So I'm not new to car audio, but I'm new to the fine tuning. Years ago, I'd wire a sub to an amp and be done with it.

Now, I've found that it's a little more technical than that. Here's my issue: I'm doing the 'gain setting,' and I'm not sure how to calculate the target voltage. I read somewhere that when you run a dual 4ohm sub, you have the double the target voltage, but I'm not sure if that's true or not. The target voltage of my current sub amp is 43.8@ 4ohms, 42@3ohms and 40@2ohms. I'm running an old JL 12W3v2, dual 4ohm sub. I have it wired in parallel, so I can bring it down to 2ohms. Does that mean that my target voltage is now 80? My brain is going to start spilling out of my ears.

Edited April 11, 201015 yr by e5r0311

You are making it more difficult than it really is. If you are trying to set your gain with a DMM, then the formula is;

sqrt(Power * Resistance) = Voltage

So if you have an amplifier that is 800w @ 2ohm, you would have;

sqrt(800 * 2) = 40V

The other option is to say screw the formula and just set the gain by ear. Considering 800w is way more power than a single 12w3v2 will be able to handle (based on the voltages you mention, it appears you have an 800w @ 2ohm amplifier), setting by ear is probably the best method anyways.

Or, if you really want to use the formula, you could use 300w (the rated power handling of the subwoofer) in the formula instead of the amplifier's power;

sqrt(300 * 2) = 24.5V

You can use that as a "baseline" and then adjust by ear from there.

...Considering 800w is way more power than a single 12w3v2 will be able to handle ...

Now why oh why would I ever want to blow my sub? Because then I wouldn't hear quite as much complaining when I haaaaaaaaaaave to buy a new one

Other than that, thanks for the input. I was very confused, and now I'm not. Cheers-

Just due what the rest of us men do......hide the new sub from the wife and install it when she's not home so she never knows

That's one of the foundations of this hobby.

This ^

My wife don't even ask anymore. The joys of seperate checking accounts. Learned that lesson the hard way with my first wife. Lol.