So I bought a new truck about a year ago and it had a subwoofer installed that never worked. I finally decided to see if I could fix it and get it running again. Turns out it was a terribly installed system and after lots of fault finding and fixing I finally got the whole system running but with very little coming from the bass and it was very rumbly sounding. I realized it was an 125w amp to power a 600w speaker. After that I ordered a larger amp (600w) to properly power the speaker but I basically have the same result...
Not really sure where to go to from here.
Speaker should be working fine (4ohms of resistance as expected)
The amp has the correct amount of current (12.something Volts)