The history of audio is littered with the skeletons of “breakthrough” signal-processing technologies that reportedly improved the listening experience. From the “Hafler Hook-up” of the 1960s to today’s sophisticated DSP-based systems, there’s been no shortage of attempts to enhance music listening via manipulation of playback signals.
The problem is that none of these systems, at least in my experience, have worked. They end up sounding contrived and hokey. Rather than bringing us closer to the absolute sound, these technologies take us further away by creating “effects” that are supposed to mimic the live experience but end up calling attention to themselves as effects. I’m not talking about the absurd DSP programs on AV receivers such as “Concert Hall” or “Jazz Club” that attempt to synthesize acoustic reflections, but rather about the long list of “spatial enhancers” and other “psychoacoustically” inspired analog-domain technologies, usually involving sum-and-difference signals, delays, and filters.
I thus regarded with tremendous skepticism the claims of BSG Technologies for its QOL (rhymes with “coal”) technology incorporated into a device called a “Signal Completion Stage.” QOL is a playback process that reportedly restores the natural phase relationships in audio signals, resulting in improved sound. The company behind QOL, BSG Technologies, plans to license QOL to hardware manufacturers in a variety of fields including car audio, cell phones, telecommunications, and motion pictures.
To demonstrate QOL, BSG Technologies developed a $3995 stand-alone box (the “Signal Completion Stage”), the subject of this review. Although this box allows evaluation of the technology, the optimum implementation is within a preamplifier, DAC, or other component. QOL decoding is so simple that an analog implementation can be realized with about three square inches of circuit-board real estate, and in the digital domain with a very small amount of processing power running on a chip. Given the development time of high-end audio products, it will likely be some months or years before QOL is available in products from a variety of high-end manufacturers—if it ever is.
The device I received for review is fairly elaborate, offering four analog inputs on both RCA and XLR jacks, dual pairs of outputs on RCA and XLR jacks, fully balanced operation from input to output, source-switching, a mono button, and a remote control. A “Bypass” button allows you to switch QOL decoding in and out of the circuit, which is convenient for listening comparisons. The Signal Completion Stage integrates into your system either between your source components and the preamplifier (thus the multiple inputs), or between the preamplifier and the power amplifier. The device is pure analog, with no analog-to-digital or digital-to-analog conversion. BSG Technologies sells the device directly to consumers and offers a 30-day money-back guarantee.
Despite my skepticism, I listened to an early prototype nearly two years ago and was encouraged by what I heard (see my report in Issue 201). BSG Technologies is quick to stress that QOL isn’t a signal-processing technology, in that it doesn’t add anything to the signal that’s not already present. Moreover, it differs from the myriad techniques used in the past (extensively referenced in the QOL patent application’s “prior art” citations), most of which involve extracting the difference channel from a stereo signal (left minus right), equalizing, delaying, filtering, inverting, or performing other psychoacoustically based manipulations of that difference signal, and then mixing it back into the L and R channels. The BSG Technologies Web site offers this explanation: “Instead of ‘adding’ a host of processing techniques intended to create ‘effects,’ we have simply found a way to extract information already present in the recordings, but otherwise hidden in conventional reproduction.”
The patent-application abstract offers a more detailed description: “The present invention relates to an apparatus and method for redeeming otherwise closed and concealed information contained in audio signals. This includes both the primary reference signal, and a plurality of redundant duplicate signals, substantially identical except in relation to magnitude and phase, for the purpose of unfolding, or opening the audio signal content into layers that result in an omni-directional acoustic signal, representing the sound as it would behave in nature. The audio reproduction system uses an in-phase circuit and a separate phase layering technique circuit to drive independent multiple mixed channels to produce an open, substantially complete sound from a discrete audio signal, for the purpose of enabling a substantially complete audio signal to be formed, or to transform existing incomplete audio into a substantially complete audio signal.”
The key term is “phase layering.” In fact, the patent application’s summary refers to the invention as a “phase layering apparatus.” I’ll try to summarize how the device works based on my reading of the patent application. The input signal (which comes from one of your sources) is used as the phase reference. This signal is split into multiple copies of itself, with each copy independently phase-shifted by varying amounts (the “phase layering”). The multiple signal components of varying phase shift are then combined into a single signal along with the unaltered reference. This single signal thus contains the original unaltered signal and multiple copies of itself that have been subjected to varying amounts of phase shift. Note that this acoustical “decoding” can be performed in an active circuit, or even passively in a loudspeaker that has multiple voice coils. The patent application states: “By applying these angles, of 45°, more or less, layers of phase form into a final, complete audio signal composite that provides a virtually spherical acoustical signal.” This is an extremely simplified explanation; those who are technically inclined are invited to read the patent application.
I’m not sure, however, how a single, fixed process can acoustically “decode” the universe of diverse audio signals. Various miking techniques—XY, M-S, spaced omnis, spaced cardioids, ORTF, pan-potted multi-mono, etc.—capture the soundfield in very different ways. Moreover, these techniques are often augmented with accent mikes on specific instruments, not to mention the use of dummy heads, spheres, and baffles, or the varying sensitivity patterns of omnidirectional, cardioid, hyper-cardioid, and figure-8 microphones, and the relationships between the microphones, the instrument, and the surrounding acoustic. It’s obvious that some fundamental loss occurs in the recording process, but not so obvious if that loss involves out-of-phase signal components that can be restored to their original condition, or how a single phase-“correction” algorithm works for all recordings.
Nonetheless, the proof is always in the listening.
I installed the BSG Signal Completion Stage in my system initially between the preamplifier and power amplifier using the balanced inputs and outputs. Before listening to the QOL technology, I confirmed that the box had little effect on the sound of the system when in “Bypass” mode (no QOL).
Sitting in my listening chair, I could switch QOL on and off via the remote control. And switch I did, hundreds and hundreds of times, with CD sources, music servers, SACD, and LP playback. I switched between the bypass mode and QOL so many times not because the change was subtle and hard to detect, but because it was so profound. Frankly, I had a hard time believing that the radical improvement in the sound was real, and more importantly, represented a step toward the experience of hearing live music rather than just a lateral (if appealing) change in the signal. It also occurred to me that QOL might simply be introducing a euphonic distortion. Whatever the case, there was no question that music listening was more engaging and enjoyable with QOL.
Pushing the remote control’s Bypass button to engage QOL rendered a significant change in the sound in several different areas. The single best description of QOL is that it caused the sound to “open up,” both spatially and in timbre. Instrumental and vocal timbres became brighter, but not in the sense of a frequency-response change (the tonal balance was unaffected), but in the impression of the timbres becoming “illuminated from within” (to use Jonathan Valin’s descriptive phrase of ARC products). QOL seemed to strip away a layer of opacity, allowing the instrument’s tone colors to become more vivid and alive. Removing this opacity wasn’t the cliché of “lifting of veils,” in which the listener has the impression of a fine scrim being removed between him and the music, but rather that the opacity heard without QOL was imbedded within the instrumental timbre itself. QOL widened the palette of tone colors, the density of those colors, their vividness, and their life. This richness of timbre and vividness was not an artificial “Technicolor” rendering that sounded hyped or artificial, but rather revealed the inner brilliance of instruments and voices—a heightened sense of chiaroscuro. With QOL engaged, Joe Morello’s superbly recorded cymbals and hi-hat on Morello Standard Time [DMP] sounded brighter, but paradoxically, not because of more treble energy. Rather, the sound had a more open and vivid quality that sounded “lighter.” Woodwinds and brass instruments sounded more like they do in life, with greater presence and immediacy, but, again, without sounding artificially forward or pushy.
The change in timbre represented about half of what QOL can do. The other half was in the expansion of the soundstage in every dimension. Hitting the remote control’s “Bypass” button to engage QOL was almost equivalent to looking at a landscape with one eye and then opening the other eye and seeing the landscape suddenly pop from two dimensions to three. The soundstage not only became wider and deeper, but the most significant difference was in the sense of individual images existing independently from other images. That is, the soundstage became less homogenized, congealed, and closed in. The sense of air and distance between images was suddenly palpable. Instrumentals and vocals were no longer “stuck” to each other, instead expanding outward, forward, and backward. QOL also fostered the impression of greater soundstage height, as though a lid had been lifted. The sense of top-octave air riding above the presentation was palpable with QOL.
Turning off QOL collapsed the sound toward the center, tended to make the soundstage congealed and homogenized by comparison, and made timbres somewhat “hooded” and veiled. The sweet spot was also narrower without QOL. Try listening without QOL and swing your torso left and right in the listening seat; you’ll hear the image shift toward the direction of movement as you hear more sound from the closer speaker. Repeat with QOL engaged and the soundstage stays solid until you get much farther away from the center-line. Dynamic reproduction was also improved with QOL. Drums and percussion had more realistic transient detail, both in the steepness of attack and in the length of their decay. The increased speed at which transients seemed to reach their full expression increased the “jump factor.”
The degree of improvement rendered by QOL varied with the recording. Some LPs, CDs, high-res files, and SACDs were somewhat better sounding with QOL; with others the difference was nothing short of dramatic. Paul Simon’s Graceland is a familiar album that most of us own, and it’s one that particularly benefits from QOL. Listen to the unaccompanied voices that begin “Diamonds on the Soles of Her Shoes” and hear how the timbre of the voices becomes more present and realistic, and how you can better hear the individual singers. Listen also to how the soundstage widens and deepens. Or how Simon’s centrally placed vocal seems to hang in space as a separate element rather than as another sound within a homogenous fabric. His voice also moves back slightly in the soundstage and becomes a little more diffuse and defocused.
To see if there was any correlation between the degree of change in the sound and the recording technique, I listened to A Meeting by the River on the Water Lily Acoustics label reissued on SACD by Analogue Productions, which is a pure Blumlein recording (a pair of figure-eight microphones crossed at 90 degrees), a recording I made using an X-Y pair (crossed cardioids), and a pan-potted multitrack mix I’d engineered. The recordings made with coincident microphone techniques (Blumlein and X-Y) seemed to be less affected spatially by QOL.
I realize that the BSG Technologies Signal Completion Stage will be controversial, and that I’m going out on a limb with my enthusiasm for it. Frankly, it seems too good to be true. But try as I might to discover something about the sound that was antithetical to high-end values, I couldn’t. From my understanding of the technology, however, it is difficult to see how QOL makes the acoustic output from your loudspeakers more like that of the original soundfield. Is it appealing? Undoubtedly. But is it more accurate? I’m not sure—it’s entirely possible that QOL is a euphonic distortion. It’s not euphonic in a way that “tubey” electronics are; rather, QOL produces a sound that I think is closer to that of live music, even if the means to that end may not entirely be in accordance with fidelity to the original sound.
Only a few people so far have heard the Signal Completion Stage in their own systems, but I’ve had conversations and e-mail exchanges with one of them, a 40-year industry veteran, whose reaction was identical to mine right down the line, from the initial skepticism, to our specific listening impressions, to the desire to keep the Signal Completion Stage in our respective systems. I’m still trying to come to grips with QOL, and am not entirely convinced by the technical explanation or that it represents greater fidelity to the source, but I can tell you this; every time I sit down to enjoy music now, I’m listening with QOL.
SPECS & PRICING
Frequency response: 10Hz–50kHz +/-0.25dB
Signal-to-noise ratio: >106dB
Input impedance: 20k ohms (balanced)
Output impedance: 50 ohms (balanced)
Inputs: Four balanced on XLR jacks, four unbalanced on RCA jacks
Outputs: Two balanced on XLR jacks, two unbalanced on RCA jacks
Front-panel controls: Input select, bypass, mono, power
Dimensions: 17″ x 3.3″ x 13″
Weight: 25 lbs. (shipping)
3007 Washington Blvd., Suite 225