BMW 5-Series (E39) Audio System Upgrades

UPGRADE I. Our first upgrade will address the biggest shortcoming of all the stock BMW sound systems, BASS, or lack thereof.
Correct speaker level wiring diagram for interfacing with factory head units.
Use only positive (+) speaker wires. Tape off negative (-) speaker wires. Connect “+” speaker wires to RCA center pin conductors. Tie shields (audio return) together and ground to case of radio at back of radio. Repeat for 4 channel system.
Use of an a/d/s/ AC502 remote subwoofer level control will allow us to control the volume of our subwoofer from the front of the car. How convenient! This way, we can match the bass level to our own personal taste or to compensate for bass masked by road or wind noise.
Our subwoofer could be the same one we chose for Upgrade I or something more.
The entire system will be powered by an a/d/s/ amp, and will use an AC502 for remote subwoofer level control This BMW system is going to sound dynamic, smooth, and musical, yet still maintain totally stock cosmetics inside the car.
Given the interior dimensions and solid build quality of the BMW 5 Series, we’ll have one excellent sounding audio system that will rival many home systems for sonic quality, and we’ve still maintained absolutely stock interior cosmetics for that low profile look. This is especially important if the car in question is leased, because even at this level of sophistication the car is easily returned to stock at the end of the lease term.

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