Moderator: John, would you like to start with who you are, what you do, and how you got there?

John Murray: I currently train for TOA. I started in college with a broadcasting background and kind of backed into pro audio. I got a job out of school for a sound contractor - I didn't even know they existed then.

Moderator: Whom do you train for TOA? Customers or employees?

John: Both, plus general audio folk in various ways - NSCA, INFOCOMM, etc.

Moderator: You were involved in the formative stages of TEF. Can you give us an overview of your contributions?

John: Well, I'm not sure I contributed to its development much, but I like to think I helped the use of measurement systems rather than “seat o’ pants” in tuning sound systems. I can remember convincing Craig Janssen that a TEF really could measure as well as an Ivie IE30 RTA (That was a long time ago!). In the early years before Crown built the first TEF 10’s, you had an array of equipment patched together by a box from Richard Heyser and used a calculator to figure out what you were seeing. It's a little easier now.

keith: John, can you discuss the differences in high-level live gain structure versus optimum fixed-install gain structure?

John: Well, the gain structure that has a 20dB peak-to-average ratio/crest factor of headroom is for fixed installs, and what concert folks use is somewhat different. They want a system that has a higher loudness and that dictates a lower crest factor.

Moderator: I ask this at the majority of chats... Can you explain crest factor?

John: I think the confusion comes from its use in describing sound systems and also for amplifiers. Amps have some headroom that is supplied by large capacitors that allow brief voltage swings greater than the line voltage supplies. This is amp headroom. For sound systems, it is strictly the difference between the peak and average program levels.

Moderator: Another thing we like to talk about is beam steering.

John: Keep in mind that this is possible only as long as the individual drivers are spaced at a fraction of the wavelength to be steered. Do no think that one-foot square horn/drivers can beam steer to several thousand Hertz. Some of the first beam steering I knew of was done by Jason Sound for touring, but this was for subs, not mid-highs.