Setting Up Speakers in an Octagon Surround Room?

Well, I found myself working with a friend to develop a suuround sound system for his listening room. A litening room that is a nearly-perfect octagon! After picking myself up off of the floor, I set about to design an appropriate surround configuration for this room. The floors will be oak hardwood. There are 3 windows in the back of room behind the couch (see Figure. 1). That is why it will be hard to place the dipole surrounds behind the couch. I could move the couch forward about 2 feet, but that would be hard on the eyes with a 61" TV at 12 feet viewing distance. There are plenty of constraints with this one.

The Problem

• Hardwood Floors: These floors are very reflective with sound, causing excessive echo and decay time when sound bounces off floor and other parallel surfaces (IE. Ceiling).
• Windows: Windows are also highly reflective with sound. Placing a speaker too closely to a window can cause unwanted reverberation of sound waves.
• Subwoofer Placement: Placing a subwoofer too closely to the listening position may be catastrophic if a cutoff frequency below what the human ear can decipher as directional cannot be selected.

The Solution

• Hardwood Floors are beautiful, but not best suited for maintaining a sound environment. I recommend placing the largest and thickest throw rug at the center of the floor to help dampen sound reflections between the floors and ceilings. You may also go one step further and place acoustic panels or tiles on the ceilings for the ideal sound environment. Check out the sound treatment offerings of www.tubetrap.com or the more economical offerings from www.echobusters.com.
• Windows can be problematic when sound is concerned, but can easily be remedied with insulated curtains and drapery. This is a win-win situation as it helps to improve the sound of your system, while it also enhances your TV picture quality by reducing ambient light of the room during the daytime.
• Subwoofer Placement is an important factor in achieving proper output and balance with the rest of the speaker system. The majority of the Receivers/ Preamps on the market only offer a fixed 80Hz Low Pass Filter (LPF) for the subwoofer output and thus limits your subwoofer placement options because a subwoofer crossed over too high can be easily localized by the human ear. In addition, it is difficult to acoustically blend bass capable main speakers with a subwoofer if the cross over is set to high.

Therefore, I recommend placing the subwoofer as closely to the front soundstage, between the two main speakers as possible. However in your situation, try to place the subwoofer closely to the front left speaker. If your cable runs are long enough, swap the sub and rack system positions.

Surround Speaker Placement

The Dipole surround speaker placement that you depict in your illustration is in their optimal position giving the constraints of your room. You may wish to experiment with height and final position before drilling their supporting brackets into the wall. I recommend placing the speakers slightly above ear level in the seated position.

Conclusion

Your system and room appear to contain all the elements of a great home theater environment. The majority of the acoustical problems of your room may be solved by simply decorating it. Adding throw rugs, insulated curtains, pictures on the walls, etc, can go a long way in improving the sound and atmosphere of the room. The beauty of this is you can improve your room on a continuous basis as your budget and decorative ideas flourish. You can't always place your speakers in exacting locations that will yield the best sound as you have to be practical and make the room livable as well. Experiment with the suggestions I offered and feel free to try some of your own ideas, after all that's what makes it all fun! Now all you need are some coasters for the beer and a table for the snacks. The question remaining is, when are you having us over?