QUOTE(Andy Westcott @ Nov 5 2007, 09:59 PM)

Electronic crossovers I've seen have outputs for low and high anyhow, so no need to miss out on this advantage.
Assuming for the moment your tops do have a built-in crossover, you could still clip the amp, and therefore introduce distortion, due to bass signals being fed to it, even if the speakers aren't using these signals. (may sound odd to some, but be assured it's true.) Far better to keep the whole mid/top chain free from bass signals. This has to be the biggest advantage here.
i see. the speakers are class d jac 15, so best to use a x over all round when using the subs ,ta