldn't go any deeper but the vastly increased surface area would still help. 4 square feet of 30% absorbtion can be similar in its effects to 2 square feet of 60% absortion. I don't think that the floor space in the room is going to be hurt that much by shaving off another 2". Of course, if you covered the whole wall with thicker absorbers, better control over that big bass standing wave.

The next thing I'm going to tell you may surprise you. Solidly covering a wall is probably not the best idea. If you cover the middle 50% of a wall the results are probably not going to sound as good as covering 50% of the wall with say, vertical strips of absorbers that have vertical strips of bare wall between them.

The other thing is that speakers generally benefit from being slapped up against a wall or even being built into the wall. The reflections from the wall are particularly beneficial at low frequencies. Of course these speakers are surrounds, and good bass is not of the essence. Nevertheless, I might favor putting in absorbers that are more like vertical strips with the speakers in the bare vertical strips between the absorbers.

I can see some romance to forgetting about putting speakers behind you and focusing on speakers on the side walls towards the back of the room.

The other thing is that there are going to be bass reflections from not only the stretch of wall, but also from the strips-like areas where the floor and ceiling meet with the wall. To further tame bass at your listening location it could be profitable to get sound absorber located in those areas.

Similar thinking applies to the side walls. It's better to have your absorbers there broken up and concentrated at ear levels. The floor and ceiling junctions are probably going to be far less important than the back wall where you want to sit.
post #6 of 7
I have the same setup with 7.2 ....I use Klipsch G-28's ...they are perfect
post #7 of 7
Quote:
Originally Posted by saladtown View Post

I had a new idea for incorporating a rear channel in a small room. Hoping some experts can chime in to let me know if the idea has merit.

I'm yet another poor soul who is stuck with a 5.1 setup in a small room (11x11). No, the couch can not be moved from the back wall.

I understand conventional 6.1 and 7.1 speaker placement was not designed to work in this scenario. Here are the classic blunders for small room rear channels:

1. Rear channel in-wall speakers: too close to listening area. Too easy to localize, ruins the surround sound effect.

2. Rear channel mounted on ceiling: sounds like it's coming from overhead instead of behind, ruins the surround sound effect.

Here's my concept, not sure if anyone has though of this before:

Mount the rear speaker(s) on the ceiling in the center of the room, firing down and angled slightly against the wall to create reflection.

Next, hang a 2'x4' 2" thick Owens Corning acoustic panel vertically against the wall, covering the speaker.

My hypothisis: Most of the sound waves traveling strait down will be absorbed and diffused, since they are passing through the length of the panel.

Reflected sound bouncing off the back wall might be easier to hear, since waves would pass through panel at a different angle.

Hoping the reflected sound would have the most presence, and make it seem as if the sound is coming from behind.

The layout:

I'm thinking about hanging three acoustic panels above my couch. This should also make my room sound quite a bit better. I'm planing to space each panel apart about 6" ... Wondering if reflected sound will pass through the gaps.

In my case, I'm consitering a 6.1 setup, using a polk cs1 as a rear channel in the center of the room. I guess a 7.1 setup would work too, but I'm not sure there's a need to cram all of these speakers in a small room.

Ok Brainiacs... is this worth testing? I understand I won't know how it sounds until I try it... just looking to see if anyone wants to shoot me down before I exert the effort.

If this is in fact a new idea that works... I'm dubbing it the BRADLEY technique!

Thanks guys, -Bradley

Try bipoler speakers mounted either on the side wall near the back wall, or on end tables at each side of the sofa. A most recent crutchfield magazine shows this configuration. The bipolars fire forward and backward to hopefully avoid localization. Absolutely no need to go 7.1. The room is too small.
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