Reply To: Allen&Heath Qu16 Suddenly goes louder and feedback

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Dick Rees

Can you tell me moren about
just a system trimmed for flat response and operated close to the GBF horizon

whats gbf

As Bob said, GBF stands for Gain Before Feedback and simply represents how loud it will get before the feedback loop(s) start their self-reinforcing howl.

A system “trimmed flat” means that most or all of the frequencies have equal potential for feedback and will all reach the limit of GBF at the same time. It is quite natural for a system to have “hot” frequencies such that one particular frequency will start to feed back before the rest. This is why we use the various forms of equalization, mic patterns and speaker/mic orientation to adjust things for maximum GBF. We want the most GBF and the fewest troublesome “hot” frequencies.

Operating your system “close to the GBF horizon” means that your system was OK for most of your use, but that “Aerosmith yell” pushed the system past the threshold of your usable GBF. Result? Feedback.

It has nothing to do with heat.

Still it’s good to know where to look to find the temperature. If it’s like all my other computer devices, getting too hot will simply result in it shutting down. Then no sound at all.