I had expected the red thing on the rear of this Amperite RB ribbon mic to be a simple on-off switch:
|Amperite RB – switch on rear
|Inside the Amperite – sliding plate, blurry photo 🙁
When open, the mic will be a normal figure-8 pattern. Closing the vent will reduce pickup at the rear, and also make the mic sound brighter by reducing the proximity effect.
The mechanism is not as sophisticated as, for example, an RCA 77DX, but at least they made an early effort to offer engineers a new flavour.
Well done Amperite!