Posted by Duke [ 63.87.108.184 ] on July 04, 2006 at 23:55:21:
In Reply to: Re: If I could bend the ear of a Valencia owner... posted by MWG on July 04, 2006 at 19:32:10:
Thanks so much for all the information!
I think that the Altec engineers were addressing the floor-bounce notch in the design of the Valencia.
There's the direct sound path to your ears, and then the first reflection to arrive is the floor bounce reflection. At the frequency where the floor bounce path length is 1/2 wavelength longer than the direct path, there will be a cancellation notch in the early-arrrival sound (it's not quite "first arrival", but within the time window identified by James M. Kates and others as being most critical in forming perception of timbre).
By using a squatty-body format, the floor bounce notch for the woofer falls above 800 Hz, and then the floor bounce notch for the horn falls below 800 Hz (assuming normal listening distances). Ingenious! The effects of the two drivers' floor bounce notches are largely eliminated by the combination of well thought-out geometry and crossover point.
It makes sense that you commment on the Valencia being known for its fine midrange, as the designers took steps to minimize a source of midrange coloration common to virtually all loudspeakers. I'm impressed with what they did.
The later Model 19 used a 90 by 40 horn and a 15" woofer, but moved the crossover point up to 1200 Hz to minimize the radiation pattern discrepancy between woofer and horn in the crossover region. Unfortunately I don't think they were able to keep the floor bounce notch out of the woofer's passband with that higher crossover point.
The information you gave me on the Valencia has been more helpful than you could imagine. I'll have to do a bit of experimenting, but something resembling an updated Valencia might yet arise.
Duke
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