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July 31, 2013 / Randy Coppinger

Beyond Figure-8 Ribbons

On July 30th the Los Angeles chapter of the Audio Engineering Society hosted a presentation by Julian David featuring guitar player Douglas Showalter titled “Ribbon Microphones: Life Beyond the Figure-of-8 Pattern.” I enjoyed hearing the difference between some ribbons that were not the native bi-directional pattern: an RCA 77 DX, RCA MI-6203/6204 Varacoustic, RCA BK-5B, and the AEA KU4. He threw in a classic RCA 44 (which is bi-directional) just for good measure.

Comparison of unidirectional ribbon microphones on acoustic guitar

We heard the 77 DX and Varacoustic in different pattern settings. Douglas played his guitar closer and farther from the microphones so we could hear the changes in color. We even listened at 180 degrees and 90 degrees off axis. I had no experience with the Varacoustic nor the BK-5B, so it was a treat to hear them.

As both a recording engineer and mic designer, Julian’s presentation included some operational theory and a look at the inner workings of some ribbon microphones. He passed around a labyrinth from inside a rare RCA KU-3a (10,001) microphone. You can see the cavity is filled curly cow hair! At the time these classic mikes were made, it was determined that cow hair worked well as a frictional absorber. More efficient, stable, and consistent sounding materials are available now.

The internal labyrinth of the RCA KU-3a or 10001 ribbon microphone featuring absorption with curly cow hair

This was also my first time to see a Beyerdynamic M160 element, the famous “piston” design where the ribbon is crimped width-wise rather than the traditional length-wise. Plosive protecting mesh has been pulled back to see the detail of the ribbon element.

Piston ribbon element of a Beyerdynamic M160 microphone

Wes Dooley was present and shared his ribbon mic wisdom too. He and Julian both confirmed a suspicion I had about all directional microphones: There is NO proximity effect at 90 degrees off axis, regardless the type of microphone element used. Good stuff.

Kudos to everyone for a thought provoking evening!

See also:
How A Unidirectional Ribbon Mic Works
Unidirectional Ribbon Mic Shootout
The $60,000 Ribbon Mic Shootout

One Comment

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  1. Curt Vincent / Jan 27 2016 2:37 pm

    Super interesting! Thank you! But the labyrinth is not filled with curly cow hair. According to Clarence Kane of ENAK, that stuff is horse hair! He told me it was because the RCA engineers want to use a material that would not rot in humidity. Cool huh?

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