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The purpose of EQing a church is to the match the performance of the speaker
system, microphones and room into a a balanced compromise of gain before
feedback, sonic performance and overall SPL.
It is a device used to compensate to some degree the errors in the sound
system design, errors in the speakers and microphones being used and the interaction of both elements on each other. (Since there is no such thing as a perfect speaker, all speakers have some
kind of error or another. This doesn't mean the speaker doesn't sound good,
it is the fact that any error in a speaker, once interacting with a room,
can show up as a problem.)
Feedback is the re-generated noise that is inherited in all pieces of electronics.
It s the noise from the Microphone, mixer, EQ, and amplifier in the audio
chain. Usually feedback starts off as being electronic noise. Then as you
filter out the electronics, then it become the reaction of the room imposing
itself onto the sound system.
A very good method for EQ'ing a room is by using the FEEDBACK Method. When
you don't have an FFT analyzer to separate the frequency response of the
room and the speaker system as a separate measurements and then seeing
the combined measurement, the feedback method is the next best thing.
In a HIS Systems, it is assumed that you are using a central cluster or
a Left/Center/Right Cluster system. It also accounts that you have accounted
for acoustical errors in the room and already have proper speaker/speaker
system alignment. Under these conditions, this method works great. For
other systems types, you will have to modify this method with trial and
error. However, it is most often, an excellent way to start EQ'ing a room.
Many suggest a method by which you go around the seating area, take measurement
and adjust the EQ to a flat setting. I have tried this method. I have also
ran pink noise and set the graph with the EQ for a flat setting. Then,
when you stand at the pulpit and talk, the sound can be muddy or just awful.
Part of the difficulty with either method is the room. It is a fact that
most churches have acoustical problems. Some problems are on the stage,
other problems are in the seating area as well. When placing the test mic
in the audience area, the room can change the response greatly when you
move the mic only a few feet away.
The 11 Steps
- 1: First, start by simply placing a mic at center stage or at a center
pulpit. Point the microphone straight back to where a person would be standing
to give a sermon or back wall. Pointing the mic the other way doesn't work
very well.
- 2: Next use a Dynamic mic with a Cardioid pattern. - The old Shure SM58
is ideal for this. (From many tests, a Dynamic mic works better than a
Condenser mic with the feedback method. If you EQ with a condenser mic,
it is less forgiving(Sorry, but I don't have a better word to describe
this) and switching to another brand of condenser mics for speaking later
can actually sound worse. With a Dynamic mic, it is more forgiving when
EQ'ing such as the old Shure SM58. The results tend to be usually better,
even when using other brands of microphones afterwards.)
- 3: On the mixer, set all of the channel EQ settings to flat for the mic
on the pulpit or center stage on a stand. It is best to use a tripod base
mic stand. If you use a solid bass stand, sound energy from the platform
can travel up the base and shaft of the mic stand.
- 4: Set you main house EQ to Center position. (Hopefully you have already
set your gain controls for the EQ, comp/limiter and amplifiers.) (Also,
bybass your comp/limiters, feedback destroyers and any other processors.
You want a clean signal)
- 5: Set the input mixer gain to off. Set the channel fader to 0dB or -10dB
(This depends on the markings of the mixer.) On the main out - set the
fader to -10 or 0dB (This again depends on the markings of the mixer.)
- 6: Raise the input gain until the sound system begins to ring. Turn the
gain down until the ringing stops. Now start using the channel fader to
make the system ring again. It should start to ring slowly. You should
be able to get an almost steady signal of a tone at a low level.
- 7: If you have a RTA, you will see which frequency is ringing. You can
also use a Multimeter with Frequency. You can get one for about $200.00
or less. I like to plug the meter into the headset out and use the PFL
output for a signal. The meter will give you a digital reading, which is
more accurate than an RTA.
- 8: Start by ducking the ringing frequency down -3dB. That should cut the
ringing out. If you don't have an analyzer, use the trial and error method
to seek the ringing frequency. 9: Once the system is stable again, raise
the fader again.
- 10: Repeat this routine until you either hear several frequencies rise
up at once or when a frequency hit -12 or 15dB. (In theory, you shouldn't
need to EQ more than -6dB, but since most churches have acoustical problems,
you will often find that you need to EQ at least one filter this much.)
- 11: If you are hitting the bottom of the EQ before you hear a chorus of
ringing, this is a sure indication of a room problem, a system design problem
or you have only a 1/2 octave or Octave EQ.
While this is not a perfect system, it can provide excellent results if
your system is designed right and the room behaves well when you don't
have a tool like a TEF, MLSSA or Smartt Pro. EQ'ing is always cut only.
If you have one of these tools, only then can you confidently considering
boosting a frequency signal if there are serious room problems like excessive
bass absorption or if speakers are misaligned and you don't have the chance
to rearrange the speaker system today.
Some may suggest using Pink Noise generated through the system and EQ'ing
base on that alone. Some people use this method as though it does not consider
the room and it only corrects speaker flaws. This is not the case. Unless
the mic is within 3 feet of the speakers, you are actually measuring the
room and the speaker combined - most likely more room when greater that
30 feet from the speaker. EQ'ing for a flat response of a speaker in room
can sound great. However, The same speaker in room "B" set to
flat may sound terrible. When using the feedback method in room "B",
it should sound as good as in room "A" - less the difference
of the room or system design.
Some have suggested to Pink noise first with the test mic as close to the
speaker system as possible, then use the feedback method. Tests have shown
that you are more like to have so much EQ'ing that you give up a lot of
system gain and overall tone is not much better. In some cases it was worse
- - especially when several different mics were active.
I am sure that others can explain this better, but since many are asking,
this is what I do for church sound. In a Typical HIS System, the feedback
method works remarkably well when you don't have proper measurement testing
tools.
By Joseph De Buglio.
His is a YouTube Video about equalizing a church sound system
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