AKG DFM 4X4 Quick Reference Manual page 9

1. Click on the "Filter Setup" tab and select the output
you want to work on.
2. Click on the first filter. The filter will be highlighted
in yellow.
3. Select the type of filter you want to use from the
"Filter Type" list.
All filters, except for the ADFE Notch, have adjust-
able frequencies from 20Hz to 20kHz. The band-
widths of the filters that support adjustable band-
width are selectable from 0.5 octaves to 2.55 octaves.
The scale of the Frequency Response screen is select-
able between ±15dB and ±30dB.
4. We advise you to carefully listen to the changes you
have made and stop equalizing as soon as the
sound is acceptable.
5. Once the room is equalized, set an ADFE and start
to turn up the volume to a point where feedback
sets in. The ADFE will notch the frequency at which
the first feedback occurs.
Repeat this until you have achieved an acceptable
volume level. Three or four fixed ADFEs, after having equalized the room, would still be OK. (Should you need
more you may want to check if your problem should not be solved acoustically.)
6. If you have some free filters left you can set these up as supplementary ADFEs: Click on the filter. The filter will
be highlighted in yellow. Select "ADFE" from the "Filter Type" list. DO NOT turn up the volume so the frequency
will not be determined.
In use, the ADFE will react on occurring feedback and reset itself when you switch power to the DFM4x4 off.
7. Save your settings to a Preset.
The compressors allow you to control the dynamic
range of the audio signal.
1. Click on the "Compressor" tab to access the com-
pressor parameters.
2. Start by selecting the desired "Compression Ratio".
You can select the "Compression Ratio" from 1:1
(no compression) to 5:1 (heavy compression).
3. Set "Threshold" (the level at which compression
starts), "Attack Time" (determining how fast the
compressor reacts when the signal is superior to
the threshold level), and "Release Time" (the time
within which compression stops as the signal level
drops below threshold again).
Note: A short attack time, excessively long release
time, and a high compression ratio may cause
"pumping" effects.
4. Save your settings to a Preset.
The limiters allow you to set an absolute ceiling to the
output level.
1. Click on "Limiter". Except for Ratio, the limiters pro-
vide the same parameters as the compressors.
2. Set "Threshold" (the level the output signal must
never exceed), "Attack Time" (determining how fast
you want the limiter to react when the signal rea-
ches the threshold level), and "Release Time" (the
time within which gain reduction stops as the signal
level drops below threshold again).
3. Save your settings to a Preset.
4 Operating Notes
4.2.5 Filters
Fig. 5: Setting up filters.
4.2.6 Compressors
Fig. 6: "Compressor" scre e n .
4.2.7 Limiter
Fig. 7: "Limiter" screen.
9