Why do DJs use slipmats?

The answer is a single mechanical trick, and it is the reason there is such a thing as DJ culture rather than just records being played one after another.

Why do DJs use slipmats?

So that the record and the platter can move independently.

A record on a bare platter is held by friction and its own weight. Touch it and you fight the motor. Put felt between them and the record floats: you can hold it, nudge it, pull it backwards, and the platter underneath carries on turning at exactly the speed it was set to. Let go and the record is instantly back in time with the motor.

That is it. Everything DJs do with their hands on a record rests on that one property.

Where did the slipmat come from?

From a specific problem, in the Bronx, in the 1970s.

Grandmaster Flash wanted to find the start of a drum break, hold it, and drop it in on the beat, then do it again on the other deck so the break never ended. Nothing sold for turntables let him do that, because turntables were built to play records rather than to be played. He lined the underside of the record with felt and waxed paper, and the problem was solved.

He described the thinking himself in a 1984 radio interview, which is worth hearing as a primary source. What Hi-Fi's feature on the man who gave us the turntable as an instrument is the best short written account.

What is slip-cueing?

Holding the record at the exact point you want to start, while the platter spins beneath it, and releasing it on the beat.

Done well it is invisible. The DJ finds the first drum hit by ear, rocks the record back and forth across it to feel where it sits, holds it there through however many bars of the other record are left, and lets go. Because the platter never slowed down, the record is up to speed the instant it is released. There is no run-up.

Do the same thing without a slipmat and you have to stop the platter, which means waiting for it to spin back up, which means arriving late. That delay is the difference between mixing and announcing.

Why does the platter have to keep turning?

Because a platter is heavy and motors take time.

Platters are deliberately massive: the inertia is what keeps speed steady and keeps wow and flutter down. That same mass means a stopped platter needs a moment to reach speed again, and during that moment the pitch rises audibly from nothing to normal. Everyone has heard it.

The slipmat removes the need to ever stop. The heavy platter stays at speed doing what heavy platters are good at, and the light thing on top is the only thing that moves.

Why does it need a direct-drive motor?

Because a belt stretches and a direct drive does not.

On a direct-drive turntable the motor is the platter spindle. Hold the record, and nothing happens to the motor at all. Release it, and the record meets a surface already turning at the right speed.

A belt-driven platter can be held back through the mat too, but the belt has give in it, and repeated hand pressure through the record is not what the belt was designed for. Belt decks make excellent listening turntables and awkward mixing ones, which is why the direct drive and the slipmat spread together.

What makes a mat good for DJing?

Three things, in order.

• Density. High-compression felt slips consistently and does not pill. Low-density felt binds, and binding under the hand is the one failure you cannot work around. Areal density is the figure to ask for: 21oz against the 16oz most decks ship with.
• A plain reverse. The underside should grip the platter while the top lets the record go. A coated or glazed back slides on the platter and the whole mat turns with the record, which defeats it.
• Nothing on the surface. Printed artwork that sits on top of the felt as a layer can be felt under a record and changes the friction unevenly. Dye sublimation dyes the fibre instead, so there is nothing there.

How far this goes as technique is best seen rather than described: WIRED's fifteen levels of turntable scratching runs from a beginner's baby scratch to things that should not be possible with two hands, and all of it is happening on felt.

Do you need one if you only listen?

You already have one, and the reasons are different but not nothing.

A mat damps platter resonance before it reaches the stylus, and it keeps grit off the label side of every record you play. Neither is why it was invented, and both are real. How much of the first you can actually hear is covered honestly in do slipmats improve sound quality.

What changed once the mat existed?

The turntable stopped being a playback device.

Everything that followed, scratching, the extended break, two copies of one record, turntablism as a discipline with its own vocabulary, needed a record that could be moved by hand against a platter that would not stop. One disc of felt, and a machine for listening became a machine for playing.

Ours is 21oz felt, high compression, 3.18 mm, 298.5 mm across, made in New York: The 21, and the 88SupplyMat if you want the mark on it. A room that wants its own name on the felt is a custom run, from four mats.