The joys of setting levels. Keep saying that Joy.

By Jim Sorensen

My home church has a first class sound system.  I didn’t build it and it’s got an Duggan Automixer.  It has one loudspeaker and very few microphones.  Life is good!

The problem is that even though there are very few microphones they are out of balance so I, of course, volunteered to re-calibrate the thing so everyone who uses it at least can be sort of heard in the church.  Being Episcopalians we always seem to have a problem hearing the sermons over the snoring.

What’s interesting is the dynamics of things.  I have a very fine Fluke portable DVM which reads AC volts in “true” RMS so it’s easy to find a calibration level across the output of the mixer, which is by a happy coincidence also the input to the power amplifier.  The problem is that I also have an HP Dynamic Analyser, a TEF, and an HP Audio Voltmeter or two all of which claim to be calibrated to the same standard and all of which appear to be so calibrated when one is looking at something boring like a sine wave.

I guess if we spoke in sinewaves life would be different but we seem to speak in waves that are everything but a sine wave which of course confuses the metering.

That’s my problem.

This whole exercise started when I got the brilliant idea that if I calibrated the front panel meter on the mixer that it would be easy for anyone else foolish enough to open the PA rack to make little adjustments from time to time in the hope that the world would be a better place as a result.

The problem is that the meter on the front of the mixer is one of those little 7 segment bar jobs that’s calibrated to whatever the crush strength of a Budwiser can is or something else, perhaps relating to the mass of the Helium atom or perhaps the atomic weight of Rhodium.  Easily remembered things commonly used and consistently measurable for convenience.  Notice there is no discussion of accuracy.  I gave that up on that.

I wonder if I can get the users to hum a 700 Hz tone for a minute or so.

Keep it out of the red!