YORKVILLE AP312 Manuel De L'utilisateur page 14

12
Tips on Getting a Good Mix
If you've never mixed at high power levels before, the following suggestions may help
you to get a consistently good sound.
• When you have live microphones, don't run the volume level right up to the
point of feedback! This is the most common mistake made by people mixing
live events. We've all heard systems on the verge of feedback and they sounded
terrible, even when no feedback was actually occurring! This happens because
working at the feedback point warps the frequency response of the system
• To understand how volume level can affect frequency response, lets look at what
happens as you increase it to the point of feedback. Notice that feedback wants
to occur at a certain frequency? This is because the entire system - the room,
the microphones, the speakers, the people, everything - is showing a tendency
to RESONATE at a particular frequency. The technical term for a system which
shows a tendency to resonate is A HIGH Q FILTER. So by turning up to the feed-
back point, you are making the whole system behave like a high Q filter. This
gives you the same sound as if you turned everything down a lot and then boost-
ed, say, the 1KHz graphic EQ to +12dB!
This is why stage feedback can be controlled by cutting certain frequencies with the
graphic EQ. However, using the graphic to control feedback means that, as the room
changes, (more people come in, it gets hotter, the dance floor empties or fills up,
etc.), the system's equalization will change. You'll be fighting the room all night.
• Having things loud doesn't make up for the poor sound produced by spurious
response peaks. Fortunately, the Q of a system decreases rapidly as gain drops.
The professional way to avoid resonance effects is to keep about 3dB away from
the first sign of feedback. The system will still be very loud, but it will sound a
whole lot better. Ideally, the graphic EQ should be used to flatten the overall
response, not to fix feedback.
• Use tone controls sparsely; Most things sound great just as they are. A little
high-end boost can bring vocals to life. If you have a mic on the bass drum,
you can probably roll off most of the treble. (Its not useful to have mics listening
for sounds that aren't there). Remember that making each instrument and voice
sound full when heard alone, will make the mix sound like mush when every-
thing is heard together. Experiment, but be conservative with tone controls.
• · Keep the vocals up front. Microphones tend to feed back, but instruments
can be turned up almost without limit. This fact biases volume in favor of the
instruments. If you just follow what the mix seems to want, you may end up
burying the vocals so that they can't be clearly heard. Most ears don't like that
• Speaking of ears, don't forget yours. You've probably walked into a show late in
the evening and had your ears blistered by screaming horns. "What's wrong with
whoever is doing the mix?" you might have said with fingers in your ears. What
was wrong was a technician with a dose of hearing fatigue and his/her unfortunate
reaction to it. After a relatively short exposure to high sound pressure levels, the
human ear shuts down somewhat, especially in the upper-midrange and high fre-
quencies where it is most sensitive. This process reduces the immediate discomfort,
but there is debate as to whether it protects the ear in the long term and much evi-
dence that damage does occur. In any case, the technician notices that the horns
sound muted and reacts by altering the EQ or the crossover to boost them (ouch!).
Apart from long-term physical danger, this sounds bad and turns off at least some of
the audience - especially the new arrivals. The solution - earplugs or other hearing
protection. Afterwards, some quiet time is in order to give damaged eardrum tissue
a chance to heal. Provided severe or repeated damage hasn't created a buildup of
scar tissue causing permanent hearing loss, you can return to hear your mix with