The drum bus
needed tidying.
A steep cut
below about forty hertz.
A little shaping
in the low mids.
You had read
that linear phase EQ
was the clean option.
No phase shift.
So you switched it on.
The low end
did get tighter.
And something else arrived.
A soft swoosh,
a faint inhale,
just before every snare.
Before.
You soloed the snare.
It was there too.
You bypassed the EQ,
and it was gone.
Here is the mechanism.
Every filter
smears a sound in time a little.
A normal EQ,
often called minimum phase,
puts all of that smear
after the sound.
It hides there,
behind the hit,
where the hit itself
masks it.
That is also
where the phase shift comes from.
A linear phase EQ
removes the phase shift
by making the smear symmetrical.
Half of it
goes after the hit.
Half of it
goes before.
It is called pre-ringing.
And the smear gets longer
the lower and steeper the filter.
A steep cut down near forty hertz
needs a long filter,
so the pre-ring
can start audibly early.
Before a soft pad
you would never hear it.
Before a snare,
which goes from silence to full level
almost instantly,
there is nothing to hide behind.
Your ear hears a sound
arriving from nowhere,
just before the hit.
Real acoustic events
never do that.
That is why it sounds wrong.
The fix is not to avoid
linear phase.
It is to use it
where it helps.
On drums,
and anything percussive,
use the normal mode.
Most EQs
call it zero latency
or minimum phase.
Linear phase earns its keep
where phase matters more than time.
Splitting a signal into bands
and summing it back.
Or processing a parallel copy
that must line up with the dry one.
If you do use it
on something sharp,
make the cut gentler.
A shallower slope
means a shorter filter
and less ringing either side.
And listen for it on purpose,
solo,
on the sharpest sound in the track.
Every tool that removes one problem
moves it somewhere.
Find out where,
before the listener does.
– Serguey Asael Shinder
