AV Police Squad

Serviceability: It’s kind of a big deal.

I was recently brought in on a multi-room project to commission the audio aspects of the systems.

The rooms were already installed and in use, but they wanted to provide a consistent experience across all rooms for their users. We adjusted the codecs and mixers to provide similar levels across the different systems. The last step was just to verify that the acoustic levels were the same in each room, given a standard talker (via an NTI TalkBox) at the far end.

Each room should have been distributing audio at 65dB-SPL, a-weighted (dB-A). To a large extent, they all provided consistent levels. There was one room, however, that was only averaging about 55-58dB-A. The codec, mixer and control system were all inspected. They behaved exactly like the other rooms. The only thing left to check was the amplifier.

I know you’re thinking to yourself, “Self? This should be easy. Just get to the amplifier and turn it up.” I thought the same thing. The amplifiers resided locally in a credenza equipment rack. The amplifiers had no knobs on the front so that users couldn’t mess up the levels.

Now, I bet you’re thinking to yourself, “Self? Just pull out the rack. Easy peasy.” I thought the same thing. As I went to pull the rack out, I made it about two inches before the top of the rack hit the top of the credenza. I found out later that the racks built for the credenza were too tall, so, when the job was installed, the tops of the credenzas were removed so that the racks could be fit in. It was later glued on after everything was terminated. The backs of the credenza were cut away, but, after all the gear was in place, it became too heavy to move without multiple people and/or destroying the carpet.

You must be thinking to yourself, “Self? Surely you can just turn the racks to access the cabling and the rear of the equipment.” I thought the same thing. I couldn’t. In addition to being too tall, the racks were also just wide and deep enough to only allow about a 12° turn in either direction. There was no access to the back.

“Self? They must have left enough slack in the wiring so the amplifier could be pulled out from the front.” I thought the same thing. And, no…they didn’t.

So, I did what any self-respecting AV engineer would do. I dropped my flashlight behind the rack and rigged a “camera fishing pole”: a BNC tool tied to a string with a camera phone at the end, set to take a picture on a timer. After a few attempts, I got my shot. I made my torso as skinny as possible and went “potentiometer digging” with my tweaker, using the camera fishing pole shot as my guide. I squeezed myself into the 12 inches I had next to the rack and side of the credenza and just felt my way around.

It wasn’t pretty, but I got my additional 8dB out of the amplifier, and the room was just fine. I’m sure it looked like the credenza was giving birth to a slightly overweight AV Tech for several excruciating minutes (for me and the credenza)…but I got my 8dB.

The moral of the story is: Don’t do drugs.

Also, keep your systems serviceable. Install systems not with the final payment in mind, but with the guy who has to live with the system for years after you leave. Your goal should be to deliver defect-free systems, remembering that if they can’t be maintained, adjusted or easily troubleshot, then that’s a pretty big, often overlooked, defect.

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