AV9000 Checklist Items Under Test:
- 5.2.1: All audio paths on the flow diagram have been verified.
- 6.1.16: All channels on amplifiers, especially on multi-channel amplifiers, are properly labeled, so users can make quick adjustments without having to refer to the system drawings.
- 6.1.17: All equipment in the rack is labeled in an appropriate and reasonable manner, and the labels match those on the drawings (equipment symbols and/or description), control system, field plates, patch panels and any labels associated with the system. This allows for easy serviceability, as well as prevents confusion in systems with multiples of similar equipment.
- 6.2.1: No power amplifier has its rated load exceeded. Record the impedance of each loudspeaker line on each power amplifier at 63, 250 and 1000Hz (“Loudspeaker Impedance Test”).
Reasoning: In “The Commish” in 2017, I am discussing some potential pitfalls that integrators and designers may encounter in the market segments that Sound & Communications is highlighting each month. In this issue, the focus is on Theme Parks & Attractions.
This brings to mind vast zones of loudspeakers distributed throughout geographically large spaces. Not only does someone have to check each and every loudspeaker to make sure they are on and operating, but they also have to be able to reference them at a moment’s notice. Thus, a complete and intuitive labeling scheme is required. Discipline with installation and commissioning these systems is the only way to assure a successful project.
The Story: “Can you hear me now?” That poor soul who was sent around to test a cellphone company’s signal strength was hilarious (especially now that he has gone over to the competition!). My friends and I would joke around with our hand up to our ear on our pretend flip phones: “Hey, Iris…can you hear me now?” It was great. One guy never took part in the banter, though. Whenever this line of imitation would start, Lucas would leave the room moping. One day, I asked Lucas why he didn’t join in the hilarity. His reply: “That’s my life, man. I get to test loudspeakers at theme parks. It’s not funny to me at all when people mock what I love to do.” It was a sobering lesson. I’ve never joked about “Can you hear me now?” since.
In most of our commissioning work, checking the loudspeakers takes minutes. Typically, there are two at the front of the room for program material, and then several in the ceiling for overhead distributed signals. It takes barely any time to walk around and make sure they are all on, sound good and produce sound at consistent levels.
However, for theme parks and attractions, this is not the case. Hundreds of loudspeakers can be distributed over acres of park. The integrator and commissioning agent must use discipline to confirm that they are all operating properly. This certainly includes verifying impedance on the lines, but that’s the easy part. Someone has to make sure that every loudspeaker is wired in the same polarity to avoid destructive interference from neighboring loudspeakers. While they are at it, they also need to confirm sound pressure levels and confirm that each loudspeaker is tapped correctly. Impedance measurements will give you some clue to proper tap settings, but it is not accurate enough to find a single loudspeaker tapped at 15W on a loudspeaker zone that is supposed to have 50 speakers tapped at 3.75W. Subjective listening is required in addition to the objective testing performed with meters.
With systems of this size, labeling becomes imperative, as well. I can’t tell you how frustrating it is when installers do not physically label devices in a system. This applies to equipment to distinguish Amp #1 from Amp #2, but it also is important to label equipment, especially multichannel equipment, with channel information. I am sure it is possible to look to the drawings to realize that the park entrance is Channel #4 on Amp #5, but if something is going wrong, I don’t think the operator will be able to find the drawings in time, much less read them under pressure to find this information. It is much better if everything is clearly laid out on the device itself.
Labels are critical for networked audio systems, as well. As systems get larger and decentralized, a clean and intuitive site file becomes all the more necessary. Signals need to be organized and color coded so they are easy to navigate and trace. Not only is it important to make sure everything is virtually labeled in the software, but that the naming convention is usable by the operators. If the installer thinks a codec should be labeled “VTC-1,” but the operator has no inkling what a VTC is, the naming convention is not successful. Now multiply that integrator/operator disconnect by 250 source names, and you have an unusable system on your hands, with endless service calls draining everyone’s profits.
In my experience, AV systems that support theme parks tend to use straightforward and time-tested technology. However, their size creates complexity. With the sheer number of channels, discipline is required to make sure every single endpoint is functioning as it should. Not only that, but integrators must make sure that operators can easily find what is driving each of these endpoints in the rack with proper labeling. Sloppy labeling and site file configuration practices that might be easy enough to work around in small systems can be disastrous in a large-scale system. Also, project managers need to plan an appropriate amount of time for testing and commissioning these expansive systems. Finishing the physical terminations may represent 75% completion on smaller systems. It is probably closer to 50% with these large systems because there are so many terminations, and finding issues is akin to finding a needle in a haystack. After a few of these systems, the “Can you hear me now?” guy may cease to be funny to you, as well.