LAPEL MICROPHONES
By Marty McCann
Question from: Ian Stott of Architectural Audio Singapore
"What EQ Settings/curve would you recommend for a lavaliere mic in a difficult
environment such as a reverberant church or hall!"
I would recommend a Cardioid pattern lapel mic, even though
the pattern is altered when placed on the chest. Some put the
mic too far down on their chest. The user should drop their
chin to their chest and put the mic directly below that point.
The farther down from this point results in even more mid-range
chest cavity resonance that colors the sound. This chest cavity
resonance and the gain before feedback is a constant battle
with lapels (Wireless or hard-wired).
Too often the church customer (who is often rather technically
challenged in the first place), tries to resolve the EQ'ing
of the lapel mic with the overall main system EQ. This of course
is a mistake, because of how it will adversely affect the overall
systems performance, i.e., normal vocal microphones and instruments
taken direct are negatively affected by the hacking away of
the main equalizer in order to chase away frequencies that
are problems for the wireless Lav mic only. A dedicated EQ
(inserted into the wireless Mic's channel) is the only way
to begin to even get any kind of a handle on this application.
Even then due to the drastic amount of Mid-range cut necessary
to get intelligibility out of the lapel Mic system (this is
before feedback suppression), there is often not enough cut
remaining in this region for further control of feedback.
Over the years, I have addressed this problem in high visibility,
high $'s installations by either using a parametric along with
a 1/3 octave to tweak the system, or more recently (since we
no longer manufacturer a parametric), I specify ½ of a 2/3
Octave EQ and a 1/3 Octave EQ to process the lapel Mic's channel.
Now here is where the problem is further complicated. In many
installations, the lapel Mic is used by more than one individual
(sometimes several). Due to the individual nature or timbre
of peoples speaking voices, along with the fundamental resonance's
of each voice (that is determined both by the vocal chords
and the size of the chest cavity), one size does NOT, fit all.
The pastor or CEO doesn't understand this at all. At times
when it can be determined that certain designated people will
be using the lapel system, I have specified 2 (yes 2) CEQ-280a
programmable Equalizers, with stored setting for various presenters
or speakers.
Now down to the EQ process. Too often the less experienced
system integrator or operator will just ring out the mic for
feed back. This results in less than desirable tone and intelligibility.
EQ for intelligibility first then go for feedback suppression
(once again you probably need more than 1 EQ to accomplish
both effectively). On the average the required mid-range notch
is centered somewhere from 315 to 630 Hz (this is the individual
variable) depending on the person speaking. This notch can
be two to three octaves wide at the -3dB down points (depending
on the lapel mic and user). Because of the small Electret diaphragm
and its proximity to the users mouth, there is often more energy
above say 8 kHz than is necessary. A variable high cut is a
good tool here (that's why I prefer the EQ-31FX over the Q-31FX,
the variable low cut is also handy here). Some people's voices
exhibit a strong sibilance in the annunciation of Ssss sounds.
This of course is mainly at 6.3 kHz on a 1/3 Octave EQ.
When the budget won't allow for two equalizers, one technique
is to first start with all of the EQ sliders at the top (this
is not a good idea with some cheaper filter designs due to
the ripple or poor summing of the filters), then to EQ for
tone, followed by appropriate cuts for feedback suppression.
With some cheap EQ's this technique would also result in a
poor S/N ratio.
While on this subject, we have had tremendous results with
the performance of our new PVM-2 wireless headset mic. Because
of it's positioning away from the chest and close to the mouth,
it needs VERY LITTLE EQ, and can often suffice on the channel
strip EQ on a decent mixer. The problem is a lot of people
think they look like a Dork with the headset on. In my case,
I have overcome the dorky feeling because the end result is
soooo much better performance.
Also, some theater productions tape the lapel Mic over the
actor's ear or into their hairline (using flesh colored surgical
tape). This works well with some of today's smaller Mic elements,
such as the PVM-1 Lavaliere microphone. |
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