Maximum long term power handling

nakamoto said:

According to WinISD, this means I could drive my sub with a sinewave at 16hz at 100db for as long as I want without risking damage. This seems unlikely.

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Very unlikely. Thermal ratings are determined by the application of pink noise, not sine waves. It's of little consequence, since we don't listen to sine waves, while what we do listen to is closely approximated with pink noise.

Amplifiers are constant voltage devices, but variable power and amperes for a given voltage.
So it is more complicated then that.

It is the amperes that cause the coil to heat up, not the voltage.
A 1-ohm sub will heat up faster than a 32-ohm sub given the same voltage,
even though they are both 18's and the voltage hasn't changed.

Each frequency will have it's own power level and amperes and excursion for a given voltage.
The more excursion the more cooling, allowing it to last longer (up to a point.)

Buy one of these from Walmart, pull the driver out and give it a sinewave.
http://www.amazon.com/Nubee-Temperature-Non-contact-Infrared-Thermometer/dp/B00CVHIJDK

Stop when the temp reaches 107F or 42C.
That will be the maximum voltage and time with that sinewave.
Let it cool down to room-temp between each test.

Each sinewave will be different, below 40hz you are likely to bottom out before smoking it, unless it is a super-small sealed box.

You could try to push it beyond 107F, but that is your risk to take.
Once you get above 20-30volts, you should be more careful.

The difference between 450watts and 900watts is 3db.
The difference between 225watts and 900watts is 6db.

As you can see, the last 3db is very expensive in terms of heat, if you think of how hot five or nine 100watt light bulbs gets... in just a small area behind the center of the cone.

I have 10 or so amplifiers in my room, which are rated for 44kW burst total.
After idling them for 8-12hours the room temp goes from 32F to 67F, or 0C to 19C.
If I boom some loud bass, the temp goes up another few degrees.
In the peak of summer time, without turning on the AC, I can only do 3 amplifiers for 5minutes. At which point it feels like you are working in a deep coal mine.
In the winter it isn't until several degrees below freezing that I have to turn on my space heaters, to get the temp up to room-temp.
I could ONLY imagine 10 Class-A amplifiers. That would be crazy hot, and a high monthly bill too.

You gotta love heat; heat is your friend. LOL! LOL! LOL!

That spec of 900 watts RMS SHOULD mean you can apply any 900 watt waveform, including a sine wave, indefinitely, and the speaker structure will be capable of dissipating that much power as sound and/or heat indefinitely.

That is a remarkable spec, since most of that will have to be given off as heat. I doubt if it can do that without overheating, but that IS what they are claiming.

To apply that to the speakers would require a 15 volt RMS continuous waveform, assuming it has a 4 ohm impedance. (V= square root of P/R), or 42.5 volts peak-to-peak.