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Plate Reverb

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Often followed by + Equalizer + Limiter + Gain

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Add a studio plate to audio

A plate reverb is a sheet of steel under tension, driven at one point and picked up at two others. It has no walls, so nothing about the sound tells you the size of a room. What it gives instead is density: a tail that is already thick a few milliseconds in and never resolves into individual echoes.

Decay, damping, modulation, and pre-delay shape it.

Why a plate is not a small room

The room reverb on this site runs eight parallel comb filters into four allpasses. The echoes it produces are the comb lengths, so its early response is a handful of discrete repeats and the density of its tail is fixed by how many combs there are.

A plate has no parallel bank at all. Its reverberation lives in a single loop whose two halves feed each other, and every trip round that loop passes through allpass filters that smear one echo into several. Density therefore multiplies with time rather than being set by a bank size. That is why a plate sounds dense immediately and why you cannot hear a single reflection in it however hard you listen.

The topology here is Jon Dattorro’s, published in the Journal of the Audio Engineering Society in 1997, using his tunings scaled to whatever sample rate the file actually is.

Decay and damping

Decay is the gain applied in each half of the tank, which sets how long the tail runs. Damping is a filter inside the loop rather than on the output, so it compounds on every pass and the tail darkens as it fades instead of losing its top end all at once.

Raising damping also shortens the tail, because energy the filter removes never comes back round.

Modulation

One allpass in each half of the tank is slowly varied in length. This is not an effect so much as a fix: an undisturbed loop of fixed delays settles into standing patterns, and the tail starts to ring on a pitch of its own.

  • 0: the raw tank, which rings metallically on sustained material.
  • 30 to 50%: enough movement to break up the ringing without being audible as movement.
  • 80% and above: audible chorusing in the tail. Good under pads and synths, distracting on piano or anything with a clear pitch.

Pre-delay

Pre-delay holds the reverb back from the dry signal. Because a plate has no early reflections of its own, this is the only control that separates the source from the tail, which makes it more important here than on a room.

20 to 40 ms keeps a vocal in front of its own reverb and readable. 0 puts the tail straight onto the transient, which suits a snare.

Where it fits

Plate is the default choice for vocals and for snare, and it is the reverb on most records from the 1960s and 1970s that sound reverberant without sounding like a room. Use the room reverb when the point is to place something in a space, the spring when the point is character, and a plate when the point is to add sustain and size without adding a location.

Put it after compression and before the limiter. A plate fed a heavily compressed signal produces a tail that is already even, which is most of why the combination is so common.

Frequently Asked Questions

Dense and smooth, with a bright sustained tail and no sense of a room. A plate has no walls and no geometry, so there are no early reflections telling you how big the space is. That absence is why it sits behind a vocal without moving it backwards.

Different topology, not a different setting. The room reverb runs eight parallel comb filters, so its echoes are the comb lengths and its density is fixed. A plate has one figure-of-eight loop whose two halves feed each other through allpass filters, so each pass smears every echo into several and density grows with time instead.

It slowly varies the length of one allpass in each half of the tank. Without it the loop settles into fixed standing patterns and the tail rings on a recognisable pitch. A few samples of movement breaks that up. Higher settings add a slight chorusing to the tail, which suits pads and hurts a piano.

The tank is one mono machine read at seven points for each output channel, and those tap positions are mutually prime, so the two channels never agree about where an echo is. That is how the physical plates worked too: one steel sheet, two pickups in different places.

Long enough to keep the reverb off the front of the word. 20 to 40 ms leaves a vocal intelligible while still sounding wet. Zero puts the tail directly on the transient, which is what you want on a snare and rarely on a voice.

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