Half speed cutting is where the source is played out and the cutting lathe is running at half the real time rate. So if you have an analogue tape recorded at 30 inches per second it is played back at 15 inches per second (or a digital file is played at half the sample rate so a 96kHz file is played out at 48 kHz) and the lathe, if I was cutting an L.P is run at 16 2/3 R.P.M as opposed to 33 1/3 R.P.M. The advantage of this is that the system is not stressed. The cutting amplifiers draw somewhere between 1/4 to 1/3 of the current they would at real time and recording stylus has twice as long to carve the intricate groove. All the difficult to cut top end frequencies become relatively easy to cut mid range frequencies. This results in cuts that have excellent high frequency response (treble) and very solid and stable stereo images. Unfortunately, it is not as simple as running everything at half rate. There is an EQ curve applied to all vinyl records and by running the lathe at half speed, all the frequencies are wrong.

The technical staff here, who patiently put up with my crazy ideas, engineered new custom built filters which allow me to activate half speed mode at the push of a couple of buttons. There was an upside for real time cutting too, these new in-house filters sounded better than the original ones so the sound quality of our normal cuts was improved too, but obviously they are not as good as the half speed cuts.

The idea came from owning a couple of half speed cuts released by the esoteric Hi-Fi label MFSL. They would licence well known recordings, get their engineer Stan Ricker to do a really good half speed cut from the original master tape and make sure the pressing was as good as possible. I have the MFSL pressing of Pink Floyd’s “Dark Side Of The Moon” and despite it being around 30 years old now, it still sounds incredible. I happened to mention to one of our tech guys here that I would love to try half speed cutting and he, being like minded in wanting to improve things, said now would be a very good time to give it a go. During the learning curve when I was working out how to do it I was able to make contact with the inspiration Stan Ricker and he was so blown away that anyone else was interested in doing half speed that he was very generous with his advice and tips. To this day Stan Ricker and myself are the only engineers doing half speed cutting at any serious level.

If you'd like any more information about 1/2 speed cuts, email mastering@metropolis-group.co.uk