This is regarding a 1993 740il (E32).

I recently purchased a sony cdx-f605x headunit which I am very pleased with.

I bought the bmw harness and spliced the positive, ground, ignition, dimmer, and 12v turn on to the headunit's harness. A website directed me to ONLY splice the positive(+) speaker wires together instead of splicing both positive and negative wires. I think this has greatly reduced my maximum volume. I tentatively spliced all speaker wires together (both + and -) and it resulted in higher volume with lower distortion; whereas with the + splicing causes my maximum volume to decrease significantly along with the distortion which comes with trying to turn up the volume on the head unit. Must I really splice only the + speaker wire to the (+) wire on the bmw harness? Any help would be much appreciated. Thanks!:buttrock

Each + should be wired to its respective channel (left front, left rear, right rear, right front) The negatives for each channel should be connected ALL together but NOT grounded. This is the way it should be done.

If your system responds better (more volume and less distortion) by wiring all + and all - together, (not all together) then wire it that way.

You audio system might or might not be common grounded.

Ah, thank you very much. I will go ahead an wire up the negative wires together (not altogether haha).

93 shouldn't be common ground (which wouldn't really work right with a non common ground radio without an adapter anyways)

Only thing I could possibly see if there was an amplifier, and the +'s were seperate and there's only one - that's shared, but still, if it worked well hooked up traditionally (which all the 740's I've done have been) than leave it hooked up that way.

Thanks for all the input guys! I wired it all up and it sounds GREAT! I really do love this headunit, even more than my alpine 7998! The interface is clean and simple with all the customization features I need, along with the 24bit burr brown

Hey 7IL,
How did you wire up the harness? I have a DSP system in my 95 IL and I cannot figure out how to wire my harness. I can wire the pos and neg and amp turn on and memory but my harness has no speaker leads that I can see. Is yours DSP?

Most DSP that I've seen you have to do a full rewire (run new speakers wires from the HU to the individual speakers). That said I have not done a system in a 7 series DSP car.

Most DSP that I've seen you have to do a full rewire (run new speakers wires from the HU to the individual speakers). That said I have not done a system in a 7 series DSP car.

Why would you run new speaker wires instead of using stock? Simply put your crossovers where the amp used to be and use the existing factory wiring...

Doug

Why would you run new speaker wires instead of using stock? Simply put your crossovers where the amp used to be and use the existing factory wiring...

Doug

its just recommended that you always run new speaker wire due to the strange noises you may get, plus the wires are cheap!