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30W RMS 120W peak coaxial 4-way speaker gets warm at 6 watts no distortion?
30W RMS 120W peak coaxial 4-way speaker gets warm at 6 watts no distortion?
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Old 5th January 2019, 09:25 AM   #1
realflow100 is offline realflow100  United States
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Default 30W RMS 120W peak coaxial 4-way speaker gets warm at 6 watts no distortion?

I have a class D audio amplifier powered by a 1 amp 12v DC power supply (cuts off it draws more than 1 amp and tries to restart after a second)
and I have two 30W RMS 120W peak coaxial 4-way speakers hooked up in a ported speaker box and the amplifier is not clipping. they speakers sound clear but I can feel them getting very toasty. all the way up to the cone I can feel a fair bit of warmth from them! and they must be getting only a few watts each and no where near 30W RMS each but they still get warm without clipping or distortion.
If I smell right up to them they smell pretty toasty. smells like heat radiating from a metal surface. no cooked or burnt smell. but pretty warm
I dont know how its possible they can get so warm from 6W RMS each
does anyone have any clue? I know its not clipping because it sounds clean and undistorted at all volumes up to the point the power supply cuts off from overcurrent and restarts itself after a second. if I back it off just a little and play the speakers with a lot of bass songs they get warm after a few minutes and I dont want them to burn up.
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Old 5th January 2019, 11:01 AM   #2
richie00boy is offline richie00boy  United Kingdom
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30W RMS 120W peak coaxial 4-way speaker gets warm at 6 watts no distortion?
Try them on a different amplifier, preferably class-ab. I wonder if your amp has a poorly filtered modulation frequency.
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Old 5th January 2019, 11:56 AM   #3
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by realflow100 View Post
I have a class D audio amplifier powered by a 1 amp 12v DC power supply (cuts off it draws more than 1 amp and tries to restart after a second)
So there is no way it puts out more than 12W DC so no way to get more than, say, 5W RMS into each speaker

Quote:
and I have two 30W RMS 120W peak coaxial 4-way speakers hooked up in a ported speaker box and the amplifier is not clipping. they speakers sound clear but I can feel them getting very toasty. all the way up to the cone I can feel a fair bit of warmth from them!
Not sure it is really happening, you always post about VERY unlikely or plain impossible "problems", but IF happening, it can not be caused by your feeding them way less than 5W RMS, NO WAY.

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and they must be getting only a few watts each and no where near 30W RMS each
my point
Quote:
but they still get warm without clipping or distortion.
no way
Quote:
If I smell right up to them they smell pretty toasty. smells like heat radiating from a metal surface. no cooked or burnt smell. but pretty warm
No way.
Quote:
I dont know how its possible they can get so warm from 6W RMS each
does anyone have any clue?
yes, you are making this up, for unknown reasons.
Lots of similar posts from you.
Quote:
I know its not clipping because it sounds clean and undistorted at all volumes up to the point the power supply cuts off from overcurrent and restarts itself after a second. if I back it off just a little and play the speakers with a lot of bass songs they get warm after a few minutes and I dont want them to burn up.
No way.
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Old 5th January 2019, 12:25 PM   #4
realflow100 is offline realflow100  United States
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I'm not making anything up?? I can feel the cone is really warm near the center when I put my fingers on the surface.
I think the amplifier could be oscillating at a high frequency above human hearing making the speakers get extra hot or something. I don't know any other way it could be heating them up unless the speakers are morbidly over rated
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Old 5th January 2019, 12:47 PM   #5
chris661 is offline chris661  United Kingdom
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Run a 5W resistor up to full power. It gets pretty hot.

Remember, 30W will be a 2-hour survival rating, based on pink noise in free air.
ie, at 30W continuous input, the adhesives will melt (usually well past 100C). Put the driver in a box, and you ought to derate it accordingly. It might only survive 20W long term.

Combine that with "bass music" that can have content that can be sine-wave-like (ie, low crest factor, so lots of heating with minimal peak voltage swing), and I can see why your drivers might get warm.

No surprises here...

Chris
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Old 5th January 2019, 03:08 PM   #6
realflow100 is offline realflow100  United States
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How warm is safe for the coil? is it safe if it gets hot but doesnt cook slowly or emit any smells? wheres the point where its too hot? is it too hot if the cone or dust cap feels a bit warmer than body temperature?
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Old 5th January 2019, 03:29 PM   #7
phivates is offline phivates  United States
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What frequency is your box tuned to?
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Old 5th January 2019, 03:29 PM   #8
chris661 is offline chris661  United Kingdom
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100C will be fine for most adhesives, but it will vary. Decent PA speakers go above 200C before any trouble occurs.

Have you got any way of checking the temperature of the coil itself?

I've accidentally had an FE126E up to the temperature where hot smells start. Still working fine, although I did reduce power levels quickly when I noticed.

Chris
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Old 5th January 2019, 05:18 PM   #9
xrk971 is offline xrk971  United States
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30W RMS 120W peak coaxial 4-way speaker gets warm at 6 watts no distortion?
Check your amp output for DC offset?
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Old 5th January 2019, 05:28 PM   #10
Galu is offline Galu  Scotland
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Quote:
Originally from Loudspeakers-Wikipedia >
"Most loudspeakers are inefficient transducers; only about 1% of the electrical energy sent by an amplifier to a typical home loudspeaker is converted to acoustic energy. The remainder is converted to heat, mostly in the voice coil and magnet assembly."
It is not at all surprising that a voice coil becomes warm!

The voice coil of a bass/mid speaker is air cooled through its vibration so its temperature rise will remain tolerable under normal operating circumstances.

The tweeter voice coil of your coaxial loudspeaker is more at risk of burning out because of its much lower amplitude of vibration.
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