Do IR Captures have a polarity?

Gamedojo

Gamedojo

Power User
I was experimenting micing the back of a cab and I figure I would ask.

I don't think there is a polarity, but wanted to be sure.
 
From a logic standpoint, it would make sense that they would. A sound wave has to start at some point, and why would two captures, from opposite sides of a speaker (at the same time), not behave in some manner like the real world, and have a canceling effect? Obviously I don't know the ins and outs of the IRs, so It'll be interesting to know the answer.
 
I should leave it to someone more knowledgable on the subject, but:

The speaker is moving in different directions relative to the front/back mics so I assume the front/back mics would be out of phase if you're shooting both front/back mics at the same time with the mics at the same distance from the speaker. The distance from speaker to mic could also produce phase issues with 2 mics in front at significantly different distances - creating a comb filtering effect (which can also be done with the delay in the cab block).

Axe IRs are Minimum Phase Aligned - which I think means that individual mic'd IRs should be in phase when mixed.

Please correct me if I'm wrong as I'm at the limits of my understanding and would like to learn more.
 
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Typically if the plan was to mix mics in traditional recording and you were recording the front & back of the cabinet simultaneously, you would flip the phase of the conventional back of the cab mic (Unless it was a PZM, in which case it would still be in phase).

When combining IR's, just as your mics to mix down to one track, I have a feeling the same phase cancellation concerns would be in effect.

In that case, I would try flipping the phase and combining the resulting IR's. If the sound does not hollow out, you are on the correct path.
 
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