Application Notes

compressor relaxes there is no gain reduction — but the upper frequency boost remains, increasing noise and making microphonic feedback much more likely.

The DN540’s presence accentuation corrects the tendency for dull sound during compression, without changing the sound of uncompressed signals. It reduces the ratio of the compressor in a relatively broad range of frequencies centred on 5kHz, and the effect is continuously variable, so as much presence accentuation can be added as needed or to suit taste.

When presence accentuation is applied, any compression acts on the high frequencies to a lesser extent than the low frequencies, by an amount set by the user. The transient at start of a sound is greatly reduced in the low frequency content, which is where all the power that needs to be controlled lies, but the harmonic content is preserved in a more natural and dynamic state.

The presence band has been specifically located in an area where we are most perceptive to sounds, so that reducing compression ratios in this area allows much greater compression to be applied at the other frequencies without sounding unnatural.

Presence accentuating compression can produce results that are very similar to multi-band compression, but with only one additional control required (as opposed to many) it is much more straightforward to set up and uses far less rack space.

Some additional corrective benefits from presence accentuation are:

• Reduction of source inter-modulationIt is very common for pop/rock singers to stand in front of drum kits, and unless suitable screens are placed between them there will be a lot of spill from the kit. Often you can hear the compressor on the vocalist modulating the spill from cymbals, which sounds very unnatural. This can be eliminated by using the presence accentuation to stabilise the higher frequencies, and if that makes the vocals sound too bright the high frequencies can be reduced a little using EQ, thus reducing the spill and reducing the chances of high frequency howl-round.

•Reduction of breathing Most processing noise occurs in the presence band and it is much more noticeable when it is modulated by the compression of a sound source. Similarly for the reduction of source inter-modulation, presence masking can eliminate this effect.

•Reduction of pumping Because human hearing is so sensitive to presence band frequencies, stabilising their dynamic response with presence accentuation can mask the pumping effects at lower frequencies.

• Reduction of dull sound and increased brilliance It is often tempting to boost high frequencies to get sounds to cut through a mix, but in sound reinforcement this increases the likelihood of howl-round. Presence accentuation can help to increase the brilliance of compressed sounds by correcting their tendency to sound dull, and with increased use it can be used creatively to add even more high frequency energy without increasing the risk of howl-round.

Thus, the presence accentuation feature of the DN540 adds another tool for the sound engineer that can be used to enhance and compliment the application of many types of compression.

	DN540
30	Operator Manual