DIY speaker wire: does insulation matter?

what kind of voltage are speaker wires subject to?

You can calculate a reasonably good approximation of that based on the relation P = (E^2)/R. Power (in watts) = Voltage (in volts) squared divided by Resistance (in ohms).

So the maximum voltage would be the square root of the maximum power that would be fed to the speakers times their rated impedance.

That is an approximation because speaker impedance is not purely resistive, and is not constant with frequency, but it should be good enough for your purposes.

Also, however, power in this context is usually specified as rms rather than peak, so the calculated voltage would be rms also. If you want to know the worst case instantaneous voltage more precisely, to assess insulation requirements, multiply the worst case rms result by 1.414 (the square root of 2) to get the corresponding peak voltage.

Regards,
-- Al

Re voltage levels, I had my calculator handy and I did a representative calculation. 200 watts into an 8 ohm speaker corresponds to 40 volts rms (root mean square) or 57 volts peak.

Regards,
-- Al

You're welcome! 75W into an 8 ohm speaker would be only 24Vrms or 35Vpeak.

By "dc" CPK meant "dielectric constant," which is proportional to the capacitance the cable will have, and the amount of "dielectric absorption." Thicker insulation will also increase capacitance, everything else being equal, and thinner insulation will reduce it.

My own feeling is that as long as it is within reasonable limits capacitance in an 8 foot speaker cable is not especially critical. It would be more important in an interconnect cable, because of the much higher output impedance of the component driving the cable. The opinions of others may differ on this, and I readily acknowledge that other factors, known or unknown, might in some systems make capacitance more important than I am envisioning.

Enjoy your project!

Regards,
-- Al