Repairing a Ribbon Microphone

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A long time ago Kostas Kofinas, the producer and sound engineer at Blueberry Production Co., requested me a modification on his Golden Age ribbon microphone. But before go deeper, let’s see first how a ribbon microphone works.

The ribbon microphone consist of a very thin ,around 1.5 – 5.0 microns, aluminium foil strip positioned between two permanent magnets. When a sound wave hits the aluminium foil, the foil vibrate harmonically and due to that motion of the body, generated the electric signal of a same form.

Because of the described movement, we need to design aluminium foils that are elastic enough to vibrate. A flat piece of foil vibrate harder than a corrugated one, the reason is the spring effect that it is providing to the aluminium foil the required elasticity and the ability to get motivated by a sound wave. A corrugated foil strip is called “ribbon”. The whole configuration between magnets and ribbon is called “motor”.

The bad news was that the original ribbon strip seemed overtensioned and baggy.

According to the Artur Fisher “The ribbon is the element where the actual electrical signal is induced, so it has a strong affect on the way Your microphone will sound.”
It was a bit difficult to find an aluminium sheet around 1,5-5 microns, so I used a lancet and carefully I opened a styroflex capacitor to collect its aluminium film. These capacitors are being winding with aluminium foil in most cases and their film thickness could be not made thinner than 10 microns. That was the closest specs to the “original”, that I could design. Although,modifications are sometimes unexpectable actions that bring in the light little diamonds.

I gave to my new foil a nice corrugated form by using two plastic gears. Unfortunately, the whole proccess was so difficult and time consuming, it was impossible to shoot with my camera all the modification stages. After a few tries, I come up with the right tension. Within next photo, you can see how nicely and corrugated the final ribbon is.

Ribboning next! Placing the ribbon in a gap, I made sure that it can be settled comfortably between the two magnets. Then I screwed the bottom nuts lightly. The foil may be cut into two pieces if tightening harder the nuts, is so thin! So, now by screwing the top nuts I gave the right tension to my ribbon. Again, I needed to be gentle with it, ribbon is very sensitive.

At the end, after testing the resistance with a multimeter, I plugged the motor in the sound interface as I wanted to be sure that everyting works fine! And Wow! The ribbon move freely all along the gap without touches the magnet and the sound came out of my speakers. I was so satisfied by my effort!

Check the Golden Age Project R1 in action at Blueberry Production Co.

Modification ended successfully and Kostas Kofinas enjoy recording with his new microphone.
Check him out at https://www.blueberryproductions.gr/

Many thanks to www.diyaudiocomponents.com and Artur Fisher for his useful articles.

 

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