Why aren't component active XOs more popular?

Suits me: I've recently been talking to a couple people that are attempting to run active crossovers on commercially built passive speakers. The more that they dig into it, the more that they realize that this is going to be a lot of work. As such, i agree that most multi-way designs with complex crossovers are best either left alone OR simply upgrading the passive circuitry that's already there with higher grade parts. Sean
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Thinkat and Serus summed it up. It is both more difficult and more rewarding if one puts forth the effort required.

As far as the "purists" go, i don't know of anyone that has heard a well designed actively crossed system that would choose a passively crossed system as being sonically superior. My brother was running custom built speakers with very simple crossovers using high grade parts and passively multi-amping. After i kept badgering him to try actively crossing them, he could not believe the difference.

Bare in mind that the huge increase in sonic performance that he noticed was achieved via an antique "pro sound" crossover that i had purchased years ago for less than $50 shipped. If one were to use a more advanced and better sounding crossover that allowed both time constants and contouring to be included in the processing, the benefits would be even greater.

As mentioned above though, the time and effort involved is a LOT more than what most audiophiles want to do. This approach is best suited for those that want to get their hands dirty and learn i.e. DIY rather than keep buying the flavour of the month and never understanding why things don't work like they should. Quite honestly, i've never seen a commercially designed product that wasn't built to a price point, regardless of the retail price. Sean
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Suits me: Have you ever seen serious test results from most "audiophile" speakers? The mass majority aren't nearly as well designed or integrated as one might think. "Audiophile grade" loudspeakers are one of the highest profit margins out there ( outside of cabling ) with the least design integrity behind them. That's why DIY speakers and forums discussing such things are so ripe for the picking with useable information. As such, experimentation in this area can typically result in steps forward in both sound and one's sonic education. So long as any "modification" is easily reversed, there's really nothing to lose here other than pre-conceived notions and an education about modifications that many consider to be "taboo". Sean
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Serus: As mentioned, my Brother went from using a 6 dB per octave passive crossover using very high grade parts in a passively crossed multi-amped system to an "antique" active crossover that was used professionally and beaten to death. After hearing the difference for himself, he pulled all of the passive parts and bought an active crossover. Bare in mind that his initial testing was done just listening to a tweeter with a cap in series vs the tweeter actively crossed at 6 dB's. Not only were the differences HIGHLY audible using even a "low grade" active crossover, there are measurable differences in amplifier performance and efficiency involved in such a situation too.

Factor in that most dynamic tweeters are far less demanding of a load on an amp as compared to a large dynamic woofer and the benefits would have been even more apparent at low frequencies.

You have to remember that the passive crossover is dealing a high level signal from the amp and the reflected EMF of the drivers simultaneously. When you use an active crossover, the efficiency of the amplifier is markedly increased due to the reduction in bandwidth. That is, the amp is no longer trying to reproduce power that ends up getting "wasted" in a passive multi-amp system. The end result is that transient response is improved, distortion is lowered, thermal stress is reduced, etc... Speed and clarity is improved in every respect. The fact that the active crossover is dealing with miniscule amounts of line level voltage whereas the passive crossover circuitry is dealing with both much higher levels of voltage and current should explain why the whole system sounds "more stressed" once those parts are introduced into the equation.

On top of that, the amp doesn't see the added reactance and phase shifts of the passive circuitry as part of the load as the amp is now in "direct drive" mode. That is, the amp sees the nominal impedance of the speaker cable and the electrical characteristics of the driver itself. As such, it is a "purer" load for the amp on top of the added benefits of active bandwidth limiting mentioned above.

Granted, some specific amp / speaker combos may sound better with a passive crossover, but that is typically because the amp itself isn't up to the job at hand. Then again, getting rid of all of the other "garbage" between the amp and the drivers themselves can also be the difference between an "inadequate" amplifier and a "good" amplifier in such a system for the aforementioned reasons. It can be a tough situation, but as mentioned elsewhere, if the drivers are good units and well-matched to begin with, anything other than an active system will degrade the sonic potential of an otherwise excellent set of speakers. Don't believe me? Try inserting a cap in series with your tweeter and see for yourself. Sean
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