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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 redfuneral

redfuneral OP
36 posts
 
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. I should clarify that I’m looking at room temperature exclusively. An amplifier’s ability to cool itself has no impact on its thermal contribution(as I’ve learned from upgrading heatsinks in my conputer)

I’d say I don’t understand how to calculate power draw of amplifiers outside of class A. I was looking at an average power AB amplifier last night with power consumption rated 25-250W. I understand it idles at 25W and when in use is pulling 250W? Or does the power usage scale with the volume and demands of the speaker? How about Class D? Can a 50-100W AB or 250W D amp play music using less power than 5W of Class A? Do they all output the same wattage to the speaker all else being equal?
redfuneral OP
36 posts
 
Can you explain how that's the case? As I understand it now amplifier efficency only covers wall -> speaker terminal efficency. The wattage output to the speaker will mostly all be turned to heat. Where I stand Class A appears the answer only because there are 2-25W amplifiers all over the market where the alternatives all have higher output.
redfuneral OP
36 posts
 
Ok, assuming I only require 2W of power at the speaker:
Class A will dissipate heat equal to its power consumption
Class AB/D will consume a tad over their idle power consumption with D being closer yo idle than AB.
Correct?

Maximizing my speaker efficency is my first priority. Also correct?
redfuneral OP
36 posts
 
I wish more manufacturers listed power draw, last night I found a few SET amp makers who listed this and I've been severely undervaluing it. 100W seems the minimum for any SE tube amp. Ok, I was assuming 10% efficency at worst hence my thought some class A was competitive. That helps put into perspective the other classes, I understand why some were frustrated with my arguments for low-power tubes.

I'd also like to clarify my dogmatic approach is about keeping the discussion as simple as possible, I won't be picking an amp based on its efficency but I will be counting out amplifiers which would prohibit summer listening moreso than my former SE Parallel EL84.

We have had a consultant look at the room before and were told it's not a candidate for AC. I do have an industrial ceiling fan down the hall but does neccitate listening breaks, it's loud. I ran smaller fans throughout the summer to blow equipment heat out the door and I couldn't tell you if it made a difference.

I believe I have the answers I set out to find, and am thankful for the posters above. Suppose next priority is finding amps which play best lower in their power band, and picking out new speakers without obsessing too much over db rating.
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