Behringer SHARK DSP110 Manual - Page 17

SHARK DSP110 2.2 The Feedback Destroyer in the SHARK The SHARK identifies feedback by splitting the entire frequency spectrum (20 Hz to 20 kHz) into sections of 1/60 of an octave and determining the level of each of these bands. The values calculated are then referenced to the level of the overall signal. The resulting level difference determines whether or not a filter is set. The SHARK allows you to adapt these decisive parameter to your needs: within a range from 1 through 100 you can edit the feedback detection sensitivity. The standard setting is 50, which ensures the best possible detection of feedback for the majority of applications. For speech-only applications you can raise the feedback detection threshold towards 100, which enables the algorithm to detect and remove feedback even more quickly. Vice versa, lower values provide for a more stable feedback suppression responding less to wanted feedback-like signal portions produced by guitars or keyboards. In FILTER LEARN mode, feedback is generated and suppressed automatically. Whenever it detects feedback, the DSP110 selects the filter parameters automatically to efficiently remove the feedback. As the filter is set to the frequency detected, this mode is ideally suitable for suppressing constant feedback frequencies produced by “fixed” microphones, e.g. those used on drums. Once set, the filters automatically enters lock mode, i.e. the frequency remains fixed but width and depth of the filter are still being adapted to the signal. The filter width is enlarged whenever the feedback frequency shifts slightly. If feedback persists, gain is reduced even more and kept low to prevent feedback from recurring. All microphones that are moved during a performance (e.g. hand-held vocal microphones) are usually susceptible to varying feedback frequencies, which should be suppressed in automatic search mode (entered when you power up the SHARK). Much like in FILTER LEARN mode, a filter automatically determines the ideal settings for all parameters, in order to suppress feedback. However, once all filters have been set, the filter first activated gets reset to automatic search mode. Thus, the SHARK makes sure that there is always one free filter to identify and remove new feedback frequencies. If your music contains wanted feedback elements (e.g. guitar feedback), the SHARK will suppress these too, because it is impossible from a physical point of view to distinguish wanted from unwanted feedback. Section 2.1.6 provides some information on how to get around this physical problem. 2. APPLICATIONS 17