The Bosch LBB 1968/00 Plena Feedback Suppressor can greatly reduce the risk of acoustic feedback when using a PA system. It does this by using a powerful DSP with a patented algorithm. The unit actively filters out unwanted room reverberations with an echo-cancellation feature and dereverberation algorithm. The device can add a little inaudible noise or shift the output frequency by five hertz. By doing this, it’s able to detect the reverb component of the signal and remove it before feedback occurs – leaving the original signal intact.

The Plena Feedback Suppressor also features an adaptive filter, which can be switched between fast and accurate modes. The fast mode is ideal for situations where the microphone is changing positions over time, while the accurate mode is ideal for situations where the microphone keeps a fixed position and the acoustical environment is more stable. This allows the adaptive filter to converge more slowly, suppressing feedback causing reverberations more effectively. Plus, depending on the environment and whether you’ve selected the fast or accurate mode, up to 12dB of gain can be added before your system starts to feedback.

There’s a built-in automatic mixer as well. The mixer is designed for the two microphone inputs. If you’re using both mic inputs simultaneously, the chances of feedback are higher. The automatic mixer reduces the gain of the mic with the lowest signal input and increases the gain of the mic with the highest signal input. This keeps the combined gain constant and provides optimal speech intelligibility for the moving speaker. This feature works even when the feedback suppressor is deactivated.