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-   -   How to compensate for analog summing mixer hardware latency? (http://duc.avid.com/showthread.php?t=347444)

ryanstewartguitar 11-24-2013 11:30 PM

How to compensate for analog summing mixer hardware latency?
Hi everybody,

I am trying to figure out how to make Pro Tools compensate for the latency that comes from using my analog summing mixer. Most of my mixes have everything bussed internally to submixes, whose outputs go to my summing mixer. The stereo signal is then recorded back into Pro Tools, however, due to the extra round of conversion I get a latency from when I record or monitor the stereo signal. Is there a way for Pro Tools to compensate for this automatically? I understand the H/W Insert Delay portion of the I/O menu, but since I'm getting the latency from the output of each submix, rather than from an insert, I don't believe it will be able to help me. Am I correct?

I know I can always nudge over the recorded track by printing ITB simultaneously and measuring the distance between the peaks. However, I often times will be monitoring the audio with picture and/or a click track that is not routed to my summing mixer, all before I print anything. So the click/picture I hear/see isn't lined up with the audio, which makes things impossible to work with.

I've also found that having active plug-ins greatly increases the latency, even when the latency added by the plug-ins does not increase the delay compensation amount (I've had ADC on at maximum [16383 samples per second] the entire time). Why would plug-ins add to this latency if ADC is on?

In my current session, which has about 65 plug-ins (mostly UAD-2 and plenty of Waves) I get a latency of a whopping 191 ms when printing through the summing mixer at 48kHz with a 1024 sample buffer size. When I make all the plug-ins inactive and change my buffer size to 128 samples, the latency is greatly reduced to 32 ms. With all plug-ins enabled, if I avoid the summing mixer I don't get any added latency. I'm running a UA Apollo 16 through a Dangerous 2-Bus LT on a Late-2013 iMac.

Any ideas? Thank you!
- Ryan

nst7 11-25-2013 06:59 AM

Re: How to compensate for analog summing mixer hardware latency?
From what I can see from the manual, you will need some kind of monitor controller. Unlike the Dbox, this does not have one built in.

The whole idea with the summing boxes, is that when tracking, you monitor the direct summed signal, rather than the signal after it goes back into your interface, precisely because of the extra step of conversion, as you mentioned.

On the Dbox, this is achieved by pressing the "Sum" button (direct monitoring) vs. the "DAW" button.

On the 2Bus or 2Bus LT, the "main" outputs on the back go to your interface for mixdown. The "Mon" buttons go to your monitors, or a monitor controller.

If you use a monitor controller with 2 stereo inputs of some kind, then you could switch between the two. One could be for the direct monitoring of the summed signal (the "mon" out of the 2bus LT), and the final output of the mixdown from your interface (which would be either two analog outs or two digital outs of the interface, depending on if your monitor has digital inputs).

Apart from this, I don't know how else it can be done. You may want to call Dangerous and ask them for any more ideas, as they are very helpful.

nst7 11-25-2013 07:08 AM

Re: How to compensate for analog summing mixer hardware latency?
Just wanted to add that if you need a monitor controller, the Dangerous Source looks like it could work in this situation. You could use the 2 bus's "mon" out into the Source's analog ins, and the Apollo's AES digital outputs into the Source's AES ins, and switch between them.

ryanstewartguitar 11-25-2013 10:22 AM

Re: How to compensate for analog summing mixer hardware latency?
Thanks for the reply. I already have a monitoring setup as you described. I go AES out of my Apollo into my Grace m903, and feed the Mon out of my 2-Bus into that as well. So I can switch between the two, but that doesn't help my problem. I still get a latency when I print any tracks, and there's still no way to monitor a click (that's not routed to the 2-Bus) along with the 2-Bus stereo print. Any other ideas?

My current workaround is to send all my submixes that go to my 2-Bus to an additional print track that's all ITB. Then I can print both that track with the 2-Bus and nudge the waveform to match. But that's just a pain, and I'd love to find another way to incorporate the 2-Bus.

nst7 11-25-2013 12:34 PM

Re: How to compensate for analog summing mixer hardware latency?
The latency from the print track is normal, and there's no way around that, because of the extra conversion that goes on. This is the case with all summers and mixers.

As for the click track, you could send it to one of your stems while you're tracking, and then when mixing (where you switch to the Apollo's output for the final mix), you can just mute the click track so it doesn't print.

Apart from that, I'm not sure what else could be done. But if anyone knows, it would be the guys at Dangerous. You may want to give them a call.


It just occured to me that you might be using a different workflow than normal, since you mentioned "printing tracks". Could you be more specific about what you're doing and how you're doing it? Because what I described is the normal workflow for summing mixers. There's no reason to monitor the final printed track when you're still tracking.

ryanstewartguitar 11-25-2013 02:11 PM

Re: How to compensate for analog summing mixer hardware latency?
This rig is actually just for mixing - no tracking. When I say "printing tracks" I just mean printing the stems and/or the final mixes in Pro Tools.

Sounds like I'll just have to have to nudge manually, and monitor everything through the 2-Bus. That's what I figured, I just wanted to see if PT could align this automatically somehow. Thank you for your help!

nst7 11-25-2013 04:49 PM

Re: How to compensate for analog summing mixer hardware latency?
Sorry I couldn't help more. I'm still not clear on why anything needs to be aligned if you're printing the final mix. I'm not sure what you're trying to align it with. Stems should be aligned with each other already since they're all going through the same routing.

MarkH 11-27-2013 12:31 PM

Re: How to compensate for analog summing mixer hardware latency?
Search "adding summing mixer to pro tools" on Google and you will see a couple of YouTube videos explaining the way to do it. I think one even uses the Dangerous setup.


Djdrew75 04-30-2016 10:28 PM

Re: How to compensate for analog summing mixer hardware latency?
Did you ever find out the root of your problem?

JuanPC 04-30-2016 10:55 PM

Re: How to compensate for analog summing mixer hardware latency?
In the I/O set up some interfaces have an option to compensate for AD DA delay...
Used when using hardware inserts.

Don't know if that feature is HD only, or if has been added to Standard ProTools in recent versions.

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