Royer R-121.
This may be a silly question, but I keep reading that some microphones' figure-8 behaviour is not equal — that is to say that the front and back pickup areas don't sound the same. Does this apply to capacitor mics like the AKG C414 or Rode NT2‑A? I'm asking as I want to use these mics for Blumlein or Mid-Sides techniques.
SOS Forum post
SOS Technical Editor Hugh Robjohns replies: Some figure-8 pattern mics do indeed have different-sounding front and back pickup lobes — and it's often intentional too. However, this is usually a feature of ribbon mics (like the Royer R-121), rather than capacitor ones, and is normally down to the way ribbon mics are put together (specifically, where the ribbon sits within the magnetic motor assembly).
For most Blumlein (X‑Y figure-8 mics) applications, different-sounding front and rear patterns wouldn't matter, assuming the fronts of the two mics were both facing the main recording area. However, it most certainly would matter for the Sides-facing mic in a Mid-Sides array, because different frequency responses on each side would potentially result in unstable stereo-image positions.
Fortunately, the various C414 models and the NT2‑A are both fine for duty as either a Mid or a Sides mic in a Mid-Sides array.