Shure Incorporated
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1. Determine the vertical separation between microphones you desire. Minimum separation (coincident spacing)
is generally desirable, but it may be necessary to provide greater spacing to accommodate the size or style of
the microphones. By repositioning the sections of the A27M, the threaded studs may be 1 1/4 inches (31.8
mm), 2 5/8 inches (66.7 mm) or 4 inches (102 mm) apart.
2. To reposition the sections, unscrew the knurled knob at the top of the A27M and slide the two black sections off
the vertical rod. Reposition the sections with the studs positioned for the vertical spacing desired. Replace the
knurled knob.
3. Attach the microphones or swivel adapters (such as the Shure A57D or A57E) to the 5/8"-27 studs.
4. Attach the A27M to a microphone stand with a 5/8"-27 mounting thread.
5. Insert the microphones in the swivel adapters, loosen the knurled knob on the top of the A27M, and position
the microphones for the desired response angles. The top of the knurled knob contains reference marks every
45o; these may be used to position the microphones at the desired angle (see Figure 1).
6. Tighten the knurled knob, attach the microphone cables, and use the supplied cable clamp to fasten the micro-
phone cables to the A27M.
7.
Raise the microphone stand to the desired height. Fig-ure 2 shows a pair of Shure SM81 microphones mount-
ed in an “ORTF” configuration on the A27M.
Stereo Recording Options
The A27M supports various popular pickup systems. Those described below result in (1) improved imaging over
widely spaced microphones, and (2) superior depth reproduction over individually miked instruments. The spaced
microphone technique creates a stereo effect mainly because of differences in the arrival time of the sound at
each microphone. Coincident systems produce minimal arrival time differences. The stereo effect they create is
due to in-terchannel amplitude differences. Closely spaced or near-coincident placement lends both time and am-
plitude differences to the stereo effect.
