New Energy (Audio)

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  • #26
turbo
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Loudspeakers are VERY inefficient, and some of the most accurate ones are the least efficient at converting electrical impulses to sound. I have built guitar amps with some fairly efficient speakers (maybe a few percent), but they are not particularly accurate speakers. Most of the power sent to a speaker is dissipated in the form of heat, which is why it is possible to overheat the voice coils and wreck speakers. Using such a device in reverse would create very tiny electrical impulses - useless for doing any work without amplification, so there is no advantage there.
 
  • #27
sophiecentaur
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Ok I see what your saying Borek, even though the molecules motion is erratic, it does not much effect the sound energy propagation.

So the reason that the energy is hard to capture is because it speeds away in every direction at the speed of a bullet and travels through most materials.

Russ, you are correct a 100W speaker at full volume is deafening.
No. The reason it's hard to capture is because there's so little of it!

Edit: Also, you can make very good use of Light Energy and that goes nearly a million times faster!
 
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  • #28
How is there so little of it? If you run 100W through the speaker coil the magnet will move with 100W worth of acceleration. Are you saying that the conservation of energy law is flawed in speakers? Speakers don't get that hot...
 
  • #29
turbo
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How is there so little of it? If you run 100W through the speaker coil the magnet will move with 100W worth of acceleration. Are you saying that the conservation of energy law is flawed in speakers? Speakers don't get that hot...
Most loudspeakers are only about 1% efficient or so in converting electrical energy into motive force, into acoustic signal. Very linear (accurate) speakers may be even less efficient.
 
  • #30
russ_watters
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How is there so little of it? If you run 100W through the speaker coil the magnet will move with 100W worth of acceleration. Are you saying that the conservation of energy law is flawed in speakers? Speakers don't get that hot...
It's been a while since I've put my hand on one, but I think the coils do get hot!

Note that a lot of the heat is also dissipated at the amplifier.
 
  • #31
sophiecentaur
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If you put the '100W speaker' into a concrete box and had a vibrating diaphragm across a hole in the box, you could probably get a watt of kinetic energy (more, if the system were tuned / matched well. But you would be better to cut out the middle man and connect the speaker leads directly to a load.

If you are just talking about using the 'wasted' sound power in a room then you have to accept that most of it will be absorbed by walls and furnishings (or, if you're outside at Glastonbury, the rest of the world) and there's precious little available for your 'sound energy collector', which will intercept a small fraction of what was produced by the speakers. If it were a worthwhile project, don't you think that they'd have something of the sort on every airfield runway, to get the power from the jet engines and inside every big noisy piece of machinery?

And, yes, speakers can get hot enough to melt the speech coil, if you drive them too hard.
 
  • #32
turbo
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It's been a while since I've put my hand on one, but I think the coils do get hot!

Note that a lot of the heat is also dissipated at the amplifier.
I have put my hands on the speaker housings and spiders, especially in applications in which I thought I was over-loading the speakers. When I built guitar amps, I almost always built open-back designs, and when I was running inverted-chassis designs (so that the tubes were head-down in the same enclosure as the speaker) and really pushing them I sometimes ran external fans to cool stuff. Probably the most iconic tones are produced Fender 5E3 tweeds and smaller Vox amps, which can run hot if pushed.
 
  • #33
sophiecentaur
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Did you ever actually measure the current and volts applied to the speech coils, though? Did you ever run 1kHz tone at a measured 100W into them? 'Loud' music is seldom equivalent to the max power single tone situation. Even with a lot of compression, the peak to mean ratio of 'interesting' guitar sounds will be a lot less than unity - you need peaks for an edgy sound.
 
  • #34
turbo
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I rarely ever benched amps with an O-scope or with a multi-meter. My concentration was on replicating tones of iconic amps. As long as the amps were performing well, and I could tweak them to get the right tones, I didn't concern myself with minutia. I built some head-only amps, and combined them with speaker enclosures that were open-backed, partial open-backed, and closed. The closed enclosures got more of my attention WRT to waste heat. Velcro a thermocouple to the the housing surrounding the voice coil (the motor of a speaker) and watch what happens when you crank the amp. I'm a pragmatist when it comes to amp-building.
 

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