Review: DEQX HDP-3 Preamp/Processor/Active-Crossover

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Tyson

Setup
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.
« Last Edit: 14 Feb 2010, 07:54 pm by Tyson »

Pez

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #1 on: 12 Feb 2010, 10:37 pm »
I like how you left out the part where you called a buddy of yours and he helped you move your heavy bastard speakers to and from various spots in your house and lifted them onto chairs to get better readings, that part of the DEQX seriously sucks.  :lol: I am so far impressed with the extent to which the DEQX can be tinkered with. I find it absolutely astounding how much data it can crunch and the customization. If I had to explain the difference between the DCX and the DEQX I would have to say this, Educated guesstimation vs software based exacting measurements. Although a lot of the same sort of thing can be theoretically achieved with the DCX the odds of a user (even a very pro user) of getting it as close as the DEQX is pretty much nil. Good stuff!

BPT

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #2 on: 12 Feb 2010, 10:48 pm »
Had a HDP-3 on loan for RMAF. Nice---these are the real deal. Tyson--you're suppose to take your speakers outside and mount them on a high pedestal for measurement. :D
Chris H.

Pez

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #3 on: 12 Feb 2010, 10:53 pm »
Chris,
That is what I told him, unfortunately Tyson lives on the 5th floor in a condo. I said we should take the speakers out to his patio at 3am and run test sweeps at high SPLs, but for some reason he didn't want to.  :lol:

Tyson

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #4 on: 13 Feb 2010, 08:05 pm »
Haha, funny guys :D

I wish I had a yard to do this kind of stuff (and a garage for building other stuff), but that will have to wait a while, alas.

JohnR

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #5 on: 14 Feb 2010, 04:02 am »
Great review, interesting to read the comparison with the modded DCX too.

:thumb:

JoshK

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #6 on: 14 Feb 2010, 04:15 am »
Very nice review.   I have an HDP-3....one minor correction.  Not all HDP-3's come with Jensen transformers.  That was an option.   I opted out in mine and I have 6 Jensens already for a lot less than the upgrade price.  I believe that was part of the tranformer/balanced upgrade.   My HDP3 has balanced out but opamp based balanced out.  Balanced out itself is an option over SE outputs.  I use SE output for all but the bass, which I connect to a Crown K1 amp that ground loops on SE output.


JoshK

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #7 on: 14 Feb 2010, 04:19 am »
P.S. the only correct way to measure bass is to do a ground plane measurement outside in a field at 3+ meters.   That is how they measure horn bass, as horn bass doesn't allow for nearfield measurement.

If you measure bass nearfield (at <1ft) and do the mid+ at 1m then you have to splice.


Tyson

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #8 on: 14 Feb 2010, 05:41 am »
Yep, you are correct.  The DEQX runs the frequency sweep for initial measurement, then shows you the impulse response and shows where the first reflection comes in (within the time domain).  You adjust it to do all corrections only within that window.  In my condo, that lets me correct down to 200hz.  Below that, it does not make corrections.  Rather, I run the room correction sweeps with the speakers in place, and that allows frequency response correction for the bass, from the listening position (or averaged over several different locations).

I use an XLR-RCA adapter and use the jensen transformer balanced outputs exclusively.  I've not used the single ended outputs at all, because when I talked with the guys at DEQX, they said the balanced outputs were "much better".

Mr Content

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #9 on: 14 Feb 2010, 07:25 am »
Sounds like a spiffy machine. Thanks for the info :D
 :eyebrows:

JDUBS

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #10 on: 14 Feb 2010, 08:53 am »
Nice review.  I'm pretty sure the latest version of the 2.6 has the same DACs as the HDP-3, though.

I'm trying to figure out what would sound better, upgrading to the HDP-3 or doing the Empirical Audio mods.

-Jim

BPT

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #11 on: 14 Feb 2010, 01:44 pm »
Jim:
Go for the HDP-3 upgrade. Another nice improvement would be to rebuild the power supply using Paul Hynes regulators.
Chris H.

poseidonsvoice

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #12 on: 14 Feb 2010, 02:22 pm »
Tyson,

Excellent review! :thumb:

So how much do these fellas run for? And did you get a special deal or did you just buy them used?
I must say that Australia has some very talented designers for amps, preamps, digital crossovers, etc...

One suggestion. Throw a link up on your original post for your Ella speakers so all newbies can learn from your trials and tribulations as well.

Excellent post!

Anand.

Tyson

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #13 on: 14 Feb 2010, 07:55 pm »
Tyson,

Excellent review! :thumb:

So how much do these fellas run for? And did you get a special deal or did you just buy them used?
I must say that Australia has some very talented designers for amps, preamps, digital crossovers, etc...

One suggestion. Throw a link up on your original post for your Ella speakers so all newbies can learn from your trials and tribulations as well.

Excellent post!

Anand.

Thanks Anand.  I did just now update the post to link to the Ellas build.  The unit I have runs for over $6k new, but I bought it used for about half that. 

ted_b

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #14 on: 15 Feb 2010, 01:57 am »
Good stuff.

I beta tested/demo'd the original DEQX about five years ago this month (wow, time flies).
http://www.audiocircle.com/index.php?topic=15516.0
I was only taking a very small peak at it cuz I was not using it for active crossover (VMPS RM/X at the time, no ability to go active) but simply to try speaker/room correction.  My half-assed attempt came to a simple conclusion at that time....for room correction it was too digital to have enough value to outweigh.  Again, that was five years ago...several decades in the digital timeframe.

If one were to use the version 3 stuff on, say, my wonderful SP Tech Revelations (currently external passive Mundorf crossovers) what would I be missing if I didn't use it as a preamp; I've read a few posts elsewhere that folks chose to keep their hi-end stereo pre (especially doing without the extra ADC-DAC)?  Is it overkill to simply (bad word) use it as an active crossover?

Pez

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #15 on: 15 Feb 2010, 04:48 am »
Just wanted to add some pics of our measuring session.

After hoisting one of these heavy bastards onto our solid wood speaker pedestal we positioned the mic to be on axis with the tweeter.


As you can see Bolder Nitro XLRs were used throughout the testing. :P We had to completely tear apart Tyson's house to accommodate this test. We also had to pull his tube amps to allow the speaker cables to reach the speakers.


Tyson running the freq. sweeps. Not a fun auditory experience. Wishing Tyson would have built that anechoic chamber I told him to build.  :duh:


any way as Tyson said, this piece is pretty killer. A tweakers delight really, a plug and play "audiophile's" worst nightmare.  :lol: yes people you actually have to take measurements to get decent sound quality.  :duh:

doug s.

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #16 on: 15 Feb 2010, 04:50 pm »
Good stuff.

I beta tested/demo'd the original DEQX about five years ago this month (wow, time flies).
http://www.audiocircle.com/index.php?topic=15516.0
I was only taking a very small peak at it cuz I was not using it for active crossover (VMPS RM/X at the time, no ability to go active) but simply to try speaker/room correction.  My half-assed attempt came to a simple conclusion at that time....for room correction it was too digital to have enough value to outweigh.  Again, that was five years ago...several decades in the digital timeframe.

If one were to use the version 3 stuff on, say, my wonderful SP Tech Revelations (currently external passive Mundorf crossovers) what would I be missing if I didn't use it as a preamp; I've read a few posts elsewhere that folks chose to keep their hi-end stereo pre (especially doing without the extra ADC-DAC)?  Is it overkill to simply (bad word) use it as an active crossover?
i have an "original' deqx pdc 2.6 - the non-preamp iteration.  i must disagree wholeheartedly that it's "too digital".  its room & speaker correction ability far outweigh any possible negatives it has, imo.  it is at least as transparent as the marchand x-over it replaced, and that was transparent enough that i couldn't hear any bad things it may have been doing to my main speakers.  digital at 96khz works for me.   maybe next time, you should try the "full-assed" attempt?   :lol:

i am certainly interested in upgrading my unit to the latest & greatest, but its preamp functions won't get used; i will be only using it as i use my present unit, as a fantastic dsp eq/crossover.  i am sticking w/my much-loved melos preamp.  i wish deqx offered a less expensive iteration, sans preamp...

doug s.

ted_b

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #17 on: 15 Feb 2010, 05:47 pm »
I'm glad it isn't too digital for you.  It was not meant as a debatable topic for me; it was indeed too digital for my use.  The resolution of the DACs at the time clearly took my system backward (and my system is considerable more detailed and higher resolution now, five yrs later), but I assume it's because of the way I was using it, simply for room correction (not as a crossover, as in your case.  I mentioned in my post that my then-current RMX speakers couldn't accept active crossovers).   I was never meaning to say it doesn't work as an active crossover.   I'm sure it does, hence my non-preamp questions here.

Tyson

Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #18 on: 15 Feb 2010, 07:29 pm »
I went from a tubed preamp and tubed DAC with the DCX to the DEQX replacing both of them.  My system actually sounds less digital now, than it did when it was tube bases analog before. 

Doug is right, the 2.6 has enough advantages that it brings to the table as a speaker correction and crossover unit, that it almost certainly makes up for any other trade offs.  But, the upgrade certainly makes it more usable as a preamp, especially if you are used to extremely high quality analog/tube preamps.  Just the move from a digital to an analog power supply alone is going to be a big improvement.  Throw in the other stuff, which almost all came from Steve at Empirical.  To my understanding, Empirical decided to stop modding the 2.6 to focus on developing their own products, so the DEQX guys used the Empirical mods as the basis for the upgrade to the HDP-3 version. 

One other cool thing the DEQX can do is pull up your room measurements graph while you listen to music, and you can set and/or alter EQ points while it's running, giving you the ability to fine tune the sound from the sweet spot, while you listen live.  That's pretty sweet.

ted_b

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Re: Review: DEQX HDP-3 Preamp/Processor/Active-Crossover
« Reply #19 on: 15 Feb 2010, 08:04 pm »
I guess I need to rephrase my question because I've seemed to miss the mark the first time (prolly cuz I mentioned my disappointing demo five yrs ago; nuff said, it was pilot error).

Ok here goes:  Would any of you who use the DEQX today buy it if you were keeping your current stereo preamp (i.e just as an active speaker crossover).  Tyson, you specifically said you needed to sell your current pre, etc to fund this thing and that's at 50% off MSRP.  Did you try it with the pre?  My assumption is that your current system is sounding better partially cuz the DEQX is significant xover improvement over the modded Behringer; just wondering how much the pre function adds or detracts, especially if sources aren't all pure-digital feeds.  The pre function certainly is part of the DEQX cost.