Speck Electronics ASC - Manual (Page 18)

14
The low/mid frequency sweep control is used in conjunction with its
respective boost/cut control and provides continuous adjustment of the
center frequency from 40Hz (fully counterclockwise) to 800Hz (fully
clockwise) for the low range selection or 400Hz (fully
counterclockwise) to 8kHz (fully clockwise) for the mid range selection.
This control provides 15dB of bell shaped boost or cut for the low/mid
band frequency range, and is used in conjunction with the low/mid
frequency sweep adjust. 0dB (flat) is obtained when this control is set to
its center detented position.
For the low/mid band, a continuously adjustable bandwidth control is
provided. This control sets the width of the frequency that has been
selected on the Low/Mid sweep control. When set fully CCW, the
bandwidth is a wide 2 octaves (Q=.5). When set fully CW, the
bandwidth narrows to .25 octave (Q=3.8). The center position is
approximately .6 octaves (Q=1.6).
In addition to the ability to contour low band audio, the low frequency
controls may be used to reduce or eliminate low frequency hum or buzz.
Low hum is typically 60Hz, whereas buzz is typically 120Hz and
240Hz. If there is a hum or buzz on an audio track, the low sweep
control and associated boost/cut control can be used to remove this.
To reduce 60Hz hum, start by setting the bandwidth control to its fully
(CW) position, the low frequency sweep control to its fully
counterclockwise (CCW) position; this is about 40Hz. Turn the Boost/
Cut control fully CCW. Return to the frequency sweep control, and
turn clockwise a little until the 60Hz hum has been reduced. This
setting is the 60Hz point. Now go back to the Boost/Cut control and
adjust as necessary.
In some extreme cases, it may be necessary to use the Low band and the
Low/Mid band of equalization in order to remove the undesirable affects
of 60Hz or 120Hz hum.
10. Low/Mid bandwidth adjust
Chapter 3 Operation Section
8. Low/Mid frequency sweep
9. Low/Mid Boost and cut