--
J Wald
"You can lead a horticulture, but you can't make her think.... "
sounds like the problem is thermal overload kicking in in the amp
output stage. Which may mean it's not the driver UNLESS the driver is
partially shorted out. Test the ohms of the driver with a meter. It
should not be significantly below the limits of the amp (usually 4
Ohms minimum). Try another driver. Or put a LARGE 4 Ohm resistor in
series with the speaker. If the amp won't cut out with the resistor in
series it probably means there is a short in the driver.
Good luck.