Music in the Round

Bit-perfect playback of multichannel files at all bitrates up to 24/352.8 PCM or DSD256 was just fine. When I asked the Nucleus+ to downsample 24/352.8 to 24/192 or DSD256 to DS64, as one might do to accommodate a particular DAC, I got messages ranging from "2x" to "4x," indicating that it had little in reserve. Upsampling, too, seemed to drain the tank, more with upsampling from DSD to DSD256 than from 44.1/48kHz to 192kHz PCM. Upsampling from 44.1kHz PCM to DSD256 was just managed as continuous play, with a headroom indication of just under "2x," but 48kHz PCM to DSD256 was unstable, with an indication of "*#60;1." I didn't consider any of these operations dependable—the headroom was so low that they might fail if there were, say, problems elsewhere on the LAN due to other users.

From all that, you might conclude that adding DSP might not be a walk in the park. I set up two DSP configurations: an easy one that included only some simple parametric EQ filters and speaker setup (channel delays and levels), and a more arduous one that added convolution processing for room EQ. All of these worked perfectly well at all PCM resolutions up to 24/352.8, though at that highest resolution the headroom indicators dropped to between "3x" and "5x." With DSD, the situation was not so happy. Only with the easy configuration at DSD64 did the headroom rise above "1.5x" and give continuous playback. Adding the convolution processing, it shrank to "1x" and played only some of the time. With DSD128 and DSD256, the headroom was always less than "1x" and playback was riddled with interruptions.

Roon does provide options that can improve this performance. Turning on "Parallelize Sigma-Delta Modulator" made only an incremental numerical improvement but in a few cases it enabled continuous play. Switching off the default "Enable Native DSD Processing" had a much bigger impact, enabling playback of all formats with conversions or DSP functions. DSD purists may wrinkle their noses at the thought of a PCM intermediary in their DSD signal path, but such an objection is merely doctrinaire in the context of a process that's already not bit-perfect. Playback with conversions and DSP was also secure for all sources other than DSD128 and DSD256. With those, the headroom was in the borderline range of "1.5" to "0.9x," indicating that, whichever i7 chip is installed in the Nucleus+, it's doing more than yeoman's work but it is being pushed to the limits of its ability.

I'd hoped that Roon Labs' Nucleus+ would be the answer to my prayers for playing and processing hi-rez multichannel files. It succeeded at the former but was a bit less proficient at the latter. It's a well-designed and beautifully made device and I do understand why any fan of two-channel music, such as our own John Atkinson, would love it. If you have a pre-pro with HDMI input (don't they all?), so that it can be used to manage multiple channels and room EQ (ditto), the Nucleus+ would be an ideal source component for multichannel music.

Actually, the Nucleus+ is the ideal multichannel Roon player for everyone. It meets with finesse all reasonable needs of the demanding listener. Does anyone other than an obsessive critic require playback of six-channel DSD256 or 24/352.8 files with DSP, conversions, and convolutions? Only to those few nitpickers do I again quote Chief Brody, in Jaws, when I suggest that "You're gonna need a bigger boat."

Upmixing stereo with Auro Technologies' Auro-3D and KEF's R8a Dolby Atmos surround loudspeakers
In 2015, as part of a review of the Marantz AV-8802a preamp-processor, I borrowed a pair of Dolby Atmos–enabled speakers from Atlantic Technology to do a quick-and-dirty survey of what the new immersive audio codecs—Dolby Atmos, dts-X, and Auro Technologies' Auro-3D—could do for music. The answer was, and remains: not much. It's not that these processes don't work, but that they add little to a good 5.1-channel recording. And so few music-only recordings have been released in these formats that they're unworthy of serious attention.

More recently, I had the great pleasure of spending an evening at the home of Floyd Toole (footnote 2), former corporate vice president of acoustical engineering at Harman International, where I enjoyed great conversation, wonderful food and wine, and his impressive sound system. Toole has configured his 9.4.6-channel system to support those immersive surround codecs, but he wanted to demonstrate his great and newfound delight in using the Auro-Matic function of Auro-3D (the codec for which is used in many Blu-ray discs, footnote 3, the decoder included free in such products as the Marantz AV8805) to upmix stereo recordings to multichannel. He played tracks he'd selected because they responded well to this treatment, and the demos were impressive. Time after time, the effect was not of a totally remixed and immersive sound but of a remastering that retained all the good and well-appreciated features of the original while somehow bringing me closer to the performance and by revealing new details in it—details that had been there all along but were now more easily audible.

On my flight back to New York I was already calculating how I could do the same thing with my more modest setup in our weekend home in Connecticut, where I've promised to punch no more holes in the ceiling or walls. I would be restricted to using so-called Atmos Surround speakers, which are intended to be aimed upward at the ceiling to reflect sound down toward the listeners and thus simulate sound sources from above. I have Monitor Audio Silver 8 left, center, and right speakers and Silver 2 surrounds—but Monitor doesn't make Atmos speaker models, which, they argue, sound significantly inferior to ceiling-mounted speakers, and I concur. Still—holes in our ceiling are no-go.

After looking around, I thought that KEF's new R8a Atmos Surround speakers ($1399.99/pair, footnote 4) would be a good physical match for my Monitors, and managed to convince KEF to lend me three pairs (!). The R8a uses the latest version of KEF's Uni-Q coincident array drive-unit, and I felt it would generate a more predictable and coherent reflected sound than any speaker with multiple spaced drivers. I placed one pair atop the L/R Silver 8s and another pair atop the LS/RS Silver 2s. After running Audyssey, the tonal match among the Monitor Audio and KEF speakers was excellent. Both pairs would be useful for Auro-3D and Dolby Atmos.

Positioning the third pair of KEF R8a's was more of a challenge. Putting them at the back of the room, to convert my base arrangement from 5.1- to 7.1-channel surround, made minimal audible impact, but no other locations were compatible with both codecs, and perching one R8a atop the front center speaker would block our view of our plasma display. The temporary solution was to place them outside the main L/R speakers, at the sides of the room, and set the Marantz AV8805 to run them as Front Wide speakers (FWL/FWR) for Atmos playback—but they'd be invisible to Auro-3D.

I experimented with this setup for about two weeks, and while the sound of suitably encoded Auro-3D and Atmos recordings was clearly enhanced by the height channels, upmixing two-channel music tracks with Auro-Matic 3D was always a trade-off, even with the tuning adjustments available (footnote 5). I could get a more spacious sound, but always with a sacrifice in immediacy; and I could get more solo detail in the center, but at the price of disassociation of the soloist from the rest of the music and the ambience. I was ready to chalk it all up as a failure and blame it on my incompetence and the unavoidable compromises. After all, it had worked for Floyd Toole.

It then occurred to me that height was not the dimension I needed to play with: What I wanted was to widen the soundstage and bring it closer to me. So I decided to connect the pair of KEF R8a's now sitting to the sides of the room to the Marantz's Front Height outputs and let Auro-Matic 3D have at them. Keep in mind that these speakers were sitting upright on shelves, just at ear height and aimed slightly upward but not directly at the ceiling. In other words, they were functioning as Wide, not Height speakers.

Right away, I knew I was on the right track. The effect was always positive, though it varied with the source material, from barely detectable to transformative. With most classical recordings recorded in a single coherent ambience, the soundstage was pleasingly wider. With pop or rock recordings, particularly those with complex mixes or recorded with a lively concert ambience, this effect was substantial. Three examples:

Of Hugh Masekela's various recordings of "Stimela (The Coal Train)," I like best the one on his live album Hope, in an excellent DSD edition that cries out for multichannel treatment but is two-channel only (SACD/CD, Razor & Tie/Triloka/Analogue Productions APJ 82020). Auro-Matic 3D drew me in to the actively raucous concert space. Masekela's voice and trumpet were as solidly up-front as ever, but the newly granular detail of everything else gave it more of the impact of a live event.

"I Heard It through the Grapevine," from Michael McDonald's Motown (SACD/CD, Motown 038 652-2), is in surround, instruments and voices in all channels. For those who find that sort of thing distracting, turning on Auro-Matic 3D widened and deepened the soundstage but kept it all in front of me.

Finally, there was "Oh Yeah"—or any other track—on Yello's One Second (CD, Mercury 830 956). It sounded bigger and bolder than ever, but was still the same fun ear candy. In addition, the transformation wrought by Auro-Matic 3D did something to the bass that added considerable impact and should give your subwoofers a workout.

I'm not suggesting that everyone run out to buy an AVR or pre-pro with Auro-Matic 3D, but if you already have one, it takes little effort to add a nice pair of Wide speakers like the KEF R8a's. You may love it as much as I do—it's worth a try.

Next Time in the Round
I'll report on Hegel Music Systems' new multichannel power amplifier and on DSPeaker's long-awaited Anti-Mode X4 DAC.

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Footnote 2: Floyd Toole's book is a treasure trove of information about acoustical imaging: Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms, Third Edition (New York: Focal Press, 2018).

Footnote 3: Auro Technologies, Galaxy Studios, Kievitstraat 42, 2400 Mol, Belgium. Tel: (32) (0)14-31-43-43. Web: www.auro-technologies.com.

Footnote 4: KEF, GP Acoustics (UK) Ltd., Ecceleston Road, Tovil, Maidstone, Kent ME15 6QP, England, UK. US distributor: GP Acoustics (US) Inc., 10 Timber Lane, Marlboro, NJ 07746. Tel: (732) 683-2356. Fax: (732) 683-2358. Web: www.kef.com

Footnote 5: Auro-Matic 3D's Preset adjustment offers options that tune the system for the type of music and size of the performance space, and its Strength control lets the user determine the degree of upmix, from 1 (no upmixing) to 16 (maximum effect).