User manual AKG C 451 B

[. . . ] Please take a few minutes to read the instructions below carefully before operating the equipment. The new C 451B, however, uses a fixed capsule to eliminate the mechanical problems of the original modular design. The microphone is the perfect choice for any application where sounds, particularly their transient content, need to be captured with maximum accuracy. [. . . ] If your mixer provides no phantom power, connect an optional AKG B 18 phantom power supply between the microphone and the mixer. You may connect the AKG B 18 phantom power supply to unbalanced inputs as well. On the XLR connector, use a wire bridge to connect pin 1 to pin 3 and the cable shield. Unbalanced cables may pick up interference from stray magnetic fields near power or lighting cables, electric motors, etc. This may introduce hum or similar noise when you use a cable that is longer than 16 feet (5 m). 1 Introduction The rod-shaped body, accurate response, and many matching accessories from AKG make it easy to use the microphone to pick up a wide range of different instruments. â· Read the hints below to get the best possible results. 2 Proximity Effect Owing to their acoustic principle, unidirectional microphones exhibit what is called "proximity effect". This means that the lowfrequency content of a sound signal will be progressively boosted as you move the microphone closer to the sound source. Proximity effect begins to become audible at a working distance of about 2 feet (60 cm). Depending on the nature of the sound source, proximity effect may be desirable or a nuisance. Place the microphone closer to the sound source to accentuate, or further away to reduce proximity effect. Feedback results from part of the sound projected by a speaker being picked up by a microphone, fed to the amplifier, and projected again by the speaker. Above a specific volume or "system gain" setting called the feedback threshold, the signal starts being regenerated indefinitely, making the sound system howl and the sound engineer desperately dive for the master fader to reduce the volume and stop the howling. This means that the microphone is most sensitive to sounds arriving from in front of it (from the sound source) while picking up much less of sounds arriving from the sides or rear (from monitor speakers for instance). To obtain maximum gain before feedback, place the main ("FOH") speakers in front of the microphones (along the front edge of the stage). [. . . ] To minimize low-frequency noise, you can switch in the highpass filter. Depending on the spectra of the wanted and unwanted signals, set the highpass filter switch on the microphone shaft from flat (1) to a corner frequency of 75 Hz (2) or 150 Hz (3). Use a soft cloth moistened with water to clean the surface of the microphone body . [. . . ]