Note: This review was originally published in The Absolute Sound issue 194 in conjunction with Editor Robert Harley's interview with Meridian Audo co-founder Bob Stuart. To read that interview in its entirety, click here.
It’s been a great privilege to have had a front-row seat listening to and reporting on the improvement in CD sound quality over the past 20 years. Every step forward in playback technology has rendered smoother textures and a more open soundstage, and fostered a greater sense of ease and enjoyment.
Despite these advances, CD has been fundamentally limited, we assumed, by its too-low sampling rate (44.1kHz) and too-short word length (16 bits)—parameters dictated by the state of late-1970s technology. Moreover, the vast majority of CDs in our music libraries were created with sub-optimum conversion and mastering technology, imprinting our favorite music with hardness, glare, and flatness. I’ve held a secret fantasy of hitting the lottery and using the money to re-master some of my favorite music (none of which has commercial potential), just so that I and other fans could replace our poor-sounding CDs with the best that today’s mastering technology can deliver. As much as CD playback has improved, it’s still fundamentally limited by the format’s parameters, and our libraries are plagued by the distortions introduced by the brickwall filters in A/D converters.
But what if it were possible to design a CD player that didn’t suffer from the characteristic distortions we thought were inherent in the format? What if the problems of CD were not primarily the result of the 44.1kHz sampling and 16-bit quantization but rather of another form of distortion that could be removed during playback? Could a CD player be designed that would make our CD libraries sound like high-quality re-masterings at worst, and approach the sound of high-resolution at best?
CD playback recently took a step in that direction, courtesy of the Spectral SDR-4000 Pro CD player (reviewed in Issue 190) and the Berkeley Audio Design Alpha DAC (reviewed in Issue 189). Both these devices ameliorated many of the sonic shortcomings that seemed endemic to the CD format. They both employ custom digital filters that avoid a characteristic distortion that is largely responsible for “CD sound.”
That distortion is “pre-ringing,” illustrated in Figures 1 and 2. Figure 1 is an impulse, created by setting one sample at full scale and all other samples at zero. The horizontal axis is time; the vertical axis is amplitude. The “impulse response” of a perfect system would look like Fig. 1. But in the real world, digital filters spread out that impulse of energy over time (Fig. 2). Notice that some of the impulse’s energy appears before the impulse itself. This time smear, which can last up to 2ms on either side of the impulse, is called “ringing” (the impulse sets the filter ringing as does a hammer striking a bell), and the energy before the impulse is called “pre-ringing.” Pre-ringing is introduced by the brickwall anti-aliasing filter in the A/D converter, as well as by the linear-phase reconstruction filter in CD players. Although analog filters ring because of the resonant elements in their filters, the ringing always occurs after the signal that set it ringing, never before it. Pre-ringing is unique to digital audio. Think of the impulse as a musical transient. Now think about how bizarre it is to hear part of a signal before the signal itself. Such a non-causal situation never occurs in nature and, consequently, is highly audible.
Ringing in the audioband can be avoided with high-sample-rate digital audio. This is why, all other factors being equal, 96kHz-sampled audio sounds better than 44.1kHz—not because we can hear information above 20kHz. In fact, this pre-ringing is largely responsible for the characteristic “CD sound” of hard textures, flat soundstages, a top-end that is simultaneously closed-in yet bright, and a general lack of an impression of instruments existing in space. Some recent products with so-called “minimum phase” filters don’t exhibit this pre-ringing. These products have greatly improved the musicality of the CD format, and have even allowed us to hear poorly recorded discs with a newfound sense of ease and enjoyment.
SIDEBAR: Features & Functions
The 808.2 comes in two flavors: a straight CD player with a fixed output level (808.2), and a CD player with a variable output and full preamplifier functions (808.2i). The units look identical from the front, and share their styling with other Meridian 800 Series products. And although the 808.2 looks like the 800 CD player, virtually every subsystem is new for Meridian’s all-out assault on the state of the art in CD playback.
The front panel contains a large display that shows the disc track and time, function (“Loading,” for example), and on the 808.2i version, the selected input and volume setting. The 808i also offers the options of using it in fixed output-level mode and accepting external sources. Transport controls are arranged in a row of very large rectangular buttons beneath the display. A fold-down door, signed by Meridian founders Bob Stuart and Alan Boothroyd, accesses less-used transport controls such as scanning and repeat. The 808.2i version adds source selection and volume buttons behind the door. The remote is a large, two-handed affair that can operate a complete Meridian system. Thankfully, it includes an absolute-polarity switch.
The rear panel contains lots of jacks and connections unique to Meridian (the 808.2 will often be used to drive a pair of Meridian’s active digital loudspeakers). In addition to the proprietary Meridian connections, an RS232 port is provided along with three trigger outputs. Analog output is on balanced XLR jacks and unbalanced RCAs, and a digital output is available on an RCA jack. Note, however, that the digital output is at 88.2kHz, not 44.1kHz. The 808.2i version offers six unbalanced analog inputs, three coaxial digital inputs, and two TosLink digital inputs. These inputs can be named by the user, with the name appearing in large letters on the front-panel display.
The 808.2 is the culmination of Meridian’s 26 years of experience in CD-player design. The unit is based on a CD-ROM drive with the ability to re-read, at high speed, sections of the disc that contain errors. The data are put through a FIFO (first-in, first-out) buffer, and clocked out with high precision. A DSP with 150 MIPs (millions of instructions per second) of horsepower then upsamples the data to 176.4kHz at 24 bits. As mentioned in the review, the digital filter is a custom design running on a separate DSP platform. The DACs are Delta-Sigma types capable of running at 192kHz. Much attention was paid to minimizing jitter. --RH
Now comes the Meridian 808.2 Signature Reference CD player and its “apodising”1 digital filter that not only doesn’t introduce pre-ringing, but also removes pre-ringing that was imposed in the analog-to-digital converter used to record/master the CD (or other subsequent signal processing). This is a startling development; the ability to remove this significant source of degradation that is imprinted on all the music in our CD libraries is nothing short of revolutionary—and a milestone in the history of digital audio. The filter, which has some other interesting properties, is described in detail in a pair of Audio Engineering Society papers by Dr. Peter Craven (“Anti-Alias Filters and System Transient Response at High Sample Rates” and “Controlled Pre-Response Anti-Alias Filters for Use at 96kHz and 192kHz”—see also Bob Stuart’s “Coding for High-Resolution Audio Systems”). The papers include an explanation of how the apodising filter can remove ringing already in the signal that was added by digital filters further up the chain.
So how does the 808.2 and its apodising filter sound? In a word or two, very “un-CD-like.” Seconds into my first listen to the 808.2 I was immediately stunned by the player’s three-dimensionality and the sense of space between instruments. Although I’ve written in the past that certain digital products had a deep soundstage with instrumental images laid out along a continuum from front to back, none of them equaled the Meridian in this regard. In fact, listening to the 808.2 was like walking into a life-sized diorama, so realistic was the soundstaging. This wasn’t one of those differences that you have to listen closely to hear, or one that takes some time to appreciate. Rather, it was a wholesale transformation of the CD listening experience. In this regard, the 808.2 is a singular achievement.
The soundstage was fundamentally different from any other CD I’ve heard. Conventional digital playback tends to sharpen image outlines and flatten them in an almost cartoonish way. Yes, one can clearly localize an instrument, but the instrument’s image has no life and breath surrounding it. The Meridian transforms this aspect of CD playback, presenting images with a halo of air around them and a jaw-dropping sense of the instrument existing in three-dimensional space rather than being pasted against a flat background. I could hear the expanding air around an instrument’s dynamic envelope, just as one hears it in life. The mighty Spectral SDR-4000 Pro and the Berkeley Alpha DAC also addressed this shortcoming of CD by opening up the soundstage to an unprecedented degree, but the 808.2 recreates acoustic spaces, the relationships of instruments to each other and to that space, and the impression of three-dimensionality like no other CD player I’ve heard. Moreover, this palpability of instrumental images was heightened by the blackness of the 808.2’s backgrounds and increased contrast between the instrument and that background. The dead-silence between notes seemed to make images that much more believable as instruments existing in an acoustic. These qualities created an almost spooky sense of palpability and realism.
The way notes decayed was also different from any other CD player I’ve heard, with the notes seemingly decaying more gradually and hanging in space longer. The sound was the antithesis of dry and truncated. I’m not just talking about the ability to hear deep into the reverberant field of the hall (which the 808.2 is also superb at reproducing), but into the duration and decay of the notes themselves.
The 808.2 playing CDs also sounded very much like a high-resolution source in its ability to resolve individual musical lines, even those of quiet instruments at the back of the stage during loud, dense passages. I experienced a sense of ease, as though my brain weren’t working as hard to unravel the sound into musical meanings. Instead, I felt what could be described as “intense relaxation,” as the music came to me in an utterly natural, unforced way.
The 808.2’s bass and dynamics were good, but not the state-of-the-art as were other aspects of the presentation. The bottom end tended to be polite and refined rather than visceral and driving. The Berkeley Alpha DAC, for example, has deeper extension, more weight, greater muscularity, and wider dynamic impact.
This minor point aside, listening to favorite and familiar music through the 808.2 was mind-blowing. It was as though my CD library had been re-mastered, so great was the improvement. To hear newfound spatiality, bloom, air, dimensionality, and ease in old favorites was immensely rewarding—and a totally unexpected technical achievement. CDs I’ve listened to for decades opened up and delivered more musical expression than I’ve heard from them before—or ever expected to hear from them. Of course, poor recordings won’t sound like audiophile discs. But the 808.2 will allow them to be heard without being overlaid with the problems we’ve long associated with CD.
The Meridian 808.2 is, in my estimation, the most significant product in the history of the Compact Disc. Through an incredible and unlikely stroke of fortune (the ability to remove pre-ringing after the fact), the genius of the apodising filter’s creator (Peter Craven), and Meridian’s 26-year expertise in CD player design, our CD collections can be played back with a degree of musical involvement no one in his wildest imagination thought possible from the CD format.
1 The term “apodising” comes from optics and radio astronomy. Sharp edges at the boundaries of optical lenses or radio dishes create ripples in the diffraction pattern, analogous to the ringing in digital filters. In radio telescopes, the contribution from the outer edge of the disc is attenuated to reduce this effect, a process called “apodisation.”
SPECS & PRICING
Meridian 808.2 CD player/808.2i CD player/preamp
Formats: CD audio, CD-R, CD-RW, MP3
Inputs: Six analog unbalanced phono, three coaxial S/PDIF digital, and two TosLink optical
Outputs:One analog unbalanced, one balanced XLR, one digital S/PDIF coaxial, one RJ45 (AES/EBU) balanced
DACs: 192kHz-capable, 24-bit, Delta Sigma operating at 4x CD sample rate
Dimensions:18.9" x 6.9" x 16.2"
Weight: 40 lbs.
Price: $15,995 (808.2)/ $16,995 (808.2i)