Shure
Beta 91A
Boundary · Half-cardioid (on a boundary) · 20–20,000 Hz · a rider regular
- Half-cardioid: the boundary surface is part of the microphone, so its pattern only exists in the hemisphere above whatever you lay it on.
- The A revision moved the preamp and XLR into the body — the separate in-line preamp of the original Beta 91 is one less thing to lose in a drum case.
- The contour switch takes about 7 dB out around 400 Hz, which is the cardboard the beater end of a kick usually needs removing.
Frequency response
Redrawn from Shure’s published response graph (approximate, ±2 dB) on the fixed MicSense scale — 20 Hz–20 kHz, −20 to +15 dB — so two microphones can be compared at a glance. No image is copied; it is a guide to the shape, not a measurement. Drawn for: contour switch flat (solid curve); low-mid scoop (dashed) not used. The maker’s graph (Frequency response graph, spec sheet p.1 ("61 cm (2 ft.) from sound source")).
Polar pattern
A boundary mic hears only the half-space above the surface it lies on, so only that half is drawn; the line through the centre is the surface. Generated from the first-order directivity formula — an illustration of the type, not a measurement of this individual model.
Specifications
| Manufacturer | Shure |
|---|---|
| Model | Beta 91A |
| Type | Boundary |
| Form factor | Boundary |
| Polar pattern | Half-cardioid (on a boundary) (Cardioid) |
| Frequency range | 20–20,000 Hz |
| Sensitivity | 3.8 mV/Pa · -48.5 dBV/Pa |
| Max SPL | 155 dB SPL (1 % THD; 2500 Ω load; 151 dB into 1000 Ω) |
| Self-noise | 29.5 dB(A) |
| Impedance | 146 Ω |
| Connector | XLR3M |
| Powering | Phantom 11–52 V |
| Weight | 470 g |
Specifications: Shure datasheet · last checked 2 Oct 2026. These are the maker’s published figures for this model. A dash never means zero: “not published by the maker” means the maker’s documents give no figure; “not yet checked” means MicSense has not confirmed one yet. Spotted an error? Tell us.
MicSense notes
| Price tier | Pro |
|---|---|
| Introduced | 2010 |
Price tier and “a rider regular” are MicSense’s own judgement, not the maker’s.
What it gets used for
- Kick in
- Acoustic instrument
MicSense tags microphones by the job on a live stage, not by studio category — so you can filter for “kick in” or “monitor vocal” instead of working backwards from “large-diaphragm condenser”.
Beta 91A alternatives: closest in published specs
Based on published specifications only — always listen at soundcheck. These are the microphones in the MicSense library whose datasheet figures sit closest to the Shure Beta 91A’s for the same live job, with the reasons. It says nothing about how they sound.
-
Sennheiser
e 901
- Same job: kick in
- Same type: boundary
- Same cardioid pattern
- Same form: boundary
- ≈ 17 dB less output — add about 17 dB gain
Not comparable: response curve not redrawn yet · max SPL not published by the maker
-
AKG
D112 MkII
- Same job: kick in
- Same cardioid pattern
- Similar published response shape (≈ 1.9 dB apart on average, 100 Hz–10 kHz)
- Max SPL as high or higher (160 vs 155 dB SPL)
- Dynamic instead of boundary
- End-address instead of boundary — mounts differently
- Needs no phantom power
- ≈ 6 dB less output — add about 6 dB gain
-
Electro-Voice
RE20
- Same job: kick in
- Same cardioid pattern
- Similar published response shape (≈ 1.2 dB apart on average, 100 Hz–10 kHz)
- Dynamic instead of boundary
- Side-address — aim it from the side, not the end
- Needs no phantom power
- ≈ 8 dB less output — add about 8 dB gain
Not comparable: max SPL not published by the maker
Compare it against the alternatives.
MicSense lets you put up to four microphones side by side — spec table, overlaid response curves and polar diagrams on one screen. Free with a free Squaresmile account.