Beta 91A

Tonal Profile

A half-cardioid boundary condenser with the preamp and XLR built into the plate, made to lie inside a kick drum or on a piano lid. 155 dB SPL into a 2500 ohm load, with a response shaped for kick rather than flat.

Headroom Notes

Shure ties the published maximum SPL, clipping level and dynamic range to the input load impedance of the preamp and recommends at least 1000 ohms; the 155 dB figure is quoted at a 2500 ohm load. The microphone runs from 11 to 52 V phantom, so it survives the weak phantom rails found on portable mixers.

Gain Staging Advice

-48.5 dBV/Pa is loud, and inside a kick drum it is very loud: the combination is why this microphone is one of the few that will clip a cheap preamp's input stage rather than starve it. Self noise is 29.5 dB SPL-A, which is high for a condenser and irrelevant where it is used.