On 5/29/2013 12:59 PM, Jeff Liebermann wrote:
On Wed, 29 May 2013 15:28:34 +0000 (UTC), Cydrome Leader
wrote:

If fuses blew on the amp, I'd not be in a hurry to start replacing them.
I'd probably disable channels in the surround decoder.
Chuckle. I have an old Heathkit AA-2010 quad channel amplifier.
http://www.audioasylumtrader.com/ca/ca.html?ca=23000
I'm down to one channel now, as the other three have blown up over the
years. When the last channel dies, I'll probably fix it and start
over.

My ears are somewhat screwed up, so quad sound never did anything for
me. In the early 1970's, I attened an AES (Audio Engineering Society)
convention, where the hot topic was quadraphonic everything. I tried
on quad earphones and heard nothing interesting. I listened to a
serious discussion between "experts" over whether the listener wants
concert hall realism, which meant sitting in front of the orchestra in
stereo, or whether he wants to be "immersed" in the sound, which meant
sitting in the middle of the orchestra in quad. Meanwhile, the movie
theaters were having a bit of a problem with quad sound, which tended
to produce dead spots.

Subsequent to the original release of quad headphones, in the late 60s,
considerable research was done on ear / brain localization and spatial
imaging, funded in part by the Air Force / DARPA (to facilitate heads up
display direction of arrival cues for pilots being fired upon from 360
degrees in azimuth). Some seminal work was done at the University of
Darmstadt, Germany, the prior art upon which Bob Carver's original
"sonic hologram' patent was granted.

The technical significance of the findings was the intra-aural spacing
of the typical human and the resulting time difference of arrival from
the earlier to the later ear, combined with the comb filter created by
the external ear's ridge structure (pinnae) allowed the brain to build a
mental map of where things arrived from acoustically. A given angle of
arrival in azimuth and elevation at a given frequency would have a
learned interpretation of where it arose from. This was in addition to
the reverb decay times and spectra influencing / defining the enclosed
space in which the audio was captured / simulated.

The bottom line was that headset design could not inherently replicate
the intra-aural delays and especially the comb filter results accurately
for all individuals, since each of us has a unique set of parameters.
Partially successful alternatives such as binaural recording and
playback have overcome this to some extent but not fully.