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DALI Callisto 2C Active Digital Speaker System

DALI Callisto 2C Active Digital Speaker System

When Robert Harley asked me to return to high-end audio reviewing after a many-year hiatus, he had a product in mind. Oh sure, he stated it was a “new class of product” that TAS would “like to have more coverage of in the future.” But really it was the ultimate system to lure an audiophile back into the fold after a long period of stagnation.

According to DALI (Danish Audiophile Loudspeaker Industries): “The Callisto 2 C is the stand-mount solution in our new wireless ecosystem that empowers you to easily access all your high-res music directly from your smart device.” A couple of tidbits in there might have put me off in the past, “wireless” and “smart device” traditionally have not been associated with the best sound. However, it turns out that the way DALI implements these into its all-in-one design is quite different. There is no downside and a good bit of upside. That ecosystem includes the DALI Sound Hub, which functions as a preamp. Inputs are in many formats including Bluetooth, WiFi, LAN, and wired digital and analog; the signal then goes to the speakers through DALI’s proprietary wireless standard. I reviewed the Callisto with the BluOS NPM-1 module, which handles networking and streaming, installed in one of the Sound Hub’s two bays. The speakers themselves include mono D/A converters, preamps, power amps, and drivers. You simply plug in the speakers and connect a wired or wireless source to the Sound Hub and start listening. Why would DALI pack so much technology into a single product? Does it sound “high-end”? Do the cost savings of including all these components inside the speaker cabinet outweigh potential sonic compromises? Or are such integrated systems an inherently superior architecture to component audio?

Parts of the Whole
Looking at individual parts of this highly integrated system, the first component in the signal path is a 50MIPS digital signal processor. This manages control signals and digital-domain crossovers for the speaker drivers. The DSP is connected through I2S to a Burr-Brown PCM1796 DAC capable of 123dB dynamic range, with differential current outputs for lower noise. Volume control is performed in the analog domain just before the amps, for good S/N ratio and true 24-bit resolution. There are then two separate amps, one for the tweeters and one for the woofer. DALI states that “the Class D amplifier is based on patented state-of-the-art technology with a global-feedback, self-oscillating design chosen for its very musical properties.” One of its benefits is that distortion stays low at all frequencies, as opposed to traditional amps which have higher distortion at higher frequencies. Rated at only 30W for continuous signals, DALI says these amps can put out 250W for periods of up to five seconds.

Then there are only minimal crossover parts needed between amp and drivers, thanks to filtering accomplished in the DSP. The speakers are technically three- or two-and-a-half-way, though DALI calls them two-way, grouping the two tweeters together as a “hybrid tweeter.” There is a 3/4″-by-2″ planar-magnetic ribbon super-tweeter with response beyond 30kHz and a 1-1/8″ dome tweeter with a membrane so thin it’s partially transparent, which handles frequencies down to 2kHz. The single 6-1/2″ woofer uses a lightweight wood-fiber cone. DALI also claims it has been designed to stay linear at large excursions, keeping distortion low at high output levels. This partly results from DALI’s patented Soft Magnetic Compound (SMC) in the pole piece, which supports magnetic penetration while reducing electrical crosscurrents. The cabinets employ thick 25mm (1″) MDF, with internal bracing to reduce side-wall vibrations. The Callistos themselves are built in DALI’s factory in Denmark, and the Sound Hub is made in a DALI-owned factory in China.

The stands recommended for the Callisto 2Cs were the DALI Connect M-600s. They were easy to assemble, sturdy, and good-looking in their shiny black finish. They have a thick steel top plate, one-piece extruded-aluminum stem,  a thick glass bottom plate, and aluminum cone spikes that attach to the underside with sticky material. My floor is concrete slab on top of earth, so it does not vibrate. The top plates were a bit small; I would have preferred a size that fit the Callisto more closely, perhaps with bolt holes to connect with the threaded spike holes in the bottom of the speaker. I did not use spikes on the Callisto, but rather attached the tiny rubber bumpers that were included.

Features and Functionality
Via the BluOS module in the Sound Hub, the system can join a multi-room network that includes many types of BluOS-equipped audio gear. The speakers can also interface with many major-brand home-control systems. Playback can be controlled through the BluOS app on different platforms, iOS and Android, Windows and Mac. The platform supports hi-res PCM audio up to 24/192, as well as quite a few other audio formats, including master-quality MQA. The whole system is MQA-certified all the way from the internet to the speaker drivers.

The Sound Hub features auto-sensing source selection. It will turn on and switch to the active input when a connected source is detected. It will also automatically go into sleep mode, as will the speakers, a few minutes after the input goes silent. So super-easy to use—created for music lovers and not just audiophiles. I was able to install the BluOS app on Kindle and Android tablets, as well as on a Windows 10 laptop and Win 7 desktop PC. All of them controlled playback just fine. In addition to the front-panel controls on the Sound Hub, there is an included remote and a volume strip on top of the speakers. Goodness, has anyone seen a system that could be controlled from so many places? My only quibble was the BluOS app volume slider is too sensitive. Tapping on the upper or lower part of the scale didn’t work for small level steps. It would be good to make the scale longer in the future. A major addition I noticed after a firmware update was a “home theater” mode available for setup in the speaker-connection menu.

For streaming I installed the Win Tidal app for the first time on my home-built desktop PC. Honestly, I did not expect much, as I was using a basic Soundblaster Audigy LE PCIE sound card running analog signals to an old cheap ($80) pair of PC speakers. Well, surprise! The Labtec Edge 418 with Slab flat-panel technology can sound quite good with Tidal. Mind you, only at low levels. My sole previous streaming-audio experience was YouTube HD music videos. What YouTube calls “high definition” is really not so high, compared to Tidal. Not only on the MQA tracks, but also on the “CD-quality” ones, the sound was really fantastic! I absolutely had to hook up the DALI Callistos if I was getting sound this good from basic PC speakers.

Listening and Tweaking
I installed the speakers in a different room, and gave them some break in. The Sound Hub was off in my main listening room, though DALI does not recommend this. It states that the 5.8GHz wireless band is less crowded with other devices, though it does not go through walls very well. I found it went through one interior drywall/wood frame wall just fine, though the distance between the Hub and speakers was not more than 24 feet. (DALI has the maximum reliable distance at 60 feet in the same room.) The first thing I noticed was the incredible amount of detail. The next thing was that the top octave was too forward on many recordings. Leaving the front grilles on helped (and that is how I did most of my listening). Then adding recording-studio egg-carton foam on the wall behind the speakers (two 2′-by-4′ pieces) helped ease the brightness a bit. I always use this type of acoustic treatment, but you can use the less visually obtrusive room treatment of your choice to achieve similar results. As I continued listening, I realized it was not so much a frequency spike in the top octave, but rather that the Callistos were brutally revealing of characteristics of the recording. This is a quality that I like.

So if we want to adjust the frequency balance for the system we… substitute some different cables? Negative, there are no cables in the Callisto system! Adding my Audioprism Power Foundation III for AC conditioning helped a little. When all you have to work with is AC conditioning, power cords, and room treatment, you certainly should address all of those areas.


Later my mind was blown, again. I did some close-in-time comparisons between the Callistos running off their included (generic, 2-conductor 18AWG) power cords, and a pair of AudioQuest NRG-Z3 (3-conductor, thick) cords. I had no idea AC cables could make such a large difference in the sound. It wasn’t just emerging from a blacker background; everything was more crisp and exciting. The soundstage was better defined, and the music seemed louder. Instruments had more separation, and their individual characters stood out more. And voices seemed to be “flesh-and-blood present” in the room with me. The incredible realism, accuracy, and liveliness that I had been enjoying for one month with the Callistos went one step further in the right direction.

Do not even consider running your Callistos with the included power cords. Since you are running D/A processor, preamp, power amp, and speaker off a single cord, it needs to be a premium one. Is it crazy to spend $500 on a pair of AC cords for a sub-$5000 system? Not after hearing the sonic improvements they bring. You may be able to find less expensive AC cords that also work well, so experiment. I was a doubter before; I thought at most AC cords could filter some noise, but no more. With a complex unit like the Callisto, they can actually render across-the-board improvements that add up to a serious upgrade. On both solo and choral vocals, a real acid test for any system, the realism was uncanny. Every emotion and delicate touch the singers were putting in there came across clear as a bell. On Siouxsie and the Banshees’ “Scarecrow” from the album Peepshow, the sound was so intimate I felt Siouxsie was trying to seduce me (though it’s not a love song). I never even realized how much she hams it up before; it’s on the border of overdone.

When streaming digitally, the BluOS controller doesn’t give you any tone controls. I used the Callistos in a very “soft” room which helped—carpet, fabric curtains, and acoustic foam on some of the walls. The frequency balance of these speakers is really very good in such an environment, very neutral. The Steven Wilson remixes of Yes (five studio albums) came across as natural and organic. I felt I was present in the room at a 70s rock jam session, complete with brown/orange color scheme, shag carpet, and bell-bottoms.

The bass is really extraordinary for bookshelf speakers. The one rear-ported 6-1/2″ woofer in the 2C does an incredible job down low. Perhaps it’s because of DALI’s SMC pole piece, or other special magnet design details. Or the fact that the dedicated amplifier is precisely matched with the digital/analog hybrid crossover, drivers, and internal wiring? It’s more low end than you would expect from bookshelf speakers. The bottom octave is still missing, of course, so no organ music, but aside from that the bass was very satisfying in a small room.

Which brings me to the dynamics of these speakers. Classical music and jazz sounded very, very fine through them—yes, very impressive. But when you put on some rock, funk, hip-hop, or dance music they really come alive. The incredibly bouncy dynamics will have your toe tapping indeed; you may even dance around in joy. Our preconceptions of something Danish might be that it would be precise, clinical, and dignified. Um, throw that out the window. These babies can get down and dirty with the best of them. They were born for rock; they love rock; and they love dance beats. Their best friend is a drum kit. It might partly be the Class D power amplifiers. I have always felt Class D amps had very explosive dynamics. My first experience was from an early prototype made by NAD in 1994. The 24 years of refinement hasn’t hurt. The Callistos are also capable of incredibly delicate, gentle, and smooth passages of acoustic music. The amps are not “rough around the edges,” and have no drawbacks from their Class D operation that I could detect at all.

“CD quality” tracks on Tidal somehow sounded better than actual CDs through this system, and the MQA tracks went beyond that. Some classical recordings, like Philip Glass Piano Works by Vikingur Ólafsson on Deutsche Grammophon, were so uncannily realistic that I felt I was standing in choir rehearsal or at an opera lesson in front of an actual piano. There is something qualitatively different about a good MQA track that takes you one full step closer to real, live acoustic music. Each instrument or singer seems easier to pick out from the mix, occupying a separate space on the stage. It is by far the finest sounding format and reproduction chain that I have ever had in my home. For under $5k for the whole system (+$20/month for Tidal), that seems like a bargain.

Since the Callisto system runs internally at 24/96 I am going to assume it is what they call “MQA Core” decoding, which performs the first unfold. On the “Bob Talks” (Bob Stuart) section of the MQA official site, Stuart says that Core decoder “sound quality is higher than from ‘No’ or ‘Authenticating’ decoders but lower than a ‘Full’ decoder.” So the Callisto falls somewhere in the middle—not quite a full decoder, which is available in some stand-alone DACs that are capable of 192 or 384kHz internally. However, Stuart also says that Core “recovers all the direct music-related information” from an MQA-encoded track.

To get the best sound from digital sources, particularly MQA, it is essential to set “Replay Gain” in the audio settings menu to “Disabled.” I discovered this late in the review process, and when I listened again to MQA sources I was even  more impressed by the sound quality. Every single MQA file was now distinctly beyond CD quality. The presentation was liquid, revealing, and natural. It sounded more like live acoustic music than any CD. Disabling replay gain is a must for anyone sending MQA through BluOS.

One limitation of these speakers, which could be a deal-breaker for some, is that they can’t play super-loud without sounding a little strained. Not an issue for me, as I have sensitive ears and listen at moderate levels. But certainly you will not get the same headroom you would from a (likely more expensive) larger system with a bigger power amp. Not a huge surprise for a single 6-1/2″ woofer, but I need to mention it since it is one of the only weak points I was able to find during my listening. For those who like the Callisto 2C’s integrated concept and ease of use but would like deeper bass extension and the ability to play louder, DALI makes the floorstanding Callisto 6C.

The DALI Callisto 2C system is highly recommended. I immensely enjoyed my time with it, rediscovering favorite music in the highest fidelity I have ever experienced in my home. It does a lot of things very well: detail, dynamics, flat frequency response, soundstaging, revealing artistic subtleties, and just plain excitement. These bookshelf models have more bass and play louder than you would ever expect from speakers of this size. However, others might have a different idea of “loud” than I do, so keep in mind they are not for true headbangers. You will want to use them with a premium AC power conditioner and AC cables. Also, the best sound comes from lossless digital sources including network-attached storage (hi-res PCM up to 24/192), Tidal Hi-Fi streaming with MQA, and digital-connected CD. Analog sources can also be connected and volume-controlled, including plugging line-level RCA directly into the speakers.

The DALI Callisto 2C is an ideal system for those who want high-end sound quality in an easy-to-use and highly capable package.

Specs & Pricing

Type: Powered wireless speakers with integrated D/A converters and separate preamp unit
Driver complement: High-frequency, 1x 29mm soft dome; midrange/low-frequency:1x 6½”
Inputs: RCA and 3.5mm phone analog, coaxial and TosLink digital, USB, WiFi, LAN, Bluetooth
Frequency range: 47Hz–30kHz (+/-3dB)
Amplifier power: 30W (250W for musical peaks)
Bass-reflex tuning frequency: 46Hz
Dimensions: 15.5″ x 7.9″ x 12.7″
Weight: 22.3 lbs.
Price: $4750/pair with Sound Hub and BluOS module; $4300/pair without the BluOS

Tags: DALI

By Muse Kastanovich

My love of music began in the Albuquerque Boys’ Choir at age ten. Then I was a member of many other fine classical choirs over the years (most recently Coro Lux). I also studied opera with Paul Barrientos, and had solo roles in local opera and musical theater. But in college I was still largely an introvert, and would sit and listen to (mostly rock) LPs and cassettes on my modest stereo system in my dorm room for hours on end. I started out reading Stereo Review magazine, which had the incredulous view that all CD players and amplifiers sounded the same. Only a few years later in my career I would find myself being able to hear sonic differences by changing just a single resistor in an amp I was building! In the 90s I slowly put together a real audiophile system, moved to Boulder, Colorado, and read Stereophile magazine voraciously. I started a couple of local rock bands where I sang and played bass. When I found out that Corey Greenberg (my favorite writer) was going to be leaving Stereophile, I wrote a letter to the editor John Atkinson. Despite my young age and lack of experience, he was interested, and brought me on as a contributor in 1995. I was fortunate enough to spend time with J. Gordon Holt (founder of Stereophile) and Steven Stone, both of whom lived in Boulder at the time. I also worked with and learned from Robert Harley, Tom Norton, Robert Reina, and Wes Philips. I look for high resolution in an audio system. Those components which can expose the most subtleties and differences in the music performance and in other parts of the reproduction chain are my favorites. I find that this quality helps improve the illusion of performers actually in the room with me, and lets me hear every individual part better—even when listening to what I consider to be the acid test, full classical orchestra with choir.

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