" wrote in message
...
I recall reading an article which described a test that allowed 2 amps to
be
connected to a single speaker. If and only if there were differences
between the 2 would the speaker make any sound at all.

Anyone know of this test?

That would be the differential test. If a) the polarity of both amps is the
same, and b) the gain setting is the same, you can test amps that way by
connecting the 2 low sides together and the speaker between the 2 high
sides. The gain can best be set by simply adjusting it until the output of
the speaker is at a minimum.

Norm Strong