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  #1  
Old 03-29-2023, 12:04 AM
Jan Christophersen Jan Christophersen is offline
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Default Sidechain causing Feedback-Loop?

Hej,

maybe it's a stupid question, but I don't understand PTs problem with what I'm trying to achieve:

- I use two Auxes for Music and Vocals
- I send from each of these Auxes to a mono sidechain-bus
- on the aux-channels I have Pro Q3 sidechained from the opposite Aux (Vocals gets sidechained by Music and vice versa)

But PT detects a feedback-loop? Why?

Cheers
Jan
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  #2  
Old 03-29-2023, 12:12 AM
Tweakhead Tweakhead is offline
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Default Re: Sidechain causing Feedback-Loop?

it's impossible to see any detail in your screenshot.
you need to use a 3rd-party image host.
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  #3  
Old 03-29-2023, 12:21 AM
Jan Christophersen Jan Christophersen is offline
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Default Re: Sidechain causing Feedback-Loop?

Okay, does this work: https://imgur.com/a/eqrbfZG ?
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  #4  
Old 03-29-2023, 09:10 PM
Tweakhead Tweakhead is offline
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Default Re: Sidechain causing Feedback-Loop?

yes, much better image.
I'm not quite grasping what you're trying to accomplish here with this bi-directional dynamic node side-chain setup.
So let's try to analyze what's seemingly going on . . . and please correct me if I'm wrong.

You're wanting the music mix to dip down by about 2.5dB at around 1.9k every time the vocals sing a line, and then that same music mix is sending that post-processed signal back to the sidechain input on the vocal mix Q3 - which was sending the signal in the first place ? (I can't quite tell what you've got the Vocal Bus Q3 doing, as the complete image is obscured)

So while it's not quite an audio feedback loop in the traditional sense, it's creating an action>reaction feedback loop. While this is probably not going to go into a speaker-damaging sonic feedback loop when doing negative processing, it could potentially go into some kind of resonance loop if you ever change the Q3 to a positive dynamic node processing setting.

Is that alert popup coming from Pro Tools or FabFilter ? (does it move with the FabFilter plugin ? or is it a one-time popup alert ?)

If the former, Pro Tools is probably protecting you from something potentially destructive from happening, especially if you were to ever audition the sidechain. I'm not in front of my system right now, so I can't remember if Pro-Q 3 has this sidechain audition capability, but I know Pro-C 2 does - and so do many other plug-ins. Avid are probably just attempting to protect users from themselves - but I bet if you really, really want to do it - you'll find a way !

Perhaps you could describe what were you hoping would happen to the sound ?

Last edited by Tweakhead; 03-29-2023 at 09:33 PM.
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  #5  
Old 03-29-2023, 10:06 PM
Jan Christophersen Jan Christophersen is offline
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Default Re: Sidechain causing Feedback-Loop?

Thanks!

The loopback-warning comes from PT itself.

And yes, it seems, that there is a kind of loop with the way I am setting these auxes up. At the moment I am only using q3 on the music aux to dynamically duck a few dbs whenever there is a signal in the vocal bus. My hope was to have a way to let these auxes react dynamically to each other. Maybe thats not a perfect solution, but whenever I am mixing in Logic it works without problems.

Again, thanks and cheers
Jan
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Old 03-30-2023, 12:16 PM
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albee1952 albee1952 is offline
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Default Re: Sidechain causing Feedback-Loop?

I still can't make out what's going on in the screen shot(due to fuzzy image) so I'll just describe what works for me:
1-Send the vocals to an open bus. This could be a single send from a mix of the vocals(via a routing folder or aux track), or by duplicating the same send to all vocal tracks.
2-with the music tracks routed thru a routing folder(or aux track); insert a compressor plugin on the music mix.
3-on this compressor, set the sidechain input to the bus that the vocals are feeding(from step 1)
4-adjust the compressor settings as needed.

Anything more complex than this is not needed, and would likely cause the feedback loop you describe. One more idea to consider: since this sidechain triggering might give you a sluggish attack(the music won't duck until the vocal starts), instead of using the send, you could bounce a mix(stem) of the vocals, import that bounced file to its own track, set the output of the track to the sidechain bus and nudge the track a bit early. This would allow the vocals to trigger the ducking slightly ahead of the actual(audible) vocals so the music would be ducked a touch early(to preserve the leading edge of the vocal vs ducking). Adjust the compressor's release time to taste. I know this may sound confusing, but read it again and play with it
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  #7  
Old 03-30-2023, 03:10 PM
Tweakhead Tweakhead is offline
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Default Re: Sidechain causing Feedback-Loop?

Quote:
Originally Posted by albee1952 View Post
I still can't make out what's going on in the screen shot(due to fuzzy image)
If you control+click on the image in his 2nd image link, open in new tab, it will be hi-res. at least it works that way in Firefox.
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Old 03-30-2023, 11:21 PM
Jan Christophersen Jan Christophersen is offline
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Default Re: Sidechain causing Feedback-Loop?

Quote:
Originally Posted by albee1952 View Post
I still can't make out what's going on in the screen shot(due to fuzzy image) so I'll just describe what works for me:
1-Send the vocals to an open bus. This could be a single send from a mix of the vocals(via a routing folder or aux track), or by duplicating the same send to all vocal tracks.
2-with the music tracks routed thru a routing folder(or aux track); insert a compressor plugin on the music mix.
3-on this compressor, set the sidechain input to the bus that the vocals are feeding(from step 1)
4-adjust the compressor settings as needed.

Anything more complex than this is not needed, and would likely cause the feedback loop you describe. One more idea to consider: since this sidechain triggering might give you a sluggish attack(the music won't duck until the vocal starts), instead of using the send, you could bounce a mix(stem) of the vocals, import that bounced file to its own track, set the output of the track to the sidechain bus and nudge the track a bit early. This would allow the vocals to trigger the ducking slightly ahead of the actual(audible) vocals so the music would be ducked a touch early(to preserve the leading edge of the vocal vs ducking). Adjust the compressor's release time to taste. I know this may sound confusing, but read it again and play with it
Right, I understand. In my case it's just a broad stroke, making room in the music-aux, whenever there's something happening in the vocals aux. It really isn't that critical to catch it that accurate. But thanks for the tip.
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