"Dave Plowman (News)" wrote in message
...
In article ,
David Looser wrote:
Oh I dunno. If you use a very low frequency tone (NOT music), say 10Hz,
and connect an LED across each speaker (not forgetting a suitable
series resistor to avoid the risk of damaging the amplifier), and being
absolutely sure that both LEDs are connected the same way round (not
always easy) and by placing the two LEDs next to each other you might,
just might, be able to see if they are flikering in phase, or out of
phase.

LEDs can fail with reverse polarity.

Indeed, so as well as the series resistor you should really use a shunt
protection diode as well!

David.