Now, was your old amp just susceptible to overheating or is this an issue for all amps?
This depends a great deal on the particular installation: How much air circulation the amps receive, how much power they draw, how hard they are being worked, how efficient their heat sinks are, whether the amps have built-in cooling fans, etc.
My current system, at first glance, should overheat. It consists of a 400 watt 8-channel amp, plus a 320 watt (nominally 160 watt but running bridged mono for a true output of 320 watts) two channel amp, plus a pair of Audio Control EQT 30-band equalizers, plus four passive crossover modules -- all crammed into a small volume (about 1/3 of the spare tire well in my Taurus station wagon) that, while not sealed air tight certainly does not allow any air circulation.
After three hours of continuous operation, the exterior heat sinks of the amplifiers are but little warmer than body heat -- maybe 110 degrees F. We had planned on installing a theromstatically controlled fan in the amp rack compartment, but decided we didn't need it.
I attribute this to two things: (1) The amplifiers are pretty high-end with very efficient heat sinks; and (2) Even though I have over 700 watts of capacity, I probably only use about 150 watts at normal listening levels.
What would happen if I parked for hours with the sun beating down into the back end of my wagon is anybody's guess. Chances are things would overheat in those circumstances.
tanstaafl.
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"There Ain't No Such Thing As A Free Lunch"