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Mixing Separate Multitrack and Stereo Recordings

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Mike Stranks » Sun Jul 07, 2019 9:04 am

People here are making assumptions of the 'I would imagine... variety'. Believe us (Hugh and me) it IS an issue.

It will vary between makes/models... some will hold sync for upwards of 20-30 minutes, others will have drifted widely after 2-3.

(FWIW early Zoom models were particularly prone to drift. I can't speak about current ones.)

There are fixes and fudges as has been outlined, but they are not quick-click solutions and for a typical live-event recording can take considerable time.

On occassion I've used three separate unsync'd recorders and then made a composite by editing - ie ACABCABCBA.

However, as stated, a mixed recording can be done, but is laborious and always involves some compromises.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby The Elf » Sun Jul 07, 2019 9:06 am

I tried to sync recordings made on a pair of Zoom LiveTrack-12s and the results were not as good as I'd hoped. If the recordings are of any significant length (more than 20 minutes), then it becomes a PITA. It's one thing having a reference to sync the files at the start, but you need something common running in both groups of recordings so that you can check sync at any point further down the files and stretch/contract as required. TBH I lost patience and faith in trying to do this and instead upgraded my system to do the job properly.

In short, it can be made to work, but it would be advisable to not have to do this in the first place.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby blinddrew » Sun Jul 07, 2019 9:14 am

My experience from syncing audio and video definitely fits into the, "it will definitely drift" camp.
How much, and how much of an issue that will be, will depend on how long your performance segments are and how you're packaging your final output.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Kwackman » Sun Jul 07, 2019 11:47 am

Is is possible to take the "line" out of the Tascam into the Sound Devices "Aux In", and record it on to 2 spare tracks on the MixPre? I don't know how the routing works in the SD unit and if it's possible to record 10 tracks this way.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Bob Bickerton » Sun Jul 07, 2019 12:00 pm

Kwack just hit the nail on the head :thumbup: :thumbup: :thumbup:

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Kwackman » Sun Jul 07, 2019 12:02 pm

Bob Bickerton wrote:Kwack just hit the nail on the head :thumbup: :thumbup: :thumbup:

Bob

That'll be a first!
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby tk76 » Sun Jul 07, 2019 2:38 pm

Wow, what an overwhelming response! Thanks to everyone for pitching in :thumbup:

The performance I'm recording is a 6 day non-stop kirtan festival in India; not the entire 6 days obviously, but a good few hours of recording nonetheless. So I'd prefer not to have to fiddle around trying to sync such huge files in the DAW.

Kwackman's solution: genius! Much thanks :bouncy:
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Tim Gillett » Sun Jul 07, 2019 2:46 pm

Kwackman wrote:Is is possible to take the "line" out of the Tascam into the Sound Devices "Aux In", and record it on to 2 spare tracks on the MixPre? I don't know how the routing works in the SD unit and if it's possible to record 10 tracks this way.


Looking at the SD unit details it seems possible, but the OP speaks of using the Tascam to make a room recording. The optimal positions for both recorders may be at different parts of the venue.
In my occasional video recordings I've often found the ability to make a stereo miced recording of the room or the audience, using a small, battery powered recorder with no cables tying it to the main recorder or the mains - or the camera - really useful. If that has meant making a time stretch in post, then so be it. The advantages of convenience and safety at the time of the gig (no leads to worry about) have far outweighed the small extra time stretch penalty later on in post. But maybe that's just me.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby tk76 » Sun Jul 07, 2019 3:38 pm

Tim Gillett wrote: The optimal positions for both recorders may be at different parts of the venue.

Does this matter using line out/aux in? I'll still be recording to the mixpre and able to place the tascam anywhere in the room.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Hugh Robjohns » Sun Jul 07, 2019 4:04 pm

tk76 wrote:Does this matter using line out/aux in? I'll still be recording to the mixpre and able to place the tascam anywhere in the room.

Your choices are: (1) Tascam remote from MixPre, the two being connected with a long stereo unbalanced cable, and short mic cables to the tascam, or (2) Tascam adjacent to MixPre and connected with a short stereo unbalanced cable, but long mic cables into the Tascam.

Either way, you've got to run one or two cables around the room... however, if it were me I'd co-locate the Tascam with the Sound Devices to minimise the length of the unbalanced cable -- ideally meaning 2 metres or less -- to minimise the risk of interference. Having the two machines adjacent also makes it easier to keep an eye on levels and start/stop the machines.

You haven't said what room mics you're using, but assuming they are balanced mics with XLRs you can run long mic cables back to the Tascam without any interference problems. All you need to be careful about is running the cables safely to avoid creating trip hazards.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby MOF » Sun Jul 07, 2019 4:44 pm

Wouldn't there be a natural delay between the close & room mic signals anyway caused by the placement?
Yes if you're clapping into a mic' on stage and the room mic's are many feet away and that was the point of my original reply, assuming I understand your original post, you can record ambience and applause on the other machine and not have to worry about any slight loss of synch.
If it has drifted you can just do a quick offset to taste, it won't have lost synch so badly that you have to work out where one machine is related to the other. If by some one in a million chance it has you just look at the two waveforms and see where the songs start/end to match them up again.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby MOF » Sun Jul 07, 2019 4:55 pm

Trying to mix it in stereo with the main inputs may be a problem.
I would convert it to mono and add ambience that way. But what do I know, I am just a hobbyist not a professional.
Don't do this, you want a sense of being there, mono atmos' won't do that, the hall sound will be sufficiently diffuse to not cause issues with phasing/flanging with respect to the stage sound, especially if there's a slight (pre) delay between them.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby tk76 » Sun Jul 07, 2019 5:06 pm

Hugh Robjohns wrote:Tascam adjacent to MixPre and connected with a short stereo unbalanced cable, but long mic cables into the Tascam.

Noted, with thanks!

For room mics I've got an Avantone CK40. Was thinking MS configuration.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby MOF » Sun Jul 07, 2019 5:50 pm

So I'd prefer not to have to fiddle around trying to sync such huge files in the DAW

It's really very easy, you zoom out on both files and align the shapes, which should be very similar, and then slip one to match to the same sound (first drum hit, guitar strum etc) and from there make sure you edit both files simultaneously.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Hugh Robjohns » Sun Jul 07, 2019 6:48 pm

MOF wrote:... you can record ambience and applause on the other machine and not have to worry about any slight loss of synch.

In terms of an absolute time offset, you're right -- it's not going to be particularly critical.

However, if the timing between the two recordings drifts significantly over relatively short periods -- and that really can and does happen in the situation being described -- then the resulting time-delay (comb-filtering) colouration will vary in an obvious and probably unpleasant and unacceptable way.

As I said before, you could get lucky and find the two machines both have very little short-term drift and very similar free-running click frequencies... And in that respect portable digital recorders are certainly much better today than they were in the 90s when the AES11 spec was drawn up.

But there are no guarantees... and even if two machines manage to stay well synchronised over an hour or two at one concert recording, there's still no guarantee they'll maintain that precision at another gig later.

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Bob Bickerton » Sun Jul 07, 2019 9:53 pm

tk76 wrote:The performance I'm recording is a 6 day non-stop kirtan festival in India;

So I’ve just had a look at what a ‘kirtan festival’ entails....... acoustic instruments - probably amplified. If this is the case have you had a conversation with the sound engineer about taking a split off the mixing desk for the MixPre? Is there always 8 mics being used on stage?

If it is unamplified, then we might be able to offer alternative solutions.

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Re: Mixing Separate Multitrack and Stereo Recordings

Postby Tim Gillett » Sun Jul 07, 2019 10:46 pm

Over the past 10 years or so, every time I recorded small live shows with my old Zoom H4 it drifted out of sync without fail. By 0.007% at 48 kHz. After time shrink of 0.007%, no drift. Always in sync over periods of 92 minutes at least, the maximum recording time of a mini DV video cassette.

I didn't arrive at the 0.007% error by guesswork. It was measured by one specific test of the H4 with a tone recorded over a period of about an hour. It measured slower than my Panny cameras by that amount.

In this live recording the unconnected H4 recorder is in the shot. The black AT mic is wired into the camera by a long lead but the musical balance was poor so I used the H4 capture.

https://youtu.be/TY3LoOOK01M
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby hobbyist » Mon Jul 08, 2019 12:33 am

MOF wrote:
Trying to mix it in stereo with the main inputs may be a problem.
I would convert it to mono and add ambience that way. But what do I know, I am just a hobbyist not a professional.
Don't do this, you want a sense of being there, mono atmos' won't do that, the hall sound will be sufficiently diffuse to not cause issues with phasing/flanging with respect to the stage sound, especially if there's a slight (pre) delay between them.

Thanks for the comment but do tell me more.

It seemed that it would be even harder to get a remote stereo mixed in with the 8 channels from the stage without other problems.

I envision the atmosphere recording mixed in at a low level or perhaps separately used during applause or similar times.

It is unclear if it is a small room, large theatre, or outdoors. But I do not yet see the problem with converting to mono to mix in any of those.

What did I miss?
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby MOF » Mon Jul 08, 2019 2:37 am

I do not yet see the problem with converting to mono to mix in any of those

Mono has less impact than stereo if you’re trying to convey a sense of space, just like adding surround sound atmos’ to a multi-track stage or sports mix is even better at giving an immersive experience.
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Re: Mixing Separate Multitrack and Stereo Recordings

Postby MOF » Mon Jul 08, 2019 3:02 am

It seemed that it would be even harder to get a remote stereo mixed in with the 8 channels from the stage without other problems.

You’re adding ‘wet’ stereo atmos’ to essentially a ‘dry’ multitrack mix, it’s no different to sending an aux feed from those tracks to a stereo reverb. Obviously the difference here is that you don’t just want reverb you also want crowd noise.

The time delay between the stage and the audience mic’s plus the random reflections in the room will prevent any phase related artefacts between early reflections and the stage sound, that’s why artificial reverb usually has a 20-30 milliseconds pre-delay to avoid confusion between wet and dry sounds and often a send eq rolling off the treble. Likewise directional audience mic’s face the crowd and not the stage/PA speakers when recording a real audience, you don’t want a clean sound of the speakers, just their diffuse room sound.
I hope that’s of some help.
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