Support and General Use > Recording
inverted phases on iaudio x5
saratoga:
--- Quote from: Chronon on July 19, 2008, 07:59:15 PM ---petur: that's fair. But this should be easy to check. Set the output in Rockbox to a mono setting. Then put two speakers facing each other and if cancel each other out
--- End quote ---
They'll still cancel each other out if they're phase inverted or not, only the location of the regions where constructive and destructive adding occurs will change.
Just record the same tone in both channels and look at it in an audio editor. Should be pretty obvious if the phase is inverted in only one channel.
Chronon:
Have you carried out this experiment? There's a stark difference between two in-phase sources and two sources with a phase difference of pi. For two speakers that are close to each other the superposed waves will exhibit constructive interference almost everywhere for in-phase waves. If you switch the polarity on one speaker then the situation changes and you will get destructive interference almost everywhere. This works well enough that everyone in an auditorium will hear the expected change in volume when you switch the polarity of one speaker.
Good point about using an audio editor to compare the two channels. That seems like the best approach -- and makes the above paragraph of only academic interest.
saratoga:
--- Quote from: Chronon on July 20, 2008, 12:39:07 AM ---Have you carried out this experiment?
--- End quote ---
Every day. I build interferometers as my day job.
(far field diffraction pattern of two sources is the inverse fourier transform of a pair of delta functions, and thus cosine if they're in phase and a sin if they're out of phase.)
--- Quote from: Chronon on July 20, 2008, 12:39:07 AM --- For two speakers that are close to each other the superposed waves will exhibit constructive interference almost everywhere for in-phase waves. If you switch the polarity on one speaker then the situation changes and you will get destructive interference almost everywhere. This works well enough that everyone in an auditorium will hear the expected change in volume when you switch the polarity of one speaker.
--- End quote ---
This would work much better then putting them facing each other. in this case all you have to do is step onto the optical axis (e.g. the origin) and see if its quiet (sin) or not (cos). I agree that its still easier to do it digitally though, you'd probably have a lot of trouble with reflections off the walls of your room unless you've got a very large space to try this in.
z-man:
--- Quote from: saratoga on July 20, 2008, 12:01:12 AM ---Just record the same tone in both channels and look at it in an audio editor. Should be pretty obvious if the phase is inverted in only one channel.
--- End quote ---
Did it. _BOTH_ channels appear to be inverted.
saratoga:
--- Quote from: z-man on July 20, 2008, 06:52:04 AM ---
--- Quote from: saratoga on July 20, 2008, 12:01:12 AM ---Just record the same tone in both channels and look at it in an audio editor. Should be pretty obvious if the phase is inverted in only one channel.
--- End quote ---
Did it. _BOTH_ channels appear to be inverted.
--- End quote ---
And you're certain they're not both non-inverted? I guess you checked a less symmetric signal then a sin wave.
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