AOM Logo June 2006

The DEQX PDC - 2.6P -- A Revolution?

Martin Appel

In my years as a reviewer, I've spent thousands of hours listening to and evaluating a substantial number of products. In all that time, from speakers to amplifiers to preamplifiers to cables to a variety of source components, there has always been one dictum that seemed to make sense: one should start a system with the best speakers one could find or afford and then add the components to fill in the remainder of the system. It's always been about the speaker. Why, you ask? Well, primarily it is a mechanical device that produces sound waves as a result of converting electrical energy into mechanical energy and it's what we finally listen to. This production of sound waves is performed by cones or ribbons or panels or some combination thereof that usually include some form of electronic crossover network, differing materials of construction, mountings, enclosure types, etc. In any transfer of energy, from one form to another, in this case electrical to mechanical, there is usually a substantial loss of energy and the actual conversion to the new form produces many unwanted by-products. In the case of speakers, heat and various forms of distortion, both time, phase, frequency and Intermodulation Distortion (IM), among others, resulting in a degradation of the electronic signal and the sound we finally hear.

Most electronics today, and for quite sometime, have had diminishing levels of distortion. So much so, that often times, the measuring equipment themselves, can skew the final result.

After discussions and e-mails with Kim Ryrie of DEQX (Ryrie has been mainly designing and building products for the pro audio field for over 30 years and his equipment is used industry wide, including the widely acclaimed Abbey Road Studios, in London) , he was kind enough to provide the following clarifications for this reviewer:

'Distortion introduced by loudspeakers and other electronics include distortion that tends to either be noticeable and disturbing, or at best, lacking resolution as distortion approaches and exceeds “1%”. Unlike the audio signal that drives them, where distortion is usually well under 0.1%, even high-end speakers typically measure over 1% distortion, and more at high volume and over crossover regions, much of it resulting in lost resolution. The PDC-2.6 can provide ‘active crossovers’ that minimize driver and crossover distortion by better quarantining frequencies to each drivers ‘linear-operating region’ (reduced Intermodulation distortion), that allows higher volume before distortion sets in, more natural dispersion of highs by reducing driver ‘beaming’, and reduced crossover distortion by introducing true linear-phase and steeper crossovers.

We also take for granted the fact that just about any piece of audio electronics has a flat (accurate) frequency response, so a CD player displaying the typical 'plus/minus 3dB' frequency response of a loudspeaker would be returned as ‘faulty’. DEQX corrects frequency response of the loudspeaker/amplifier combo to typically plus/minus 0.5dB (near-field on-axis). Even more important when trying to achieve ‘realism’ is time-domain accuracy, or phase and ‘Group–Delay’ accuracy. Group-Delay accuracy is rare in affordable loudspeakers, and among the most important factors that determine our perception of a real performance. This is where some ‘frequency groups’ actually lag in time behind others. In amplifiers, these timing or phase errors are minimal, being measured as phase shift, or at worst, a slight delay measured in microseconds. In loudspeakers however, these errors are measured in milliseconds! We believe that DEQX’s patent pending group-delay analysis and correction process is the first affordable and low-latency solution for loudspeakers. The bottom line is that however ‘good’ a speaker might sound, these tiny timing errors give the ‘is it real’ game away to our ever vigilant hearing mechanism'.

Thank you, Kim, for that extended treatise. I do believe that adds some clarity to the situation for those of you with a technical bent. For the rest of you, keep reading. The PDC-2.6P is his solution, along with his design team, currently headed by Sasha Case, to the problems of speaker induced distortions all in one tidy compact package. This endeavor represents twenty-one man-years of software development.

What is the 2.6P? This one box contains a DAC/preamplifier, a digital speaker corrector/equalizer, a room correction device, as well as an active, steep slope, crossover network. There's a lot to explain here so stay with me.

The unit is barely 1 3/4 inches high and 17 inches wide and 11 1/2 inches deep. It comes with a detachable power cord, USB cable as well as a microphone and its accompanying cable and most importantly, the software CD, the key to the system. The included remote control unit offers input selection, volume control and a 3-band (Lo Med. and Hi) parametric equalizer that offers control of the full frequency spectrum. The 2.6P looks very unassuming but looks can be deceiving. It typically comes in black with the option of a clear metallic faceplate finish achieved with a polyurethane paint that has the slightest of violet tints. For those who require more info check out the website. Using the basic equalization via the remote does not require a computer or microphone, but only your ears. You can save up to a hundred settings with the remote. It only begins to scratch the surface of what the unit can do. The PDC-2.6P processor can be connected between an existing stereo or home theatre pre-amp and power amp for equalization, speaker correction, and room correction, and act as the sole pre-amp. The remote control selects from four inputs, two digital (XLR balanced and RCA unbalanced) and two analogue (XLR balanced and RCA unbalanced). One PDC-2.6P unit processes two input channels in analogue or digital (PCM) to 96KHz - compressed or surround digital formats are ignored. The preamplifier section is not appropriate for use in a system that has more than two analogue or two digital sources. For that, your system would require the use of a separate preamplifier that is connected to the PDC-2.6P or save money by using the 2.6 (the DEQX unit without the preamplifier section) and use your own preamplifier to control volume and system functionality.

Michael Levy, a friend and colleague, who piqued my interest in the DEQX, came over and helped me install it. Let me preface this by saying I'm not a strong technical or computer person and if one wants to maximize what this unit can do to your current system, you will need the help of someone with a facility for dealing with technical issues. An understanding of speaker behavior wouldn't hurt. Ryrie assured me that long strides have been made in making the PDC's software more user friendly. There is also strong e-mail and phone support provided by DEQX. Onward.

I connected the unit after my Innersound i Control preamplifier using the balanced out to balanced in of the PDC-2.6P with Wasatch ULTAMA interconnects. Unfortunately the PDC I was using didn't have the balanced output option and I had to use single ended from the PDC-2.6P to my Innersound i 330 amplifier.

Now the fun begins.

We connected the microphone and cable to the PDC as well as the USB cable to Mike's laptop. All cables and microphone are included and you really need a laptop computer unless your desktop computer is in your listening space. The key to all this is the included programming CD that has to be loaded on to the pc. It's the brains for the entire operation. Once everything is connected and loaded the speaker calibration is next on the agenda.

The process of calibrating each speaker begins by getting the speaker as far away from any surfaces in the room and placing the measuring microphone 1 meter from the speaker, on axis, pointed at the center of the midrange driver. Then the actual measuring takes place when a test tone is generated from the lowest frequencies through the entire audio range. This frequency sweep repeats several times and the resultant measurement is plotted on a graph on the computer screen showing the fluctuations, from neutral, across the entire frequency range. This measuring is performed individually for each speaker since differences can occur between supposedly 'identical' units. Each of the speakers in the system can be individually corrected. Then by setting up certain parameters on the computer, it applies the correction to the frequency fluctuations and you are left with a new graph that is for all practical purposes, ruler flat "to the extent that power remains in the speakers design range".

I've simplified the actual procedure but outlined the essentials and after Levy worked with the laptop computer and the new speaker correction responses went into the PDC-2.6P and we were ready to listen. For a more technical description read the following supplied by Ryrie.

'Unique to DEQX, is not only that it corrects frequency response at thousands of frequencies simultaneously, but also that "Time Domain" errors such as Phase and Group-Delay are corrected along with Frequency-Response using DEQX’s “Proprietary very Low latency FIR (Finite Impulse Response) and IIR (Infinite Impulse Response) filtering”. To be “DEQX Calibrated”, a speaker’s "native" performance (i.e. excluding the ‘power response’ caused by room interaction) is "flat" and accurate in time in the near field (anechoically). When doing room correction, the "flat" DEQX calibrated™ speaker is measured from the listening position to indicate its "power response" (frequency response in room). From the sweet spot of the listening room, DEQX recommends a flat frequency response (power response) between 100Hz and 3kHz, above which highs should tend to roll off slowly (about 2dB/octave) to be roughly 5dB down at 20kHz. Bass below 100Hz may be a few dB "hot" at 50Hz. This is all subject to personal taste however and you can use the parametric EQ to make any personal adjustments to taste'. I did not use this recommendation but used my ears and preferred the flat response. Now we can start listening.

Folks, I would like to refrain from being overly exuberant in my comments, but I can't. What I heard was truly amazing, jaw dropping, illuminating, eye opening, ear opening…well, you get the picture. Nothing I've ever introduced into what I would call a pretty good system produced such an enormous improvement to the quality of the sound. Not even close. I'm not going to go through listing specific CDs or LPs but simply say that whatever the source the improvements were consistent and wonderful.

The soundstage is always is a good place to start. All the audiophile parameters that usually apply were extended and broadened. Height, width and depth were all bettered. Instrumental layering became clearer, as well as their separation. Air around instruments took on a more vibrant quality and at the same time the instruments themselves took on solidity and three dimensionality that was beguiling.

Continuing. Detail levels increased across the entire musical spectrum without adding any clinical edge to the sound. Quite the contrary, an analogue-like smoothness and liquidity pervaded what I heard. Scary.

Instrumental timbres took a further step towards reality with greater body and inner detail where subtle textures were further revealed. Voices were given a lifelike reality that hitherto didn't realize recorded music was capable. Orchestral dynamics, both macro and micro, were more dramatic in intensity, with greater orchestral weight bringing me closer to the live experience.

In my past experience, there have been many touted 'Black Boxes' that have been tried out in my system that purported to improve sound staging, dynamics, palpability of instruments and voices, harmonic accuracy, etc. Some worked to one degree or another but they all seemed to suffer from one major problem, a loss of clarity and transparency. Put more electronics in the chain and the sound always lost more than it gained…until now. The level of transparency, with the 2.6P in the system, was affected-by being further enhanced. Truly remarkable. The DEQX shows us that by removing speaker inaccuracies and distortions our listening window becomes clearer and more transparent then ever. Wait, we still haven't done the room correction yet.

Room correction is a much easier task then speaker correction for the end user. Plug in the mic and place it in your listening position and the computer reads the response and makes adjustments as needed. DEQX recommends that you might like to take several readings around the listening area. These can be averaged, or just used to see what’s happening near by for informational use. Being the rule breaker that I am, I only took one reading, holding the mic dead center on my forehead at my listening position. And away we went.

I guess my room didn't have too many problems because the changes I heard were more subtle than the speaker correction. A further improvement in clarity in general and more specifically, of the bass performance and an incrementally broadened sweet spot, (which had considerably grown with the speaker correction). I also noticed another increase in overall system smoothness and airiness that further increased my appreciation of the capabilities of the DEQX. Even after all these processes were completed and one still wanted to further tinker with the sound one could use the three-band parametric equalizer on the remote control, make adjustments in real time and save any changes. I didn't. I was too happy. I leave further experimentation for future times.

The final chapter in this story took place in Las Vegas at the Consumer Electronics Show where I heard the full embodiment of the use of DEQX technology. Remember that part in the introduction of this review where I touched on crossovers and their contribution to the distortion picture. What if you eliminated the internal speaker crossovers and designed speakers using DEQX’s ‘linear-phase’ 100dB per octave slope crossovers in the PDC 2.6P. Now, you have practically zero driver overlap negating driver interference allowing each driver to perform optimally. Another source of distortion is now eliminated and further gains in clarity can be achieved.

WASATCH ACOUSTICS, an offshoot of WASATCH CABLE WORKS, the makers of some truly fine audio cables, showed their “DEQX-HD Calibrated™ Musina Music System at The CES in Las Vegas. The WASATCH system incorporates the full DEQX technology, (ala 2.6P) including preamplifier section, using the steep slope crossovers and six individual amplifiers (each driver gets it own amplifier) contained in a one-box unit called the UINTAH 2.2 AMPX. Connecting the MUSINA 2.0 full range monitor speakers and MUSINA .2 subwoofers with the included ULTAMA speaker cables completed the package. The high gloss black finish was simply gorgeous and only foreshadowed what I was about to hear. Total system cost was roughly $40,000 US. You supply your own source components.

This is not meant to be a review of the MUSINA system but a description of the full use of DEQX technology in speaker design. As good as adding the 2.6P into an existing system is, it is only when the full capabilities of the active crossover network is used that we get to hear the full sonic impact that such a system can produce. The room at the show was not good at all but when the room correction was applied the changes were dramatic. Revelatory and revolutionary would be appropriate adjectives to describe what I heard [the system was magnificent - Ed] . Full system review will be upcoming. Suffice it to say that it was my pick for best sound in the show. The system was going against manufacturers whose speakers alone exceeded the price of the total MUSINA system. Mike Levy, V.P. of product development (who designed the speaker system) and Brian Fitzpatrick, president and CEO of WASATCH ACOUSTICS, informed me that this is only their first effort. Other products are on the drawing boards and if the MUSINA is any indication of what's coming the future looks awfully bright. Bravo, gentlemen.

Audiophilia Star Component AwardBack to 2.6P. I couldn't finish this review without a few nits to pick. Like the Innersound i control preamplifier, the very narrow casework of the 2.6P makes connecting today's cables difficult due to the cramped quarters and the casework itself was at best utilitarian. And as stated earlier this is not a plug n' play product, but requires some diligence and work. The PD2.6 takes some working at it to properly obtain the maximal results that the unit is capable of. But once it's in your system and properly set up be prepared for some serious audio delights. The future has just said 'Hello'.

When I had to return the unit to the manufacturer I went through 'withdrawal' and 'grief counseling' from my audiophile buddies. If ever there was a product that deserved an Audiophilia 'star' rating for sonics and its impact on your system, this is it. This reviewer has placed his order with DEQX and impatiently awaits its arrival. Viva La Revolucion.

[It is with great pleasure that we award The Audiophilia Star Component Award to the DEQX PDC-2.6. Congratulations! - Ed]

Associated Components

BIRDLAND AUDIO SILVER AG w/UPDATED CLOCK; MELIOR MUSEATEX CD-D TRANSPORT by ED MEITNER TOTAL MEDIA SYSTEMS (TMS) ADAIBAT 8.5's (a ribbon cone hybrid customized by the designer-no longer in production)
ACOUSTIC ZEN SILVER REF. II and ABSOLUTE interconnects. GARGANTUA II and ABSOLUTE power cords, HOLOGRAM II speaker cables; WASATCH 'ULTAMA' speaker cables and interconnects


Manufactured by DEQX Pty Limited

Unit1, 1 Roger Street, Brookvale, Sydney NSW 2100 AUSTRALIA
Tel: +61 2 9905 6277
Fax: +61 2 9905 80666736

web: e-mail:

Price: US$3,500, balanced outputs, calibrating microphone and other options are available. PDC-2.6 without preamplifier option is US$3,000

Source of review sample: Manufacturer loan

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