There are equalizers and there are crossovers. Both are separates, yet have very different aims.
An EQ takes the audio signal and modifies it with user controllable options, like adding or subtracting the level of certain frequencies. The output of an EQ is always the same as the input, stereo.
An electronic crossover is different than an EQ. The goal of the crossover is to separate frequencies and feed the divided signal into separate power amplifiers. The output of the amps are connected to the drivers in a speaker: tweeter and woofer in a 2-way.
Electronic crossovers are rare. You see them built into subwoofers, but not so much as standalone boxes anymore.
I suppose that's because their appeal must be more focused on the DIY crowd rather than the person who just wants a speaker plopped down in their living room. And that is, of course, what most of us want.
Of those you can buy today, the majority I see are digital. Careful. If you're even thinking about a DIY project where you need an electronic crossover, try and stay with analog if you can.
Once you enter the world of digital, it's a sonic can of worms you probably don't want to open unless the manufacturer really cares about sound quality. Hard enough for those of us that know what good sound is to make A/D D/A come out without too much loss. Throw that requirement at a textbook-focused engineer and he'll have you a circuit in less than a week - and whatever benefits you might have hoped for vaporize into poorly executed digital chains.
Tomorrow let's look at one of the more famous of the great electronic crossovers.
