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The Shure 737 ‘Monoplex’ was a super-cardioid crystal microphone, from 1947, for high-quality public address communications, all types of recording and similar applications. It was available in polished-, or satin-chrome, like the one shown here.

It was nicknamed 'The Waffle Iron' and this was by far the most directive of its type, the 737 picked up sound coming from the front and very little from any other direction. When tilted upwards, it could be used as non-directional.

The element was ‘Metal Seal’ covered to resist humidity and high temperature, two conditions potentially harmful to this sort of microphone. Production of this model ended in 1967.

Shure has not made professional quality crystal mics, since then, though their dynamics would conquer the world.

Crystal microphones were based on the piezo electric effect: crystals which are compressed by soundwaves can convert that sound into an electrical signal. They were low budget, and their sound quality was limited; the frequencies of human speech could be registered faithfully, but the wider spectrum, necessary for music reproduction, was impossible.

They were however very good to accompany amateur tape recorders and great for ham radio use, which became their main purpose in later years.

In fact the Monoplex was the only crystal microphone with a directive recording pattern, all others were non directional, even though some companies claimed that their models were 'semi directional'.

I have opened the casing to show what Shure's acoustic phase shifting network consisted of: a number of holes at the back of the capsule, probably with some dampening, as can be observed in the pictures.

Today ‘bullet’ type crystal microphones are often used by harmonica players, who love the raw and somewhat distorted sound they produce when overloaded.

Another modern use for piezo electric signal reproduction is found in contact microphones built into musical instruments, like the saddle mounted pickups in acoustic guitars, or as ‘triggers’ that sense drum hits.

Shure's other famous crystal microphone, the 'Green Bullit' , from the same era, remains in production, but the capsule is replaced by a dynamic which has been tuned to sound like the earlier crystal element.

The original crystal elements are sought after and fetch around $ 100, but most no longer function.

This is one of the types that feature in my book Witnesses of Words, the only existing book about vintage microphones.

More information about that can be found at

wow cover


Shure 737
737 color ad
737 opened

Above: the 737, 737 ad & opened

Below: specsheet of the 737 &

the back of the capsule

data sheet 1
data sheet 2
737 capsule