The Model 809 Microphone is designed especially for surface-mounted applications. It is a superior quality, per­manently-biased (electret) condenser microphone with a hemispherical pickup pattern (omnidirectional in the hemi­sphere above the mounting surface).

The 809 is particularly suited for sound-reinforcement and recording of speech, singing, or acoustic instruments—in locations like churches, schools, conference rooms, and theaters. Whenever an inconspicuous high-output, high-fidelity omnidirectional surface-mounted microphone is de­sirable, the 809 is a logical choice.

The microphone design relies on the fact that sound pressure doubles at a barrier or boundary compared to its-value if the boundary is removed. When placed sufficiently near the boundary surface, a microphone has effectively 6 dB higher sensitivity and approximately 3 dB greater rejec­tion of random background noise.

Because of its high sensitivity and extremely flat re­sponse, the 809 can be used for distant pickup in circum­stances where close miking would not be practical. The fixed low-frequency rolloff permits using the 809 in some environ­ments where low-frequency background noise (e.g., from fans or air conditioners) would otherwise make distant pick­up unfeasible. The omnidirectional polar pattern of the 809 means sound is picked up equally in the full 360° hemi­sphere around the microphone; there is no off-axis sound coloration or variation.