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Heat/Efficency of Speakers

What % of power sent to the speakers is turned to waste heat? That's the short version of my question.

I'm looking to minimize waste heat accross my stereo as my listening room is unforgiving come summer; no cooling and a computer system which cannot be relocated. I understand amplifier efficency & the classes as well as speaker efficency measured as W/db however the interplay eludes me.

Taking two hypothetical amplifiers: a Class A amplifier outputting 10W w/ 100W from the wall & a Class D outputting 200 w/ 220W draw I understand the D will be the cooler operator however this is where the discussion tends to end, D only wasting 20W vs the A amplifier's 90W. Considering appropriate speaker matches to each amp(as well as a standard HE speaker at say 95db/w), how do I determine the wattage converted sound and the watts spent as heat?

I'm asking because I was previously running a 10W tube amplifier in this room(4xel84 tubes) with 96db speakers. This was bearable in two hour doses this last summer. My friend assures me any Class D amplifier and many AB amps would have no such heating problems and says it's class not wattage that is my issue. Before I move to a different amplifier technology(and swap speakers, these voiced for SE tube partnering) I want to understand this issue fully. I'm unconcerned with power usage and only care about the heat.
redfuneral

Showing 4 responses by cleeds

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cleeds
5,639 posts
 
shadorne
Speakers typically churn out between 99% and 90% of energy as heat.
You might want to check your math - most speakers are much less efficient than that. A speaker with 92 dB sensitivity is only about 1 percent efficient.

As for the OP, the heat in his room is overwhelmingly from the amplifier - not the speaker. His hypothetical 95 dB sensitive speaker is about 2 percent efficient.
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cleeds
5,639 posts
 
redfuneral
So I should assume all power(90+%) drawn from the wall will end up as heat. I should be looking to minimize the wattage at the speaker terminals
No, not at all.  You can achieve substantial increase in efficiency by choosing an efficient amplifier. As your friend suggested, you should be looking at your amplifier's class of operation.
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cleeds
5,639 posts
 
shadorne
You might want to check your reading comprehension while I am checking my math!

 If 99% of energy is lost as heat as I stated then this makes a speaker very inefficient - a mere 1% being converted to acoustic energy - exactly what you concluded!
But that's not what you wrote:

Speakers typically churn out between 99% and 90% of energy as heat.
I don't know of any speaker that's 90 percent efficient. That's why I wrote:
most speakers are much less efficient than that. A speaker with 92 dB sensitivity is only about 1 percent efficient.
 
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cleeds
5,639 posts
 
shadorne
... if I say a speaker churns out between 99% and 90% as heat then that equates to an efficiency of 1% to 10% in sound energy ...
Quite so. But I don't think you can cite a loudspeaker system with 130 dB sensitivity, which is what would be needed to have a 99 percent efficient speaker.
 
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