Originally Posted by my530i' post='254056' date='Mar 13 2006, 01:37 AM

OK, before upgrading L7 sound system, let's analyze it first to see what we can do.
L7 consists of (7ch x 40w for mid and high) + (2ch x 70w for two under seat subs)
Upgrading can be done by just upgrading amps for two underseat sub or the whole system.
For upgrading bass only, you can buy any 300w two-channel amp and replace two underseat subs with Earthquake SWS-8 (150W RMS). These two subs are more than enough for your rattling your seat and license plate. SWS-8 is the only aftermarket sub that can be replaced E60 underseat subs perfectly w/o modifying anything. If you want to go with this, grab sub output signals from amp in the trunk and feed it to the 300w amp. If you buy amp with no speaker level input, you need to buy line-out converter to convert speaker level down to line-out level and feed it to the amp with RCA wire. Upgrading subs only will minimize noise injected into your sound system because signal wire does not travel far from the trunk.

If you want to upgrade the whole system, I would recommend you to replace existing speakers with MB Quart QSD for $99/pair first before adding an amp because RMS of MB Quart match well with L7 RMS. Adding amp to drive high and mid speakers will easily induce engine noise, and I wouldn't recommend.

You can go to the www.the12volt.com to see professional installer asking questions on how to eliminate noise. Search for keyword "noise".

Let me know if you have any more question.