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What do you think is a good maximum temperature for the voice coil?
What do you think is a good maximum temperature for the voice coil?
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Old 13th March 2020, 02:14 AM   #1
guferr is offline guferr
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Default What do you think is a good maximum temperature for the voice coil?

I have a 10'' sub that I rebuilt using market parts, but there is no info about power rating of the coil. Even why, the actual power rating will depend on how well the coil will be able to dissipate heat during operation.

So I thought of installing a thermocouple in the top of the voice coil and connecting it to a thermometer outside the enclosure, so I can read the temperature in real time.

This temperature, however, is not going to be the actual wire temperature, but the temperature of the aluminum foil.

I think this might be even a better measurement, because I suspect the first problem that is going to happen is the deterioration and softening of the epoxy resin that holds the cone, the coil and the spider together.

I know that, by the temperature limit of the epoxi resin, it needs to be at max 100 C, but I'm not sure about other stuff like the paper cone or poly cone (If I decide to rebuild it again). And even if I find some info online about their limits, they rarely will be considering a operating regime of constant stress and vibration.

So, what you'd say is a good temperature for me to set as a operating limit?

Thanks!

Last edited by guferr; 13th March 2020 at 02:18 AM.
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Old 13th March 2020, 12:47 PM   #2
MAAC0 is offline MAAC0  Portugal
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There are PA speakers working with temperatures up to 300.
They usually use kapton for the voice coil former.
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Old 13th March 2020, 02:11 PM   #3
kipman725 is online now kipman725  United Kingdom
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you could buy a re-cone kit and find out
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Old 13th March 2020, 10:47 PM   #4
Mark Tillotson is online now Mark Tillotson
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Thin film thermistors are worth considering as sensors for this too.
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Old 14th March 2020, 02:27 AM   #5
SamAnytime is offline SamAnytime  India
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Any sensor is going to alter the properties of the speaker, e.g. the weight of the sensor will increase the effective mass of the cone, and the stiffness of the connecting wires will mess with the compliance.



There are temperature indicating paints both non-reversible and reversible, and thermochromic thermometers based around them. These might be less disruptive.


Infrared thermometers would also be useful if there is line of sight to the heated element.



Maybe you could use the DC resistance of the coil itself to measure its temperature. You could rig up a test button to supply a calibrated test tone to the speaker and a circuit to measure the current (before the coil starts cooling down when the main drive signal is replaced by the test tone). Tracking the coil resistance in real time while the speaker is playing actual music is going to need some serious computing power, I would assume.



http://www.diva-portal.org/smash/get...FULLTEXT01.pdf
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