Microphones are composed of three basic parts: the housing, internal wiring and a capsule that houses the microphone element. The function of a microphone element is to accentuate the audio response of a microphone which allows transmitted signal to be heard even under poor radio conditions. It eliminates distortion and adds a punch to the signal, making the sound clearer. The frequency range for microphone elements is between 300 to 3,000 hertz as regulated by federal broadband rules. Broadcast microphones, such as used for singing and public speaking, contain elements with the widest frequency range. The elements in amateur radio microphones are limited to normal speech range. The Heil HC-5 is the second of two microphone elements designed in1983 by Heil Sound, Ltd.
The element dimensions are .530 by .850 by .310 inches. Copper wire is wound around voice coils in the construction of this dynamic element. A labyrinth made of tubing 1 ½ inch long and 3/32 inch in diameter tunes the diaphragms to each peak. The sensitivity of the Heil HC 5 is -68dB. The impedance factor is 1,000 ohm at 1kHz. The element is designed for one to two inches of speaking distance into the microphone.
Hearing Loss Curve
The Fletcher Munson curve was discovered by Bell Labs in the 1930s. This discovery proved that the human ear has hearing loss at 2,000 Hz and depends on the volume level of the signal to pick up sound. Based on this information, Heil Sound, Ltd. designed the HC5 microphone element which equalises the hearing loss reported in the Fletcher Munson curve.
Bob Heil founded Heil Sound, Ltd. in 1966. Mr. Heil was known as the pioneer of the live sound and recording industry. Some of his clients included major acts of the 1960s and 1970s such as the Grateful Dead, Peter Frampton and the Who. In 2007 he became the first and only manufacturer invited to the Rock and Roll Hall of Fame. He was given this honour so that he could display his famous Heil Talk Box, a quadraphonic mixer that was the first modular console invented.