Matrix Being Controlled By Input

[2PhatCCParticipant]

So I’ve got a subwoofer connected to output 14, directly on my SQ7. Matrix 2 is configured to use the Main L/R mix and is configured to use output 14 to the sub. I had a microphone plugged into input 13, and I noticed when I was EQing it that the sub started roaring. It didn’t take me long (although in a theater with people watching, it seemed to take way too long) to realize that adjusting the gain on input 13 was also adjusting the gain on Matrix 2. I can’t find any reason why this is happening… I don’t see anything in routing that would cause these to apply the same settings. All inputs/outputs are plugged directly into the board. The only “digital” piece of this is the board and I’m not seeing any reason this should be happening. Anyone have any thoughts? I did move my microphone to a different input and it seems to be working without issue now, but I’d like to figure out why this is happening…

[SQuserParticipant]

Unfortunately, it’s not really clear to me yet what you do:

> Matrix 2 is configured to use the Main L/R mix and is configured to use output 14 to the sub.
So your Main is routed to Matrix 2 (mono) and this signal goes to the subwoofers via output 14 – correct?

> … to realize that adjusting the gain on input 13 was also adjusting the gain on Matrix 2. I can’t find any reason why this is happening…
It seems logical to me that your microphone goes via Main always to the Matrix 2 and thus also to the subwoofer.
But this would have to be the same also for every other microphone channel.

[BrianParticipant]

Matrixes don’t have a gain setting. The overall volume of a matrix is directly related to the gain structure of all the inputs/groups/aux being fed into that matrix. It is completely normal that when you turn up the gain on input 13, it would cause the volume of the matrix to increase as well. From the description you provided, input 13 was likely routed through the LR and therefore being outputted through matrix 2 and into the sub. When you adjusted the gain structure on that input, it went into feedback because the output from the sub was being picked up again by the microphone. Given the fact that you said the problem went away when you changed inputs, I suspect that input 13 is “double patched” somewhere along the way. So instead of just a single instance of that audio being routed to the LR mix (and therefore the subs), there are two or more “instances” of input 13 being routed that way. That can quickly mess up your gain setting because every time you duplicate the input, it adds 3db of volume to the signal. Another possibility is that input 13 was sent to a group or a DCA that was increasing it’s output level beyond what the other input was when you changed it and it stopped causing feedback.

[2PhatCCParticipant]

Yeah, it’s not my board and I only use it one week out of the year. I’m not sure why they have things set up the way they do, but they don’t seem to know how they have it set up… All inputs are going through the main and thus through the sub, so I’m not sure why this particular one is causing problems. I guess for now I just deal with it. I think when I do it next year I will just completely wipe the board and start fresh with my own settings instead of trying to figure out what they did wrong.

[TobiParticipant]

Use an Aux for the sub and ONLY send Signals which are really needed (Not the mic for example)

[TomParticipant]

Adding to Brian’s explanation:
Input 13 could also be set as Mix Ext In.
You wouldn’t see that in the IO screens, only in the output channel’s settings.

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