Allen&Heath Qu16 Suddenly goes louder and feedback

[Dick ReesParticipant]

Tell him not to yell or set up the vox mic comps as brick-wall limiters so when he screams into the mic it doesn’t drive the system past the threshold of feedback.

Everybody pay up, please…

[[XAP]BobParticipant]

Run below the gbf limit….

I wasn’t taking that bet.

[frankdubbeParticipant]

Where can I check the heat ?

[frankdubbeParticipant]

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

whats gbf

[[XAP]BobParticipant]

Gain before feedback.

In a given room, with a given setup there is only so much gain that can be applied before feedback kicks in. So you need to run a bit quieter 🙁

Temperature is shown on the home screen somewhere – can’t recall which tab, but the manual shows it..

[Dick ReesParticipant]

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.

[frankdubbeParticipant]

How do you work with GBF

[[XAP]BobParticipant]

You make sure you are under it.

You can help raise the bar by judicious use of the output eq features available to you.

Raise the volume until feedback *just* starts, then notch out that frequency, repeat until you run out of notches or until you are just getting broadband response.

[Dick ReesParticipant]

How do you work with GBF

Bob has mentioned a method for increasing your GBF, but I already posted how to stay under the threshold:

Learn how to set up the compressors on your vocal channels as LIMITERS.

This will allow you to keep these channels from exceeding your GBF limit when the “yells” should occur.

Compressors have traditionally been referred to as “compressor/limiters”. Their mechanism can function in two ways.

1. Compressor. In this use the processing functions to reduce the overall dynamic range of a signal into a more usable “packet” to sit better in the overall mix.

2. Limiter. In this use the function is to “put a lid” on the signal and make it difficult or impossible for the output of the channel to exceed a set limit NO MATTER HOW LOUD THE INPUT. This is what you want.

To set a compressor to function as a limiter, adjust the THRESHOLD control to a high level so that only an undesired sound such as a shout or scream brings the signal over the threshold, the RATIO to a high setting such as 10:1 or greater, the ATTACK as fast as possible and the RELEASE around 150 ms.

This information should be available via Google search and can also be found in the PDF manuals for various compressor/limiters available on the open market.

Again, this is just “Live Sound 101”.

Good luck.

[Dick ReesParticipant]

I forgot to mention the “knee” settings.

For compression, “soft knee”, for limiting, “hard knee”.

Here’s a link:

https://www.doctorproaudio.com/doctor/temas/dynamics-processors-compressors_en.shtml

[scruffydParticipant]

Kudos to all you sweet people for giving someone such great help when it is clearly not really a troubleshooting issue. (y)

[Dick ReesParticipant]

It’s actually quite user friendly with the Qu.

Go,to the Factory Library on the desired channel(s) and look for the starter presets for compression, then select LIMITING and apply that to your channel.

No fuss, no muss…eezy-peezy.

[basadzijaParticipant]

Listen at 15 seconds to hear the feedback. appears out of nowhere and I do not know whether the problem is in the AH or something else. You Tube link here

[AndreasModerator]

I guess the speakers in the back are off, otherwise all mics are positioned before the speakers. Not a good idea, for obvious reasons…

[basadzijaParticipant]

you’re right, but this is what happens when speakers are not directed toward the microphones and when they are away. Feedback occurs always at the same frequency as far as I could hear… Maybe we should reduce volume 🙂

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