Shure SH55 Series II Руководство по эксплуатации онлайн [19/48] 776214

What obstacles (technical, political, geographic) needed to be overcome?

Before the Unidyne, the prime method of creating a microphone with a directional response

used an omnidirectional element combined with a bidirectional element. Both elements were

xed into a single microphone housing. By electrically combining the two signals from the two

elements, a variety of directional patterns could be obtained.

These dual element directional microphones had many drawbacks. First, they were large,

heavy, and bulky. Second, they were expensive to manufacture, as each microphone required

two elements and a signal mixing circuit. Third, the two elements did not possess the same

frequency response and could not occupy the same physical space, so the resultant directional

pattern was irregular and difcult to control, as was the frequency response. This meant

performance inconsistency and wide tolerances in the manufactured products.

Ben Bauer inherently understood that the best way to deal with these drawbacks was to develop

a directional microphone that required only one mic element. He began by examining the

underlying physics of a microphone and sound waves. Bauer knew that when a mic element was

exposed to sound only on its front side, an omnidirectional pattern was obtained. In contrast, a

bidirectional “gure eight” pattern was created when both sides, front and back, were exposed to

sound. With these facts in mind, Bauer calculated that if he could partially block the back side

of a microphone element, he would create

a directional pattern somewhere between

omnidirectional and bidirectional.

Eventually, Bauer designed an element

with precision openings at the front and at

the back of the element. Sound waves that

entered the rear openings passed through

acoustical material that delayed the waves

in relation to the sound waves entering

at the front. By varying the amount of

acoustic delay, it was feasible to create

different directional patterns using only a

single element. This principle was dubbed

Uniphase and led to the development of

the single element crystal microphone, the

Uniplex, and the single element dynamic

microphone, the Unidyne.

Crystal microphone elements were

inherently unreliable due to the effects

of heat, humidity, and physical shock. In

contrast, dynamic microphone elements

were virtually unaffected. Natural

selection dictated the success of the

IEEE MILESTONE AWARD

S.N. Shure addresses employees at the Chicago

manufacturing plant in 1943