Way back in the earliest days of sound recording, up until the rock ‘n’ roll era of the 1950s, the only way to get quality reverberation was to use a real space. The major studios had chambers – large, highly reflective rooms with a loudspeaker at one end and a microphone at the other to capture the wet sound. Smaller studios had to make do with bathrooms or crude electro-mechanical reverb boxes containing garden gate springs. By the mid 50s, spatial effects were also being created with tape echo. Think Elvis Presley’s Heartbreak Hotel or Gene Vincent’s Be-Bop-A-Lula for that classic slap-back sound.
Around this time, Dr Walter Kuhl, working for the Institute For Broadcasting Technology in Hamburg, developed an artificial reverberation device utilising a large metal plate suspended inside a rectangular box enclosure. It was brought to market in 1957 by the company EMT – Elektromesstechnic – and designated the model number 140. A stereo version, the 140S was launched in 1961.
These were the first commercially available units to provide good-quality reverb without the need for the vast spaces taken up by echo chambers (reverb was commonly referred to as echo in those days).
That’s not to say that the EMT 140 is a small piece of kit, though. The box is around eight feet long, four feet tall and one foot wide, weighing in at 600 pounds. Inside, a large, thin sheet of steel (the plate) is suspended by four springs hanging from each corner of a rigid metal frame. A transducer, similar to the voice coil of a loudspeaker, is attached to the centre of the plate, causing it to vibrate and resonate when an audio signal is fed into the unit. Microphone-style transducers attached to the edge of the plate pick up these vibrations and the signal is brought up to line-level via an internal amplifier. Early models contained valve amps until they were replaced with solid-state devices in the 1970s.
EMT plate reverbs can be heard on thousands of records from the late 1950s onwards
The EMT 140 can provide up to six seconds of reverb, but this is too long for most applications. To achieve more usable reverb lengths a fibreglass damping pad, suspended parallel to the plate, can be moved closer to reduce the decay time. A dial on top of the casework allows for continuous adjustment of reverb time from less than one second to the full six.
The sound quality of the EMT plate is excellent, producing a dense and diffuse-sounding reverb that is velvety smooth. Smoother than most chambers, in fact. The tone is also darker and less natural than a physical space. Although the internal electronics of the 140 roll off low frequencies to reduce unpleasant rumbling artifacts, it’s advisable to filter the audio signal being fed to the plate to attenuate frequencies below 600Hz or so. Frequencies above 10kHz are also best reduced to avoid unwanted ‘zingy’ effects.
Inside the EMT 140S. Photo by Ben Wooff. Plate courtesy of SOA Studios, Bristol. www.soastudios.net
EMT plate reverbs can be heard on many hundreds of thousands of recordings from the late 1950s onwards and are still regularly used today. Its thick and smooth sound is particularly suited to vocal tracks, and many engineers like to use them on drums, often with a short pre-delay. Most digital multi-effects units contain settings for plate reverb and EMT even designed its own rather primitive digital reverb (the 144) in 1972, but it wasn’t very successful and very few survive today. EMT has produced other plate reverb systems over the years but it has never topped the 140, still regarded as the best plate reverb ever made.