Study Hall

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The PA Trifecta: Handing Off A Live System That Checks Out

No matter what the back-story, the guy or gal coming in only wants to know that it works and works properly...

“Here…these are for you.

“Let me count that back – One (1) pair floppy plaid shoes; one (1) Bravo-52 latex red rubber nose (with custom strap); two (2) mechanical chickens with servo-waste evacuation system; and three and a half (3 1/2) cans of I told you so (generic substitute).

“I must ask you to put on these garments, pick up the chickens and proceed about your business until load out.

“This demand is in accordance with our technical rider, which clearly states in verbiage Grouping 3, Subsection F, Line U: ‘…all drivers must exhibit the correct DC polarity as specified by their manufacturer’.

“Should a DC polarity inversion be suspected and confirmed through qualified empirical method by (the artist’s) engineer, the specified and introduced lead system engineer (A1) for the sound system provider must and will don a garb of traditional JESTER SUPPLIES (as provided by artist’s representative) and wear said fashion until such time as artist’s engineer deems the A1 has reached a sufficient level of contrition.

“We appreciate your cooperation in this matter.”

It doesn’t really say that. The production manager for the artist that I mix does, however, begin the sound portion of our show advance with this caveat: our front of house guy will confirm the DC polarity of your rig using a combination of software-based FFT and handheld pulse checkers.

If he’s just been mugged prior to load in and the thief has absconded with all his gear, he will still stagger naked up to your PA with a 9-volt battery and a screw gun. This will happen. If there is a problem, he will find it.

Along the way, he will also find every off center diaphragm, sketchy cone compliance and secret TRS-to-Edison connection in your rig. To spare yourself the misery of having your pants pulled down in public, please confirm that everything is moving the right way before it leaves the shop.

Is he kidding? Nope—we burned out two Makita batteries this year alone opening boxes. I’ve officially dubbed last summer the “Summer Of Left Isn’t Right.”

Using my nifty calculator with LOG function, I’ve determined that there was a 13 dB increase in the amount of systems we were provided that had a significant difference between the left stack and the right stack.

Some days it was subtle…pink noise coming from the left, the sound of me asking if the all amps were powered up coming from the right. Then there were the 4 dB to 5 dB (SPL) inconsistencies in magnitude responses I was seeing in April, which paled against the 9 dB to sometimes 10 dB (again, SPL) variances I was encountering in September.

This wasn’t comb filtering from a spherical array in a geometrically symmetric room; this was daddy’s leaving the house on one side and mama’s coming home for the night on the other. Big deluxe, textbook inversions with a very demonstrative phase wrap right through the middle of a null at crossover.

I call it the PA Trifecta: the sound of the Left, the sound of the Right, and then the composite of both. Pick one, flip front of house, and make sure management stands only there, with their heads strapped into a neck immobilizers.

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My hands-down favorite was panning a signal to the left and getting three of the six compression drivers on one side and four of the 12 cone drivers on the other.
Panning it right yielded all of the compression drivers on one side, a front fill, two subs, and I’m pretty sure the soda machine started vending skittles.

Time to pause for a second and make sure something is clear—I am ALWAYS pulling for the PA company. Honestly, what I want to do is turn to the system tech, shake his/her hand vigorously and gush about how truly splendid the boxes are. (I’ve also found that proffering a half-eaten yet properly wrapped Milky Way will also go a long way toward cementing a friendship).

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