DEQX represents a new generation
of digital audio that improves the experience of realism by correcting
the timing errors (group-delay and phase), as well as amplitude balance
(frequency-response) in a way that does not compromise sound quality.
Loudspeakers introduce by far the majority of errors and distortion
that we hear from our audio systems. We have learned to overlook
these problems because there has been little we could do to remedy
the situation except pay extreme prices for designs that minimise these
problems. Even so, our familiarity with naturally occurring real sound
makes it easy for us to pick almost any loudspeaker, regardless of
price, as a sonic imposter.
DEQX can be implemented at several levels,
the ultimate being DEQX-HD, DEQX's High Definition ‘active’ implementation.
This attacks the most serious and measurable problems at their source;
the loudspeaker and its component drivers. For virtually any speaker
design, the introduction of DEQX-HD’s active implementation
can result in dramatic improvements in performance.
When DEQX-HD’s
requirement to 'go active’ is not
practical, significant improvements can still be realised with simpler
implementations.
Regardless of the degree of implementation, DEQX’s PDC-2.6P preamp processor
contains extremely transparent Analogue to Digital Converters (ADC),
two SHARC 32-bit floating-point DSPs, highest grade 24/96 Digital to
Analogue (DAC) converters and finally, a 256-step resistor ladder analogue
volume control to maintain the full dynamic range of the DACs at low
listening levels. Nine separate power-supply regulation stages, including
four to provide the main analogue rails, provide very low measured
distortion and fatigue-free listening transparency.
Despite the attention
to audio-path transparency, the key difference that DEQX represents
is found in its software, that you can’t
see, and you can’t hear. In fact DEQX’s digital filters
introduce less than 0.00001% (-140dB) of distortion and noise in
the digital domain (see measurements). Over 300,000 lines of program
code, representing over twenty-one man-years of development and debugging
distinguishes DEQX from all other digital processors and digital
crossovers. Other digital crossovers and correction systems
typically simulate traditional analogue filters with no detailed time
domain or analysis capability for critically important group-delay,
phase correction, and detailed frequency-response correction.
One
of DEQX’s most amazing features is its ability to correct
time for different frequency groups in a loudspeaker. DEQX’s Group Delay correction
is a first, and any audiophile knows how speakers, and even amplifiers,
can cause some frequency groups to lag behind others. DEQX’s
measurement and analysis procedure discovers which frequencies the
loudspeaker (and amplifier) has caused to be delayed compared to others.
Its FIR (Finite Impulse Response) based time-domain filter then delays
all other frequencies, differently and phase accurately for each frequency
group, to allow these to catch up. The extent of this delay depends
on how low in frequency bass is corrected. Typically, just several
milliseconds will bring most of the audio spectrum into time coherency.
The
other necessary correction is frequency response, where the volume
of every pitch needs to be reproduced equally. Speakers are unique
in their inability to provide an accurate frequency response, even
directly in front of them, let alone ‘off-axis’. But natural
sound sources such as musical instruments and voice tend to distribute
all of their frequencies and harmonics far more equally in all directions
(omnidirectionally). This is why much of what we finally hear comes
from the room itself, so we ‘know’ how a real or ‘live’ sound
should sound in a given room! Yet speakers only distribute bass and
mid-range omnidirectionally…higher frequencies (and harmonics)
tend to ‘beam’ mainly forward to the sweet-spot,
not getting a chance to contribute to the room’s subtle reverberations.
This is not normal, and however hi-fi it may sound, we know we’re ‘not
there’.
DEQX-HD allows an accurate rendition of frequency balance
that reflects what a naturally occurring sound in our listening room
would provide. If our room is moderately ‘live’, this requires a full-range ‘off-axis’ as
well as ‘on-axis’ frequency balance, rather than highs
being directed mainly at the sweet spot. DEQX-HD can radically improve
high frequency dispersion in typical speaker designs.
DEQX’s speaker
correction measurement and analysis ignores room reflections in its
measurement, for the purpose of achieving accurate native speaker
performance in the time (phase and group-delay) domain as well as frequency
response. After the native behavior of the speaker is corrected we
have less to be concerned about regarding room correction, other than
the lowest several octaves. Once the speaker is corrected, DEQX then
measures its behavior in the room from the listening area, the results
are displayed graphically using a PC for set-up, and up to ten bands
of DEQX’s
minimum-phase parametric-EQ can be set automatically or manually
to taste.
Beyond DEQXs timing and frequency-response correction, the
DEQX PDC family of products allows the seamless integration of subwoofers
whereby the crossover from the main speaker and subwoofer is properly
crossed over and time-aligned.
Up to four completely different combinations
of speaker and room corrections can be stored in the PDC units for
instant recall. These can include ‘uncorrected’ bypass
mode to remind you (and demonstrate to friends!) what your system
used to sound like before DEQX Calibration™. The PDC-2.6P Preamp’s
remote control also provides up to a three-band tone control for
quick Media Correction with a difference. The difference is that
without any PC connected, you can store 100 different tone settings
for different recordings or simple room EQ. You can use the fast
and simple bass, mid and high default settings, or for more detailed
control, you can move a band’s centre frequency across 10 octaves,
with semitone resolution. You can also adjust a band’s width
from just a semitone to four octaves, and provide cut/boost in one
dB increments.
The PDC-2.6P ‘Preamp’ model provides the
same correction and optional active crossover features as the PDC-2.6
processor, except that it also comes with a remote control and has
an ‘analogue’ volume
control following each of the DACs outputs so that full digital resolution
is preserved even at low listening levels. The remote control chooses
from up to four inputs; two analogue and two digital. For example,
one of the analogue inputs may receive the output directly from a phono
pre-amp, an existing analogue pre-amp or surround decoder for example,
while one of the digital inputs may take the digital source (co-ax)
from a CD or DVD player.
While the DEQX PDC family does not decode surround sound formats,
it easily integrates with external surround sound decoders, preamps
or home theatre receivers. A single DEQX PDC can be used to correct
the left, right and subwoofer speakers within a home theatre system,
or multiple PDCs can be used to correct all speakers within a home
theatre system for the ultimate home theatre experience.
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