Room size audio issues

DonnMac · 02-09-2005, 07:25 PM

Here's another basement layout problem. The finished basement HT space is 16' w x 9'h x 22' deep, but no effective rear wall will exist at the 22 foot depth, just a half-height (3') partition. The open space then continues another 28' across the basement, so essentially the rear wall is 60' away from the front wall. My HT question: How will the audio be compromised without a rear wall? The HT plan is for a 3-4 seat front row and a 4 seat 2nd row (on a riser), with a just a half-wall for the rear. The audio only needs to work for the viewing area, definitely not intended to power sound through the entire 60' opening. I realize anything is possible for enough $$, but does the lack of a rear wall consistently compromise any reasonable investment in electronics? Any suggestions would be appreciated. I suppose an easy answer is to build the half wall into a full height rear wall, but that won't fit with the rest of the basement plans. Spousal veto power to the nth degree!
Regarding audio budget, I'm planning for $6K - $8K total in electronics, including speakers.
In a space like this, will the elctronics be able to be appreciated?

Thanks for any guidance.

Donn

Wayne A. Pflughaupt · 02-10-2005, 02:32 PM

Welcome to the Forum, Donn!

The size of your room isn’t a big problem, but there are some things to be aware of.

Sound will bounce off a wall 60 ft. just as it will a wall 15 ft. away, so don’t imagine that a distant wall can be ignored. The problem with a distant wall is that the sound takes much longer to get back to your ears than with a close wall, so you can end up with “slapback” echo. At that distance you’re looking at close to 100 ms delay between the original and returning signal, enough that the secondary reflected signal would probably be fairly distinct. To get an exaggerated idea of what I’m talking about, it’s like what you’d get yelling into a canyon, only with much less delay between the original and return signal.

Bottom line, make sure there is some treatment in place at the back wall to diffuse and/or absorb sound.

The biggest obstacle you face is adequate low frequency performance. It’s difficult to fill a large room with high-output bass that reaches the lowest frequencies, so I expect you will need at least a pair of highly-capable subs if you desire performance approaching reference levels with extension to 25 Hz or below.

Likewise, you’ll need to careful choose your main speakers. As noted, large rooms “soak” bass frequencies, so if you choose little speakers with small diameter woofers, they may be rolling out before the subs take over, resulting in poor response in the 100-400 Hz region. I’d make sure your mains have at least dual 6-1/ 2” woofers, or perhaps an 8-inch, at least for the L/R pair.

Hope this helps.

Regards,
Wayne A. Pflughaupt



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