Two walls, 45° each
A stereo groove has two walls at right angles, each tilted 45° and each carrying one channel. Side-to-side wiggles carry the mono sum, up-and-down movement carries the difference between left and right.
at the lathe
A 12" acetate is on the platter. Choose the speed, set the level and the bass – then cut the Mamba Bite riddim (K-Gibi Records) into the lacquer. The cut takes as long as the tune.
In this mix the bass carries a stereo effect – we added it for the lesson.
TUNE: Mamba Bite riddim · K-Gibi Records · 0:49 · cut 0 s
Game model after a manufacturer’s typical guidance: a 12" holds about 9 minutes per side at 45 rpm, about 15–18 at 33⅓ – the louder the cut, the less.
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field trip
Ridim.House cuts acetates only – each plate is the record itself. So come along on a little field trip: what happens to a lacquer when records are pressed from it, and the detours via copper and plastic.
know your groove
Why the bass goes mono, why 45 sounds better, why long sides are quiet.
A stereo groove has two walls at right angles, each tilted 45° and each carrying one channel. Side-to-side wiggles carry the mono sum, up-and-down movement carries the difference between left and right.
Deep bass makes the groove swing furthest. If the bass differs between left and right, the cutter has to move up and down a lot – digging too deep one moment, nearly lifting out of the lacquer the next. That is why mastering engineers make the lowest bass mono.
Between neighbouring grooves is a thin strip of uncut lacquer: the “land”. Modern lathes use variable pitch – wider spacing for loud or bassy passages, closer for quiet ones – to save space on the side.
Louder cuts and more bass need wider grooves, so less music fits on a side. Put the other way round: the longer a side, the quieter it has to be cut.
Typical guidance from a manufacturer: a 12" at 33⅓ rpm holds about 15–18 minutes per side (22 at most), a 12" at 45 rpm about 9 (12 at most), a 7" at 45 rpm about 3½ (4½ at most). Longer is possible – but quieter.
When a record is cut, the bass is turned down and the treble turned up (the RIAA curve, standard since the mid-1950s). The phono stage reverses it on playback. Less bass keeps the groove narrow; turning the treble back down also turns down hiss and clicks.
The record turns at a fixed speed, so near the label less groove passes the needle each second than at the edge – on a 12" LP about 510 mm per second at the start and only around 200–210 mm at the end. High frequencies get squeezed, so inner tracks distort more easily.
At 45 rpm more groove passes the needle every second than at 33⅓, so detail and high frequencies come through better. The price: less playing time per side.
The groove is tiny: a V-cut with a 90° angle, a few hundredths of a millimetre wide. The 1978 RIAA standard says a stereo groove must never get narrower than about 25 micrometres.
The groove is one long spiral. A stylus maker estimates that one hour of cutting produces nearly 1.6 km of groove.
Columbia introduced the 33⅓ rpm LP in June 1948, RCA Victor answered in 1949 with the 7" 45 with the big centre hole; before that, 78 rpm shellac discs were the standard. And the inch sizes are nominal: under the RIAA standard a “12-inch” is 11.875".
in the cutting room
Tap the things in the room – or read them here.
The cutting stylus is a tiny gemstone, such as ruby or sapphire, wrapped in a little heating coil – a warm stylus cuts a smoother, quieter groove. Styli wear out and are replaced after a limited number of cutting hours.
Cutting peels off a fine thread of lacquer – the “chip” or “swarf”. A suction tube next to the cutter head pulls it away. Nitrocellulose burns very easily, and some cutting rooms keep the collected chip under water in the jar.
Every cutting lathe has a microscope: the engineer checks the fresh grooves with it and uses it to set up the cutter.
A lacquer dubplate wears out faster than a pressed record, because lacquer is softer than vinyl. It loses a little quality every time it is played.
Very few factories in the world make blank lacquers. In February 2020 a fire destroyed the Apollo/Transco plant in California – which left Japan’s MDC as the only other maker at the time.
from Kingston to Rennes
Why a one-off acetate became the most wanted record in a dance.
In Jamaica, new recordings were often first copied onto one-off acetates for the exclusive use of sound system operators – known as “soft wax” or “dub”, later as dubplates.
Sound systems competed for exclusive tunes. A “dubplate special” is a one-off version in which the artist praises the sound system by name – cut to win a sound clash.
King Tubby (Osbourne Ruddock, 1941–1989) worked as a disc cutter for Duke Reid’s Treasure Isle from 1968 and ran his own sound, Hometown Hi-Fi – popular partly because of its exclusive plates.
In 1968, sound system operator Ruddy Redwood was reportedly given a cut of a Paragons song at Treasure Isle with the vocal left out. The crowd loved the instrumental “version” – one of the roots of dub.
Dubplate culture came to the UK with sound systems such as Sir Coxsone Sound. London cutting houses like Music House (since 1985) cut plates for reggae, and later for jungle, drum & bass, garage, grime and dubstep.
the house
Ridim.House in Rennes cuts acetate dubplates on 12". Part of the Rennes crew with Ikobox (K-Gibi Records) and Ruff Recordings.
Ridim.House on Instagram ↗ K-Gibi Records – Ikobox’s studio →