ATC uses analogue crossovers, as do Focal and few others. Other school of thought is use of digital crossover implemented in DSP, which gives more flexibility. But DSP has inherent limitation in precision of DAC they use. Common setup even for speakers with digital input assumes that volume control precedes crossover logic. When volume control is implemented digitally, audio stream looses resolution (1 bit for every 3dB of power below maximum), That can have negative impact on sound. Analogue crossover adds dither due to natural noise of the circuit. This is why active speakers better have volume control AFTER digital crossover or be fully analogue. This difference may explain why some active speakers sound better than others.
Active Speakers Don't Sound Better
I just wanted to settle a debate that has often raged in A’gon about active vs. passive speakers with my own first hand experience. I’ve recently had the chance to complete a 3-way active center channel to match my 2-way passive speakers.
I can absolutely say that the active nature of the speaker did not make it sound better. Or worse. It has merged perfectly with my side speakers.
What I can say is that it was much easier to achieve all of the technical design parameters I had in mind and that the speakers have better off-axis dispersion as a result, so it is measurably slightly better than if I had done this as a passive center. Can I hear it? I don’t think so. I think it sounds the same.
From an absolute point of view, I could have probably achieved similar results with a passive speaker, but at the cost of many more crossover stages and components. It was super easy to implement LR4 filters with the appropriate time delays, while if I had done this passively it would require not just the extra filter parts but all pass filters as well. A major growth in part counts and crossover complexity I would never have attempted. So it's not like the active crossover did any single thing I couldn't do passively, but putting it all together was so much easier using DSP that it made it worthwhile.
I can also state that as a builder it was such a positive experience that I may very well be done with making passive speakers from now on.
All the best,
Erik