- February 2004 -
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Listening to High-Resolution Audio:
Over 60 million DVD players have been sold into American homes since they came on the market 6 years ago, making DVD the fastest adopted consumer electronics product in history.
By the end of 2003, 30 percent of American homes will have home theater systems-that is, DVD players hooked up to something more than a TV set or a TV and a stereo system. Finding space in the living room for those 5 extra speakers plus a subwoofer-not price-may be the biggest impediment to the inexorable advance of home theater into US homes. But Home Theater in a Box (HTiB) solutions are making headway here-a one-stop purchase that gets you a surround sound capable receiver (the engine of home theater and multichannel audio) and the 5 speakers plus sub you need for that immersive experience.
But in this rush to video and multichannel audio, we shouldn't forget the new music-only disc formats that offer not only surround sound, but also high-resolution audio.
While high-resolution audio may be a harder sell to consumers ( who appear to be happy with the fidelity of MP3-encoded music), it is something that audiophiles and others who care about the fidelity of music reproduction are intensely interested in.
The theme of this techno-lite essay is: How to get from "A" to "B," with "A" being high-resolution audio on an SACD or DVD-Audio disc, and "B" your ears (or mine, for that matter). Much has been written-too much-about the format wars between SACD and DVD-Audio. Enough to say here that both deliver considerably more fidelity than the 44.1 kHz/16-bit CD that we all-or most of us-have come to embrace, and that multi-format players are now commonly available, at a price.
SACD uses a recording technology called direct stream digital (DSD) that employs single-bit recording and a sampling frequency of 2.8224 MHz per channel (64 times the sampling rate used to create a CD). DVD-Audio uses PCM technology and can deliver up to 192 kHz/24-bit stereo and 6-channels of music at up to 96 kHz/24-bit resolution. Increasing the sampling rate, resolution, and peak frequency capture more of the audio spectrum. And both formats offer substantially increased dynamic range over CD.
Multichannel DVD-A recordings are sampled at 96kHz, which limits their frequency response to 48kHz. SACD captures frequencies up to 100kHz. (However, to remove some of the extreme high-frequency noise introduced by noise shaping, some SACD players incorporate a 50 kHz low-pass filter that limits the audio signal's high-frequency response.)
The 44.1kHz sampling frequency and 16-bit quantization of the CD passes 20kHz audio but rejects signals above 22.05kHz. The full spectrum of analog sound and analog musical sound extends well above the rather artificial cut-off established by the original CD specs-a cut-off that rather neatly matches the upper frequency limit traditional loudspeakers can produce. The vast majority of loudspeakers cut off at about 30 - 22kHz, the generally accepted upper limit of the average listener.
Let's pause here a moment… If SACD and DVD-Audio discs are able to capture a much more realistic representation of the full audio spectrum than CDs, and we have the means to deliver this high-res signal from a DVD player through a high-definition capable A/V receiver (and trust me here, this is doable in a home system), then one might ask: What's the sense of pumping high res audio into a box (or 5 boxes) that can't reproduce it?
Exactly my point. Well, part of my point. Because there are loudspeakers on the market that can reproduce an audio signal above the 20 - 22kHz threshold. But only a very few.
High-Resolution Loudspeakers: the Pros and the Rest of Us
While a number of manufacturers are producing 5.1 loudspeaker systems for use in the production and post production processes, relatively few have product that addresses the reproduction of the upper frequencies.
Professional monitors from ProAC (a U.K. manufacturer), ADAM (a German manufacturer), and France's Focal-Jmlab, in particular, extend frequency response above the 22kHz brick wall. And some, like the Focal-Jmlab SM11, accept a digital audio signal as well (and convert it on-board), allowing studio engineers another option for maintaining the high-res integrity of the signal chain.
Residential loudspeakers from a few manufacturers are capable of extended frequency response. A few examples are: KEF's Reference Series with its Hypertweeter; a few models from B&W; Jamo's THX certified system; Meridian's DSP series of loudspeakers (advertised to handle frequencies, "over 20kHz"); the Swiss Piega loudspeakers.
But one manufacturer has its feet planted firmly in both the professional and residential markets with high-resolution loudspeaker systems for each- the 75-year old U.K.-based loudspeaker company, Tannoy (www.tannoy.com). Over eight years ago, Tannoy began pushing the frequency response envelope, first with the introduction of its Kingdom range SuperTweeter, an add-on product that extends the useful range of their classic Dual Concentric residential loudspeakers as well as their classic studio monitors. In short order, Tannoy brought its high-res Ellipse series of professional monitors to market, while simultaneously revamping its line of residential loudspeaker systems for full-bandwidth response.
To date, eight of their 10 residential product ranges (there are multiple offerings within most ranges) are what Tannoy terms, "WideBand." Each one of these product ranges offer complete loudspeaker systems (that is, center channel and rear speakers as well as front L/R) with extended frequency response out to 54kHz. And the separately mounted SuperTweeter does the same for the company's professional products, both current monitors as well as their highly regarded vintage monitors.
WideBand Audio & Dual Concentric Technology
Part of the reason Tannoy has been able to ramp up to high-res monitoring so rapidly in both its professional and residential lines is its core technology-the patented driver configuration that made their monitors a fixture in studios around the world for nearly three decades: the Dual Concentric driver.
While this is no place to proselytize for Dual Concentric technology, it's important to note why it works very effectively when coupled with an extended frequency drive unit in a high-resolution loudspeaker.
First of all, the Dual Concentric is an integrated full range driver; that is, instead of frequencies being split among multiple drive units as with traditional loudspeaker designs, all frequencies in the Dual Concentric design emanate from the point in space (point-source). One result of this design is that the Dual Concentric drive unit produces a consistent 900 conical directivity pattern across a much larger portion of the frequency range than a discrete driver arrangement can. Except for the very low omni-directional frequencies, what you get on-axis is an even response, and what you get off-axis is the same even response.
Secondly, over the frequency range that a Dual Concentric operates, it does a far better job of preserving the harmonic content of instruments compared to conventional discrete drive unit arrangements. This is because the low and high frequency sounds are generated from a single point-source, and there are no time and phase differences between harmonics below and above the crossover point, as with discrete speakers.
The WideBand SuperTweeter operates between the roll-off point of the Tannoy Dual Concentric high frequency unit and 54 kHz. The SuperTweeter reproduces the leading edge of individual notes, allowing the listener to experience the entire bandwidth information of instruments. (See the sidebar: "Audio Above 20 kHz: What's Up There, Anyhow")
Tannoy's interest in expanded bandwidth is, in part, an extension (pun intended) of their concern with issues of phase, as addressed in the Dual Concentric driver design. The Dual concerns itself with the time coherence between the midrange and the tweeter. Likewise, the SuperTweeter, time-aligned to the acoustic center of the Dual Concentric, reduces high frequency phase error by moving the low pass roll off point much higher, typically -6dB @ 54kHz, -18dB @ 100kHz. So even if, for the moment, we ignore the perception of sound above 20kHz, the bandwidth expansion of a SuperTweeter better preserves the overall harmonic relationship between instruments.
Without getting too technical-or rousing knowledgeable audiophiles to a debate-phase shifts are additive. By extending the bandwidth of any part of the recording/playback chain, you reduce in-band phase error. For example, a traditional loudspeaker rolls off typically around 18 - 20kHZ and a CD rolls off around 22.05kHz. Since both of these "filters" occur in near proximity, they add to each other and both contribute to the errors in-band.
By moving either the CD's low pass up (by using an SACD or DVD-A source) or the loudspeakers' low pass frequency (by using WideBand-capable loudspeakers), the sound will be improved. If both the source and the loudspeaker are high-resolution, then the sound is improved further still. This is why even the lowly CD sounds better through a wideband loudspeaker. It's not about actually hearing information above 20kHz, so much as it's about the energy in-band at 20 - 20kHz sounding better due to less phase error.
Still, still… it must be admitted that SACD and DVD-A do not represent the leap forward for most people that that CD did. The new high-res media offer nothing like the major advance in convenience and durability that of the CD offered over vinyl. And the sonic improvements of the new high-res media are smaller in degree. In order to be appreciated fully-the theme of this article-they require an audiophile-grade, high-resolution system from start to finish.
But if all audio for both home theater and multichannel music listening is inevitably headed toward high-resolution-and this seems to be Tannoy's assumption-then there may come a time in the near future when traditional, limited-bandwidth loudspeakers are as hard to find as a simple stereo receiver is today. We won't exactly be forced to upgrade our playback systems to take advantage of the new de facto standard, but it just may make less and less sense not to.
Universal DVD Players and High-Definition A/V Receivers
Essentially, what you need to deliver a high resolution audio signal to high resolution loudspeakers, such as Tannoy line of WideBand monitors, is a Universal DVD Player and a High-Definition A/V Receiver.
While the DVD player has become nearly ubiquitous, DVD players that can play both SACD and DVD-Audio discs-called, Universal DVD Players-have only recently become available. Onkyo, Denon, Yamaha, Pioneer, Marantz-the usual suspects-offer player at about the $1000 price point. The Pioneer DV-563A breaks ranks, coming in under $200… However, not all DACs (digital audio converter chips) are alike.
A high-end A/V receiver that accepts both DSD (SACD) and DVD-Audio signals (and provides other inputs as well) and converts those signals to analog at the highest resolution possible is what you want. The big names in residential audio all now have flagship receivers of this nature, Yamaha's RX-Z9 being as good an example as any, listing at $4,499.00 (www.yamaha.com/yec/products/RECEIVER/RX-Z9.htm). The RX-Z9 provides 192 kHz/24-bit D/A converters for all 11 output channels, and offers a Pure Direct signal path for 2-channel or multi-channel analog inputs as well.
A surround sound receiver may not suit everyone's taste…There are other solutions to the distribution of high-definition audio to 5.1 channels or more, such as: a universal disc player, surround sound controller, and powered loudspeakers. But most folks will probably prefer the all-in-one receiver solution.
A footnote here… while some of the professional studio monitors mentioned in the body of this article accept a direct digital signal, very few residential loudspeakers (the Tannoy iDP line of products among them) can accept a digital signal-as well as an analog signal, of course. The catch is that there are no receivers or consumer A/V amplifiers on the market that can deliver a multichannel, digital audio signal. The reason for this has much more to do with copyright protection of what is essentially "master level" audio signal than it does with any technological barriers.
And last, but not least, you need software…
Currently there are about 1600 SACD titles available (in three flavors, all of which any Universal DVD can play), and over 600 DVD-A titles. Virtually all of the major record labels are producing high-resolution music discs, along with many smaller labels. (Source for these recent statistics: www.highfidelityreview.com)
Much of the material being released in high-res surround, especially in the rock and pop genres, consists of titles that have been remastered from high-res multitrack digital source material or "classics" remastered from multitrack analog source material. The original mixes of these releases were, of course, in stereo, so the high-res remixes are creative reconstructions of a sort. Some may make audio "sense," and others may not. You'll be the judge here.
High-res, multichannel releases of newly recorded material are mainly in the classical and jazz genres where acoustic instruments predominate. But this is changing.
It's important to note that just as with CDs, some high-res releases are going to be better recorded than others. The entire recording signal chain-from the microphones, to the mic preamps, to the console (if there is one), to the recording and/or editing equipment-affects the quality of any recording, high-res or no. Foolish as this may sound, the musical material and the performance will always be of prime importance in judging the worth of a high-res release.
And just in case you were wondering, yes, Pink Floyd's "Dark Side of the Moon" is available, in at least its fourth incarnation since its first release on vinyl, this time on SACD.
A good portion of newly recorded, high-resolution audio releases of are in the classical genre. Classical music-or more generally, acoustic music-shows off the new high-res formats' ability to capture the full spectrum of perceivable sound as well their significantly increased dynamic range.
Leon Botstein, London Symphony Orchestra - Liszt: Dante Symphony & Tasso (Telarc SACD-60613)
For an instructive trip through the vagaries of remastering and re-releasing of classics from the pop music catalogue, take a look at the history of Bob Dylan's Blood on the Tracks, Bring It All Back Home, and Blonde on Blonde.
Blonde on Blonde (orgininally released by Columbia, now Sony, in 1965 on vinyl) was released in Nov 2003 as a hybrid SACD (ASIN: B0000C8AVU), meaning it contains, spread over two discs: a standard stereo CD mix, a stereo SACD mix, and a 5.1 SACD mix.
By all accounts, the stereo SACD mix puts to shame all previous releases of this material-including Sony's own first attempt at an SACD version a few years back.