The Shure Beta 91A is designed for use with kick drums, piano and other traditional low frequency applications. Tailored for bass-heavy environments, this microphone features a powerful low frequency response and integrated preamplifier and XLR connection for easy setup and minimal stage clutter. The Beta 91A combines superior attack and punch for studio-quality sound, even at extremely high sound pressure levels (SPLs).
This table lists the most common applications and placement techniques. Keep in mind that microphone technique is largely a matter of personal taste; there is no one "correct" microphone position.
Location and room acoustics strongly affect the sound quality of microphones. To achieve the best overall sound for a particular application, it may be necessary to experiment with microphone placement and room treatments.
|Application||Suggested Microphone Placement||Tone Quality|
|Kick Drum||Inside drum, on a pillow or other cushioning surface, 25 to 152 mm (1 to 6 in.) from beater head.||Full, natural sound.|
|Contour switch activated; 25 to 152 mm (1 to 6 in.) from beater head.||Sharp attack; maximum bass “punch.”|
|Piano||Mount microphone on underside of lid over lower treble strings. Experiment with lid height and placement to hammers for desired sound.||Bright, well-balanced, strong attack; excellent isolation.|
|Mount microphone vertically on the inside of the piano frame, near the apex of the piano’s curved wall.||Full, natural; excellent isolation and minimal hammer and damper noise.|
If desired, attach the microphone to a prepared surface using the mounting holes on the bottom of the microphone.
This boundary microphone has a cardioid polar pattern in the hemisphere above the mounting surface. Keep sound sources within a 60° range above this surface.
A two-position switch on the bottom of the microphone lets you selectively filter the low-mid frequency response without additional tools. Use this filter to enhance the attack and clarity of bass-heavy instruments.
Flat response: Provides the most natural sound in most applications.
Low-Mid Scoop: This setting tailors the microphone’s frequency response to provide a strong ‘punch’ in the low frequencies, and plenty of attack in the higher frequencies.
Maximum SPL capability, output clipping level, and dynamic range vary with the input load impedance of the preamplifier to which you connect the microphone. Shure recommends a minimum input load impedance of 1000 Ω. Most modern microphone preamplifiers meet this requirement. Higher impedance results in better performance for these specifications.
This microphone requires phantom power and performs best with a 48 Vdc supply (IEC-61938). However, it will operate with slightly decreased headroom and sensitivity with supplies as low as 11 Vdc.
Most modern mixers provide phantom power. You must use a balanced microphone cable: XLR-to-XLR or XLR-to-TRS.
Zippered Carrying Bag
25 foot (7.5m) Triple-Flex® Microphone XLR Cable with Switchcraft connectors
20 to 20,000 Hz
Half-cardioid (cardioid in hemisphere above mounting surface)
EIA rated at146 Ω
at 1kHz,open circuit voltage
-48.5 dBV/Pa(3.8 mV)
1 kHz at 1% THD
|2500 Ω load||155 dB|
|1000 Ω load||151 dB|
|2500 Ω load||125.5 dB|
|1000 Ω load||121.5 dB|
20 Hz to 20 kHz, at 1% THD
|2500 Ω load||12.5 dB|
|1000 Ω load||7.5 dB|
equivalent SPL, A-weighted, typical
29.5 dB SPL-A
(20 Hz to 200 kHz)
7 dB of attenuation centered at 400 kHz
11–52 V DCphantom power, 5.4 mA
Positive pressure on diaphragm produces positive voltage on pin 2 with respect to pin 3
470 g(16.6 oz.)
Three-pin professional audio (XLR), male, balanced
 1 Pa=94 dB SPL
 THD of microphone preamplifier when applied input signal level is equivalent to cartridge output at specified SPL
 S/N ratio is the difference between 94 dB SPL and equivalent SPL of self-noise, A-weighted
 All specifications measured with a 48 Vdc phantom power supply. The microphone operates at lower voltages, but with slightly decreased headroom and sensitivity
This product meets the Essential Requirements of all relevant European directives and is eligible for CE marking.
The CE Declaration of Conformity can be obtained from: www.shure.com/europe/compliance
Authorized European representative:
Shure Europe GmbH
Headquarters Europe, Middle East & Africa
Department: EMEA Approval
75031 Eppingen, Germany
Phone: 49-7262-92 49 0
Fax: 49-7262-92 49 11 4