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Author Topic: Who Wants to Make $25...... OK Now $50 Seriously - Need Help  (Read 3349 times)

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Offline Todd R

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Re: Who Wants to Make $25...... OK Now $50 Seriously - Need Help
« Reply #15 on: June 27, 2018, 03:30:47 PM »
That is bizarre and fascinating. Which decks have you noticed this with?

The speed of sound changes with temperature and humidity.  So the speed of sound will be different in a club at the beginning of a show when people just walked in, vs later in the evening when people start to sweat and raise the temperature and humidity level. 

If you're mixing 2 pairs of audience mics in the same spot, the differences will mainly be due to clock drift between the two recorders.  But if you're mixing a video (speed of light) with audience mics, or a soundboard feed (close enough to the speed of light) with audience mics, you will have the issue of clock drift between the recorders and also the drifting speed of sound (which changes subtly) relative to the constant speed of light or electricity.  Short answer, the varying speed of sound will make the drift between sources change over time, beyond that from clock drift between recorders alone.
Mics: Microtech Gefell m20/m21 (nbob/pfa actives), Line Audio CM3, Church CA-11 cards
Preamp:  none <sniff>
Recorders:  Sound Devices MixPre-6, Sony PCM-M10, Zoom H4nPro

Offline ycoop

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Re: Who Wants to Make $25...... OK Now $50 Seriously - Need Help
« Reply #16 on: June 27, 2018, 03:34:21 PM »
That is bizarre and fascinating. Which decks have you noticed this with?

The speed of sound changes with temperature and humidity.  So the speed of sound will be different in a club at the beginning of a show when people just walked in, vs later in the evening when people start to sweat and raise the temperature and humidity level. 

If you're mixing 2 pairs of audience mics in the same spot, the differences will mainly be due to clock drift between the two recorders.  But if you're mixing a video (speed of light) with audience mics, or a soundboard feed (close enough to the speed of light) with audience mics, you will have the issue of clock drift between the recorders and also the drifting speed of sound (which changes subtly) relative to the constant speed of light or electricity.  Short answer, the varying speed of sound will make the drift between sources change over time, beyond that from clock drift between recorders alone.

Interesting!
Mics: Avantone CK-1s, AT853 c+o
Pres: CA9100
Recorders: DR-60d mkII, DR-2d

Offline morst

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Re: Who Wants to Make $25...... OK Now $50 Seriously - Need Help
« Reply #17 on: June 27, 2018, 11:33:21 PM »
Short answer, the varying speed of sound will make the drift between sources change over time, beyond that from clock drift between recorders alone.
Oh very good point.

My favorite handy widget for calculating stuff related to speed of sound is
https://www.apple.com/downloads/dashboard/calculate_convert/soundreference.html
Sound Reference (sorry windows and linux folks)

It shows that the speed of sound at
44 degrees F as 1100 f/s
72 degrees F as 1131 f/s
92 degrees F as 1153 f/s

 

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