How do you maximize gain before feedback of a podium microphone
using Smaart? Why would you want to do this? Podium microphones can be
tricky right if someone stands at the proper distance and you have the sound
system you know in front of the podium microphone if if all of the factors are
lined up in your favor it's usually not a problem but what happens more often
than not with the podium microphone is that you have people of all different
shapes and sizes who use the microphone in all different ways so you'll have
someone who walks up to the microphone and they're like at the perfect distance
and they speak loudly and they project no problem and then you have another
person comes up who's way too tall or way too short and they stand way back
from it or worst case scenario they grab the microphone and like shove it over
here or over there and now it's in completely the wrong place and you can't
get enough game before feedback so you're like bringing up the microphone
that's starting to feedback and then you have to try and figure out which
frequency is feeding back so what I used to do in the past when that happened is
I would start out in my mix console and what I would do is I would run all of my
vocal microphones including my podium microphones through some kind of a focal
bus and then I would put a graphic EQ on that bus and then I would turn the
microphone on and just bring it up in the house and first frequency that would
feedback I would turn that down and find the next one and the next one and the
next one and then you know by the end of it I would end up with you know a real
cut-up graphic EQ that looks something like this totally changing the response
of the system at that point okay so let me show you what I've started doing
instead so last year Chris Leonard came over and did an interview with him for
the podcast and one of the things he shared with me is that when he worked on
the presidential inaugurations the sound engineer who did that event used this
process where he would take a transfer function measurement of the sound system
from behind the sound system what the podium mic is the measurement
microphone instead of a regular measurement microphone out in front of
the sound system let me show you what I mean I'll show you how I have this
routed okay so over here in smart now these are the transfer functions I'm
normally running with on a show and I've got this one called Mon which is short
for a monitor and very simply it uses the same reference input as all my other
measurements here so ABC are all just different microphone inputs with the
same reference input now over on Mon I've just routed the
monitor output of my console into another input on my audio interface that
way I can solo up any channel on the board in this case I would solo up the
podium microphone or the vocal bus that it's running through and now I've put
that entire signal chain into the measurement so it's going to measure all
of the processing I have on my podium mic input channel and it's going to
measure the processing that I have on this vocal group and that's what I
wanted to do so let me show you a couple more setup things so I showed you the
input here it's just another input on my audio interface I can't show that to you
because it's not connected right now and then over here in the x32 the
routing is like this so on the aux output aux output 1 I'm just taking a
pre fader pre low-cut pre processing output from matrix one that I'm using
for the main system out and then that's pretty much it because the monitor
output is already automatically going to send out whatever I have so load so
these are my monitor settings here so I hit solo on the vocal bus here that's
gonna send that out of the monitor output that's going to come into my
monitor input here and I already showed you how the reference was routed so
here's the measurement that I get then I oh by the way I should mention that I
always mute this so I don't actually put the podium microphone into the sound
system mom doing the measurement some people do that though and I haven't
tried that much it's probably the next thing I should try I posted about this
on Facebook last year and a few people told me that when they do the exact same
thing for their monitor wedges with their vocal microphones and what they
will do is actually put the vocal mic into the monitor wedge into the sound
system and bring it up until it's about the feedback and then do that
measurement I'm not doing that I'm muting the podium microphone in the
sound system but I'm soloing it so that it goes to the monitor bus so that I can
use that for my measurement input okay so here's the measurement that I get you
can see that coherence is really bad and that's because I'm only measuring sound
coming if there's any direct sound it's coming from the back of the sound system
which is probably why it looks like I locked on to the measurement here you
know using the low frequency drivers or the back of the speaker which is why we
have if we have relatively good coherence here and flat phase here
that's where it's locked on I didn't see this until now but you can see that the
peak in the live IR is actually way up here and I think I probably didn't see
it because I was probably zoomed in like this and I didn't see anything but
if you zoom out you can see that there's a peak up here which is at about 27
milliseconds so although this measurement was made at 87 milliseconds
I probably could have turned it down to 60 milliseconds to actually get this
peak here right here at zero and maybe get better coherence overall anyway I'll
have to pay attention to that next time so this is the measurement that I get it
almost always looks something like this with a lot of like 200 Hertz coming in
and more would be coming in it would probably just keep going the trend would
just keep going up and up and up if I didn't have a low-cut here at 178 on the
podium microphone and that's why it stops going up after it gets here to
about 150 okay so this is the first measurement I'm going to take the
coherence way so we can just look at that
thing I looked at was I said hey there's this peak here at 200 let me get rid of
that so this peak here at 200 is around the 60 B mark this second peak here is
around the 0 DB mark so I'll cut 6 DB around 200 that's what you see here 200
Hertz minus 6 dB here's that and then I said hey let me
just put in a low shelf to try and make all this stuff down here at around the
same height here the same level so this is at around minus 12 so I'll need to
put in minus 12 so I actually started this like that which seems crazy right
like that's a lot to cut but that got it down to a flatter response so I took a
measurement afterwards which looks like this so now you can see much flatter
response here and that has been my goal so far
let me just return the response to flat and see if that does it for me
this is probably not the best way to do it
flat is probably not the best target in this case because once sound check
starts I always have to make adjustments so once sound check started I basically
just listened and dialed this low shelf back until it sounded natural so
someone's speaking on the podium microphone and I'm just reducing this
low shelf until it sounds natural and it's not feeding back and and things are
working well that makes me think that probably in the future I should try
shooting for not a flat target but maybe something more like the same target that
I use for measuring in front of the system instead of behind it because if I
hide this guy and bring this guy up it doesn't quite match
so I don't know I'll have to play with this some more but I'm thinking I need
to develop a different target that's for stuff behind the system for things that
are just like doing a load study just measuring bleed overlap that kind of
stuff because I didn't get rid of this you would think if this were a problem I
would have cut it out of the input channel around 900 Hertz but we can take
a look at the input channel if the x32 doesn't crash and we can see that I'm
not cutting around at 900 Hertz cutting several other places I have been
testing this out over the last few months trying to kind of work it into my
system tuning process it takes a little bit more time and I know we're all busy
and there's never enough time so I had to practice and really force myself to
try it until it became something that I could sort of do quickly and get
together what I needed was one more input on my audio interface basically so
I needed one more cable so now there's one more thing I have to do during the
setup process but now that I've practiced it a few times it's become
quick enough I have the cable right there in my measurement rig so I just
pull it out connect the monitor output from the console to the third input on
my audio interface and I'm ready to go all right I would love to know if you
guys have tried this so if you're doing this already let me know some other
places that you've tested it maybe on a podium microphone maybe on a vocal
monitor wedge that kind of stuff basically anywhere where we're measuring
overlap from the sound system reflections build up bleed that kind of
stuff so let me know what your experience has been