Topic: Is there an inherent phase relationship between Soundboard and Audience sources?

[Roving Sign]

From the point of view of mixing SBD and AUD sources in post...?

[easy jim]

In short: no.

When post-mixing, it should not matter so much either once you align the sources.  If, however, you align them perfectly and the .wav is above the zero line for one source and below it for the other (like mirror images), then flip the phase on one of the sources.

[terrapinj]

In short: no.

When post-mixing, it should not matter so much either once you align the sources.  If, however, you align them perfectly and the .wav is above the zero line for one source and below it for the other (like mirror images), then flip the phase on one of the sources.

it would be pretty audible if its out of phase correct?

[imgoinmad]

if you have a mono button on your audio device, it will be very obvious because switching from stereo to mono, you'll hear sound disappear if it has phase issues. the worse the problem, the more disappears. A 100% out of phase problem would make 100% of the sound disappear.

[JasonR]

Mixing the sources is more about time alignment.  However, if your microphone preamp happens to be reversed phase due to a design oversight (as was the case with some Lunatecs for a while), you may find that the best time alignment results in an inverse phase relationship between the two sources.  Flip one and you'll get better results in that case.  I don't claim to be able to hear absolute phase, but when combining with other channels, consistent phase can become important.

- Jason

[easy jim]

In short: no.

When post-mixing, it should not matter so much either once you align the sources.  If, however, you align them perfectly and the .wav is above the zero line for one source and below it for the other (like mirror images), then flip the phase on one of the sources.

it would be pretty audible if its out of phase correct?

Yes.  It is generally more apparent in the low end where phase cancellation/comb filtering tends to stand out more.  Most often, it is an obvious lack of bass/low end that is the tip off.  When post-mixing, though, it is easier to identify graphically whether the two sources are out of phase.

Mixing the sources is more about time alignment.  However, if your microphone preamp happens to be reversed phase due to a design oversight (as was the case with some Lunatecs for a while), you may find that the best time alignment results in an inverse phase relationship between the two sources.  Flip one and you'll get better results in that case.  I don't claim to be able to hear absolute phase, but when combining with other channels, consistent phase can become important.

- Jason

Similarly, there is an exception vis-a-vis SBD feeds I recently came across: some SBDs have pin 3 hot outputs on their XLR outs (generally a portion of older consoles from the 80s and earlier).  Since our recorders/pre-amps conform to the now standard pin 2 hot set-up, a SBD source from a console with pin 3 hot XLR outputs will be inherently out of phase with any AUD source when captured on a recorder configured to expect a pin 2 hot line feed over the XLR inputs.  

[bhakti]

also not sure if i'm right in saying this, but if you're recording on two seperate devices [for example something recording off the desk and you somewhere else out in the audience with another recording unit] the sample rates might not be 100%. i had that problem when recording preston reed... got a desk feed straight into a computer and was in the audience with my mics and later in post, the speed of the recordings were very different... some recorders are at exactly 44.100Hz, and others might be at 44.097 or 44.103 for example... am I right in saying this?

[Roving Sign]

also not sure if i'm right in saying this, but if you're recording on two seperate devices [for example something recording off the desk and you somewhere else out in the audience with another recording unit] the sample rates might not be 100%. i had that problem when recording preston reed... got a desk feed straight into a computer and was in the audience with my mics and later in post, the speed of the recordings were very different... some recorders are at exactly 44.100Hz, and others might be at 44.097 or 44.103 for example... am I right in saying this?

You are correct - but that is a separate issue. For the sake of this argument, lets assume the sources all created with the same clock frequency and will time align properly.