How do you reverse the polarity of a track in GB?

Question

Level 1

41 points

How do you reverse the polarity of a track in GB?

I use GarageBand to mix multi-channel audio (while listening to a stereo mix) then export it to A.Pack or SurCode for the final 5.1 mix to disc. I have a less than one year old Pioneer 7.1 receiver and 5 polk audio speakers from my attempted home theater that i now occasionally use to watch DVDs on my mac (using the optical audio). I was wondering if i would be able to set the tracks to certain balances (i.e. FL -127 C+0 FR+127) to output a form of Dolby pro logic to my reciver to simulate a final mix, but to get a rear channel in the mix, i would need to make one of my rear tracks' polarity reversed. Is there a plug-in to do this, or any other suggestions?

Mac Mini Intel 1.83Ghz; PowerBook G4 1.0Ghz, Mac OS X (10.4.8), 500GB Seagate, Lacie Lightscribe, Pioneer 7.1VSX-526, Polk Audio RM6005, iPod Nano

Posted on Dec 2, 2006 10:20 PM

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Answer 1

Dec 3, 2006 12:54 AM in response to johnny_jared

A quick trawl in Google didn't throw up any Audio Units which would reverse the phase, but possibly if you did a more exhaustive search you might find one. This would be the easier answer.

Otherwise you could do it by getting 'Amadeus II' from
http://www.hairersoft.com
This costs $30.

To do this: choose the tracks you want to be on the rear channel. Centre them with the pan control and mute all the others. Export to iTunes. drag the resultant file to the dekstop and open it in Amadeus. Select one channel only.
From the 'Effects' menu choose 'Stereo Utilities' then 'Invert Phase'. Save, and then drag the file back into GarageBand. You can now mute or delete the tracks which made up this rear channel.

Strictly, to be a proper Dolby ProLogic track the rear channel should be Dolby B encoded: it might be worth turning up the top a bit to allow for this.

Remember that in playback on a ProLogic decoder the rear channel is filtered below 100Hz and above 7kHz (it is only intended as an effects channel).

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Answer 2

Schneb

Level 5

4,957 points

Dec 5, 2006 2:18 PM in response to Roger Wilmut1

I recommend Amadeus as well, however, go for AmadeusPro instead of the earlier version.

http://www.hairersoft.com/AmadeusPro/AmadeusPro.html

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Answer 3

johnny_jared Author

Level 1

41 points

Dec 12, 2006 11:34 PM in response to johnny_jared

i want to monitor the audio while i mix it in GB, i have something called the SFX Machine Pro as a plug in (i do not know where it came from), and it does have a inverse polarity for the selected track. thanks for your help

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Answer 4

Dec 13, 2006 4:10 AM in response to johnny_jared

i want to monitor the audio while i mix it in GB, i
have something called the SFX Machine Pro as a plug
in (i do not know where it came from), and it does
have a inverse polarity for the selected track.
thanks for your help

It's available at:
http://www.sfxmachine.com/
and costs $75 for the basic version and $150 for the Pro version. The basic version is good value for money, with a lot of effects: I haven't tried the Pro version. It comes as both AU and VST.

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