in the e46s and e83s there is a combination of both active as well as passive.

The amps will have some crossovers built in to filter our the mid bass/mid range and there is a cap to filter the tweeter from the mid range.

I'm assuming the e53 will have something similar but if your amps have been removed then you should only be dealing with a full range signal coming from the Xtron.

Do you have any amplifiers or the speakers just straight wired to the Xtron?

Is there any crossover settings in the Xtron you can adjust?