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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
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.
almarg's avatar
almarg
9,670 posts
 
Hi Bill (Brownsfan),

I mostly agree with your points, as far as they go.  But regarding the relevancy of the speakers, I would add a couple of things.

First, for a given listening volume a given class AB or class D amp will draw less current from the wall if higher efficiency speakers are used than if lower efficiency speakers are used, resulting in less heat being introduced into the room.  Second, as Swampwalker noted greater speaker efficiency would allow the use of a less powerful amp, which within a given bias class will tend to correlate (at least loosely) with reduced power consumption.

Also, regarding "All of the energy in the room is conserved.  It does not disappear," some of it will in a sense disappear.  Although it is pretty much just an academic point some of it will disappear **from the room,** assuming the temperature of the room is higher than the temperature of the adjacent spaces (both indoor and outdoor), given that the thermal insulation between the room and those spaces will not be perfect.

Best regards,
-- Al
 
almarg's avatar
almarg
9,670 posts
 
Redfuneral 12-12-2016
... my former SE Parallel EL84.
OK, then my previous supposition that the amp was biased in class AB was not correct, as a SE parallel amp will operate in class A.  So the 60 to 75 watt estimate I stated for the power consumption of the amp under typical listening conditions was probably somewhat low.

Regards,
-- Al
 

onhwy61's avatar
onhwy61
5,303 posts
 
Why don't you take a look at cooling vest/jackets.  They can be active or passive and are designed to keep your body core cooler than the surrounding environment.
brownsfan
1,508 posts
 
Al, thanks.  All of the caveats you listed I assumed would be understood so I did not explicitly state them.  Of course, the 2nd law demands that heat moves from an area of higher temperature to one of lower temperature.  If the listener is in a poorly insulated room, and the exterior is 40 degrees lower, and he opens the window, then the "disappearance" would be significant.   I also made an assumption that everyone participating in this discussion knows that less efficient speakers draw more energy into the room in order to afford a given dB level, and that energy ends up as heat. 
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