[denverdoc]

I will try to keep this short and to the point. I have owned many high end products over the years, nothing too over the top--maybe a max system cost of 30K. Point is i love audio and over the years with varying levels of intensity, have always kept an eye on the audio world, and made it a point to check in with the local high-end dealers to see whats new.

Usually, when one subtracted hype, wasn't much new;  just refinements of various sorts and debateable merit as speakers gradually with the new tech, at least until  1994 when I first heard the Meridian system front to back. Thought it very good, and kept an eye on it and revisited various iterations, but at more than the cost of a couple cars, had to pass. Then after having had various speakers in my system, decided to explore the DIY route. As for my background, as I biomedical engineering student I had to have some knowledge of circuit theory and complex variables, but was shy to design/build anything more than subs.

At this point, came across the DEQX with all its abilities and figured with the xo issues removed, I can build a really good speaker at a fraction of commercial cost. This unit is so good and so flexible I am only writing to say it kicks butt, and within an hour of opening the box was able to transform a 300/pair JBL bookshelf into what might cost 10 or even 20 times the cost. This is a great product, granted the opening bid of 3 to 4k seems steep, but consider its as a preamp/eq device combined, cheap at twice the price. Especially as it will extract performance from your present gear to an astonishing level. No BS cable fix, or other snakeoil--this item rocks. AndiIf you have ever had the hankering to roll your own speakers: invaluable!!!
John

[mac]

One of the most impressive demo's I've ever experienced was the one that DEQX performed at the '05 CES.

Using a pair of B&W N705's along with subwoofers they did an instant comparison of the system DEQX bi-amped with high-level crossovers disconnected Vs stock. As expected, the tonal balance was dramatically better when running in DEQX-calibrated mode, but what was shocking was the way the speakers completely disappeared in the room. (Yeah, it's a way overly/improperly used cliché but in this instance was true).

One really needs to experience this device in their system (in multi-amped mode) to fully appreciate what it's capable of doing.



Cheers, mac.

[JohnnyLightOn]

How does this product differ from a digital equalizer such as the Behringer Ultracurve Pro DEQ2496?

I'm not very familiar with either, but I assume they both automatically equalize the room so the frequency response is flat (or whatever you choose it to be).  Is that right?

[mac]

The DEQX PDC-2.6 is a 3-way digital electronic crossover and performs driver and room correction.  Unlike the Behringer gear, the PDC uses ultra-steep slope linear phase FIR filters.  Their calibration process will correct the measured acoustic frequency and phase response to near-perfect levels.  The white paper on their site describes its capabilities in detail.  http://www.deqx.com/downloads/What-is-DEQX-Technology-Whitepaper.pdf

[denverdoc]

Mac,

Yea, still kicking myself for missing their exhibitors invite to CES in sin city.  I hope they plan on coming out to Denver this Fall for the Rocky Mountain Audio Fest which should be very well attended--as CEDIA takes place here the following week. Hope you can come out too, last years was a lot of fun and even the bottom of the line Overkill Audio powered by DEQX/Manger Drivers was over the top good. You can drop by for a beer and hear my Line Arrays    you helped to inspire.
John


DIY/DEQX Advocate #2

[BeeBop]

So you are saying that this like a "crossover-in-a-box"? I could buy my own drivers, build my own cabinet, and use this as a user-adjustable crossover?

[JLM]

Why would anyone want to use multiple drivers?

Wouldn't two sources hurt imaging, especially nearfield?

Wouldn't two different drivers (woofer/tweeter) each with their "sonic signature" sound "funny" as they crossover (no matter how steep the filters)?

Wouldn't having the sound jump from one driver to another at the crossover frequency be unnatural?

Wouldn't the ideal synergy between amp and speaker use one amp channel per driver?

BTW, I own Bob Brines FTA-2000 floorstanding mass loaded transmission line speakers that use a single, highly regarded, Fostex F200A driver.  For $1500 I get 89 dB/w/m, 8 ohms, 30 - 20,000 Hz in room in custom finished cabinets.  The MLTL design makes these very easy to drive (a $500 6 wpc Clari-T does just fine).

[Bingenito]

BTW, I own Bob Brines FTA-2000 floorstanding mass loaded transmission line speakers that use a single, highly regarded, Fostex F200A driver. For $1500 I get 89 dB/w/m, 8 ohms, 30 - 20,000 Hz in room in custom finished cabinets. The MLTL design makes these very easy to drive (a $500 6 wpc Clari-T does just fine).

You know what they say about opinions My speakers may sound funny to you and your speakers may sound like they lack the top and bottom octave to me. It is all what you like.

I like what the DEQX can do. Instead of jumping on the wagon early like a normally do I have decided to sit on the side lines for a yr or so and watch the prices come down as this technology becomes more common place.

Right now there is DEQX and Tact. Within those two DEQX seems much more advanced. Then you take a major price drop to the Behringer and DBX DriveRack systems. I have owned the DBX and it was very simple to use but very limited in functionality compared to the DEQX and Tact.

If I was going to eliminate passive crossovers I would purchase the DEQX without hesitation.

[denverdoc]

So you are saying that this like a "crossover-in-a-box"? I could buy my own drivers, build my own cabinet, and use this as a user-adjustable crossover?

Exactamundo my man, and one of the big incentives for me as I didn't want to diddle with voicing xo's for a year or more. Plus with the steep slopes 96 to 300 dB/octave one can use the best drivers around that otherwise are difficult to employ--as in SEAS magnesium excel woofers, Manger drivers, etc. No accident that the highly regarded NHT and Overkill DEQX based units use these respective drivers. As for myself I am using the B&G 75 inch ribbons which are a bit troublesome otherwise as they have a cavity resonance at 5KHz and roll off a bit at the very top. The DEQX eliminates the need for a notch filter or using tweeters to extend the last octave. For midbass, will likely use SEAS aluminum 8 inch drivers (nine per side) which because of the filter slope all the metal hash will be literally 100's of dB's down. For bass, 2 Avalanche 18 inch in IB setup. All seamlessly integrated by the "brain." BTW the DAC's are damn good as well, eliminating yet another piece of gear unless one is really, really picky.

And this is my first DIY project apart from car audio and subs!

I think the issue of driver blending is way overstated--likely this phenomenon can be attributed to phase error/differences  as one goes from one driver to the next in a conventional xo. As Mac points out the DEQX erliminates phase angle for the lower half of the audio band, and group delay is all kept to very manageable and inaudible amounts.  So driver blending is better, not worse than with conventional XO's.

This unit rocks!
John

[Rick Craig]

Exactamundo my man, and one of the big incentives for me as I didn't want to diddle with voicing xo's for a year or more. Plus with the steep slopes 96 to 300 dB/octave one can use the best drivers around that otherwise are difficult to employ--as in SEAS magnesium excel woofers, Manger drivers, etc. No accident that the highly regarded NHT and Overkill DEQX based units use these respective drivers. As for myself I am using the B&G 75 inch ribbons which are a bit troublesome otherwise as they have a cavity  ...

You'll really like those 8" Seas drivers. I've used them in some of my designs and their bass extension is exceptional.

 One area I would disagree with you on. There was a controlled study done on the audibility of driver breakups and these steep 96+ db/octave slopes really aren't needed. I don't remember the exact AES preprint number but I believe Sean Olive was the author.

[denverdoc]

In the interest of keeping things brief in my original review, did not get into some other features that make the DEQX even a better value and more flexible product.

First off, is the fact that you can optimize 4 different systems with one unit; mind you, you can only use this to play back one of the 4 at any given time, but in my home I have 3 different rigs, and as my PPDC-2.6P has balanced out options, I will be conceivably able to run all 3 in their fully optimized glory from the one unit. Another option is digital outs which would make this even less cumbersome, tho cabling it well might get pricey.(Not sure about digital interconnect length issues)

The other feature available only on the preamp version is in addition to all the speaker and room correction, there are 100 programmable 3 band parametric EQ's, the bass and treble have fixed Q, adj freq, while the midband has both adj Q and center freq. Really have no idea what to use these for, but obviously screechy soundtracks or poorly recorded pieces are one option. Another I wish to investigate is creating a personal Fletcher-Munson loudness filter set for say 8 different volumes.   Even with the 3 audio systems, that leaves 76 presets for whatever.
J

[denverdoc]

You'll really like those 8" Seas drivers. I've used them in some of my designs and their bass extension is exceptional.

 One area I would disagree with you on. There was a controlled study done on the audibility of driver breakups and these steep 96+ db/octave slopes really aren't needed. I don't remember the exact AES preprint number but I believe Sean Olive was the author.

Rick,

I doubt we disagree--I suspect 36dB to 48 dB/octave is plenty for even a worst case scenario. I only mentioned 96 as this is the minimum slope available for 2 of the 3 XO's and was the choice of the DEQX designers.

The other filter set normally used for sub integration offers butterworth and L-R alignments as well as minimal phase, all of much lower order.

[ted_b]

I thought the minimum  for all crossovers was 48db/octave (48-300 range).  At least that's what my documentation says. When I had the DEQX I had single amp so I'm not at all crossver-experienced.  

Ted

[John Ashman]

How does this product differ from a digital equalizer such as the Behringer Ultracurve Pro DEQ2496?

The Behringer is nice and affordable, but is incredibly limited compared to the DEQX.  The DEQX has about 4000s points of resolution and actually draws a curve that compensates for the drivers rather than just doing parametric EQ.  It is phase correct.  It can do VERY steep crossovers.  It can do much more advanced room correction.  Even if you add the Behringer crossover, there's no comparison between the two systems, like comparing a go-kart to a car.  Both will get you around, but the experience is totally different. The Behringer is probably as close as you can get though for such a low price.

[John Ashman]

So you are saying that this like a "crossover-in-a-box"? I could buy my own drivers, build my own cabinet, and use this as a user-adjustable crossover?

Yep, and you wouldn't even have to be that GOOD at it, though it does help.  It's way more than a crossover though.

[mac]

So you are saying that this like a "crossover-in-a-box"? I could buy my own drivers, build my own cabinet, and use this as a user-adjustable crossover?

Yep, and you wouldn't even have to be that GOOD at it, though it does help...

This is why loudspeaker designers will soon become dinosaurs in the very near future (they already are in my book).  The DEQX unleashes the power for the average Joe to achieve results that cannot be achieved by conventional means.  

[denverdoc]

I thought the minimum  for all crossovers was 48db/octave (48-300 range).  At least that's what my documentation says. When I had the DEQX I had single amp so I'm not at all crossver-experienced.  

Ted

Ted,
You are correct--my mistake.
John

[John Ashman]

Why would anyone want to use multiple drivers?

Full range sound?  Lack of driver resonances?  Low distortion?  Good dispersion?  All the OTHER things you get since one driver can't do it all?  

Wouldn't two sources hurt imaging, especially nearfield?

No, steep crossovers virtually eliminate driver interactions, making the speaker appear as a true point source even as little a 1' away.  Dispersion is nearly hemi-spheric, done properly.  And much more coherent and wider dispersion than a single driver which will begin to beam by 2000 Hz or so.  

Wouldn't two different drivers (woofer/tweeter) each with their "sonic signature" sound "funny" as they crossover (no matter how steep the filters)?

No, if the driver is behaving pistonically (choose decent drivers), the driver has no "signature" and therefore, the handoff is utterly seamless.  The reason drivers have signature sounds is that shallow (or no) crossovers allow the driver cone resonances that are eliminated by high-order crossovers to be audible.  If the cone is rigid and used within its bandwidth, it has virtually no sound, especially when it is also EQ'd to be flat.

Wouldn't having the sound jump from one driver to another at the crossover frequency be unnatural?

No.  Hearing is believing.  

Wouldn't the ideal synergy between amp and speaker use one amp channel per driver?

That's how DEQX works.  Each driver has its own amplifier, no crossover.  It has all the advantages of a single driver, but none of the substantial disadvantages.  It does cost more, but no single driver system could keep up, nor any conventional passive speaker of remotely similar design.  

BTW, I own Bob Brines FTA-2000.

That makes you the perfect future customer for DEQX because it gives you what you already have and a whole lot more.

[denverdoc]

[This is why loudspeaker designers will soon become dinosaurs in the very near future (they already are in my book).  The DEQX unleashes the power for the average Joe to achieve results that cannot be achieved by conventional means.  

Hey Mike,
I resemble that remark!  
J

[John Ashman]

One area I would disagree with you on. There was a controlled study done on the audibility of driver breakups and these steep 96+ db/octave slopes really aren't needed. I don't remember the exact AES preprint number but I believe Sean Olive was the author.

Rick, I don't know the specifics of that study, but I find driver breakups of metal drivers to be extremely audibly.  Every passive, metal cone speaker I've ever heard, except for the Genesis titanium midrange models has exhibited them often to the point of being unlistenable.  The worst was Velodyne's D661.  AWFUL.  I couldn't listen to it for more than 60 seconds.  Genesis dropped the 4" titanium cone mid (which is small enough, rigid enough and crossover steep enough in that app to be problem free) from its APM2 speaker and the sound, with dual 6" aluminum cones was bright, yet lacking in detail and the imaging was poor.   I couldn't figure out the problem until I read up on breakup modes and then it made sense.  It never sold well and was almost discontinued by the time it made it to market.  I had a customer bring by Axiom M80s.  They just about ripped my ears off and became fatiguing within minutes - he sent them back and bought poly-equipped NHTs.  But most people think Axioms are "detailed" rather than bright.  And don't get my started on Kevlar and B&W, I can't even believe people like them at all.  "it's like they're TOO detailed".  Like there is such a thing.  That's what you call breakup modes in action.  

You can try to notch out the breakup, but I suspect that doesn't work well at all volume ranges from what I've read and, of course, you add other problems with notch filters, so it is a bandaid at best.  The best way to deal with it is to crossover steeply enough that they are never an issue at all and there is no energy reaching the driver by that frequency.  Even if it weren't audible, there's no real downside to eliminating them, at least with a device such as DEQX.  I confess to not having heard the SEAS Excel without DEQX, but it sounds fantastic with it.  NHT insists that they couldn't use the Excel without DEQX because the sound would be unacceptable, so it won't find its way into any of their passive designs.  NHT uses a 2000Hz, 110dB/octave crossover, partially to avoid the ringing at ~4800Hz and partially to preserve dispersion.  I suspect that DEQX on the big Selahs would simply make the speaker smoother and more refined, though, with that many drivers, the cone resonances would probably relatively small.  

Speaking of dispersion, Rick, is it an actual fact or wive's tale that line arrays actually increase horizontal dispersion?  I was arguing this, but then it appears that one of your white papers you posted seems to indicate something else.