How do I measure in EQ and how do I make sure that I'm actually
getting good data? First let's check our physical routing our digital routing
make sure that we've got our measurement set up correctly and then look at the
results. Looking over here at my audio interface this is what we have
from before right? I've got my reference input I'm coming from the back of the
x32 and I've got my measurement microphone
in here so if we want to measure the x32 then I'm going to need to take a post EQ
right so I'm gonna have a reference here that is pre EQ and then I need something
else to measure it against so that'll be post EQ and so I'll put my EQ in the
middle and that'll be my device under test so the reference will come before
the EQ and then I'll have the EQ in the middle device under test and then post
EQ that'll go into this third input that I have open here so I'm using this
output already so I got another TRS the TRS cable here and I'm just going to use
the next input up so here is I'm sorry I say input I'm in output so here's output
five on the x32 and I'm gonna take the other end of that and I'll plug that
into my third input here on my audio interface
okay so that's the physical patching and you can see here that on inputs 1 & 3
here that I'm using they have the exact same settings okay gains all the way
down none of these buttons pushed in
so let's look at the x32
let's go to routing and here let's take a look at the aux outputs this tab here
and now output six you remember from my previous videos that this is a pre
everything pre EQ pre fader output from matrix one
so everything's coming out of matrix one it's just that I've just hooked up a new
one out of output 5 aux out 5 that is post EQ so I'll put six pre EQ output
five post EQ and I know it's hard to see but this is purple and this is red and
I've got this legend down here so that's how I know what's going on so let's take
a look at in smart and see if that's actually set up correctly so we'll hit
play on my own I should show you how I created this so on my inputs here I
change the name of input 3 to X 32 post so that would be clear to me and then
under measurement config my third measurement is now called X 32 I'm
measuring the X 32 and I set my measurement signal to X 32 post and my
reference signal to reference but let's just look at ref first turn on the
generator okay so I'm getting the reference let's
it play on the x32 okay they're already pretty much matched
in level that's great now let's see if I like the EQ when I manipulate the EQ I
should see a change in my x32 measurement this purple one post EQ but
no change in my reference the pre EQ
so I'll just grab one of these and I'll pull it down okay this is what we wanted
to see right we've got a cut here in the purple guy post EQ but none in the green
now if I had done this wrong I'll open up routing again
if I had done this wrong and let's say that this one was also pre EQ then we
see no change here right but output 5 is post fader post EQ post
everything so we see the EQ change there all right so I'll reset the EQ
and it might just be interesting to see if we're totally matched in level so
let's switch to a sign and here we'll just be a quick piece of trivia we see a
big peak here but then what are these little Peaks and as we go farther closer
to the noise floor there's even more of them so if you know what this is
what are these Peaks comment below this video and we'll see who gets it first
200 Hertz where we expected to be because that's where the signal
generator is right 400 600 what even the next one is going to be 800 we were
gonna check and see if we were completely matched here and we are I'm
gonna call that completely matched okay we could be super picky if we want to
can we get any closer probably not
alright I'll just leave it where it was cool so let's head over to our transfer
function and let's talk about what we expect to see before I turn this on I'm
expecting to this to be almost exactly like the microphone cable right
I expect to see in the eye our response here just a click quick up-and-down it
should just be but book you know there's no there's no sound coming out of
speakers or traveling through air so it should be all frequencies up and down
and the magnitude response here I expect to see a completely flat line 100%
coherence and the phase response same thing completely flat line all this all
completely boring this is what I expect to see just measuring EQ where
everything's completely flat right this EQ I just reset it in the channel
configuration no insert yet alright so let's hit play on this X 32 we'll hit go
on my analyzer whoa
all right this is not what I expected to see okay I remember the problem from
last time okay I forgot this chain this back to pink noise right okay
no why do I have all these weird wrap arounds here
okay I remember from last time I can also see up here that this delay is not
right where it's supposed to be so it must be because this delay is
wrong so let me hit the late racking goes to zero okay
everything flattens out no my expectations have come true right so
flat flat flat just a quick blip here up and down great no we can actually start
manipulating the queue and seeing what that looks like sort of the picture of
the shapes that EQ make in my mind are what they really make on an analyzer
when I can start connecting those things then I can start having trust in the
analyzer and I can start working more quickly so just for example if we go
back to the EQ here and let me turn off this spectrum thing because it's kind of
distracting our TA
so now my question is if I make this kind of a shape with an EQ and it looks
like this on this graphic display and I have in my mind okay that's what the
shape is then over here and smart in the
amplitude display here is that the shape yeah they look very similar right
so then I can play around with this and I start getting some ideas for what
these shapes are and I can take a look what's the difference between p eq and v
eq and then I'm choosing the wrong one yes
p eq and v eq okay and is it the same thing when I boost
and when I cut the EQ and P EQ and I can make this go a little bit faster because
again we're not measuring in a room with air so everything can be faster look at
that okay good
what about a low shelf
and I can also then observe the effects of what's happening with phase okay and
again I'm not talking about any of the theory about why this is happening with
these first steps I'm just suggesting that you don't change anything just
start getting used to what the graph looks like what things are what things
look like when you measure them what changes look like when you measure them
and so now we're just observing when I measure an EQ when I make changes what
does that look like in the magnitude trace here what does that look like in
the phase trace here okay an important thing to note here about the EQ is that
if I turn it off and on no delay changes okay so if I hit the light here again
still zero if I go back here and turn on the EQ so turning on the channel EQ
doesn't seem to have an effect on the delay but if I go over here let
me reset this first
if I go over here to the insert
and put that in okay look at this change of phase display I've got some coherence
problems up here I know this is the delay problem and I can also see the
impulse response up here has gone back a little bit
so I'll turn on delay tracking okay great everything's going back to flat
and now I I can see that when I put in an insert like that it adds 0.67
milliseconds of delay just round trip through the x32 okay so this little bit
of extra processing here I need to keep in mind and this is why you can't just
do parallel processing of drums for example where you send one to your
compressor and back again you have to send both through the same signal chains
that they both have the same amount of delay okay just this is just a thing in
the x32 it's a thing you have to keep in mind
with a lot of digital consoles ok so let's take a look at that graphic EQ for
a long time I think probably I don't know the first ten years of being a
sound engineer this was my main tool you show up at a gig and this is the first
thing you want to use to do your sound system tuning to do your ringing out of
stage monitors through your ringing out of the system it's a really powerful
tool right it's it's right in front of you got all these things you can grab
and I'll tell you for a long time I thought that these were really surgical
tools right I thought that if I just grabbed this and like boom pull it down
that's like an ice pick right and then just killing that one frequency
so let's see what that actually looks like I think I feel like everyone should
do this because it wasn't until I actually did this exercise myself that I
found Oh maybe graphic EQs aren't really doing what I thought they
do and again this is just a good exercise to connect what I think is
happening in my mind to what is actually happening when it's measured
okay I know that this speaker normally doesn't sound so great around the
crossover between the low friction driver and the high frequency driver so
I might pull this down a little bit and I'll pull both of these down a little
bit like that okay and I know that I want a little
low-end boost for that HiFi sound so I'll turn all of these up a bit
especially at 50 that's a good frequency right
okay great this is like the Nathan lively the Nathan Lively curve all right
this is gonna give you that HiFi sound you know let's add a little bit of
sparkle on top that's gonna sound good but I don't want the feedback so I'm not
going to turn it up too much all right so this is where I might start this is
just like the the curve I always start with on a graphic EQ and then I might
say okay let's ring out the system okay so I start it up and like oh it's
ringing a take a just kill that frequency oh you know what it turns out
it's not 8k it's like between 6k and a case so I need to bring down 6k a little
bit to because it's in between there okay where's the next frequency that's
gonna ring out we've got some low-end build up okay so I need to kill 500 and
you know what's actually between 500 and 630 somehow so I need to bring this one
down to okay so I might do some work like that and so far this is not a
crazy-looking EQ this is the kind of EQ setting you might see going into any
concert venue right and any sound engineer this is not necessarily
embarrassing right I'm not gonna say anything to anyone who's using this okay
what I think most people don't realize and what I didn't realize for a long
time is what this really looks like I feel like I'm doing this gentle thing
here and like these really specific cuts here now if I bring this down
and we take a look at what's actually happening on the measurement here wow
this is not quite what I thought it was first of all these cuts are not as
surgical as I thought they were they sort of like gang together right and
also this is not as smooth as I thought it was it's like these little saw two
things so I think when I see this I start realizing this is not a great tool
for sound system optimization number one I can't put filters exactly where I need
them because I kept having these moments where I was like you know what it's
between 8k and 6k but I can't put an exact filter there and I can never get
the filter to be the width I want it to be here it's not narrow enough down here
I wanted to be more wide but it's fixed bandwidth okay plus then
ganging up these filters I have this weird stuff going on with the phase I
don't know what this is plus it does kind of a weird thing to the impulse
response up here I'll just show you now if we go back to this and I reset all of
these okay here's what the impulse response
should look like before I add it all this okay if you want to keep using
graphic EQs please be my guest I know they still show up all the time I just
want you to be aware of what's happening when you know what's happening like
that's the power okay at least you know what's going on and in your head you can
be like okay it's just it's always a balance of compromises right balance of
compromises one more thing I'm going to tell you
about the graphic EQ as related to smoothing this is another great test for
you to do on your own let's say that we do a boost here okay I've got my locked
cursor here and what does this say in the white here it says 500 Hertz 15 DB
okay yep 500 Hertz 15 DB that's what we've got in our graphic EQ so far here
it looks like we're looking at the truth right and I learned this from Mauricio
Ramirez and this is why he says when you use smoothing you're looking at lies
because if I switch the magnitude smoothing here to 1/3 octave whoa this
goes down from look here at the white numbers I can't put my cursor up there
it goes from 15 to 11 maybe that's not a huge change but all of a sudden we're
looking at a lie this is not we should be looking at a 15 DB boost but with the
smoothing all the way down to 1/3 octave like that maybe the picture looks better
but it's not really a truth anymore it's not quite helping us you notice that the
filter also got wider here so let me just show you the change one more time
again here's 148
and here's 1/3 octave smoothing okay so just keep these things in mind again you
just want to know what the tools are doing so you're not sort of is using
them in a haphazard manner and these really basic methods of measuring things
under control and just taking little steps are what give us confidence in the
tools okay so that was measuring an EQ Syrus
was so long but like taking these initial little steps I don't want anyone
to be left behind or have too many unanswered questions I'm sure you have
some questions so from watching this video please post them below the video
and I would love to get into them with you and have more conversation about
this stuff let's just recap again real quick what we learned so measuring this
EQ if I want to measure EQ I need a pre EQ tap and a post EQ tap and that's my
reference and my measurement signal into my audio analyzer and then the thing I
expected to see was you know when everything is flat let me go back here
reset this what I expected to see was totally flat and when there was no
insert in I expected to see little to no delay and then I put the insert in I
expected to see a little bit of delay okay so expectations validated
sound design