Klark Teknik DN540 specifications Threshold, Presence

Threshold

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.

+10
+0										MAX
-10
dBu --3020
-40										MIN
-50
-60	20	50	100	200	500	1k	2k	5k	10k	20k	50k	100k
10
						Hz

Figure 4: Presence frequency response curves

DN540
Operator Manual	21