Derate 300W amp for SW?

Annoy everybody who is sitting peacefully in their homes and minding their own business in a six block radius; that's my guess.

People who operate these "thumper cars" need to be shot.

Jon

Wow, human hearing-threshold curves down to 2Hz!

I have a JBL BP 300 mono subwoofer amp (300W) that I would like to feed with a continous sinewave within the spec. range of the unit which is 10-320Hz.

What is the rule of thumb for derating the wattage where this type of use is concerned.

I assume I then would put a suitably rated power resistor in series with the woofer.

Regards,

Louis Robson

It's a switching amp, so the output stage is probably not going to get much hotter at full power than at low power.

Since it is rated at 300W into 2 ohms (or 150W into 4 ohms), the supply rails must be considerably higher than 12V; it is powered from 12V, so the power supply itself must be a DC-DC converter, presumably also switching.

Therefore, you probably don't have to derate for continuous sinewave operation in the same way you would a class-AB amplifier or linear power supply. But you do need to derate for your load impedance - the higher the load, the less power will be delivered, since the constant here is the supply rail voltage.

That assumption is incorrect unless you are trying to do something peculiar. What is it that you are trying to accomplish?

"Louis Robson"

Only testing will show how long it can hold up at 300 watts .

Woofer impedance is non simple function of frequency.

......... Phil

There is no rule of thumb- that 300W rating is a "music power" rating with underlying assumptions about what percentage of the power lies within the 10-320Hz band, and that will be far less than 300W. Contact the manufacturer and ask for the "continuous power" limit.

That's one way to do it.

Better use this:

Or build one yourself using a RC helicopter collective pitch control system :-)

and

martin

Wow, $13k. No amp, no cross-over. (I suppose some might consider this cheap?)

"Walter Harley"

Seems to have a lot of heastsink area for one of them.

The JBL site says it has a SMPS.

......... Phil

F*ck, man, if peple have that much money to spend on noisemakers, please let them know I'll give them a bl-w j-b for only $1000.00.