Cheap simulated stereo kit

Posted by K. Rice on May 27, 2006; 8:39pm
URL: http://elecraft.85.s1.nabble.com/Cheap-simulated-stereo-kit-tp390270.html


Hope this is OK to post here.  If not, please let me know.

I found the thread on binaural / simulated stereo post-processing interesting.
Seems like an area worth exploring.

Did some reading.  Good search terms are "simulated stereo", "haas delay",
and { stereo "comb filter" }.

As seen above, the two main techniques seem to be:

1. Haas delay, in which the mono signal is split into two identical
channels with a little bit of each signal subjected to delay and mixed
to the opposite channel.  This simulates sound from a wide source hitting
two ears at slightly different times.  There are several parameters that
can be tuned, e.g. to shift sources left or right on the "soundstage".
These might be used to shift interfering signals' apparent positions in audio
space, especially if combined with some differential EQ to shift tones
left or right depending on their pitch.

2. Complementary comb filtering in which the mono signal is split as
above and then routed to two comb filters with the combs' bandpass
centers offset in complementary fashion on the two output channels.
(e.g. the left channel gets 64 Hz, 1 kHz and 4 kHz bandpass centers,
while the right channel gets 32 Hz, 500 Hz, and 2kHz).

I heard a monaural Horowitz piano track played through a complementary
comb filter once and it made the piano sound like it was 30 feet wide.

The effect was fascinating, but not neccessarily preferable to the original.
Still, it might be  useful for separating two distinct CW tones in a contest
type situation.

There's a cheap ($8) analog kit to do complementary comb filtering:

    http://store.qkits.com/moreinfo.cfm/fk651

Also there are complementary comb filter and Haas delay plugins
for all the major Windows and Macintosh digital sound editing
packages.  Obviously this would be the way to go if you wanted to
experiment.

No connection with the above vendor, except ordering the kit today.

73,
Ken
K3VV
Coopersburg, PA





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