No one talks about it much but the best-kept secret in audio is there’s no speaker system on Earth than can keep up with the signal at the inputs. A little delay is okay if all frequencies are delayed equally… but they never are! Speaker systems always delay some frequencies or frequency groups to one degree or another. In the critical midrange these delays may be a millisecond or more -- sound travels about one foot per millisecond.

Psychoacoustically speaking we experience these frequency-dependent timing coherence errors as a lack of life or openness. These group-delay errors are impossible to correct in the analog world, which is why you rarely hear anyone talking about it. After all, why dwell on a fact of life that no one can do anything about.

Nevertheless even the most revered audiophile speakers introduce an astonishing 10-times more phase and timing errors than the signal driving them! Add to that a myriad of frequency-response errors that pile on, plus a listening area that’s -- in most cases -- drenched in room reflections, and it’s a wonder we hear any detail at all.

The distortion in the signal itself represents just a few percent of the total distortion you hear; incredibly, the rest is produced by the speakers, and again counter-intuitively, to a lesser extent by the room. What a concept; errors and distortion produced by speaker driversare greater than those produced by the listening environment!

But this is the 21st century. Accepting speaker distortion as par-for-the course is no longer required. It’s true that some enthusiasts overstate small changes into big ones, but as per all reports, auditioning a DEQX-equalized system -- each speaker's timing, phase and frequency response errors reduced to fractions of a decibel with microsecond precision -- creates remarkable improvements. Click here to read the many accolades.

Think of DEQX as a Loop Processor that measures your speakers and applies sophisticated correction filters. There are two ways to become DEQXified. DEQX Inline works with your stereo amp, speakers and crossovers as a complete package. In a typical audio system you might use the available DSP channels to optimize a 1-way, a 1-way plus sub(s), a 2-way, or a 2-way plus sub(s) system.

A popular home theater setup uses a single DEQX Inline to integrate, correct and time align one or a pair of subwoofers with main Left/Right speakers, and then adds room compensation and Preference EQ. A remote control for a 3-band equalizer with one fully parametric band adjustable across ten octaves makes fine tuning easy.

DEQX Inline’s powerful DSP technology is transparent to the speaker’s internal crossover and measures the cumulative output of your speakers, vastly improving the immersive experience by correcting timing errors (group delay and phase) and amplitude balance (frequency response). Lowered intrinsic distortion and room compensation makes playback startlingly more coherent. The much enhanced sense of realism makes suspending disbelief and fully engaging with music or video easy.

While DEQX Inline works with your amp and speakers’ total in-room response, upgrading to top-of-the-line DEQX XO does away with traditional crossovers with their traditional problems. Instead DEQX XO goes amplifier-direct and replaces the crossover with up to three DSP-equalized channels driving a separate amplifier for each type of driver (typically bass, midrange and tweeter drivers), also known as active tri-amping in a traditional 3-way, although DEQX goes far beyond traditional active systems. DEQX Inline measures the cumulative output of your speakers and corrects for phase, group-delay and timing errors.

DEQX XO gives the processor direct control of the signal feeding each driver. Unlike traditional digital and analog active crossovers, it provides steep linear-phase crossover filters that dramatically reduce break-up distortion, intermodulation and crossover distortion while restoring natural dispersion characteristics. The immediate effect is a larger 3D soundstage with increased resolution which improves volume capacity, dynamics and slam. The immersive you-are-there realism produced when distortion is reduced to these levels will surely surprise. Adding DEQX XO to any speaker, regardless of type and cost, results in dramatic improvements in performance.

DEQX Inline and DEQX XO are available as options on the HDP-Express and HDP-3

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

DEQX HDP-Express Pre-amplifier / Processor.

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. …Read More

Michael Levy, Audiophilla