From bruce@ashbysolutions.com Sat Nov 04 09:43:53 2006
Subject:Re: rotor syncing

Hi Rock,

>I think "masking" is the correct term. It's when one
>sound in the same frequency band is significantly
>louder than another in that same band, it effectively
>negates the softer one. With two speakers playing the
>same signal you're only going to hear the one closer
>to you if the other one is significantly farther away.
>As you approach the mid-point "sweet spot" between
>them, you'll hear both.

The technical audio term is called the "Haas Effect," and applies completely to monaural signals, and to a somewhat lesser extent to very similar stereo sounds -- ex: a pair of Leslies. The Haas Effect, simply stated, is that if two similar sounds reach the ears within about 30-50mSec of each other, the brain will add the two together, and "hear" both sounds coming from the closer source. This accounts for the occasional feeling that one speaker of a mono PA "isn't working." If the sounds are quite different, the ear detects them as two different sources.

Hi Joost,

>okay,
>
>but how is it for the audiance? when miced? and PAed?

Unless the Leslies are loud enough to compete with the PA itself, the audience receives little or no benefit from multiple Leslies -- unless one of them is panned hard left and the other hard right. Mostly, it's something that the band enjoys. This is also true of a single Leslie: the stage sound is often very different than the PA sound. I have a difficult time telling my BX-3's Leslie sim from my real Leslie through a recording; on stage, I could tell them apart blindfolded in about two seconds.

Regards,

-BW

--
Bruce Wahler
Design Consultant
Ashby Solutions™ http://consult.ashbysolutions.com
978.386.7389 voice/fax
bruce@ashbysolutions.com

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