Are caps rated at 50V adequate for using in series in a crossover? I've stumbled across some polycarbonate film caps I'm dying to try in series with my tweeter but they're only rated to 50V. I've never seen film caps rated less than 100V
Yes, a 50V bipolar rating is pretty standard for a tweeter capacitor, and allows for 100V peak to peak,
or 150W into 8 ohms. Also check the current rating. Metallized film capacitors have much less
current capability than film/foil types, and some may be inadequate.
or 150W into 8 ohms. Also check the current rating. Metallized film capacitors have much less
current capability than film/foil types, and some may be inadequate.
Last edited:
Well, at 30 watts power into an 8 ohm speaker, you need ~22 peak AC volts; less voltage (more current) for a 4 ohm speaker. So I'd say a 50 volt rated cap would be just fine. And, BTW, it's NOT a dumb question!
Power rating on even a tweeter circuit is very important, just as important as voltage rating. Capacitors that are expose to higher current levels will run hot, and most likely be damaged. I made that mistake once, and started to notice the sound quality from the tweeters was deteriorating and distorted in a really irritating way. Replacing them with the proper cap fixed it immediately.
Mike
Mike
Yes, their core temperature (like semiconductors) climbs higher and remaining useful lifetime (RUL) starts running out much faster due to the increased stress. Besides, smaller voltages across a capacitor with larger rating is best for linearity, even for film capacitors.
And I agree with dotneck, it's definitely not a dumb question, but an important point to be taken care of.
And I agree with dotneck, it's definitely not a dumb question, but an important point to be taken care of.
the formula to calculate volt RMS from speaker is V = sqrt(P * R) where P is the watt and R the (nominal) impendance of the speaker. So it's about 22v AC like said above. For the voltage needed for your cap, it's best to double that (headroom/safety) so i would say a 50v cap (as 44v caps hardly exist) or higher is suited.
I made some calculations with different caps in a tweeter circuit. All are 4,7uF, the film types are 200V and the bipolar electrolytic has 100V nominal, 35Vrms.
20Vrms 20kHz 100W continuous into a compression driver that is heavy duty
bipolar 2.10€ tan delta 0.1 heating loss 23.6W will explode (even if the loss goes down with frequency)
MKT 1.95€ tan 0.01 loss 2.3W also too much
MKP 2.50€ tan 0.004 loss 0.09W
https://www.tdk-electronics.tdk.com...1513474ba/pdf-generaltechnicalinformation.pdf
20Vrms 20kHz 100W continuous into a compression driver that is heavy duty
bipolar 2.10€ tan delta 0.1 heating loss 23.6W will explode (even if the loss goes down with frequency)
MKT 1.95€ tan 0.01 loss 2.3W also too much
MKP 2.50€ tan 0.004 loss 0.09W
https://www.tdk-electronics.tdk.com...1513474ba/pdf-generaltechnicalinformation.pdf
Last edited: