5.1 surround mix plays back lower than stereo

Hey all,

I'm authoring a DVD for my friend's short film (45 mins.) and his sound designer gave me a stereo file (two AIFFs) and a surround mix (6 AIFFs). I synced them up in FCP with the final video and exported the audio to Compressor and used presets to make ac3 files. The 5.1 mix is apparently playing back somewhat lower in volume than the stereo mix, even lower than what the filmmakers heard when they mixed the final sound (I can't monitor 5.1 on my computer so I could not tell).

Is this a common issue with 5.1 mixes in DVDSP? Or perhaps my Compressor settings are to blame?

Presets used:
Stereo - Dolby 2.0 192kbps (in DVD: Best Quality 90 minutes)
Surround - Dolby Professional 5.1 448 kbps (in Formats>Audio)

OSX 10.5.8, FCS 3

TIA,
JVK

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SCQT! Self-contained QuickTime ? pass it on!

A lot would depend on how the sound mixer did the stereo fold down.
Is it an LtRt or a LoRo?
Did they use a dolby encoder to do the fold down?
If done correctly there is a reduction in the center and surround channels during the fold down to compensate for the summing affect. If this wasn't done then the stereo mix will sound louder.