I've been running my Ella speakers in active mode for a while now, using a pair of upgraded Dynakit VTA ST70's built by Bob Latino for the mids/highs, an audio-gd fully differential solid state C1 amp on the bass, and a highly modded DCX2496 (by mgalusha) as the active crossover with frequency response EQ and room correction built in. I also used a Mapletree 2a SE Octal based tube preamp, and a NOS Havana DAC for a source, with a USB Thingee doing USB-SPDIF conversion from my PC based playback system.
You can see my build of the Ellas in this thread, warning though, there's lots of pics: http://www.audiocircle.com/index.php?topic=73155.0
With an active system, it's critical that you have a good calibrated mic and measurement software. I have a Behrenger mic that was individually calibrated for me, and I use the HOLM Impulse measurement software with a USB based M-Audio preamp hooked to my laptop. The Journey
I was very happy when I went from passive to active in my speakers, the overall dynamics, clarity, ease, and coherency all took a major step forward, especially once I figured out the measurement software and got them dialed in very well. The modded DCX I was using is very nice in that it lets you set any crossover point, and use almost any crossover slope. It even lets you use asymetric slopes (or no slope at all). As a means for really dialing in a sound you like, and having almost god-like power over your speaker's output, it's unsurpassed. And the mods that mgalusha did on it took it from a good sounding piece to a world-class sounding unit.
One thing I discovered as a listened, is that I'm fairly sensitive to phase and timing errors. When I used lower slopes with less phase and timing errors, I liked it better. Using higher order slopes sounded "cleaner" in the short term, but I found them fatiguing in the long term. I lived with my speakers using 2nd order Linkwitz Riley filters very happily, for quite a long time.Enter the DEQX
Then I heard about the DEQX, which does most of the things the DCX does, but takes it a step further. It measures (and corrects) phase and timing errors within a single driver, it does the same thing with very steep crossover slopes, giving you the option to do (for example) 96db slopes that are phase and timing perfect. It time-aligns all of your drivers. It measures and corrects group delay.
I started reading about the unit, and I was very intrigued, but at close to $6k for the unit that I wanted, it was out of reach. Then I saw the exact unit I wanted come up for sale on audiogon for half the new cost. I figured I should at least try it, and if it didn't work out, I could sell it for exactly what I paid for it. On the other hand, if I did like it, I could then sell my much-loved DCX, MHDT Havana, and Mapletree 2a SE.Arrival and Setup
First thing to note is that the HDP-3 is FAR more advanced and better built/engineered than the previous 2.6 model. Gone is the crappy digital power supply, a very good analog linear supply is there now. The balanced outputs on it use super high quality Jensen output transformers. The grounding has been improved. The DACs are much better. The op-amps have been seriously upgraded. The Chassis is more robust and befitting of a truly high end piece of equipment.
After making all the connections, installing the measurement software, and hooking up the DEQX via USB to my laptop, I spent quiet a lot of time reading the 200 page manual. Yes, 200 pages. And you need to read all of it. This thing is amazingly flexible and powerful. But there's a lot of ways you can screw it up. So read the manual. Grok the manual. Once you have, you are ready to proceed. Hook up your microphone, put your speakers in the center of your room, elevate them 3 feet off the floor (this is all to avoid reflections and floor bounce) and start measuring.
After a few sweeps, you are done with the individual driver measurements. Next, you configure the crossover points and slopes, instruct the unit to correct for phase, group delay, and time alignment. The slopes are calculated, all the corrections are calculated, and then it has you do more sweeps to verify that the output actually matches the input and all the corrections.
Finally, put them in their normal spots in your system and run more sweeps for room correction. Once this is done, you are ready to rock and roll!Impressions
The DEQX is LOVELY! It's a bit of a pain to take the initial measurements (have to move the speakers to the center of the room, and elevate them 2 or 3 feet off the floor). But, once the measurements are done, you can set the speakers up any way you want. I've loaded 3 different crossover slopes and points at a time in it and can toggle between all 3 in real time. Then I can keep the one I like best and try out a couple of new slopes/points. It's letting me very quickly cycle through the settings to end up with the best sound.
Moving from the DCX to the DEQX, the biggest improvement (IMO), is getting perfectly flat frequency response. That alone makes the whole listening experience more relaxed and pleasurable. Your ear/brain is no longer having to "work" to fill in gaps in the presentation. The DCX was very good, and got me much closer than any other crossover/speaker setup I've heard, but it is limited to maybe a dozen or so points of correction that you can do before it runs out of CPU. With the DEQX, you have a thousand points available for correction. That level of granularity is a big improvement in what you hear.
The second big improvement is phase correction and time alignment. That just moves the whole sound out of the "digital" realm and gives a very relaxed, analog type presentation. Of course, this is the HDP3, which has things that the old 2.6 does not, like a much better power supply (linear analog instead of digital), better op-amps, better grounding, and balanced outputs using Jensen transformers. So it's going to sound less digital than the 2.6 for those reasons as well.
Mine's still breaking in, since the guy I bought it from had it upgraded from the 2.6 to the 3.0, but never actually used it due to a change in living conditions/space. But I can say this - for the first time in a while I'm able to just kick back and enjoy the music and not feel the need to fiddle with everything with each new recording. It's the most non-digital sounding system I've ever heard. To me it sounds perfect, it sounds closer to how music and voices sound in real life.
I'm able to enjoy my old Billie Holiday, Louis Armstrong, and mono classical recordings much more than I ever have, on any of my systems. The DEQX is the real deal, especially if you use it fully active and can take advantage of the super steep slopes and phase correction.
In fact, right now I'm listening to a recording of Rachmaninov playing his own piano concertos from the early 40's. I've had this for a long time, and I've always respected the performances, but I've never loved them. I have now fallen in love with them, thanks to the extra color, emotion, passion, and beauty that the DEQX lets through. And when I listen to more modern recordings, like the difficult Eva Cassidy recordings, or the superb Patricia Barber recordings, it just gets better and better. Conclusion
I got it for a steal, but I still have to (reluctantly) sell the modded DCX, the Mapletree, the Havana, the Scott Nixon, the USB Monica, and the Bolder modded Duet to recoup my investment. I'd prefer to keep these pieces around for a second system, but finances dictate that they must go.
The upside is that my system is MUCH simpler now, with way less cables and junk in my AV cabinet. And I'm re-discovering a bunch of music that I'd shunted off to "poor recording" land a while ago. How cool is that, an upgrade that lets you enjoy more of your music collection, not less! It's the opposite of those pieces of hi-fi gear that "show you how bad this recording really is". Instead, you can hear that the recording is not perfect, but the DEQX presents it in the best possible light. Or, put another way, it shows you what there is to love in any given recording, and does not focus on the things to dislike.