Plena uses powerful floating-point DSP, together with a patented echo cancellation and de-reverberation algorithm, to actively filter out feedback from system loudspeakers to the microphone, while allowing the original signal to pass through. The process is continuous and automatic, with the filter constantly adapting to detect and remove the reverb component before it can cause feedback. As it takes place automatically, no adjustment is required during operation.
The adaptive filter can be set for 'fast' or 'accurate' mode, to give the most suitable feedback suppression performance for any particular situation. Fast mode is ideal if the microphone position changes frequently, or multiple switching microphones are used, for instance in a congress or discussion system. Accurate mode is for applications with a fixed microphone position, such as on a pulpit or in a large hall, and allows the adaptive filter to suppress the reverb still further.
The system also incorporates an automatic mixing function to suppress feedback when the inputs from two separate microphones are connected. Part of the Bosch's Plena PA product family and successor to the Bosch Profecta, the new feedback suppressor uses an improved version of the Profecta's algorithm.
(Mike Lethby)
