Shure SH55 Series II [7/48] Historical origin

These early dual element unidirectional microphones had drawbacks. Their size tended to be

large and bulky, and consistent performance was challenging to maintain. As the omnidirectional

and bidirectional elements did not possess the same frequency responses, and occupied different

locations within the housing, the resultant frequency response and polar pattern were irregular

and difcult to control.

Ben Bauer recognized that the best way to address these difculties was to use a single element.

He began by examining the underlying physics. He understood that if a single element was ex-

posed to sound only on its front side, the result was an omnidirectional pattern. A bidirectional

microphone would result if both sides – the front and back – were exposed to sound. With those

two concepts in mind, Bauer realized that if he could partially block the back side of a micro-

phone element, in theory he would achieve a response between an omnidirectional and a bidi-

rectional, which would be cardioid (heart-shaped). His research led to the Uniphase acoustical

system, which was used in Shure’s rst single element microphone, the Uniplex, and later in the

Unidyne.

Bauer’s Unidyne was congured with an acoustical network of front and rear openings that en-

abled sound waves

to reach both sides

of the microphone’s

diaphragm. The

sound waves reach-

ing the diaphragm

from the rear had

a longer path and

passed through

openings that pro-

duced a time delay

between the sound

entering from the

rear and sound waves

striking the front of

the diaphragm. By

varying the acousti-

cal resistance in the

rear openings, Bauer

was able to achieve a

cardioid, a supercar-

dioid, or a hypercar-

dioid pattern using a

single element, and

the rst unidirection-

al dynamic microphone became reality.

HISTORICAL ORIGIN

B. Bauer, M. A. Cope, J. Berman, and S. N. Shure meet

in Mr. Shure’s ofce, ca. 1943