DEQX provides many different features that improve loudspeaker performance, and each of these will make noticeable improvements to any loudspeaker system, from DIY designs (where improvements will be dramatic if implemented ‘actively’) to the highest-end $100,000+/pair of audiophile speakers. The degree of improvement will depend on the accuracy of the speaker being corrected and the degree to which DEQX is implemented.DEQXs processor products such as the PDC-2.6 Processor and the PDC-2.6P Preamp/processor provide a comprehensive range of features; some or all of which may be implemented. The same DSP and super-high transparency electronics are used for even the most simple of these features; so if you initially plan to implement the most basic of features you can be reassured the PDC family of products will grow with your audio system.   The most basic implementation of the PDC-2.6P (preamp) is very easy to use and does not require any PC set-up, or require the DEQX Calibration/measurement kit. The 2-ch (stereo) PDC-2.6P provides 4-input Preamp, DAC and volume control, with 3-band parametric EQ. All control is by the remote control.The remote sets volume, selects inputs and also controls the 3-band parametric room and media correction EQ. A resistor-stepped attenuator maintains full DAC resolution at low listening levels and the minimum-phase EQ does not compromise sound quality.The EQ has 100-memories to store and recall the correction settings. The three bands are; a bass shelf filter with variable frequency and Q, a full mid parametric band (20Hz to 20 KHz) with bandwidth (Q) variable from one semitone to four octaves wide, and a high shelf filter also with variable frequency and Q.The Lo, Mid and Hi settings default to simple tone controls, but precision EQ can be applied by first selecting the approximate frequency in octaves (0-9) And then the < and > buttons move in semitone increments - the up/down buttons adjusts level in 1dB steps. A 0dB button resets the band being set to ‘no-EQ’, and an ‘EQ reset’ button ensures all 3-bands are set to zero. For simple tone control, a Lo, Mid or Hi buttons is selected then the up/down button provides quick gain or cut for each of the three bands.The PDC-2.6P processor can be connected between an existing stereo or Home Theatre pre-amp and power amp for equalization, or it can be 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 2-input channels in analogue or digital (PCM) to 96KHz - compressed or surround digital formats are ignored.Multiple PDC-2.6P units can be used to provide surround formats when driven by a surround decoder’s analogue outputs. However, a single PDC-2.6P can be used to correct only the main left/right speakers of a surround system, ensuring that Stereo CD and film music sound their best (also see BASIC+RC plus Sub config). In addition to the features offered in the BASIC PDC preamp configuration, in this scenario the DEQX Calibrated™ microphone, supplied with the DEQX Calibration Kit, is used to measure th room and speaker behavior at the main listening area. The calibration kit also includes DEQX’s measurement, analysis, and correction software that runs on a Windows XP PC, connected to the PDC via USB or RS-232.Seven bands of DEQX’s minimum-phase Parametric EQ are provided for room correction, or 10-bands if DEQX Media Correction is not used. Measurements are shown graphically on the ‘Equalizer’ display. Following a measurement or measurements, the ‘auto-set’ control brings up a wizard that provides default suggestions, and asks what frequency range ‘auto-correction’ should be applied to (default is 20Hz to 300Hz), how many bands to allocate (default is 5), and what maximum boost and cut is allowed (default is +6dB, cut is -10dB).Multiple measurement locations can be made around the listening area. When ‘auto-set’ is chosen the correction will be based on the average chosen. Four different room correction curves can be saved in the PDC, so correction profiles can represent a small or wide listening space for example.The EQ bands work in real-time and can be manually added or subtracted. When ‘auto-set’ is chosen, the suggested correction is graphically overlaid above the room measurements. Any of the filter bands can be selected and adjusted manually while music is playing.The “Auto-set” feature automatically sets correction parameters for the lower three to four octaves specified, where equalized room correction is most relevant. However, any band can be manually centered on any frequency up to 20KHz, with bandwidths adjustable from one semitone to 4-octaves. Installation in the audio chain is the same as for BASIC install. In addition to the features offered in Basis plus room correction, this implementation provides DEQX’s uniquely powerful Speaker Correction. DEQX Calibrated™ speaker correction corrects the frequency-response and time-domain group-delay errors in fine detail, essentially at thousand of frequencies. This implementation corrects your speakers using their existing crossovers, and does not require ‘going ‘active’. Connection to other components in your system is the same as BASIC.DEQX Calibrated™ Speaker Correction involves measuring the speaker using a pseudo-anechoic measurement technique whereby the software minimizes, or eliminates, the effects of sound reflecting back from the room. This is necessary in order to measure and correct the speaker’s native time and frequency domain performance before the measurement is corrupted by room reverberation. ‘Room Correction’ requires far less detailed correction than DEQX Calibrated™ speaker correction.When measuring a speaker, the microphone is placed one to two meters on-axis to the speaker (further for larger speakers). The measurement produces an impulse response display whereby time (in milliseconds) moves to the right and amplitude is shown vertically. The initial ‘impulse’ at the left represents the signal generated by the speaker and its first reflection comes from the nearest room surface, usually the floor (sound travels about 1 foot per millisecond). By positioning the Impulse Truncation Cursor the time-domain correction can include or ignore varying degrees of room reflections.With measurements complete, you simply specify the frequency range that you wish to correct and the software automatically creates the perfect phase and frequency response correction filters for your speakers. The DEQX Calibration software is easy to use. Its graphical user interface and "wizard" assisted operation provides default suggestions, but also gives you complete control over the correction parameters applied to your speakers. A DEQX-HD configuration provides the same features mentioned earlier but utilises its active crossover outputs. In order to achieve the ultimate performance from any loudspeaker design, DEQX-HD corrects each driver individually. It then combines the necessary time and frequency domain correction with DEQX’s linear-phase crossovers that can essentially eliminate the loss of resolution caused by traditional passive and active crossovers:We have been patient with the performance of loudspeakers for a long time, when compared to the performance of every other component in the audio chain. The loudspeaker alone has kept the High Definition ‘Being there’ experience elusive, even after heroic efforts and the highest prices. Finally this experience is available reliably, and affordably! The benefits of going to DEQX-HD’s active architecture are extraordinary, because DEQX’s unique amplitude and time correction are added to the advantages of going active! The result is a raft of improvements that are necessary to provide the HD listening experience!Individual control over each driver: DEQX-HD’s active crossovers provide a signal to a separate amplifier for each driver, such as a woofer and tweeter. The audio signal has been reconstructed from its basic sine-wave components to allow both frequency-response (amplitude) and phase (time) correction to occur at thousands of frequencies independently and simultaneously! This is the only way that is possible to correct amplitude, time and phase differently for thousands of frequencies simultaneously. DEQX_HD processing introduces only 0.00001% distortion (-140dB) in the digital domain! By contrast, ‘passive’ crossovers must separate and distribute amplified bass, mid and high frequencies to their respective drivers, with no ability to compensate for even the most gross errors and distortion that each driver introduces.Reduced high frequency distortion: DEQX-HD’s active crossovers can provide far steeper slopes than normal passive, active or digital crossovers to ensure frequencies are quarantined to where the drivers behave best. Bass energy that causes tweeters to distort is withheld, allowing the crossover frequency to be reduced so that its speed and character matches the mid/bass driver’s at the crossover frequency. resolution better matches the tweeter can provide more highs at lowe distortion than is possible from the mid/woofer.Reduced mid-range distortion: We are used to hearing tweeters strain to provide a significant degree of midrange frequencies, which passive (shallow) crossovers force them to do, however reluctantly. A bass/mid driver is deigned for mid-range however, so DEQX-HD can direct all mid-range frequencies to it, while protecting it from distortion-causing low-bass energy. Meanwhile, crossover-distortion such as comb-filtering is audibly eliminated because drivers are precisel time-aligned and interaction between drivers is over a very narrow frequency region in any event if steep crossovers are used.Reduced bass distortion: Good bass resolution requires minimizing room reflections of bass energy and relieving low-bass energy from smaller bass and mid-range drivers. DEQX-HD minimizes bass distortion from drivers by directing all low-bass energy to the sub-woofer/s or low bass drivers rather than forcing the smaller drivers to share the load in the way that passive crossovers insist they must! DEQX also facilitates the easy integration of one or two sub-woofers by providing a high-pass, time aligned filter to the main speakers, to relieve them of bass energy that can increase their distortion. The use of two Subwoofers is advantageous because it allows higher sub-main crossove frequencies and if room-corner loaded, they provide more coherent bass that can be synchronized to main speakers placed several feet in front of them, in both time and amplitude, minimizing th need for complex room correction.More natural dispersion: Naturally occurring sound from most musical instruments and even voice tend to distribute all frequencies in all directions – omnidirectionally. However speaker drivers only do this until their diameter causes higher frequencies to ‘beam’ forward only. A 6” mid/woofer increasingly beams frequencies forward above about 2KHz, whereas a 1” tweeter remains omnidirectional until its starts to beam noticeably above about 10KHz. DEQX-HD’s steep linear- phase crossovers can be made to quarantines each drivers output to where its dispersion remains similarly omnidirectional to naturally occurring sound. This not only makes the speakers sound more natural from anywhere in our listening room, but even the sweet-spot will sound more realistic du to the more ‘expected’ room reverberation contribution.Accurate amplitude with frequency balance: Only DEQX-HD active crossovers correct frequency- response precisely at thousands of frequencies simultaneously.Group delay correction: In addition to perfect time alignment, only DEQX-HD active also correct the absolutely critical issues of timing phase and group-delay differently for thousands of frequencies simultaneously.Driver isolation: Only DEQX-HD active additionally provides linear-phase filters in the crossovers up to 300db/octave to isolate or minimise driver interaction.Affordable amplifiers: Only the most heroic amplifiers can drive the ten-octave range of a passive speaker almost flawlessly, so these tend to be extraordinarily expensive. DEQX-HD active allows far simpler amplifiers to be chosen for what they do best. This is because amplifiers used with DEQX-HD only need to operate perfectly over the three to five octave range that each individual driver type requires. They are also not asked to drive ‘reactive’ crossover electronics found in passive speakers. This especially reduces the dynamic and power related distortion and intermodulation distortion that we hear, but traditional measurement techniques don’t measure.Goes louder: Since DEQX-HD’s steeper crossovers quarantine energy to the frequencies where each driver performs best, it follows that distortion is usually lower compared to passive configurations, meaning that volume levels can be increased, sometimes dramatically, before equivalent distortion sets in! This means less drivers, less cost, physically less intrusive for better W.A.F. (Wife Acceptance Factor), and remembering that DEQX-HD provides mono and stereo sub-woofer integration that allow high resolution compact 2-way designs to perform better than enormous audiophile floor standers…regardless of price!DEQX-HD takes active to its logical conclusion: The PDC-2.6P and PDC-2.6 can both provide DEQX-HD crossovers for up to 3-way speaker designs. A recommended configuration is 2-way main speakers integrated with dual sub-woofers for coherent low bass in the room. Its steep crossovers essentially eliminate crossover distortion by providing stee p slopes from 24dB/ocatave to 300dB/octave, with sub to bass slopes of typically 60dB/oct and bass to tweeter slopes of 100dB/octave. The steepest slopes can be used when using drivers whose sound character and dispersion characteristics are similar at the chosen crossover frequency. Fortunately DEQX-HD makes this easier because steep slopes also the lower crossover frequencies necessary to allow this more transparent transition.The difference between DEQXs High Definition™ “being there” loudspeaker performance and today’ s passive speakers can be as dramatic as the difference between standard definition (SD) TV and HDTV where improvements are obvious to everyone! DEQX-HD Calibrated™ now makes this affordable for every type of loudspeaker system.DEQX is used to provide the ultimate listening reference standard in some of the worlds most prestigious mastering studios Now anyone can incorporate DEQX Calibrated™ and DEQX-HD Calibrated™ processing to experience the most transparent and accurate listening experience possible.