Fine Tunes #2 Page 2

"To determine initial speaker placement, multiply ceiling height by 0.618 (10' * 0.618 = 6.18') to determine the distance from the rear wall to the center of the woofer (or the acoustic center of a panel). Then multiply the room width by 0.276 (width * 5 ÷ 18) to determine the distance from the side wall to the center of the speaker (16' * 5 ÷ 18 = 4.4'). I have run into times when the geometry of the situation makes this setup less than favorable. So I've derived a simple plan 'B' that inevitably works if plan 'A' doesn't. In plan 'B' the speaker side-to-side placement is the same (room width * 5 ÷ 18), but woofer face-to-rear-wall distance is the same as the speaker center-to-center distance (room width * 8 ÷ 18). It's usually easy to try both positions by sliding the speaker straight forward a foot or so. If you play a good bass cut while you move the speaker, you'll hear the sound sweeten up when the speaker hits the 'pocket.' I've yet to find a symmetrical rectangular room where one of these two setups didn't work."

Whew, I'm glad that's over with. Even though I'll continue concentrating on things you can do for free, here's some computer software that can help you out:

You might try Visual Ears for Windows, $89 from KB Acoustics, P.O. Box 50206, Eugene, OR 97405, Tel: (541) 935-7022. You'll move simulated speakers and a listening chair around your simulated listening room, looking for best performance.

The left-hand screen in Visual Ears for Windows allows you to drag an drop your loudspeakers and your listening chair around a rectangular room, while the right-hand screens instantaneously show the effect on standing waves (top) and boundary reflections (bottom).

Then there's ETF (Energy Time Frequency), an application that works with a PC, a sound card, and a microphone. You record a test signal played through your system and let ETF analyze the data for you. You'll get information regarding room-related frequency response, room resonances, early reflections, late reflections, comb filtering, and lots more. The software will set you back $199.95, plus a sound card and an appropriate mike.

Next month we'll look into larger listening areas (such as my own loft space), and placement strategies for irregularly shaped rooms. Hint: This is where walking around clapping your hands (while no one's looking) can pay big dividends. And we'll take a look at toe-in and find out whether your speakers will sound their best cross-eyed or locked into a thousand-yard stare.

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