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Operation:No special precautions beyond ordinary
care are necessary in the operation of the Model 556 Dy-
namic microphone. It will operate efficiently and depend-
ably under all ordinary conditions in hot and cold climates.
Dropping the microphone or other severe mechanical
shocks should be avoided.
Acoustic Considerations: The expression "Su-
per-Cardiod type" response simply means that the polar
characteristic of the microphone approximates a modi-
fied cardioid of revolution. There is a wide, useful pickup
angle at the front of the microphone while the response
at the sides is down 8.5 db from that at the front. The
rear response is down of the order of 15 db over a broad
range of frequencies.
The true unidirectional charac-
teristic of the "Unidyne" should not be confused with the
relatively slight directional effect at high frequencies only
which can be produced by baffle effects in the conven-
tional pressure microphone.
By directing the rear side of the microphone towards
the audience or other source of interfering sound, pickup
can be concentrated on the desired source. Reverbera-
tion energy pick up is decreased over two-thirds. The
microphone can be placed close to reflecting surfaces
without objectionable effects if the rear side of the micro-
phone is toward the reflecting surface. This is particularly
valuable in small broadcast studios.
It is desirable to experiment with microphone place-
ment and orientation in order to secure the greatest
benefits from the unidirectional characteristic.
Specifications
1000 C.P.S. Response:
Model 556 "L" Position:
Open Circuit Voltage Level. . . . . . . .-84.1 db. (*)
Loaded With 40 Ohms. . . . . . . . . . . .-90.1 db. (*)
Power Level Into 40 Ohms. . . . . . . . . . .-56.1 db. (**)
Model 556 "M" Position:
Open Circuit Voltage Level. . . . . . . . . .-76.8 db. (*)
Loaded With 250 Ohms . . . . . . . . . . .-82.8 db. (*)
Power Level Into 250 Ohms. . . . . . . . .
-56.8 db. (**)Model 556 "H" Position:
Open Circuit Voltage Level. . . . . . . .-57.5 db. (*)
Loaded With 100,000 Ohms . . . . . . . .-60.1 db. (*)
(*) 0 db. = 1 Volt Per Dyne Per Sq. cm.
(**) 0 db. = 1 Milliwatt with 10 Dynes Per Sq. cm.
Recommended Load Impedance:
Model 556 "L" Position 30-50 Ohms.
Model 556 "M" Position 150-250 Ohms.
Model 556 "H" Position 100,000 Ohms or More.
Model 556 Microphone
Horizontal Polar ResponseFREQUENCY-CYCLES PER SECONDFig. B. Typical Frequency Response, Model "556" Microphone.MODEL 556
Code WordRUMUB
Net Wt.2¾ lb.
Shipping Weight4½ Ibs.
Height, Case *
8-3/8"Width*
4-7/16"
Thickness* 3-3/16"Height, Overall *
3-9/16"
FinishSatin Chrome
*See Fig. C.
BOTTOM VIEW OF ISOLATION UNIT
Guarantee:
Each microphone is guaran-
teed to be free from electrical and mechanical
defects for a period of one year from date of ship-
ment from the factory, provided all instructions are
complied with fully. In case of damage. return the
microphone to the factory for repairs. Our guaran-
tee is voided if the microphone case is opened.
27A32 (7-48)
