Mobile Fidelity Sound Lab - Half-Speed LP Mastering

Half-Speed LP Mastering

MFSL initially became known to the public for the Half-Speed Mastering technique, which has since been employed by many other record companies. It was the first label to use this as standard on all of its LP releases. The use of this technique was pioneered by engineer Stan Ricker, who mastered all of the early MFSL releases. Ricker's work can be recognized by the signature "SR/2" carved between the run out grooves.

With some notable exceptions, MFSL uses the original master tape as its source. This tape was then played back at half its original speed (if the master tape were recorded at 30 inches per second, it would be played back at 15 ips.) Simultaneously the record cutting lathe runs at 16 ⅔ revolutions per minute (half of its regular speed of 33 ⅓ RPM.)

The Half-Speed Mastering technology allows for cleaner reproduction of high frequencies (by cutting the actual transfer frequency in half) and allows twice as much time to carve a groove that accurately represents the sound on the master tape. It also permits extended high frequency response, extending into the ultrasonic region.

Jack Hunt ("JH/2") mastered many of MFSL's releases in the 1970s and 1980s. Some later titles were mastered by John LeMay and Paul Stubblebine, with a few uncredited releases. Currently, Shawn R. Britton and Rob LoVerde are mastering most LPs for MFSL. CD, SACD, and audio cassette mastering has been done by a variety of engineers, most recently by Britton. The company has only had a handful of engineers in its history.