From: BlueChip <cs_bluechip_at_webtribe.net>
Date: Sat, 04 Jun 2005 17:29:39 +0100

> 1. Is is true that phase matters?

Yes - very - especially in-car where it is REEAALLYY obvious.

> 2. Is there a way to reverse the phase of one channel of an MP3 file
> so you can determine the correct phase by listening to the sound
> while playing the original and reversed versions?

Yes, the Audio_3587 plugin does this with the Phase Control (+/-) button on
the Custom Stereo screen
http://homepage.ntlworld.com/cyborgsystems/Rockbox

> 3. Or maybe there's an easier way to find out the phase of a set of
> speakers?

Get a THX setup disk - Moulin Rouge; Tron R-1 Collectors Edition; Evil Dead
Box set; Indiana Jones box set; etc. etc. and follow the instructions.

Or make your own:
# Create some mono "white noise" with goldwave/cooledit/whatever
# copy this mono sound to both sides of a stereo track
...so you have an effective stereo recording of a mono sound
# Play the sound

If the speakers are IN-PHASE the noise will appear to come from somewhere
between the speakers.
If the speakers are OUT-OF-PHASE, the noise will have no discernable source
point - aka "dispersed"

If you wish to make an OUT OF PHASE recording, just flip the Right Channel
(or left if you prefer) waveform upside down, so when you zoom in with
cooledit or whatever, the two waveforms appear to mirror each other.

>>Play a mono sound, and put the speakers facing eachother. The sound
>>will cancel out (become lower volume) if the speakers are out-of-phase,
>>and louder when the speakers are in phase.

Will damage the speakers.

However, for new speakers, you can wire them OUT of phase and point them at
each other and "run in" the new coils. but NEVER IN-PHASE

BC

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Received on 2005-06-04