Filter
Top Products
Threshold
DN540
Operator Manual 21
Threshold
The compression threshold is the point at which the compressor begins to operate.
Signals that exceed this point, that is, go over threshold, will be affected by compressor
actions. However, signals below the threshold do not trigger any compression, but may
still be affected by compression releases from previous over threshold signals.
If the compressor is being used as a limiter, the threshold level is the level at which the
limiter begins to operate.
Presence
The presence function protects the mid-high frequencies during compression. It does
this progressively, so that the compressor appears to operate with two different ratios,
one for low frequencies (normal) and the other for mid-high frequencies (reduced
ratio). The primary effects of this are:
• Heavy compression and dynamic control can be applied without the programme
sounding unnatural. Reduced compression in the presence band where the ear is
most sensitive (and where there is comparatively little acoustic energy) masks the
dynamic control that is applied to the high energy high and low frequency signals.
• The compressed material sounds brighter. However, because no high frequency gain
is added when compression is not required, noise during quiet passages is reduced
and the tendency for high frequency howl-round (which can often be a problem if air
brightness is added by conventional EQ post compression) is also reduced.
• Side effects of this approach are that the high frequency content of spill remains
more consistent, and pumping is therefore much less noticeable.
Some DN540 frequency response curves are shown in Figure 4, “Presence frequency
response curves,” on page 21, which help to illustrate the effect of the presence
function. The curves were produced with the compressor at -50dB attenuation, and
with the PRESENCE control knob set to MIN, MAX and an intermediate value. Note
how the MIN setting produces the flat line towards the bottom of the graph. At this
setting all audio frequencies are attenuated by the same amount as set by the
threshold, ratio and input signal level, which effectively defeats the presence feature
completely. As PRESENCE is turned clockwise the protective filter is activated. At the
MAX setting, which is -3dB at 5kHz, the frequencies around 5kHz are hardly reduced in
level at all, whereas the lower frequencies and very high frequencies are still
compressed significantly.
Figure 4: Presence frequency response curves
+10
+0
-10
-20
-30
-40
-50
-60
10 20 50 100 200 500 1k 2k 5k 10k 20k 50k 100k
Hz
dBu
MAX
MIN