Originally Posted by proprone
what does a crossover do, exactly?
Its mostly for older decks without built in cross-overs.
In older decks they only had one set of pre-outs, which wasn't good if you planned on running a multi-Amp system. The cross-over also splits up the audio signal and give you additional Highs, Mids, and Lows (Sub) pre-outs that would then goto an amp.
If a deck didn't have a built in crossover and the preouts were plugged into an amp (again without a built in crossover) you would hear vocals coming out of your sub, which you dont want. You want only the low frequencies (hence some amps have built in low pass filters)
Cross-overs are becoming less and less popular bcus most decks and even amps come with built in cross-overs.