Pressing Matters

It is my sincere hope that this blog provides entries of interest to music lovers, musicians, and audio enthusiasts, as well as folks who make records.  A few previous entries, such as Can you hear what you’re doing? (Part 1) and Can you hear what you’re doing (Part 2), were aimed specifically at those setting up studios in order to make records, among whom there are a great many musicians.  Of course, it has been my hope that others would find these of interest as well.  So it is with the current entry.  While it is intended primarily for those who make records, if I’m lucky, those who purchase and listen to records will also find something of value herein.

With audio mastering completed for the new Work of Art album entitled Winds of Change (first mentioned in the August 22, 2014 entry of this blog, also called Winds of Change), and with the album artwork approved, it was time to contact the CD replicator in order to get the “pressed” versions manufactured.  Actually, CDs are not pressed like vinyl records.  They are made using an injection molding process, but the term pressing seems to have endured in common use.

Those familiar with my label, Soundkeeper Recordings, know that we release each album in several different formats.  In addition to the regular CD, we offer six custom burned formats, including CD-R and five formats with higher resolution than a CD can provide:
–   Music-only DVD-R with 24-bit, 96 kHz audio, playable in most regular DVD players
–   24-bit, 96 kHz .aif files-on-disc
–   24-bit, 96 kHz .wav files-on-disc
–   24-bit, 192 kHz .aif files-on-disc
–   24-bit, 192 kHz .wav files-on-disc

For more about the different resolutions, see the May 22, 2014 entry in this blog, Is “too much” not enough?

As far as standard, 16-bit, 44.1 kHz CD resolution, the reason Soundkeeper Recordings offers our releases in CD-R format, and the true subject of this entry, is something I’ve said since I heard the finished product for the very first CD I mastered, back in January of 1983—CDs made at different plants all sound different from each other and none sounds indistinguishable from the master used to make it.  This may sound strange in view of the marketing that has accompanied the CD format from the beginning, primarily in the form of the slogan “Perfect Sound Forever” and the widely accepted idea that nothing can change once the signal is in a digital format.

Imagine my surprise then, when I first started mastering CDs and found that the same digital U-Matic tape (the format used at the time to send CD masters to replication facilities) sounded different depending on which side of the Sony DAE-1100 editor I used to play it.  The DAE-1100 was commonly used at the time to assemble CD masters.  The unit controlled tape machines for the ¾” tape cartridges that comprised the U-Matic format.  One or two machines could be used on the Playback side and another machine was used on the Record side.  The CD master was assembled on a U-Matic tape in the machine connected to the Record side of the editor.

Early on in my experience with this system, I wanted to compare a tape that was copied from another, just to hear for myself that a digital copy was indistinguishable from the original, as we’d all been told.  Unfortunately, the test never got that far.  What I found was that the original tape, played from the Playback side of the editor sounded better than the copy.  Something was getting lost on the copy, as it seemed coarser and less well defined than the original.  I don’t recall what made me try it but I decided to swap the tapes, listening to the copy from the machine attached to Playback side of the editor and the original from the machine attached to the Record side.  To my surprise, now the copy sounded better (i.e., more like the analog source tape I was using) than the original digital conversion.  When heard from the Record side of the editor, the original digital tape now sounded coarser and less well defined than the copy!  Clearly, there was something else going on.

Perhaps it was this experience that diminished the surprise when the finished CDs for that first CD mastering project came in and I compared them with the CD master used to make those discs.  Here the coarseness was even greater than what I’d encountered on the different sides of the DAE-1100 editor.  The finished CDs almost sounded “out of focus” compared with the CD master, such was the extent of the loss of clarity and fine detail.

Things got more interesting when I created CD masters for albums where large sales were expected.  In those days, there were fewer CD plants than there are today and they were all working at capacity.  In order to accommodate expected demand for the big sellers, the CD master would be cloned and those clones were sent to multiple replicators in order to get back sufficient numbers of finished discs to meet the demand.  This was an education in that I discovered that CDs from different plants all sounded different from each other.  Sometimes CDs from different lines within the same plant sounded different from each other.

So much for “Perfect Sound Forever”.  The format has been claimed to deliver perfect copies of the master.  Logic would demand that if this is the case, all those perfect copies would sound indistinguishable from each other and they’d all sound indistinguishable from the masters from which they were made.  But they weren’t then and they still aren’t today.  (There is an exception that I’ll get to shortly.)

Having sent CD masters to plants all over the world and all over the USA, I’ve had the opportunity to compare a lot of finished product to the masters from which said product was made.  Happily, the days of U-Matic tapes are long gone and the advent (long ago) of computer workstations made for many improvements.  Still, even with the most sophisticated CD mastering tools, the reality from the replication facilities remains—the finished discs don’t sound like the masters.

In my experience, a slow-burned CD-R made directly from the computer-based CD master, sounds more like that master than any pressed CD, even the best in my experience.  This is why Soundkeeper Recordings offers our releases in CD-R format as well as replicated CDs.  But how then, to select a CD replicator?  If they all produce discs that sound different from the CD master, how does one find the most faithfully made discs?  This is the question that was on my mind when I started the label.  Knowing that a lot of folks just prefer a factory-made disc to a burned version, even if the latter is more faithful to the master, I needed to find a replicator for Soundkeeper CDs.  My whole reason for starting this label was to avoid the compromises I feel are too often part of the record making process.  I wanted a no-compromise replicator — if such a thing existed.

I reached out to contacts at most of the plants I’d sent masters to over the years.  I told them about my concept for the label and that I needed the most faithful to the master, highest quality discs.  All but one of them told me essentially the same thing.  They said their CDs were perfect replicas of the CD master.  Since my own experience consistently told me something quite different, I could only conclude they were not hearing it the same way I was.  Or they just weren’t listening and were simply repeating the received mantra.  I thanked each in turn and moved on to the next person on my list.

Out of all the replication facilities, only one person at one facility told me, with no prompting from me whatsoever, “Oh the finished CDs will never sound like the CD master.”  I wanted to hear more but knew by then that I’d found my CD replicator.  Here at last, was someone who appeared to actually be listening.  It turned out, this replicator took an unusual approach to making their finished CDs too.  Where many plants increased their throughput – and hence, their income – by speeding up the process, this plant kept with the slower methods.

The first step in manufacturing a CD involves cutting what is called the glass master.  The CD master from the mastering facility is fed into a Laser Beam Recorder (LBR), where a laser is used to create the pits in a photoresistant coating on a glass disc.  This disc is used in the subsequent steps of CD manufacturing.  Most plants cut the glass master at high speed.  Some will cut the glass master in real time, at additional cost.  Many folks have found real-time glass cutting to result in finished discs that sound closer to the original CD master.  The person at this plant told me they cut all their glass in real time, at no additional cost.  It is just how they do it.

In addition, most CD replicators have moved to shorter injection molding cycles.  The faster the cycle, the more finished discs that can be produced in a given day.  Typical injection molding cycles for CDs are now about 4 seconds long.  The person at this plant told me they use a slower cycle, closer to 9 seconds long.  This makes for better formed pits on the finished discs, making it easier for the laser in the CD player to read the discs and minimizing the incidence of playback errors.

Whether the real-time glass cutting and slower injection molding cycle are the reasons or whether some other factors might be involved, I don’t know.  What I do know is that when I master an album, I listen to it so many times that I become intimately familiar with all the details of its sound.  Often, when I hear the finished CD that comes back from the replicator, it takes only a few seconds to hear the typical loss of focus and fine detail.  Something like a chord strummed on an acoustic guitar becomes a loose mélange rather than the six discrete, individual string sounds heard on the CD master.  With CDs from this replicator, the sound is so much closer to the CD master, I need to synchronize playback of the finished disc with the CD master in order to discern the remaining differences.  (Still not as close to the master as the CD-R but closer by far than I’ve heard from other CD plants.)

Now earlier on in this entry, I mentioned an exception.  In fact, I wrote about this in the February 23, 2014 entry in this blog, entitled Listening to Tomorrow.  Basically, what I’ve found is that what I’ve written about in the current entry comes into play when the CD is played in a CD player or via a CD transport.  This has been my experience regardless of the player or transport, or its price.  However, when the CD is properly extracted to a computer, the audible differences do go away.  To date, after 31 years of the CD format, it is only via computer that I’ve heard the audio from a CD disc sound indistinguishable from the master used to create that CD.  Still, those listening to computer music servers with CD or better resolution (as opposed to mp3 or other reduced formats) are in the minority.

Most of the music lovers I know of who purchase CDs will listen to them in CD players or via a separate CD transport feeding an external digital-to-analog converter (DAC).  In order to provide these folks with a CD that truly represents the CD master approved by the artist and producer, selection of the replicator is critical.  To this end, I feel very lucky to have found Bryan Kelley and the folks at GrooveHouse Records, who I have been recommending to mastering clients since my first conversation with Bryan, and who, as far as I’m concerned, are the official CD replicators for Soundkeeper Recordings.

Digital grows and first experiments in stereo

When I first heard of digital audio, it seemed full of excitement and promise, with claims of perfect sound, perfect copies and a noiseless medium that was indestructible.  When I first experienced the subject of all these claims, I heard pain-inducing sound, questionable copies, new forms of noise and found the media more than a little bit fragile.

The earliest digital systems did well in the published laboratory measurements.  Frequency response was flat, without the “head bump” in the bass or the diminishing energy at either end of the spectrum suffered by analog tape.  Measurements of gross speed inaccuracy showed there wasn’t any.  Signal-to-noise ratio measurements also revealed devices capable of hiss-free recordings.  But when one sat down to listen to the recordings created with these digital systems, they just didn’t sound very good.

The news got better as some designers who heard the flaws in the technology began to study and address its weaknesses.  The devices used to convert signals from analog to digital got better, as did those used to convert digital audio back to an analog signal for playback.  While it had the edge in terms of measured response, there was still a very long way to go before the sound of digital was going to be competitive with analog.  One of the major stepping stones on that road to progress was the personal computer, which was just coming into popular use at the time.  In the second half of the ‘80s, I was introduced to one of the first computer-based digital audio systems.  Where the first digital editing systems I’d seen seemed like futuristic machines allowing edits I couldn’t have imagined doing with the razor blade and Edit-All bar from the analog tape days, the computer-based system, called a digital audio workstation (or DAW) took the concept an order of magnitude further.  Access was fully random and instantaneous.  No more having to first record everything prior to an edit point because the old system required masters to be assembled in sequence.  No more waiting for tape to wind to a specific place to hear a specific passage.  The entire program (or a tiny fraction of a second of that program) could be viewed on screen at once.  A click of the mouse was all that was required to hear any part of that program instantly.  All sorts of sonic adjustments could be made that could not be made before, at a level of detail unattainable in the past.

Another promise of the digital audio workstation was something I had long looked forward to, which was the elimination of tape.  While it had served well as an analog medium, my experience with tape for digital audio was that it was quite fragile.  A particle of dust was all it took for playback to suffer a “dropout”, a momentary muting of the audio.  Digital recordings on tape didn’t age well either, as our digital tape analyzers confirmed with significantly increased incidence of the digital system’s error correction coming into play as a tape got older.  Some tape formats, like the miniscule DAT (Digital Audio Tape, a digital audio cassette of sorts) used tape so thin and so fragile it was not uncommon for 6-month old DATs to no longer be playable, the audio devolving from music into something more closely resembling a fax transmission.  The digital audio workstation had an accessory disc recorder, which recorded on blank discs, recordable CDs (or CD-R).  The first blank discs I saw sold for $75 each and the failure rate (the creation of “coasters”) was high.  How far we’ve come since then, with very high reliability, no-failure discs selling for 35 cents apiece!

At this point in my experience, however, I got suspicious.  I’d been there before with new technologies offering undeniable improvements in certain aspects of the quality or in certain aspects of the mechanical operations required to capture audio and turn it into a finished recording for the listener.  There was always that little detail though:  the sound.  Almost a faux pas to mention it in some circles but it is what all this is about, isn’t it?  So I wanted a real demo of this new computerized system.  I wanted to hear what happened to audio that passed through it.  I wanted to compare a CD-R made on one of these systems with the signal used to burn that disc.

While all these developments were occurring, I had been engaged in a related pursuit with my early experiments in recording in stereo.  I had learned and used the techniques common to most studio practices where multiple microphones were deployed to capture multiple sounds which were later combined during the mix down to (the 2-channel, dual mono result that is commonly but erroneously referred to as) “stereo”.  As interesting as this was and as interested as I was in honing the techniques in order to create something more convincing—something that sounded “in here” (in the control room) more like it sounded “out there” (in the studio with the musicians), I found the idea of a much simpler approach even more intriguing.  I began to experiment with a more first principles strategy, questioning every single aspect of record making, every single component of the process and every single decision involved.  This was the beginning of what I later came to think of as “The Questions”.  These are questions that need to be asked if one is ever to arrive at answers. They are the questions I’d never seen mentioned in any of the books on recording I’d ever read or in any of the magazines.  They are the questions I was never taught to ask when I was an assistant engineer, the questions that students in today’s “audio engineering” schools never encounter.  How fortunate I was that it ultimately occurred to me to ask them.

The questions are in fact, simple; so simple, they and the answers they might lead to tend to get overlooked:
“Why this microphone?
“What results do I expect from selecting this microphone?”
“What results of selecting this microphone might occur which I do not expect?”
“Why place it here?”
“What results do I expect from placing this microphone here?”
“What results of placing this microphone here might occur which I do not expect?”
“Why am I turning this particular knob to adjust the sound?”
“What did I do wrong in a previous step that I believe will be remedied by turning this knob?”
“What results might occur which I do not expect?”

There are an infinite number of questions, as many as there are decisions to be made in the process of making a record, from conception to manufacturing the finished product.  As I set out to find the questions and hopefully some answers to same, I started making recordings in an entirely different fashion.  Rather than layering multiple recordings, each picked up with a large number of microphones, I sought to capture real performances in a single shot, recording “live” (for the microphones), using only as many microphones as there would be playback channels.  In the case of stereo, that meant only two microphones.  (I’ve developed the technique since then to allow layered recording, i.e., overdubbing, where players do not all have to perform at the same time or where a musician or vocalist can perform more than one part.  However, I became increasingly taken with the idea of capturing real performances in real stereo.)

The first tests were solo piano recordings and these provided a great deal of education in terms of capturing what I’d hoped to capture but even more regarding certain aspects of the results that I did not expect.  For all of these tests, with the goal of maximum fidelity in mind, I was using microphones more commonly employed for critical measurements of sound than in making actual music recordings, where microphones with more pronounced sonic character were (and remain) much more the rule.  These were the Danish microphones from Brüel & Kjaer (B&K, now Danish Pro Audio or DPA), with relatively small diaphragms compared to the large diaphragm mics generally used to record music.  The B&Ks were also omnidirectional microphones—they “heard” sounds from all directions—whereas most studio mics have a more directional pickup tending to focus on what is directly in front of them.  (This most common, front-hearing type of microphone directivity is called “cardioid” because of the vaguely heart-shaped laboratory representation of how it “hears”)  Over time, I came to believe that all microphones are in fact omnidirectional but some (the sort called “directional” ) apply more color—are less transparent—to off-axis sounds, those coming from the sides or behind them.  True omnis are more neutral in terms of timbre than their directional counterparts.  They’re better at getting out of the way.  (Of course, not all recordists want their gear to get out of the way.  What is “good” depends entirely on the results one seeks.  For the purpose of making a recording that sounds like what occurs in the presence of the microphones, I want gear that gets out of the way.)

The mics captured so much of what was occurring in the room, they showed me things I had up to then failed to consider in the recording.  Prime among these is the room in which the performance occurs.  In hindsight, this only makes sense since the departure from close mic placement means the engineer is no longer simply mic’ing the instrument; they are mic’ing the event.  The place in which it occurs is very much a key sonic component of the event.  A fine grand piano sounds very different in a nice auditorium than it does in even a large domestic room.  The latter has intimacy but the former is required to access the grandeur—assuming the music and performance call for this.  (Here again, what is “good” depends entirely on the results one seeks.)

For the next experiment, I got permission to use a more suitable space:  Atlantic’s Studio A.  The instrumentation for this project consisted of grand piano, synthesizer, saxophone, bass and drums.  I’d been giving a lot of thought to how I would deploy the microphones this time.  For the earlier solo piano experiments, my thinking was really in terms of the piano, though the results taught me I should have taken a wider perspective to include the space.  Now I was also considering the relationship between the positions of the two microphones during recording and the two speakers during playback.  I thought there might be some reciprocity between the both ends of the chain.  (I will return to this concept in a future entry.)

The recording I made that night had a sense of coherence and focus I had heard on only a tiny number of recordings before then.  Though it was far from perfect and offered a number of new insights on what I should (and should not) do, it was a personal landmark insomuch as it really did offer a sense of being there, of bringing the listener to the performance, in the space in which that performance occurred.

When the folks offering the demo of the digital audio workstation responded to my skepticism by offering to burn me a CD-R, I knew exactly which recording would tell me the most about how passing through that computer system would affect the sound.  When they delivered the disc, I spent a lot of time doing synchronized comparisons of the disc playback with the original recording, switching back and forth between the two.  In the end, at the time, I could not detect a sonic difference.  Further tests of the workstation also revealed that while the existing (pre-computer) system introduced new types of distortions during certain operations, those same operations could be performed on the computer-based system with transparent results.  (There will be more to say about this in a future entry about the evolution of digital audio.)

Happily, digital audio was to make some great progress to get to where it is today.  Before that was to happen though, a perhaps even more earth-shaking experience was coming.  Despite what I’d been taught and what I’d read about in all the years I had enjoyed playing back recorded music, I was soon going to hear stereo for the first time.