# Automobile Speaker Voltage

1. Jun 20, 2007

What voltage do car speakers typical run at?

2. Jun 20, 2007

### chroot

Staff Emeritus
That would depend upon many things:

1) The size of the speakers.
2) The efficiency of the speakers.
3) And most importantly: the position of the volume knob.

- Warren

3. Jun 21, 2007

### rcgldr

Typical car speakers have an impedance of 4 ohms, but multiple speakers could be wired up in parallel (reducing impedance) or in series (increasing impedance) or a combination.

Power = voltage^2 / impedance.

I assume that for sound, the voltage is the RMS average output of a sine wave like signal. This is .707 times the peak voltage, so a 4 volt RMS ac source has voltage peaks of + and - 5.657 volts.

Code (Text):

Watts per channel versus voltage:
0.25 watts = ( 1 volt )^2 / 4 ohms
1.00 watt  = ( 2 volts)^2 / 4 ohms
4.00 watts = ( 4 volts)^2 / 4 ohms
16.00 watts = ( 8 volts)^2 / 4 ohms
64.00 watts = (16 volts)^2 / 4 ohms
100.00 watts = (20 volts)^2 / 4 ohms

4. Jun 21, 2007