What is a Crystal Microphone.
When pressure is applied to a crystal of Rochelle salt (sodium potassium tartrate tetrahydrate), causing it to flex, a tiny electrical charge is induced on its surfaces which is proportionate to the amount of pressure applied. Below is a simple diagram illustrating how this piezoelectric property is utilised in a crystal microphone.
As sound waves cause movement of the diaphragm, varying pressure is applied to the crystal. The electrical signal thereby created can then be amplified to produce audio.
Rochelle salt is fragile and susceptible to damp and the passage of time has not been kind. These days it is becoming increasingly difficult to find crystal microphones that are still in working order. Even though later crystal microphones used ceramic materials such as lead zirconate and barium titanate which were somewhat more durable than Rochelle salt, the stock of working crystal microphones has been steadily dwindling. In the 60’s with the arrival of cheap, reliable, dynamic and electret-type condensers the crystal microphone was quickly superseded.
During the 1950’s home tape recording became a popular hobby, and there was a super-abundance of budget machines aimed at the amateur recordist. Although some of the more upmarket models came with a dynamic microphone, most of these tape recorders were supplied with a cheap and cheerful crystal microphone…………… Which brings us to the Ronette ‘CORONATION 53’
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The ‘CORONATION 53’ is a high impedance microphone and comes with a standard 1/4inch balanced jack.
To record my voiceover on the video I used an inline Hosa MIT-129 50k Ohms- 200 Ohm transformer which enables connection to an XLR mic input.
Not perhaps the flattest frequency response graph, but nevertheless a bargain for the princely sum of 52 shillings! (20 shillings to the pound in 1953). Based on the Ronette 088-u7 ‘Soundball’ already in production, Ronette spared absolutely no expense in creating the ‘CORONATION.53’. A quick mod to the plastic moulding to create a short handle, and the words ‘CORONATION.53’ in small raised letters on the ball. Job done!
BBC TV live coverage of the Coronation launched mass television viewing in the UK. Demand was so great that electrical shops everywhere sold out of TVs. Unlike today, the British royal family were at a high point of post-war popularity. Amidst all this flag-waving and razzmatazz Ronette saw a marketing opportunity. However, even in 1953, I really can’t imagine many people rushing out to buy a cheap, plastic, crystal microphone just because it called itself the ‘CORONATION 53’!
Today they are somewhat rare. Until I bought this one I had never seen one before. However, in fairness to Ronette it does sound a lot better than I thought it would, and might still come in handy for something!
And it is very shiny!