Accuphase DG-68 Digital Voicing Equalizer

We hold these truths to be self-evident, that all men are created equal.

A great concept—sound enough to serve as the foundation for an independent democratic nation.

Yet what's sound in one sphere doesn't necessarily apply to sound in another, namely the rooms in which our systems reside. As much as we audiophiles may wish to declare our independence from room resonances, image smearing from first-order reflections, slap echo, and every other environmental and speaker-related factor that can handicap system performance, no mere declaration will make it so. Not all rooms—and not all components—are created equal.

To reference American mythology, Dorothy may have closed her eyes and clicked her ruby-red heels together three times as she declared, "There's no place like home," but she knew exactly what home felt like. Audiophiles who have only heard our components in compromised sonic environments have only a general idea of what their systems can sound like under optimal conditions. There is no there there when you don't know what "there" is in the first place.

Finding the way home
Enter the Accuphase DG-68 Digital Voicing Equalizer ($24,000). The fifth iteration of a unique component that debuted in 1997—a very different era in digital audio—as the DG-28, the DG-68 combines soundfield correction, which Accuphase defines as "Voicing," with soundfield creation, which the company equates with "Equalizing." In "Voicing" mode, the company claims that the DG-68 "measures room acoustics accurately and eliminates extreme dips and peaks such as standing waves. This improves the localization of vocals and the expansion of sound stage dramatically." The DG-68 can perform voicing automatically: A repeating sequence of preprogrammed, cascading multioctave tones generated by the unit is measured by a supplied microphone placed at the listening position. Manual voicing, in which the user creates a preferred target curve before the tones sound, is also possible. Optional custom equalization, in turn, can be performed manually, using a supplied stylus to tailor the frequency-response bands on the unit's large display. Accuphase says that "by performing 'Voicing' and 'Equalizing' [VC/EQ] (footnote 1), it is possible to achieve the ultimate ideal sound."

Accuphase's awkwardly translated, 12-page online pdf elaborates on the difference between "Voicing" and "Equalization": "The Voicing function involves measuring the acoustic characteristics of the room and provides the compensation to achieve ideal reproductive conditions automatically or manually. The Equalizer allows adjusting the tonal result by boosting or attenuating the level of signal in specific frequency bands. Any desired frequency response can be created."

There's a third function: "The Spectrum analyzer makes it possible to display the actual frequency components of the music being played by real-time analysis."

The equalizer displays 80 frequency bands extending to 100kHz. Adjustments can be made while music plays, allowing instantaneous evaluation of the resulting sound. The spectrum analyzer divides the frequency spectrum into 35 bands extending up to 50kHz. The level of each band is analyzed and shown on screen, enabling users to determine where adjustments may be most effective.

After I had spent enough time with the unit to know what I wanted to ask, Arturo Manzano, head of Accuphase USA and of AXISS Audio, its US distributor, suggested I submit queries in writing to Accuphase's design team in Japan. Unfortunately, the company was on an extended vacation and unable to respond until well after the review deadline, so we did the best we could. (Manzano proved quite knowledgeable about the product.)

During one of several phone and WhatsApp exchanges, Manzano succinctly summed up the Accuphase DG-68's raison d'être. "Not all rooms are perfect," he said. "Despite the fact that you have room treatment and room-tuning devices, there may be no way to resolve problems that the Digital Voicing Equalizer can address electronically. The product is equally effective in situations where room treatment is not an option."

The DG-68's plain-as-day main menu, which appears on its large, dimmable front panel, allows four choices: "Auto Voicing," "Equalizer," "Manual Voicing," and "Analyzer." All four choices are explained in a detailed, copiously illustrated, expertly translated 68-page product manual that's included with the unit.

In Auto Voicing mode, the DG-68 can create two very different curves: "Smooth" and "Flat." Once the curves are completed, given a unique name, and stored in memory, you can easily view the curves for the left channel, the right channel, and the two channels combined. You can also see uncorrected curves for left and right channel. Up to 30 curves and settings can be stored on a USB flash drive inserted into the DG-68's USB slot on the rear panel.



Frequency response at the listening position with the Accuphase DG-68's "smooth" (top) and "flat" (bottom) room correction engaged.

"Smooth," the Auto Voicing option Accuphase recommends, is designed to minimize frequency-response differences between left and right channels as it "brings out the characteristics of your speakers and the room." Smooth creates "a very smooth response curve [that] helps to eliminate [standing waves] and emphasize the sound localization of the music source. The smooth voicing feature prevents excessive correction based on the speaker's low frequency reproduction capability, further improves measurement accuracy and enhances the effectiveness of sound field compensation."

"Flat," the less enigmatic Auto Voicing option, is what you'd expect. During the course of the review, I created "Smooth" and "Flat" voicings many times over and spent many hours comparing their sound.

During our conversations, Manzano noted that not all room acoustics are fixed. Sonics change when more than one listener occupies the space. Some DG-68 owners create unique VC/EQ curves for different numbers of listeners (footnote 2). If the microphone is already set up, new curves can be created in 9 or 10 minutes.

And then there is equalization. Because many CDs are less-than-demonstration class—Manzano called some "virtually unlistenable"—some users create custom curves for their favorite imperfect recordings. The DG-68 is able to store up to 30 custom-labeled voicing and equalization curves in memory; users can recall whichever is most appropriate for a listening situation, music genre (footnote 3), or recording.

During the approximately monthlong review period, which included four hellish days during which I lost all connectivity, I stuck to the unit's extremely powerful automatic voicing functions, which are the ones Manzano suggested I explore. Perhaps a follow-up review will be in order to explore the DG-68's manual equalization options.

Behind the curtain
In a nutshell, the DG-68 consists of a high-quality analog-to-digital converter (employing four parallel AKM 32-bit AK5578EN), a high-quality DAC (utilizing eight ESS ES9028PRO channels operating in parallel), and a DSP based on an Analog Devices ADSP-21489 that enables 40-bit floating-point processing up to 384kHz. Both the ADC and DAC circuits are equipped with Accuphase Noise and Distortion Cancelling circuitry, which utilizes feedback and feedforward loops to cancel distortion. A built-in signal generator creates the test tones used in assessing room acoustics. This technical complexity is masked by a simple-to-use automatic voicing function. After 24 years, in what's its fifth iteration, this is a mature product.

The backstory
When Jim Austin emailed me to say that of several Accuphase products available for review, he preferred the DG-68, he added, "That should be an unusual and fun review." He was 50% correct.

The DG-68 arrived during a crucial time in the evolution of my dedicated music room. Although my existing room treatment was quite fine, certain areas in the bass and treble have been calling for more attention. Two months before the DG-68 entered the system, I went whole hog on some relatively inexpensive, broad-spectrum room treatment, whose efficacy was seemingly confirmed using the REW (Room EQ Wizard) room acoustics measurement program.

That's when I ran head on into the limitations of relying on measurements alone. While REW declared that my new ceiling panels (four of them) and sidewall panels (also four) had mostly leveled the room's response from top to bottom, my ears and heart told me the treatment had suffocated my system. He who laments daily the loss of his flat abdomen was now gazing at flat measurements and longing for curves.

During the same week I was coming to terms with my unsuccessful room-treatment choices, Demian Martin, cofounder of Spectral Audio, founder of Entec, and audio consultant to Crosby Audio Works, Rockport, Monster Products, and NuForce, wandered into Port Townsend with his wife Peggy. After a visit to the Olympic National Forest, Demian visited my music room, helped me interpret my REW curves, and played with the manual room equalization option in Roon. All the while, I was dying inside: This was not the sound I wanted a distinguished designer to hear. Nor was it conducive to reviewing equipment and recordings.


Taking my cue from The Wise Men of Chelm (footnote 4), a delightful collection of Jewish folk tales that I laughed out loud to as a child, I sat for seven days and seven nights, pulled my beard, twirled my curls, and took advantage of post-Chelm technology to come up with a marvelous solution. With more than a little help from my friends—you know who you are, bless you one and all—out went the "new" treatment and in came eight Stillpoints Clouds and four Stillpoints Aperture panels. All that remained of the previous treatment were two ceiling panels that did some good in some areas of the audio spectrum and some bad in others. Those panels, too, came down during the course of this review.

Each time I altered room treatments, or cabling, or power treatment, or equipment supports, or component resonance damping, I created new "Smooth" and "Flat" curves with the DG-68, turning VC/EQ on and off and listening intently. Over the same period, I also changed optical (internet) cabling and upgraded optical-to-electrical converters and SFP (small–form-factor pluggable; don't ask) modules. In due time, I created and implemented 18 different "smooth" and "flat" VC/EQ curves.

Under ordinary circumstances, making changes to my reference setup during the course of a review would be verboten. But in the context of a Digital Voicing Equalizer review, each change provided a new opportunity to evaluate the DG-68's efficacy. While the journey was more stressful than fun, it led me closer to Oz. In nonmythological terms, as I made successful changes, the system sound with the Accuphase bypassed got progressively closer to sound with the unit activated. The room itself was doing more of the heavy lifting, and the Accuphase was proving itself a useful tool.

Constructing the set
I placed the DG-68 on one of the two top shelves of the Grand Prix Monza equipment rack and used Nordost Odin 2 balanced cabling to install it between the D'Agostino Momentum HD preamplifier and D'Agostino Progression monoblocks. I set the ADC sampling rate to 352.8kHz, its highest setting. Arturo said "yes" to using the AudioQuest Niagara 5000 power conditioner, so I plugged the Accuphase (along with everything else in the music room) into it.

He said "no" to support feet, so none were used.

For music, I stuck to the Roon Nucleus+ music server and dCS Rossini DAC/Rossini Clock combo for file playback from my NAS and streaming from Tidal and Qobuz.

Footnote 1: VC for, apparently, "voi-cing" is one of the more peculiar initialisms I've come across in a while.—Editor

Footnote 2: Nagata Acoustics, designers of Walt Disney Concert Hall in Los Angeles, covered the bottoms of the hall's seats with absorptive material in an attempt to compensate for changes to acoustics brought about by empty seats.

Footnote 3: Like it or not, some speakers work better for some types of music than others. Limited-range bookshelf speakers, for example, are often better suited to small jazz combos, single soloists and guitar, and chamber music than to full-range organ music and up-against-the-wall orchestral blockbusters.

Footnote 4: The Wise Men of Helm & Their Merry Tales by Simon Solomon, illustrated by Lillian Fischel.

Accuphase Laboratory Inc.
US distributor: Axiss Distribution Inc.
17800 South Main St., Ste 109
Gardena CA, 90248
(310) 329-0187

Anton's picture

I would think your room has to be OK for it to be able to produce a decent room curve to begin with.

Your idea of continuing to tweak your room while you have the toy is genius.

It would be cool to have a "mother module" to use to set the room, and then a much less expensive "servant module" or chip that could talk to your DAC that you could then plug in to keep 1-3 curves while allowing the mother ship to continue her sonic journey.

Archimago's picture

Nice to see audiophilia using (at least not afraid of) EQ and finding benefit in "room correction" techniques.

So, basically, from a technical perspective is this performing 2-channel 35-band parametric EQ (settings up to 50kHz)?

Is there any time-domain correction being done when fed with room information (doesn't look like it?)?

teched58's picture

$24,000 seems a̶ ̶l̶o̶t̶ ̶o̶f̶ ̶m̶o̶n̶e̶y̶ very affordable for a 35-band parametric equalizer!

Anton's picture

Wow, what a great addition that would be.

RichT's picture

Something very unexpected here - the flat response curve is incredibly flat, I would estimate -3dB +1dB. This is a flatter response than most professional studios achieve, even the best. It’s totally flat 30Hz to 90Hz, which is absolutely remarkable. This Is very special room.

Kal Rubinson's picture

And not everyone wants flat. ;-)

MatthewT's picture

Perfect is boring.

Kal Rubinson's picture

And, under some conditions, undesirable.

MatthewT's picture

Is the sum of its flaws, and I love them all.

latinaudio's picture

are a necessity. What is certain is that the sound perceiver must be taken into account: the brain. And since no two human beings are alike, it will ALWAYS be necessary to adjust the bass, treble, midrange to each person... in order to have a pleasant experience. Tone controls ARE an unavoidable necessity, and hifi manufacturers builders would be arrogants if they don't accept it. So remember: it´s not only the room, are the persons, specially the owner of the equipment :)

Ortofan's picture

... published in the November 1973 issue of Audio magazine.

It includes a description of the then new Altec 729 Acousta-Voicette one-third octave equalizer and the Altec/HP 8050 real-time analyzer.

Presented is a rationale as to why the corrected frequency response should not be flat over the entire audible range.
The proposed optimum frequency response is flat up to 2kHz, followed by a roll-off above than point at the rate of 3dB/octave.

Kal Rubinson's picture

Good stuff at the time but acoustical science and audio componentry have moved on.........................

Ortofan's picture

... the latest developments in acoustical science (and audio componentry) suggest is ideal?

Kal Rubinson's picture

Toole's book is a good place to start.

Ortofan's picture

... those under the Harman umbrella, agree with Dr. Toole's findings and implement them in their products?

Kal Rubinson's picture

I suspect that all the current AVRs and prepros incorporate them in their EQ options.

zuman's picture

I've been listening seriously and buying good gear for over 40 years, and I firmly believe that the effects of some "tweaks" CAN be measured while we haven't yet discovered how to measure other audible tweak results. However, I also believe that many tweaks are placebos. Is the DG-68 sufficiently sensitive to identify/quantify/adapt to some of the supposed "night-and-day" effects of some of these tweaks?

Anton's picture

Of course, no matter the outcome no minds would be changed.

We are audiophiles, after all. ;-D

pbarach's picture

I wonder how this unit's results would compare to some of the other (much less expensive) room correction systems, e.g., Audyssey, ARC, Trinnov.

Kal Rubinson's picture

Hard to compare correction systems which reside in different hardware.

georgehifi's picture

Love to have this thing, but I would have liked to have heard the comparison of what Rossini Ring/Dac was like from the Accuphase's digital outputs compared to it's own ESS dac (never been a lover of the ESS converters). (was it done???)

Cheers George

AudioBang's picture

Back in the late 90s I bought a Sigtech for $7,300 which, in addition to room EQ, performed time alignment, cancellation of late arriving ceiling, floor and wall reflections out to 50mS, and had the ability to compensate for spectral build up [from room corners, etc].
I owned a pair of Dunlavy Vs at the time, later upgrading to the SC VI.
Since the Dunlavy's are all time-aligned to begin with, as expected, the impulse response did not visually change after a correction filter was applied. I too found it easy to get caught up in jumping from correction filter to correction filter and being distracted from the music. The Dunlavy recommended listening position was against the long wall so the speakers could be placed with a wide listening angle - up to 120 degrees! [per the manual] and obtain the smoothest bass response by eliminating room nulls. I liked mine at about 100 degrees as there was a level of psychoacoustic wonder at hearing a phantom center image with the speakers 12 feet apart while still presenting a reasonably proportioned soundstage. I later learned from the SigTech measurements, that with the listening position against the rear wall, the room buildup in the bass was enormous! A significant contribution in my system that the Sigtech made I felt, was ameliorating the room build up against the rear wall as well as smoothing a 12dB delta from 30hz to 90hz - I suspect from the interactions between the bass drivers positioned at the floor and the top of the cabinet. The low frequency measurements of my speakers from Dunlavy's very large anechoic chamber showed a similar 12dB peak to null although at slightly different frequencies from my room. Also, I recall, not all of that 12dB difference could be flattened as you wouldn't want to add unprecedented gain at high listening levels at the null which could blow the drivers. In a nutshell, in my room, taming the bass [overhang] was a significant factor in arriving at more transparency and I felt that manually treating the room [absorption in my case] for first sidewall reflections worked better than relying on the Sigtech's ability to cancel them out - even though these reflections were eliminated on the filtered impulse response. The measurement capability of these reflections was instrumental in confirming the before and after effects of midrange smearing that was eliminated after applying absorption from first reflections. I was not successful attempting to fix bass problems with corner traps.
The 2khz -3dB/octave rolloff was the recommended default filter. The flat filter sounded dry and sterile and was not pleasurable to listen to although I look back and wonder if part of the reason was that the recommended rolloff starting at 2khz may have masked the sub-par 90s digital in my system [Wadia 270 Transport/27ix DAC]. For what it's worth...

John Atkinson's picture
AudioBang wrote:
Back in the late 90s I bought a Sigtech for $7,300 which, in addition to room EQ, performed time alignment, cancellation of late arriving ceiling, floor and wall reflections out to 50mS, and the ability to compensate for spectral build up [from room corners, etc].

Stereophile's December 1996 review of the SigTech system will be posted to the website the week starting August 9.

John Atkinson
Technical Editor, Stereophile

tonykaz's picture

I recall setting up our Listening Rooms at Esoteric Audio in the 1980s.

We ended up with a Semi-Anechoic type result that needed the Largest Mono Amps pushing thick MH-750 Music Hose Speaker Cabling.

Do our brains re-calibrate room accoustics for us ( to some extent ) ?

I suspect that Room Problems are exasperated by Loudspeakers with too-powerful Bass circuits and no balancing electronic circuits..

B&O make that gigantic Beolab 90 that features built-in Room Correction.

Full Range Loudspeaker Manufacturers should include some sort of Bass management system as an included component. ( Genelec )

Leaving Accoustic Engineering in the hands of purchasing Consumers seems irresponsible.

Accuphase Gear is Georgous

Tony in Venice Florida

AudioBang's picture

I concur that our brains recalibrate room acoustics for us - to some extent....
Interestingly, per MF and other Stereophile reviews on the ISO Acoustics speaker isolators, I tried three sets on my Dunlavy SC VIs [650 lbs each] and they completely altered the bass. On the one hand, I agree with one of the reviewer's comments that they were "different" and on the other, the bass overhang that I am used to [assuming] from room modes, was reduced an order of magnitude as if "where did it all go?" But the transparency, depth and expanded soundstaging these footers offered was unexpected and unprecedented. I'd take these results 10X over any EQ solution. Because the rebuilt 4-way crossovers reside outside the speaker, while I was contemplating trialing the footers, I had disconnected the bass completely out of the picture to test whether the vibrational bass coupling to the floor made any difference to the midrange/treble. I didn't hear any difference. But after installing the footers everything transformed at the magnitude that MF stated in his review. I can only assume that even with just midrange and tweeter operating, something vibrationally is happening to/within the 650lb cabinet causing blurring to occur. My brain can not connect how that happens. BTW Stereophile, thanks for your value-add here. This was one of the most profound improvements I've experienced.

tonykaz's picture

Can we hear from the Loudspeaker Manufacturer on these devices.? Why don't they include these with every speaker?

I probably consider them to be like Engine Mounts for a vibratingly harsh Car, Truck, Boat Engines.

NoiseVibrationHarshness is a science, we should be able to explain these phenomenons and bring about consistant effects/affects.

In the 1980s I sold large quantities of Audio related do-dads, Audiophiles love to tinker around with this stuff.

Tony in Venice Florida

Kal Rubinson's picture

Can we hear from the Loudspeaker Manufacturer on these devices.? Why don't they include these with every speaker?

Good questions and there are a couple of speakers with them on their way to market The general answer is that it will increase the price of the speaker and manufacturers have to compete on price in the real world.

It evokes the memory of an amp manufacturer who told me that I could not realize the full potential of his product without a particular after-market power cord. I was surprised at that and asked why he would not just include it. He replied that it was a matter of price. I bought one anyway (who would not want his new amp to sound its best) but I found it was absolutely not audibly different from the stock cord. He should not have opened his mouth.

Ortofan's picture

... is including shock-mount feet.
Speaker prices range from $1,850 to $4,250 each.

Kal Rubinson's picture

PSB, too.

tonykaz's picture

Good Better Best has been a Sales Standard in all sorts of Product types..

I'd expect better from the Full Range Transducer System manufacturers, just as we've come to expect ( and rely on ) Stereophile Reviewing and Editorial Standards.


Audiophiles are typically DIY kinds of folks.

I'm a Fan of Meridian type of Music Systems approach from Manufacturers. I can enjoy a high performance designed full System from one Company.

Still Tweaking one's music systems can be a nice little distraction from the World problems crushing our shoulders.

Big Fat Stiff Power Cords are visually impressive, you could say "those power cords alone cost Thou$$$$$$and$$$ of Dollars!! ( even toss a handful of hundred dollar bills on the floor behind the speakers ( to show off even more )

Audio stuff can still be fun! I think

Tony in Venice Florida

tonykaz's picture

I just heard that the NY Auto Show is cancelled.!!!

We're not out of this China Plague yet

Tony in Venice Florida where masks are still optional

Kal Rubinson's picture

But what about the NY Audio Show?

tonykaz's picture

It seems that we are entering a new phase of China Pandemic hysteria with this Fresh Strain that can be understood but isn't..

So, we might usefully predict that Big Shows will set the pace for all the little Shows like Audio and/or things like Tool Shows.

CDC is predicting the New Strain will take the rest of this year to run it's course ( in USA that has less than 100% Vaccinations depth ).

Global Vaccination percentages have barely scratched the surface so we are a looooooonnnnnnnngggggg way from Herd Immunity!

Will it predictably take the Standard 3 to 4 years for this blight to run it's course ???

Will the politicians and media continue to foster Health condition Panic among the innocent polis ?

I have the feeling that Streaming and DACs like the dcs Bartok will have overwhelmed HighEnd Audio by the time this Virus is tamed.

It's time to sell off my Koetsu & Vinyl collections

Tony in Venice Florida

AudioBang's picture

I think you would be a very cool neighbor to have Tony :)
I enjoy your industry stories and commentaries from your experiences.