On top of a desk, an audio system must be able to deliver satisfying sound in a nonoptimal environment: a flat, reflective plane (the desktop) cluttered with keyboard (or maybe a laptop computer); a mouse; assorted papers, books, and trash; and, perpendicular to that, another flat, reflective plane (the computer display), which, if it’s not a tiny laptop screen, will block some of the soundwaves emanating from the speakers. Such sonically inhospitable spaces can consign 3D stereo imaging (and other desirable sonic traits) to the realm of the imagination.
My workspace is especially challenging. My two-tier triangular desk is wedged into a corner and bisected by a diagonal roof line that cuts across the listening space at a 142° angle. You’d think that would boost the bass, but somehow, instead, it traps it.
I decided to try Sony’s SA-Z1 nearfield active desktop speaker system ($7999) to see how well it could cope with my workaday acoustical nightmare.
The only thing it shoots is sound
The SA-Z1 speaker system, with a unique appearance that evokes some futuristic weapon from a Marvel cinematic thriller, is the latest addition to Sony’s Signature series, which also includes a headphone amp (TA-ZH1ES), two high-end Walkmans (NW-WM1Z, NW-WM1A), a couple of high-end headphones (MDR-Z1R, IER-Z1R), and the DMP-Z1 Digital Music Player that John Atkinson reviewed in the August 2019 issue of Stereophile. The series originated during the 75th anniversary year—2016—of the company that brought you the Walkman and is dedicated to creating the ultimate personal listening experience. Yoshiyuki Kaku (Kaku San), who designed Sony’s SS-AR1, SS-AR2, SS-NA2ES, and SS-NA5ES speakers and appears in a seductive video on Sony’s SA-Z1 website, also designed the SA-Z1, in cooperation with electrical designer Masaki Sato.
The SA-Z1 system consists, of course, of two speakers. Each one contains a ¾” tweeter with a titanium-sputtered soft dome flanked vertically by two smaller, similar tweeters, all mounted on a narrow, tapered plate in front of the front baffle. Mounted on that front baffle is a 4″ forward-firing woofer with an anodized aluminum cone; behind that is a similar 4″ woofer that faces to the rear. Various buttons and controls sit atop each speaker.
The SA-Z1 system took three years to develop. “That’s a really long time for Sony,” Greg Carlsson, a San Diego– based electrical engineer and member of Sony’s senior staff who participated in one of the SA-Z1’s prototype listening stages, told me during an extended chat, which also included Kevin Portaro, Sony’s very helpful senior product marketing specialist. “It’s a really complicated digital-hybrid design that took an hour’s conversation with Masaki Sato for me to fully understand,” Carlsson told me.
Like most desktop speaker systems, the SA-Z1 includes a DAC, but it does not use an off-the-shelf, chip-based DAC. At its heart is an FPGA that converts all music data to PWM—pulse-width modulation, the generic term for DSD, which is a trademark. PWM and class-D amplification have many similarities: Both are single-bit technologies, meaning that at any given time, the signal occupies one of two levels, high or low, fluctuating between those two states at very high frequencies.
Sony takes advantage of the similarity between the two technologies to combine digital conversion and amplification. “Sato-san calls it a ‘power DAC’ because it amplifies the PWM or DSD signal before filtering it,” Carlsson explained. “The amplifier and DAC are together as one; they are not separate stages. This is effectively a discrete DAC and Class-D amplifier design.
“In parallel, the PWM or DSD signal is routed through another DAC, the output of which is amplified in the analog domain and used as a feed-forward signal for error correction. It’s a very unconventional and challenging design, but the result is a lower noise floor and lower distortion. Since there are two paths, we call it a Digital Analog Hybrid, or D.A. Hybrid, amplifier. It’s quite complicated, and I’m struggling to explain it in a simple way because it’s hard to wrap your head around.”
Rather than employing MOSFET transistors, which Sony says can produce ringing distortion due to slow switching speeds, the amps use gallium nitride (GaN) transistors, which allow faster switching and so less ringing. Sony claims that with GaN, “amplification errors are significantly reduced, even before the signal is error-corrected by the feed-forward analog amplifier.”
Yes, there’s an analog amplifier, too, another way in which the SA-Z1 is a digital/analog hybrid. Every woofer has its own amplifier pair, as does the main tweeter; the two assist tweeters are driven together by the fourth amplifier pair. That’s eight amplifiers per side.
“The SA-Z1’s D.A. Hybrid Amplifier design was initially deployed in our high-end TAZH1ES Signature-series headphone amp,” Carlsson said. “We don’t think that there’s anybody else out there that’s been able to pull off this kind of design. A lot of people speak about high-powered FPGA or gallium nitride MOSFETs, but this whole D.A.–hybrid amplifier design is quite unique.”
“With a conventional speaker system, getting the room-speaker-listener positioning just right to achieve an expansive soundstage that extends to all the way beside you or even further is very difficult,” Carlsson stated. “The SA-Z1 system achieves an amazingly large soundstage easily, and there is much less influence from the room when you listen in nearfield,” because “in the nearfield, there is a lot less impact from early reflections.”
Sony calls its unique coaxial tweeter array “I-Array.” “A larger dome tweeter can produce a lot of sound pressure, but it has narrow directivity, which means that the high frequency response starts to drop off as you move off-axis,” Carlsson explained. “Smaller tweeters such as our assist tweeters can’t produce as much power (SPL), but they have much wider directivity and higher bandwidth, in this case up to 100kHz. Putting the three tweeters together in the I-Array creates a larger and more transparent soundstage and combines the strengths of the larger- and smaller-aperture tweeters in a coaxial layout for better imaging. … [T]he coaxial design allows us to achieve coherence in the nearfield.
“Time coherence and a flat, broad frequency response are also required to achieve a coherent impulse response. Typical multiway speakers can have good frequency response, but their impulse response is compromised, because getting the wave fronts aligned in time between driver units is very hard due to driver placement and passive crossover networks. We also use the FPGA to synchronize all drivers and achieve full time-alignment, which ensures a coherent soundfield. Any music signal can be described by convolution of an impulse, which means [that], if the speakers can reproduce an impulse accurately, you can listen to the sound as it was recorded. This is a key detail in the SA-Z1’s design.”
The SA-Z1’s two 4″ woofers are placed back to back in a layout that mimics that of the traditional Japanese “tsuzumi” drum (and also any number of subwoofer and loudspeaker designs). Sony claims that the two woofers’ vibrations cancel out when both are active. (On one setting, the rear woofers are deactivated; see below.) The layout is said to reduce enclosure resonance and deliver precise imaging. Bass disperses forward and through side vents located on either side of the rear-facing woofer.
The SA-Z1’s aluminum enclosure is comprised of two different aluminum alloys; each of its six panels has a different thickness. Specially designed trapezoidal rubber dampers between panels prevent vibration transmission and reduce resonance. An aluminum bridge between the front-speaker section and the amplifier and digital processing circuitry at the speakers’ rear, as well as a 5mm–thick steel plate, create a “frame beam wall” chassis intended to prevent vibration from reaching the electronics.
Doing the numbers
The choice of digital input determines the maximum PCM and DSD sampling rates that the SA-Z1 can accept. I used the most versatile input, USB, which can accept native DSD up to 22.4MHz (that’s 8×DSD), DoP (DSD over PCM) up to 5.6MHz, and PCM up to 32/768. The Walkman/Xperia input accepts DSD native up to 11.2MHz, DoP up to 5.6MHz, and PCM up to 32/384, while the poor old optical input is limited to PCM up to 24/96.
The SA-Z1 offers several options for digital playback: automatic upsampling of “Red Book” PCM files to high-rate PCM (32/384 for files input by USB; note, however, that all data eventually ends up as PWM, aka DSD); resampling of PCM to high-rate DSD (DSD256 when input via USB; this is called DSD-RE, for DSD Remastering); straight playback of DSD files; or what Sony calls “optional enhancement of compressed music” via the company’s “Digital Sounds Enhancement Engine.” “DSEE-HX” attempts to restore what’s been lost from compression with a combination of upsampling and what Sony calls “harmonic restoration.”
Neither the DSEE-HX nor DSD-RE functions operate with the SA-Z1’s analog inputs—which should convince you that it’s best to use the system’s digital inputs instead. Just try feeding high-resolution signal from your computer to a high-quality DAC—I used Mytek’s Manhattan II—and connecting its RCA outputs to the SA-Z1’s analog inputs. I did, and I found the sound rather flat and disappointing. “SA-Z1 is designed as a digital system,” Carlsson told me. “As such, it definitely sounds best with digital inputs. It won’t benefit from an external DAC like a purely analog system would; in fact, it will not be able to perform at its best. The analog inputs are provided for flexibility.”
The two speakers are connected by a digital sync cable (supplied), which attaches to each speaker’s rear, across from the power-cable inlet. Speaker A’s front panel includes power (on/off), input selection, and DSEE-HX and DSD-RE buttons. There’s also a volume control knob and an LED readout that displays input, volume level and muting state, bit/sample rate, and a few other things.
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