Wednesday, May 8, 2013

How Records Are Created - Analog VS Digital

Understanding how things are built and created is a constant obsession of mine. It could be an engine, a computer or hell in this case, how records are made. No matter what the object of attention is, I have to understand the core principles of how it works. Like a fly a to a bug zapper on a hot summer night, I get consumed in trying to understand all the moving parts and details that will eventually come to life.

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"While the rest of us were enjoying the dulcet tones of Bing Crosby, Amanda Ghassaei of Instructables was as busy as ever over the holiday: she posted a 'compilation' video of her experiments in 3D printing 12” records, for which she has unsurprisingly published the plans on Instructables, on the day after Christmas. "In order to explore the current limits of 3D printing technology, I've created a technique for converting digital audio files into 3D-printable, 33RPM records and printed a few prototypes that play on ordinary turntables." Suffice it to say that it's a significant improvement upon Fred Murphy's diverting Fisher Price records:
This project was my first experiment extending this idea beyond electronics. I printed these records on a UV-cured resin printer called the Objet Connex500. Like most 3D printers, the Objet creates an object by depositing material layer by layer until the final form is achieved. This printer has incredibly high resolution: 600dpi in the x and y axes and 16 microns in the z axis, some of the highest resolution possible with 3D printing at the moment. Despite all its precision, the Objet is still at least an order of magnitude or two away from the resolution of a real vinyl record. When I first started this project, I wasn't sure that the resolution of the Objet would be enough to reproduce audio, but I hoped that I might produce something recognizable by approximating the groove shape as accurately as possible with the tools I had.

The project isn't a major breakthrough in 3D printing (per our Year-in-Review prognostication), but it's certainly an inventive bit of lateral thinking. Ghassaei notes that even the top-of-the-line Object Connex500 cannot emulate the traditional process of stamping vinyl (video after the jump), citing digital equivalencies to denote the low fidelity of the 3D printed records, which sound something like listening to a radio broadcast through a thin wall.
Though the audio quality is low—the records have a sampling rate of 11kHz (a quarter of typical mp3 audio) and 5-6 bit resolution (less than one thousandth of typical 16 bit resolution)—the audio output is still easily recognizable... The 3D modeling in this project was far too complex for traditional drafting-style CAD techniques, so I wrote an program to do this conversion automatically. It works by importing raw audio data, performing some calculations to generate the geometry of a 12" record, and eventually exporting this geometry straight to a 3D printable file format.

The effect is most felicitous for Radiohead's "Everything in Its Right Place," where the lo-fi crackle and narrow frequency range somehow underscore the warm solace of the opening track from Kid A. Daft Punk, on the other hand, sounds better with more bass as a rule of thumb, while Aphex Twin's "Windowlicker" needs more treble; the alt-rock cuts need a more volume all around. (The song selection is something like the weeknight playlist at any given bar in the Mission or Williamsburg... not that there's anything wrong with that: it's easier to judge the quality of familiar tunes than obscure ones.)


Meanwhile, the rotational meta-metronome of the slightly warped 3D printed records—each one has a subtle swish at 66BPM, about half the tempo of "Blue Monday"—conjures some kind of breathing apparatus... or, perhaps a printer or scanner arm moving back and forth across a two- or three-dimensional stage. In fact, it has an uncanny resemblance to many of the sounds that comprise the Printer Orchestra version of "The Times They Are A-Changin'" or James Houston's brilliant rendition of Radiohead's "Nude," below.

Sonic associations aside, Ghassaei's project piqued my interest in the traditional process for pressing vinyl, which is pretty remarkable in itself. This two-part Discovery Channel segment on YouTube is well worth ten minutes of your day (I gotta admit that I didn't know that records are made of polyvinyl chloride, a.k.a. PVC):

For reference, here's what vinyl looks like under a microscope:


Of course, Ghassaei works from the digital versions of audio data, or "the set of numbers that defines the shape of the audio waveform," using Processing to "[parse] this information to set the height of the bottom of a spiral groove." In effect, a 3D waveform is inscribed along the grooves of the disc, such that "the turntable stylus moves along the groove... in the same path as the original waveform and recreate the original audio signal."


Alternately, the renderings of the CAD-ified waveforms are fascinating despite (or perhaps because of) their opacity, literally reflecting an oblique relationship to the original waveform. The short teaser video for Benga's "I Will Never Change" nicely illustrates the more familiar form in a stop-motion audio visualization that also happens to be a digital riff on vinyl.


(Ok, I'm done free-associating now.)