dbx Pro PX user manual Music High Ultra Narrow Notch

DriveRack® PX

Getting Started Section 2

•You will now use the <DATA> wheel to select the number of fixed filters. This will range from values 0-12. The total number of filters will stay at 12, and the number of live filters will be = Total Num Filters – Num Fixed. Live and Fixed filter types differ in that FIXED mode filters are automatically assigned to a frequency creating feedback, thus remaining at that frequency until cleared by the user. In LIVE mode, live filters automatically detect and remove feedback frequencies in the presence of audio (music or speech). When all of the live filters have been used, they begin to round robin. Essentially this means that the first filter set is replaced where a new feedback is detected and notched out. This mode is useful because feedback frequencies may change as the microphone is moved, and/or as the characteristics of the venue change.

The Fixed/Live filter usage will be indicated at the bottom of each page of the AFS menu. ‘F’ indicates an available fixed filter, and ‘L’ indicates an available live filter. A blocked out F or L indicates a filter that is set, or in use. Once the desired number of fixed filters has been selected, press the <NEXT PG> and the display will read:

Music High

Ultra Narrow Notch

•These types pertain to the Q, sensitivity, and algorithm type. The filter is established by using the formula: Q= Freq divided by Bandwidth. This means that a higher Q will produce a filter that is more narrow. Values are: Speech (Bandwidth = 1/5 octave and Q=7.25), Music Low (Narrow notch filter, Bandwidth = 1/10 octave and Q=14.5), Music Medium (Very Narrow notch filter, Bandwidth = 1/20 octave and Q=29), Music High (Ultra Narrow notch filter, Bandwidth = 1/80 octave and Q=116). To guarantee that feedback is suppressed at lower frequencies, the AFS may place wider notch filters at these lower frequencies (below 700 Hz). Once the desired fixed type has been selected, press the <NEXT PG> button and the display will read:

•You are now prompted to raise the output gain of the mixer to the level of the performance. Once the desired level has been set and all of the fixed filters have been assigned, the unit will automatically move you to the page that indicates the fixed filter setup has been completed. If you have reached the performance level setting and all of the fixed filters have not been used, you may want to return to the page that selects the number of fixed filters and re-adjust the number of fixed in order to provide you with additional live filters. Regardless, once you have completed the setup, the display will read:

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