The DEQX HDP - Express Processor

by admin on May 18, 2011 · 1 comment

in Digital, Preamplifiers, Stars

By Michael Levy

Every now and then the audio world makes a breakthrough. Sometimes that breakthrough is so large that it promises to make an entire segment of the industry transform itself. DEQX produces that kind of transformational engineering design.

Richard H. Small and A. N. Theile compiled the basics of loudspeaker design in a series of articles in the Audio Engineering Society, while both were working in Sydney Australia in the early 1970s. Their work resulted in several speaker tuning parameters now called the Small-Theile parameters. Nearly every loudspeaker design has been based on their work.

Any engineer looking at speaker design will recognize two inherent problems. The first is the interaction of the speaker with the room. This can alter the sound of a speaker so greatly, that in one room, for example, it will have overwhelmingly powerful bass, and in another room, the bass will seem to disappear! These room interactions alter the sound of the speaker throughout the audible range, although they are usually most obvious in the bass.

The second problem is that the entire audible frequency range cannot be put out by a single element for several reasons I will not get into here. That is why speakers have woofers, tweeters, and even midrange elements. For these elements to each output their part of the audio spectrum correctly without interfering with the other element, the audio signal must be divided to feed them accordingly.

In the prior art, this was accomplished using a crossover network. A combination of resistors, capacitors, and inductors were used to funnel the appropriate signals to each driver. When done passively, this network would impose a load on the amplifier that could greatly alter the sound of the amplifier depending on the design. An active system where each driver is connected to its own amplifier would solve this problem, but these networks had other problems, such as phase inaccuracies in all but the least effective gradual slope designs.

Also, this did not address the room interaction problem. Most speakers were designed in anechoic rooms. They were never used in such a room. The sonic results in a normal room are quite variable.

In the modern digital age, DEQX has created a solution that is both elegant and comprehensive. The processor uses a calibrated microphone to listen to and adjust inaccuracies in the frequency response, phase, and timing that are inherent in all speaker designs. It also corrects the anomalies caused by the room.

It can also create active crossovers that are linear in phase and very steep, preventing driver interactions. Additionally, it includes a state of the art equalizer for personal tailoring of the sound. I first had the chance to use this system in 2005. It worked like a dream. I designed speaker systems using the DEQX and so did several other designers. The results were always a major sonic improvement from the prior state of audio design.

Another feature of the DEQX system is that it accomplishes all of this with a delay that is less than the timing of one frame of a movie or video, making it compatible with home theater systems.

Now, DEQX has updated their system. There have been both hardware and programming changes. Listening to the updated units is a marvelous treat. The level of inner detail, dynamic accuracy, and three-dimensional imaging is nothing short of amazing.

Additionally, they have come out with a bare bones unit called the HDP — Express. While it lacks some features that make the HDP-3 unit a state of the art design, the sound quality has been maximized. It comes so close in sound to the top of the line unit that the only way to tell the difference is by comparing them directly in the same system. And, when you do, it still takes some listening to find.

For comparison, I played the CD layer of “Pictures at an Exhibition” through the digital input, (Telarc, SACD 60042 Lorin Maazel, The Cleveland Orchestra). This is a wonderful recording of the symphonic version as transcribed by Ravel from the Rimsky Korsakov modified Moussorgsky piano concert. Compared to the HDP-3.0, the image shrunk, but only slightly, and the size and shape of individual images were not quite as clear. When the analog input was used, these differences increased, but, the quality of sound was still first rate.

I encourage the reader to try this out. First, use the DEQX to correct the frequency response and phase anomalies that are inherent in all speakers. The DEQX will realign the timing throughout the frequency range. Then, use the room correction feature.  You will find the improvement is amazing. But, if you have speakers that can be bi-amplified, or tri-amplified, or if you are willing to modify them to use the DEQX electronic crossover, you will never want to go back. The difference in clarity, detail and dimensionality will astonish you. Also, you will be surprised in the total lack of digital artifacts in the sound. It is smooth and analog clean.

For audiophile sound quality, and value, the HDP — Express definitely deserves an Audiophilia star.

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

The DEQX HDP — Express Processor

Manufactured by DEQX PTY Limited
Unit 1, 1 Roger Street, Brookvale, Sydney NSW 2100, AUSTRALIA
Tel: +61 2 9905 6277
Fax: +61 2 9905 8066


Price: $1,950 USD
Source: Manufacturer Loan

{ 1 comment… read it below or add one }

Hann 05.30.11 at 2:41 am

Hi, could you please describe your equipment setup for the evaluation of the Deqx Express. Was it bi-amp or tri-amp and what speakers were used? Thanks

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