Low Cut Filter
Low bass is good. What's lower than that isn't. In the
octaves below 75Hz lurk all sorts of low-frequency grunge. Caused by stage
or room rumble, wind noise and mic thumps, it can muddy your sound on
stage or in the studio, drain PA amplifier power, or worse, actually cause
The Low Cut Filter on our compact, SR Series, and
8•Bus mixers inserts a 75Hz low cut (high-pass) filter
into the channel's signal path (fig. 1). Why did we pick 75Hz? Well,
the very finest microphones have a switch that lets you roll off their response
below 75Hz, the very lowest fundamental frequency of the male voice. When
you use this filter you notice that it doesn't have any audible effect on
the human voice... but it cuts off mic thumps and room rumble. Our Low Cut
filter emulates this bandwidth.
1. Mackie 18dB/oct. Low Cut filter.
2. Shallow Low Cut filters.
3. Theirs vs. Ours.
Beware of imitations.
Don't confuse our sharp 18dB/octave filter with the shallower 6
or 12dB/octave "Low Cut" circuits found on some other compact mixers (fig.
2). Not only do they sacrifice audible bass, they don't effectively
cut subsonic rumble either. Figure 3 shows the difference between Theirs
Mackie's true Low Cut Filter is handy for minimizing traffic noise, popping,
and other unwanted low frequency sounds. In fact we suggest you leave it
permanently switched in on all of your mic channels. But don't go away.
Put your Lo EQ back to work.
|4. Mackie Low EQ boost with Low
Without our Low Cut Filter, using any amount of Lo EQ boost on
mic channels is impossible – stage rumble and mic thumps become destructively
exaggerated. Kick in the Low Cut Filter and the audible bass range is boosted,
but unwanted frequencies below 75Hz are chopped off. Now you can use Lo
EQ without risk – and use midrange for, well... midrange!
Sweepable Low Cut Filter (SR408
Our large-format SR40•8
console has a roving 12dB per octave Low Cut Filter that
allows you to select the roll-off point anywhere from 30Hz all the way up
to 800Hz. Now you can not only cut mic thumps from vocal channels, you can
use the filter to cut low and midrange frequencies from mics placed near
cymbals. And this is just a "fer instance." We're sure you can come up with
even more ways to use the SR40•8's Low Cut Filter.