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Tips & Tricks
Low-Cut Filters (AKA High Pass Filters)
Most small mixers lack this really useful feature. But once you learn how to use it, you’ll never want to mix a show without it. There really are only a
few instruments on stage like kick drum, larger toms, bass and keyboards that are even capable of producing low frequencies. For most everything
else, low frequencies just cause problems. Even a low male voice doesn’t produce frequencies much below 100 Hz. By using the low cut filter to
eliminate low-frequencies from channels that have no lows, we can reduce microphone handling noise and potential feedback. And by keeping low
frequencies from the bass and kick-drum out of (for example) the vocal microphones, we can keep these instruments sounding cleaner. Many of the
TouchMix presets already include appropriate Low-Cut filter settings.
To set up a Low-Cut filter manually, just ask the performer to speak, sing or play in the lower register of their range. Raise the Low-Cut filter frequency
until it begins to make the channel sound too thin. Then back it down until the thinness goes away. The Low-Cut Filter is handy on drum overheads,
snares, hi-hats, horns, guitars and vocals.
Here’s just one example of some of the things you can do with high and low cut filters. If you ever mike a Leslie® speaker, one neat trick is to take the
Low-Cut filter for the top rotor channel up to 800 Hz. That’s the cross-over frequency for a Leslie so anything below 800 Hz is going to be wind-noise
from the rotor or bleed from other instruments. For the bottom rotor microphone – you guessed it – use the High-Cut filter set to 800 Hz.
Compressor Latch
When the band is playing, everything is just fine but between songs the lead vocal microphone starts feeding back. What’s going on? You may be a
victim of Compressor Latch. Here’s how it works. The compressor’s threshold is set so that it is reducing channel gain pretty much all the time that the
band is playing. During a song, the mixer operator brings up the lead vocal channel because it’s not loud enough. Of course it’s not loud enough, the
compressor is bringing down the channel level all the time. Once the song ends though, the level coming in to the channel is no longer hot enough to
reach the compressor threshold. So now, the compressor is not reducing channel gain. Without the gain reduction, the channel is unstable and starts
taking off. The solution is to turn the channel down and raise the threshold setting of the compressor so that it is not reducing gain all the time. Think
about it. If you’re reducing gain all the time, you’re really not compressing anything. You’re just turning down the channel during a song and turning it
back up again between songs.
