DSPXmini-FM operational manual V1.2
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This section has more detailed information on setting up the DSPXmini-FM’s processing.
Bass enhancement
The frequency contouring effect of multi-band audio processors often leaves the bass lacking a little. The sum-
mation of the bands tends to give a boost to the presence frequencies and leaves the bass sounding a little thin.
This effect can be compensated somewhat by enhancing the bass prior to multi-band processing.
The DSPXmini-FM has a pseudo parametric style bass equalizer control that allows you to sweet tune the
bass. Four frequencies, amplitudes and Q's are provided giving you 6 different bass curves to select from.
Frequencies selectable: 60Hz, 76Hz, 9Hz and 120Hz. Q's selectable: 0., 1, 2 and . Gains selectable: 0,
1.dB, dB, .dB, 6dB. A starting setting of 9Hz, Q of 1 and gain of .dB warms the bass up quite nicely but
you are free to experiment to get the bass sound you're after.
Multi-band AGC
The multi-band AGC in the DSPXmini-FM employs an RMS based level detector for superior performance. This
enables the DSPXmini-FM to control input level variations based on the true loudness of the input waveform
unlike other simpler average responding peak detectors used in other digital audio processors. When you couple
the advanced detector with the user adjustable and hidden intelligent controls you really do have a powerful lev-
elling tool.
The Multi-band AGC stage of the DSPX has two main functions.
1. To re-equalise the program material to provide a consistent tonal balance and sonic signature.
2. To prevent excessive limiting by the following peak limiter stages.
Because of the RMS based level detectors the multi-band AGC can re-equalise the sound in a more natural
manner than the peak limiter stages which use peak detectors. As the human ear works on average loudness
rather than peak level the re-equalised audio will sound more natural when dynamic range reduction is per-
formed by RMS based level detectors.
Because the peak to average ratio of the program material can be quite wide it is still necessary to control the
peaks of the audio with the multi-band limiters but unlike most other audio processors the bulk of the work has
been performed by the multi-band AGC and the limiters can be fed with a more controlled level allowing them to
operate in their sweet spot.
Over the course of the next few pages we have included several scope shots clearly illustrating the input and
output of the single band AGC together with the AGC control signal. The effect of the control signal is clearly evi-
dent on the output audio waveform. These scope shots help to visually illustrate the concepts under discussion.
The multi-band AGC stage is designed so that a 0VU input level to the processor will drive the multi-band AGC
to the midway resting level of 0dB.
Individual drive controls are provided as a way of equalizing the audio before processing. This can be used to
add a touch of more presence or bass. Keep in mind that the mutli-band AGC by it's very nature will tend to
compensate any cut or boost you make here.
The attack and decay times of the AGC have a range of 1-10 and this corresponds to time constants of 100mS
to 0S. We suggest an attack somewhere in the region of - and a decay setting of 1 or 2 positions higher than
that.
AGC attacking and decaying with faster time
constants
AGC attacking and decaying with slower time
constants
The effects of time constant speeds
