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2013/07/31

Inside the Beyer M360 (again) ...

Beyer M360 cardioid ribbon mic

Back in May I posted about the Beyer M320 and M360 directional ribbon mics and mentioned that they used acoustic labyrinths to provide damping to the ribbon, adding omnidirectional character to the ribbon's native figure-8 pattern, to give, hopefully, an overall cardioid behaviour.

Since then I have had the opportunity to peek deeper inside the M360, and below is a picture showing the labyrinth. It is not a great photo as the shiny varnish on the top confused my autofocus, but we can see what is going on.

Beyer M360 labyrinth (left) and motor.

The magnet assembly is larger than the standard Beyer motor, in order to accommodate a smooth curved cavity at the rear of the ribbon. This tube curves through 90 degrees and out through a hole in the aluminium base plate. This connects to the inlet of the acoustic chamber, which consists of 25 interconnected tubes that go up and down through the block. There does not appear to be any kind of outlet at the far end, and the tubes are stuffed with string to damp internal reflections.

The mic is really directional, with relatively little pickup from the rear of the ribbon. The back pressure from the sealed rear chamber also has the consequence of making the output brighter and lower than it would otherwise be. These are really very bright sounding for ribbon mics.

SJT 31 July 2013