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James Price[_6_] James Price[_6_] is offline
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Default Why don't these signals null?

On Friday, October 18, 2019 at 10:47:52 AM UTC-5, Tobiah wrote:
On 10/16/19 10:51 PM, James Price wrote:
Let's say I record a DI guitar part into a looper, then re-amp that
looped part and record the output twice to separate tracks in a DAW,
time-align them and invert the phase on one. I know the tracks won't
null, but I don't fully understand the why.


When you run the signal through an amp, through the air, into a microphone
you open yourself up to some variables that may change between passes. Were
you in the room during the recordings? Did you move at all, or breath with
a different pattern the second time? Was the ambient noise exactly the same
both times? The acoustic space that you sent the signals through will never
be the same during both passes. Even if you recorded the straight and inverted
tracks at the same time, you'd use two different mics that would collect altogether
different signals because of their mismatch, and necessarily different positions.


These were short (approx. 10 seconds), close-miked recordings, recorded
in two passes, back-to-back using the same mic, through the same cab and fed
a DI guitar via a sampled loop. The recordings were time-aligned perfectly at
the sample level.


What was the result anyway, if not null? Was it pretty quiet anyway?


The residual noise fluctuated somewhere between -30 to -50 dB.