Tuesday May 14, 2013
There's a revolution coming and its name is 3D printing. From prototyping to components, through jewellery and Transformers accessories all the way to firearms and lunar housing, the potential of 3D printing has probably only been tapped to a very small percentage.
So what does a creative person do when they have time on their hands? Why, 3D print a 'vinyl' record of course. And that is exactly what Amanda Ghassaei has done.
See and hear for yourself...
For a full explanation you should read her description of the process. Don't start reading before you've finished your work for the day, otherwise you'll get nothing else done.
I don't want to repeat what you can read in more detail elsewhere, but there are some points of interest for the audio specialist here.
Firstly, although 3D printing a record is undoubtedly a fascinating achievement, the audio quality falls far short of even the earliest vinyl records from the 1950s. In fact I've heard 78 rpm records that sound better, and they are made from beetle secretions.
The shortfall in quality manifests itself in the form of a restricted frequency range and a poor signal-to-noise ratio.
The reason for the restricted frequency response is the comparatively low resolution of the 3D printer used, at 600 dpi (dots per inch) in the horizontal plane and 16 microns (equivalent to around 1600 dpi) in the vertical. Putting it simply, the groove can't make the stylus wiggle fast enough to reproduce the highest audio frequencies (but maybe a 78 rpm turntable would have helped).
Ghassaei interestingly talks about sampling rate here as though the finished product had one. The printer does, but the printing process performs the necessary digital-to-analog conversion. Ghassaei clearly thinks in computer engineering terms rather than audio terms so this is understandable.
She also interprets signal-to-noise ratio in terms of bit depth, saying that her records have a resolution of 5-6 bits, where an audio person would say that the signal-to-noise ratio is around 30-36 dB.
There is one puzzle that I can't work out from the text. Ghassaei has chosen to modulate the groove vertically, because the printer has its best resolution in that direction. There is only one direction of modulation, for simplicity, and the two channels of the original stereo signal are summed before printing. However, if a record bearing a groove that contains only vertical modulation is played on a normal stereo record player, then the signals on the two channels will be out of phase. What I hear in the audio examples is mono, so I assume that either only one channel has been used, or one channel has been flipped before summing the two back together, which should in theory give an extra 3 dB of signal-to-noise ratio, at least on the playback side of things if not the printing.
If the quality of a printed record can't match traditional vinyl, one has to ask what exactly is the point? Well the point here is clearly an engineering exercise, and fun, in a Big Bang Theory kind of way. But the quality of the records produced is way better than I would have imagined, and all it needs to equal and surpass conventional vinyl is a higher-resolution printer. If you compare 3D printing to printing from a computer onto sheets of paper, we are probably at the daisy wheel stage of evolution. Give it a year or two and the resolution may be well in advance of anything that could be achieved on good old analog vinyl.
So where there have been rumors of a vinyl revival, there may actually be a vinyl revolution in the air where anyone can print their own records at home. Now, the next step will be a printer that can print a gatefold sleeve...
By David Mellor, Course Director of Audio Masterclass
Tuesday May 14, 2013