I'd have to disagree about all speakers being powered. Stuffing an amplifier into a speaker cabinet imposes restrictions with regards to heat and noise that are simply not an issue with a self contained unit that can fit into a rack. Add to that the fact that electronics generally don't like sustained mechanical vibrations (such as those produced by a speaker and transmitted through the cabinet) and you can see where I'm coming from. But the idea of active crossovers and digital equalization? Absolutely. The best possible integration without phase issues can be had with active crossovers. Phase Technology DARTS system is a move in the right direction, imo. The speakers are passive, but utilize an active crossover system that resides in the rack with the rest of your gear. While it might not be up to my standards for true high-fidelity reproduction, I think the concept is great.
But on the subject presented by the OP, the better quality you have heard is most likely due to the reasons put forth by other posters. That said, Abbey Road Studios uses B&W 800D speakers for their monitors. They're not powered, but the speaker itself possesses a flat frequency response, no audible cabinet resonances, and sufficient off-axis response to be useful in a near-midfield environment like a studio control room. A powered speaker is not necessarily higher quality than a passive one. In fact, many powered "studio monitors" are as colored and NOT high-fidelity as any home speaker. The monitors from ADAM are a favorite example of mine. The cabinet resonance colors the midrange to the point that it's laughable, yet they are considered to be quality studio monitors. Maybe that's part of the reason a lot of modern recordings sound like garbage...(that, and the obsession with the compressor as a tool to be used for good sound).
