So there I was, system engineer at a county fair gig. The act of the day was a traveling ’60s reviews with three or four artists who were, shall we say, past their prime.
They weren’t carrying engineers, so we got the duty.
Soundcheck went fine. The artists cruised through their paces and the hired back-up band was surprisingly good. Nothing to do but hit catering and wait for the “white hair, blue hair and no hair” crowd to show up.
Show time. The band started the intro, everything was rocking in an old school sort of way and the emcee/star came out. He was much more animated than he had been at soundcheck – running around the stage, exhorting the crowd to put down their walkers and dance, generally getting them in the mood.
Suddenly I heard a phantom kick drum that was waaaay off the beat. I cued up my cans and began to solo channels.
The offending thump came and went, but I finally put my eyes and ears together and realized that the star, we’ll call him “Frankie” for the sake of this article, was running around clapping his hands while holding his SM58.
At first I tried riding the mute button on his microphone, but I was spending so much time on him I couldn’t mix the rest of the show.
So I reached for the variable high-pass filter knob and ran it up to 300 Hz. It thinned his voice out a bit but I doubt anyone noticed but me.
Combat The Unwanted
High-pass filters are probably one of the most under-utilized features on the console. The most common use has traditionally been to combat unwanted proximity effect, which is the tendency of directional mics to increase their output at low frequencies as the sound source gets closer to the mic.
Cardioid and hypercardioid mics get their directional characteristics from ports in the mic capsule that allow sound to impinge on the rear of the diaphragm as well as the front. The added length of the ports creates a difference in path length between sounds hitting the front of the diaphragm and the rear.