The Origins of EMT Reverb

Reverb History

By the mid-1920s, recorded reverb was essentially the audible byproduct of a physical distance between a sound source and a microphone. Record companies sought out appropriate rooms for a desired effect. Right from the outset of early recording, those early pioneers were already working with mic placement and rooms for a desired ambient effect.

As the years went on, and recording and playback equipment improved, so did the opportunities to experiment with new recording techniques.

To the Chamber

Engineers, most notably Bill Fine, used distant miking — typically a single mic — to give Mercury's "Living Presence" series of classical records from the late '40s and early '50s a stunning, natural ambience.

But it was UA's own Bill Putnam, Sr. who first used artificial reverb creatively on a pop recording in 1947, with the use of the first reverb chamber — the studio bathroom! The result was a huge hit by The Harmonicats called "Peg o' My Heart" on Putnam's own Universal label. Having the ability to control reverb amount and turn the effect on and off at will was also a major breakthrough developed by Putnam, and a big part of the record's  sound.

Putnam went on to build dedicated chambers for his studio in Chicago, as well as his later Los Angeles studios. Chamber reverb is to this day a technological and architectural art all to itself. The sound Putnam created captured the listening public's imagination, and artificial reverb was popularized as a production tool for the production environment. But for most of the '50s, room recording and echo chambers were the only options.

Enter EMT

However, German company EMT (Elektromesstecknik) made a huge breakthrough in 1957 with the release of the EMT 140 Reverberation Unit — the first plate reverb. EMT was birthed from the Broadcast Technical institute in Nuremburg and the Institute for Broadcast Engineering in Hamburg. EMT in its day was by far the most popular developer and manufacturer of artificial reverb solutions for the recording industry.

What's a Plate?

And what are the defining sonic elements of a plate? I got to find out with my own ears during a visit to The Plant Studios in Sausalito, where they have multiple plate reverb units, including the ubiquitous EMT 140.

How does it sound? Dense, with heavy diffusion — wonderful, warm, open, and natural. Not necessarily like a room, yet it has room-like qualities.

Plates are still widely used in many studios — the only drawback is their enormous size and weight. An EMT 140 weighs 600 pounds. Still, it's an easier alternative to the design and space concerns of a dedicated chamber, and that was the idea, particularly in 1957.

Interior of the EMT 140

The plate reverb is made up of a large (2 x 3m), thin piece of sheet metal suspended from a steel frame by spring tensioners at each corner. An electrical transducer mounted to the center of the suspended plate induces plate movement, which creates the effect. One or two (mono or stereo) pickups are mounted to the plate as well, for the reverb return. A damping plate controlled by a servo motor, allowed adjustment of the reverb time. All of these simple elements were built into a heavy wooden enclosure.

Typically the engineer set the decay with the damper control, and runs the reverb return through additional EQ at the board for greater tone shaping capabilities.

Although the EMT 140's legend was growing, many engineers and producers were not crazy about the original electronics, so many 140s were retrofitted with updated circuits. In 1961, EMT hit another first by adding a stereo return, and by the '70s, they were manufactured as solid-state instead of the original tube circuit. Further improvements were made, and EMT made many other plate systems, but the EMT 140 is still considered the final word in plate reverb.

EMT Goes Digital

EMT released a primitive digital reverb in 1972, the rack mount 144, but its capabilities were limited, and very few survive. But in 1976, EMT teamed up with American electronics company Dynatron to create the EMT 250 Electronic Reverberator Unit-and the first "practical" digital reverb was born.

A floor-standing unit that looked like equipment from a '70's sci-fi movie set, the EMT 250's feature set was impressive, with pre-delay controls and high and low frequency decay times.

But the 250 was more than a reverb — it was also the first multi-effects unit, featuring modulation effects like chorus and phase, as well as echo and delay. The controls were simple — large lollipop-shaped levers and a few pushbuttons.

There were only 250 EMT 250's made, but the unit was soon updated to the 251, which was a similar design with an LCD display and a larger feature set. The 251 offered extended frequency response, additional parameter controls and more programs.

These early digital units are considered some of the best sounding artificial reverb units ever made-quite a legacy for anything considered early digital technology. Both units easily fetch over $10,000 on the used market.