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Delay


Tim M

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Does anyone has problems with delay...and I don't mean the FX version. I'm wondering why on the Sound Devices 744T anyone would need to necessarily delay the inputs. Of course there could be the very rare occurrence. But by the time you even notice a delay wreaking havoc on something isn't it too late? I'm assuming delay in the process does occasionally occur...but at what points have you found it to interfere. I can only imagine how long correcting a delay problem onset a run and gun style deal could take..."waiting on sound"

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One foot of acoustic travel is roughly one millisecond. Flanging starts to occur around 10 milliseconds.

Of course it depends on the relative volumes and whether all the distances are to remain fixed or will be moving, but there are definitely times when delay compensation can improve the sound.

Not to mention (since Soundguy already did) that any digital processing or even DAC/ADC conversion will introduce noticeable delays.

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One use:

If you are mixing analog and digital wireless systems on the same project, the delay adjustment allows you to compensate by delaying the analog wireless to the same delay (or really close to it) that the digital systems impart. It's usually on the order of only a few milliseconds.

Can someone please explain how a person would calculate the appropriate amount of delay compensation? My assumption is that there are many variables, however the conceptual path to calculation could be addressed.

This is something I have also noticed in the 744t, and in the past I have performed post production on other people's projects and had to sync sound files to the waveform to remove the delay. Being able to fix this in the field for post would be amazing. But again, how do you calculate it?

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Can someone please explain how a person would calculate the appropriate amount of delay compensation? My assumption is that there are many variables, however the conceptual path to calculation could be addressed.

This is something I have also noticed in the 744t, and in the past I have performed post production on other people's projects and had to sync sound files to the waveform to remove the delay. Being able to fix this in the field for post would be amazing. But again, how do you calculate it?

One way is that most manufacturers publish figures on how much delay their systems introduce. If you can't find it, ask, and they'll tell you.

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One way is that most manufacturers publish figures on how much delay their systems introduce. If you can't find it, ask, and they'll tell you.

Oh man, I made it much more complicated in my head by mistake. I was thinking of having to roughly calculate it somehow based on... Well, I didn't know...

Haahaha. Can't win 'em all.

So back on track, conceptually, you would look up piece of wireless equipment's delay stated in the manual or by contacting the manufacturer, and then apply that delay appropriately to the correct channel. Then use your ears and if everything sounds great you're gold.

I'm wondering how often people on this forum actually use this feature, and if not, are we missing a great opportunity...

I have never used it yet, but now I am motivated to try!

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if you have a post audio editing system (pro tools, etc) you can easily make some test recordings that will at least get you pretty close. I can't think of a digital wireless manufacturer that doesn't post or know what amount of delay their system contains.

Above all, trust your ears. I for one, much prefer to time align digital, analog wireless and analog mics. And as a post engineer, I would much prefer for this to be done at the mixer/recorder.

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I think this goes along with big EQ decisions and trying to guess which camera they might use, so whether to mix a lav in or not or how much. You're not going to guess right every time.

From a narrative standpoint, I feel that these sort of issues are best left to post. We might not get a rehearsal, or the action might change, so to guess on delay seems foolish (unless it's a fixed and guaranteed value). The post folks can just as easily dial in a delay and do a quick remix from the ISO on those rare occasions it matters.

On set, we might only get one crack at it, I wouldn't want to be experimenting with delays in a production environment.

Robert

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Robert, see now that is exactly how I was thinking, dialing in delay based on distance seems like a very dangerous act when microphones no matter how stationary always seem to move, whereas in like a line-array system things of that nature can be calculated out with very good precision. I would rather not dial in a delay on a channel and then forget to dial it back out on the closeup they just decided to throw in last minute. When it comes to a steady delay like what John was saying with the differences between digital and analog systems that makes a lot more sense...and is essentially the answer I was seeking...so in that regards thanks!

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If you have an acoustical delay, you need to be able to compensate. Sure, they can fix it in post, but what about all the bleed between mics? how are you going to properly monitor?

Without setting your delays, you cant.

It's really not that hard, it's division.

This is the difference between a guy that does sound and a sound engineer.

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Yes, that makes sense in a concert venue, but I'm still not seeing a film application. Why delay the boom guy who is standing more than 35 feet away when you won't be counting on using his feed anyway. If I remember correctly it takes a delay of like 35ms before delay becomes apparent to the human ear. As in your example the guy in the back of the room, I first of all think that version of the take would most likely not be used but could be a great reference for the post guy to recreate it, and then you would have to have it be an accurate non-delayed signal for it to be a good reference for the post guy. I think perspective wise it wouldn't make sense if you were doing a majorly wide shot and the input be delayed, because then his mouth would move but you would hear the sound after because you matched it with the boom in the back of the room. If you did the opposite approach then it would still mess with perspective because there wouldn't be that slight natural delay. I don't know...I guess all I'm saying is I probably wouldn't mess with it and frankly it wouldn't mess with my ears either. I guess the best option is if you have time to call post haha!!

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It's interesting what ones brain can do with processing sound. With headphones on a delay of only a couple of milliseconds in one ear with identical material to both ears will make the other ear sound around 5-8 db louder. Somehow the brain focuses on the leading sound and you'll swear its significantly louder when it isn't!

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Can someone please explain how a person would calculate the appropriate amount of delay compensation?

The only time I can see where it might be used for location sound would be if you had a mixture of wired and wireless mikes being mixed to mono, and you were concerned about phase delays. I believe both Lectro and Zaxcom digital wireless systems add a total of about 3ms of delay (entire chain from microphone to receiver), so if you wanted to dot the "i's" and cross the "t's", that would be the right way to do it. This info is available on the manufacturers' websites and in the manuals.

In post, I would occasionally deal with syncing dailies where I could see they had a wired boom on 1 and a wireless on 2, and we could easily see the phase shift on the latter channel. If I was concerned about how it was being heard, I'd drop in 3ms of delay myself just for dailies, knowing that the dialog editors would figure this out later on in conforming from the master files. 90% of the time, we only dealt with a mono mix, so it wasn't a big deal.

35ms would be a huge delay, relatively speaking, equal to 1 film frame. 3ms is maybe a 6-foot difference (if that) in terms of placement. Not gigantic. We often had to deal with a 165ms delay (5 film frames) because of doing HD dailies with a simultaneous standard-def downconversion, which is not done anymore. I think it's fine to do it on location, provided you're not in a situation where you're constantly swapping inputs or changing wireless to wired booms; only the hard-wired mike(s) need be changed.

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I mixed digital and analog radios in my bag ONE time. Was a zaxcom studio rx. It definitely was not was I was expecting. It did not feel right living there along with my lectrosonics.

I didn't end up hanging on to that set, even though it was a great kit. Adjusting delay might have helped me get over the feeling.

Is anyone using digital and analog radios in the same bag? Or is it a situation where you really just use one or the other.

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" please explain how a person would calculate the appropriate amount of delay compensation? "

simple, basic arithmetic:

" most manufacturers publish figures on how much delay their systems introduce "

" One foot of acoustic travel is roughly one millisecond. "

" If I remember correctly it takes a delay of like 35ms before delay becomes apparent to the human ear. "

refresh your memory...

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" in order to be a good mixer, you need to know "

while we do have a discussion thread concerning things we all "need to know",

it really isn't quite so black and white...

" I guess I'm a bad mixer. "

it certainly isn't just "good or bad", maybe some mixers are a little more versatile ?? ::)

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