modifying factory sub/amp to aftermarket

kenhoeve

Junior Member
First post, let's see how this goes.

My car came with a factory sub installation that includes a separate amplifier(12" sub and 150W RMS amp). This installation mounts in the rear cargo hold above the spare tire. The existing harness to run the setup contained power, ground, line level taps to the rear speakers, and remote. I re-used all these connections except the remote which went to ground instead of +12v. I solved this by running an accessory lead to a power source up front that is switched, problem solved.

I used an Alpine MRP-M450 mono amp (220W RMS @4ohm) with a RockfordFos P3SD410 10" low profile sub, and mounted the sub into the existing sealed enclosure. I modified the enclosure to increase the volume to 0.5cuft. The amp accepts the line levels from the rear, so I hooked up both L and R.

I fired everything up after install and adjusted gain, eq, and crossover. It all seemed fine on bass heavy tracks. I have the cross set to 85hz. The problem I am having is the audio quality is not good. There is obviously some large holes in the frequency curve. Some tracks will even suddenly have a loud bass response that is suddenly clipped... not good. However, other tracks seem to play decently even if some frequencies seem missing.

The factory head unit is passive, all speakers are amp'd. It does have dolby PL, but I do not use that setting, it's obviously garbage.

Does anyone have any suggestions on where to start trouble shooting? I'm inclined to think it has something to do with the line level feeds, but the factory amp was fine with them so not sure. All connections are good shape and very accessible. Thanks for any help. Cheers. Here are some pics of the setup.

IMG_1363.jpg


IMG_1362.jpg


 
The correct answer was disconnect one of the channels of the line level feed. I know RCA only takes one side, but since the previous took L/R and the amp had feeds for both, I used them. Not sure why it doesn't work with a different amp. Anyway, wow, huge improvement. The rockford is really tight, just need to do some dynamatting and this might be the best stock stereo out there. Oh, waiting on the JBL eq though, but then it won't be stock except for the HU.

IMG_1360.jpg


IMG_1358.jpg


 
Activity
No one is currently typing a reply...
Old Thread: Please note, there have been no replies in this thread for over 3 years!
Content in this thread may no longer be relevant.
Perhaps it would be better to start a new thread instead.

About this thread

kenhoeve

Junior Member
Thread starter
kenhoeve
Joined
Location
OC,CA
Start date
Participants
Who Replied
Replies
1
Views
722
Last reply date
Last reply from
kenhoeve
IMG_20260516_193114554_HDR.jpg

sherbanater

    May 16, 2026
  • 0
  • 0
IMG_20260516_192955471_HDR.jpg

sherbanater

    May 16, 2026
  • 0
  • 0

New threads

Top