Good chance there's a different/bigger transformer in that bigger body. LF doesn't like to go through tiny transformers.
The Beta 52A does not use an output transformer, it contains a passive EQ circuit consisting of “two capacitors, an inductor, and a resistor.” A cheaper solution than using a large diaphragm like in the EV RE20 or RE27 or other big old mics.
The passive R/C netwoork is responsible for most of the B52 "sound", but isolating the large LF boost from mechanical coupling requires a larger elastomeric isolation de-coupler than microphones without a boost as low as the B52. Without the de-coupler, it would go into a mechanical feedback loop at high volumes on anything but a concrete stage.
