Subwoofer Amps, Watts. Etc

[jackf]

I'm exploring adding a powered subwoofer to my 73 coupe to improve the sound. I'm currently running a modest Alpine head (60-80 watts?) through two 6 x 9 speakers in the package tray and a dual cone speaker under the dash. I also have a classic auto air air conditioning system installed. My question is, can I safely run the sub-woofer with the stock 55 amp, externally regulated alternator? Most of these powered subs have a 10- or 15-amp fuse, so I assume the max draw is less than that, but they all require eight- or ten-gauge power wires, which has me a little concerned. Any advice from the electrically minded would be welcome. Thanks as always.

 

[tony-muscle]

I think you need to look at amp draw, which is related to watts power, in combination to its distance from the battery and an acceptable voltage drop.
A good target is about 3% voltage drop, but you can certainly go to 5% and still would work. That said, for a wire length less than 10 ft, for 10-15 amps, 14 gauge should work. As you say the draw won't be 15 amps all the time so 14 gauge should work for a short distance.

This is a quick source for a wire size calculator: https://www.wirebarn.com/Wire-Calculator-_ep_41.html


This is a quick source from https://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/

 

[Bentworker]

I think you would be fine with 600 watts or less. The amp is only going to draw what is needed to output the desired power. Most of the time it will be drawing a fraction of 600 watts. That being said size conductors and fuses for max load.

Here is a good visual from a music festival (in Thailand?). It is powered by some gigantic diesel gen set that does not have a diesel particulate filter. The plume of soot gives a nice visual of the power spike.

Watch the diesel generator in the background of this video.