E30 Zone

The head unit only has remote amp outputs for the rear speakers which current the setup.

Can these be used instead to power a pair of subs and reconnecting the rear speakers to the head unit or is there a better way without replacing everthing?

you can send the rear output signal to a active crossover unit, which will in turn send the correct frequencies to the sub amp , and the amp for the rear speakers. you wont be able to fade between the front and rear without fading the rear and sub together.not a big deal though as you can adjust accordingly anyway.

alturnativly if your happy just powering the speakers using the headunit inbuilt amp, then just send the rear signal RCA output direct to ther sub amp, and cross it over on the amp, if the amp has no crossovers and you cant control the crossovers for the rear channal via the head unit then dont run it at all otherwiser you will be sending full signals to the sub whcih will only be designed to play low frequencies..

hope this helps.

Also worth pointing out that amping both the sub & speakers (& the fronts too, preferably) is miles better - almost any amp will sound far better than the tiny things built into headunits. But you knew that...

Virtually all amps have some kind of crossover built in don't they? Just use an RCA splitter to effectively get another pair of outputs, if you don't want to fork out for a separate crossover.

Didn't think of an RCA splitter, thats what I'll do for now as I have a spare amp and both have inbuilt crossovers.

Thanks for the advice