﻿Hi, and welcome back. Responses to my last video had two main themes:
lots of people apparently struggled to hear the difference in my example, citing too complex and
confusing parts used for the demo. And there was also a lot of discussion
on the subject of why and how hard my example music sucks.
So now I find myself responding to the first point, by creating a very simple and sparse
arrangement that nevertheless has two parts deliberately arranged to clash with one another…
while reflecting that this is hardly likely to help with the second.
Oh well. Here's a nice simple piano part, courtesy of Arturia's very nice Piano plugin. Got that?
That's part one. Now here's some guitar, playing the same chords in the same register.
That's part two. Now both together.
And now in the mix, which I'll just keep to drums
and a bass part that stays well out of the way.
Nice and conventional, right? Not too challenging so far I hope?
Now here's my delay channel: I've called it SS this time, for Super Separator, rather
than "comb". I think this confused some people last time: to be clear, this channel is just
delay, plus optional low and high pass filters. It only becomes comb filtering when I blend it with
the dry signals. I've used stock plugins this time, just to show that it doesn't matter.
If I show the routing for this track: here are two recieves
from the keys and the guitar, with the polarity flipped for just the guitar.
Ooh, a modulation. I hope this mixolydian flat 6 mode isn't too spicy for you?
Ok, you ready for a listen? I'm going to start with the most extreme possible version, with
the delayed signal at unity. That means we'll be getting hard notch filters in the midrange where
the filters aren't touching the signal, which will sound way too coloured in most cases.
I suggested that you should avoid this extreme case even when sweeping the delay time around
looking for a good setting, but on second thoughts it probably wouldn't do any harm
to do an initial sweep like this, just to tune your ear in to what to listen for.
So let's listen to the difference…
that's pretty clear, right? I assume you're all hearing that. But I would struggle to
call it an improvement, as it's just way too coloured and obvious. So let's drop the gain
a bit for the delayed signal, so the notches turn into gentler cuts… and listen again…
That's more like it, right? But still too coloured in my opinion.
So let's drop the gain a bit more.
This is always going to depend on the part of course: electric instruments will likely be able
to take more of this type of effect than acoustic instruments before starting to sound too coloured,
as there's much less of a "correct" sound that we can hear the deviations from.
And by the way, I'm probably never going to do this with a vocal.
And this is also part of the reason my examples in the last video were quite synthetic and unnatural
sounding; I could simply get away with mixing in more of the delay before the comb filtering
became a problem. Honestly, I was worried I'd overcooked it if anything. Apparently not so!
Anyway, the point is, this trick can make a meaningful difference even when used very
subtly and tastefully. I find that, if I've made a good choice of delay time setting,
I can usually find a level for the comb filtering that provides a useful
increase in separation without sounding too obviously coloured.
And to address another point that was made: that I'm simply making those parts louder
by adding extra energy. Well, it's true that they do seem louder with the comb filtering in… but
that's largely because I've tuned the delay time to find subjectively flattering comb filtering.
If I invert the polarity of the delay channel to invert the comb filtering… or in this case put it
back in phase because I already had it flipped… it doesn't really make them seem louder anymore.
Incidentally, it doesn't really make sense to think of the delay channel as
in or out of phase, as one of the signals is flipped either way. If I had happened to flip
the send from the piano instead of the send from the guitar… then I would now be running
the return channel without a polarity flip, and getting exactly the same result.
Don't forget that you're allowed to adjust the send level to the delay as well:
if I turn down the send from the piano track I can reduce the comb filtering for that part,
and focus it more on the guitar instead, which might be able to tolerate more of it.
Ok, let's talk about the "and beyond" part:
first of all let's note that I've so far kept both parts panned to the middle of the mix,
to make them clash as hard as possible. But there's no reason not to pan them left and right:
it's a stereo send, so the delays will pan as well, and nothing unexpected will happen.
But let's switch the delay channel pan mode to Stereo Pan:
and now we have a width control to play with as well.
So let's try mono-ing the delay return, to focus the comb filtering in the middle of the image…
notice this doesn't really reduce the sense of width at all in stereo…
but now the comb filtering will be relatively much greater for the mono version of the mix,
where you need more of that separation.
Ok, let's go further beyond: let's dial in negative width, which just swaps the left
and right channels around… and now we've got Haas delay trickery in stereo, adding a lovely
sense of depth and space to the mix… while still giving us full super separation in mono.
Ok, even further: what if we add some gentle downwards expansion
to the delay channel as well… I've kept the ratio down very low for this…
and I prefer to use downward expansion rather than upward, as I want to avoid
ever boosting the delay signal up to unity or higher. But you could use upward expansion,
so long as you had a range limit parameter, and you trimmed the gain down to compensate.
Now the comb filtering will increase as the two parts get louder.
But because it's a single expander processing both parts it will naturally open up more
when both parts are loud simultaneously and the combined level increases, so when the separation
is more needed… and the comb filtering will become more subtle if one part drops out,
or if the two parts start to play around one another instead of at the same time. It's a good
way to make the comb filtering less noticeable without losing too much of the benefit.
Ok. So, I'm hoping I've convinced you that this is a useful and worthwhile technique.
And I'll play you out with some weird wonky music that you're probably going to hate.
That's all, thanks for watching.