Digital Processor Reviews

This is all standard procedure for Dirac Live and has been for a while. What's new is ART—Active Room Treatment (footnote 7). ART is the long-awaited fruition of Dirac Unison, which Dirac tantalized me with way back in 2011. It has been described as a "patented MIMO mixed-phase impulse response correction technology," which implements bass management with co-optimization of the subwoofer(s) using a single all-pass filter for the redirected bass with individual all-pass filters for the full-range channels, individually or in groups. In practice, ART utilizes the low-frequency output of all the speakers and subs (each within its own useful bandwidth) "to control the room by sending out antisignals to cancel low-frequency resonances," taking into consideration the in-room acoustical interaction of all the speakers and subs up to 150Hz.

It does this by allowing each and every speaker to play as far into the bass as it is capable of going. However, each and every speaker is also used, within its range below 150Hz, to implement room correction and bass extension for the other speakers. In the enhanced "Filter Design" phase of DL-ART, the user has the option of assigning which main speakers and/or subs will be used to support which main speakers or subs, because in very large systems, one might want to segregate the speakers into groups by room location. In my relatively small, simple system (for an Atmos setup), I had all of them supporting each other. This resulted in greatly enhanced "fill" among all the speakers in all three dimensions as well as improved definition from the lowest frequencies through the upper bass and accurate bass localization without introducing "bass management" per se. Evidence of this in operation can be seen in ISP Evo screen displays, which show all 12 channels active even during stereo-only playback. See the display below.

I was listening all along
This long preamble before saying anything about sound and music is not representative of my real experience. There was music playing through the Evo from the moment I established the first, if faulty and incomplete, connection from source to speaker. Playing through the Evo, my system had its expected tonality and detail even before I optimized the routing (via Aneman) and acoustical balance (via Dirac Live). Playing through the Evo fully configured was consistently even better.

A simple example is playing a wonderful stereo recording from my library, such as the collection of György Ligeti's pieces for groups of winds (24/96 download, Harmonia Mundi HMM905370). I love these, especially the Six Bagatelles for Wind Quintet, and I was particularly taken with the delineation of the instruments when I reviewed the Estelon AURA loudspeaker. None of that was lost with the KEF Blade Twos and the ISP Evo. DL-ART opened up the soundstage and, with the accompanying Chamber Concerto (François-Xavier Roth conducting Les Siècles), there was more richness in the lower instruments and enhanced awareness of the hall acoustics.

The ISP Evo with ART was even more rewarding with a full symphony. I can recommend a thoroughly entertaining new disc/download of juicy orchestral excerpts from Italian operas, Verismo - Preludi e Intermezzi, from Domingo Hindoyan and the Royal Liverpool Philharmonic Orchestra (16/44.1 download, Onyx 4242). This is romantic, heart-on-the-sleeve stuff, and it benefits from Hindoyan's commitment and the big sound of the RLPO in its home hall. Start anywhere, but don't miss the rich brass and soaring strings of the Intermezzo from Act III of Mascagni's L'amico Fritz or the sparkling, delightful Overture to Il segreto di Susanna by Ermanno Wolf-Ferrari. Perhaps these are not the media or the programs that one immediately associates with an Atmos-enabled prepro like the ISP Evo, but it does a bang-up job with them. Switching off the DL-ART correction filter, everything fades very noticeably, losing clarity and presence. Restoration evoked a sense of "now it's right."

Another instance of that same perception happens when listening to streaming from the Berlin Philharmonic's Digital Concert Hall (footnote 8). I am addicted to this service for its live streaming on Saturdays and for mining its archives for "live" performances, recent and past. Many of their recent concerts are offered in Atmos, albeit via the lossy codec option that is standard these days. Even so, switching from HD stereo to Atmos restores the ambience and tonal balance so appreciated by those of us who have heard live concerts in the Philharmonie Berlin. What trade-off there is in going from lossless 48k to a lossy stream is fairly inconsequential while the soundstage opens wider and deeper. Would I like that lost resolution back, sure I would, but I opt for Atmos every time.

Having moved on to multi-channel and immersive media, the differences between DL-ART and no DL-ART assumed larger proportions. Back in October 2023, I attended the AES Convention in New York City and greatly enjoyed a joint "Enveloping Masterclass" by Thomas Lund of Genelec and Morten Lindberg of the record label 2L. They discussed "factors of recording, mixing and reproduction that make 'immersive' worth the effort," demonstrating their points with 2L recordings played through a myriad of Genelec speakers in front, in back, and arrayed on an open girder structure that enveloped the audience. That audience—mostly studio professionals—was clearly impressed, as was I. I couldn't wait to attempt this at home with the recording that evoked the greatest response: Kim André Arnesen's Tuvayhun—Beatitudes for a Wounded World (2L-171-SABD), which is available as an SACD/Blu-ray set and as downloads in every modern format that I can think of (footnote 9).

This is almost 80 minutes of beautiful music, sometimes sad, sometimes joyous, always engaging, and often thrilling. It is comprised of 18 sections variously scored for vocal soloists, chorus, and orchestra. Lindberg has arrayed the performers around the conductor, the microphones, and—thus—the listener, and that is what was heard at AES, with clarity and impact.

At home, I decided to take an incremental approach, beginning by streaming Tuvayhun from Apple Music—that is, as a lossy Atmos bitstream. It was pretty good. There was a sense of immersion in the wonderful Nidaros Cathedral, with performers all around, with sufficient balance and detail to enjoy the experience. But it lacked the impact of the AES demo. Something was missing.

Could the problem be that my ad hoc audio system is just not up to the standard of the all-Genelec array at the show? Or is there more to Atmos than the lossy version from Apple Music? The answer is: both.

Switching over to the downloaded Dolby Atmos TrueHD file—lossless 24/48!—was a revelation. I was still sitting encircled by the performers in that lovely ambient space, but now everything was in sharper focus. The individual instruments and singers were clearer and more corporeal, but the acoustics of the space also seemed much more distinct and real. The result was a more discrete presentation of all elements, such that, instead of being immersed in a cloud of sounds, I was in among the sounds. I think that is what Thomas Lund was getting at when he made a distinction between immersion and envelopment.

Since I had the ISP Evo, which can play anything, I also compared the Atmos options with the 7.1.4 Auro-3D (96kHz) and MCH 5.1 DSD, both from the physical discs. The Auro-3D popped, with great detail and spaciousness, but something seemed amiss with the hall ambience, likely because my speaker positioning was optimized for Atmos and not to Auro's specifications. The 5.1 DSD was transparent and powerful but suffered by direct comparison to TrueHD and Auro-3D. Without the height dimension, a bit of the air was let out.

Only 48kHz. Does it matter?
Clearly stated in the ISP Evo's specifications: "Post-Processed Outputs: Up to 32 channels, 48kHz." So, the sampling-frequency limitation was not a surprise. Still, I must admit that, conceptually, the global limitation to 48kHz is a downer (footnote 10). In practice, however, the sound with the ISP Evo was remarkably clear and undistorted, fully capable of distinguishing between lossy sources and higher-resolution, discrete, lossless sources—eg, as already demonstrated, lossy streamed Atmos vs Atmos TrueHD. The ISP Evo does what it can with lossy codecs, but it's impossible to make up for the lost musical information. With full-resolution material—CD-rez or better—it is outstanding.

Digital resolution is a primary determinant of good sound, but there are limits. Anything over the CD standard of 44.1kHz approaches the point where further increases are indistinguishable—hence, pointless. Exactly where that point comes depends on many things, including the system, the listener, and the source material.

In any case, I do not think very many people would typically trade CD-quality stereo for a higher-rez mono. Similarly, there is little appeal for me in trading down from true 48kHz multichannel/immersive to higher resolution stereo. 48kHz can be sufficient. And, yes, I did the experiment. I bypassed the ISP Evo to confirm.

Finally, there is the matter of Dirac Live–ART, which contributes greatly to the subjective perception of resolution, tonal balance, and spatial resolution. It accomplishes this by reducing the influence of spurious reflections and room modes, smoothing frequency response and applying these operations across all the speakers so that they operate cooperatively. I have always felt that the subjective value of modern speaker/room correction greatly outweighs the reduction in resolution that almost always accompanies it in consumer devices. The ISP Evo is the most explicit demonstration of that fact that I've heard.

Conclusions
I have but scratched the surface of what the Storm ISP Evo can do. I have not assessed its video capabilities or its ability to operate several home theaters at once. Heck, I haven't even played a movie. So far, this has all been about audio, pure and (not so) simple. I'm confident that the ISP Evo, as a purely digital processer, is not imposing significant, audible coloration on the sound, unless you do it intentionally via one or another of the DSP functions.

What's more, the sophisticated yet lucid configuration procedures and the smooth integration of functions and controls are up to the standard that one expects from a high-end product. In particular, the ISP Evo offers the most integrated and effective implementation of Dirac Live I've ever used. Some may balk because of the 48kHz resolution limit, but I question whether any other prepro can match it, with any of the source material available today.

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Footnote 7: See dirac.com/introducing-dirac-live-active-room-treatment. Also see StormAudio's webinar series at stormaudio.com/webinars/ and the helpful YouTube video at youtu.be/dJc3_ GqDjA4?si=nNq3DIyw2DBliSD7.

Footnote 8: See digitalconcerthall.com/en.

Footnote 9: MQA stereo, DXD stereo, 24/96 surround 5.1, DXD surround 5.1, 24/96 Auro-3D in 5.1 FLAC, Dolby Atmos in MP4, Dolby Atmos TrueHD and Auro-3D in MKV, DTS-X in 7.1.4 and DTS-HD in MKV, 24/88 discrete WAV 7.1.4 immersive, DXD discrete WAV immersive. Whew.

Footnote 10: I've asked StormAudio about this; they replied: "Our chips are capable of 96kHz processing, so a bypass is possible and likely in the future."