subwoofer not as loud

[wraith]

Might be assuming that nothing has changed. Had the same thing before customer adamant the stereo still had the same settings since they swapped into another car. Looked at it. Nope factory settings.

 

[AmmoJammo]

make sure the positive wire on the amp isn't connected to the negative on the sub/terminal
make sure the negative on the amp isn't connected to the positive on the sub/terminal

if you have taking the sub out of the box, check them wires to (sub to terminal)

i have done that once and the sub was moving alot but no sound ^

reversing the phase of a single woofer on its own won't result in no output.
but reversing the phase of one woofer out of a pair, either sharing a common chamber, or even in separate boxes, will result in cancellation.