Front-Rear Pan Law not being obeyed?

I’m mixing a 7.1 (side surround ie what Nuendo calls “Music”) project and something is off with the front-to-rear pan law. I currently don’t have my surround speakers set up as I’m doing the stereo mix first, so I’m monitoring off a stereo downmix bus with the Mixconvert 6.0 plugin that is inserted in the panner by default. (The bus is 7.1 input to 2.0 output).

My left/right pan law obeys the project setting (equal power) so moving objects left to right results in consistent volume across the stereo sound stage as expected. However, when i place a sound midway between say front/side or side/rear I am getting a 3dB level bump compared to if it’s only in the fronts, or sides, or rears. Positioning a sound at a single speaker or midway left-right between a pair of speakers gives me the correct level. So left-right pan law is ok, but front-rear seems to be using a 0dB pan law so the sound gets louder when panned to a position between the speakers.
Moving a sound from surrounds to fronts over time thus causes inconsistent volume changes which is unacceptable, and not what I’m used to in Pro Tools. Doesn’t matter what downmix levels I set for surrounds in mixconvert (0dB, -3dB, -6dB) I still get the level increase when in a midway position.

Any ideas?

(After setting up my surround speakers I will test whether this is occurring in the 7.1 soundfield or in the MixConvert Plugin)

Unless I am terrebly mistaling, Pan law does not come into play in Surround Mixing.

Make sure you set the Mixconvert values correctly.
For smooth front/rear panning, the sides and rears must be set to -3dB.

And it also depends if you are mixing for theatre or for DVD/TV.
Theatre has the rears set @ -3dB (85dB front, 82dB side and rears), while for DVD or TV, the rears are equaly calibrated to the fronts. 79dB for all speakers.


If you leave aside the 82/85 difference for cinema speakers I always thought that the general rule with pan laws was: power in = power out, so
something equally split to two speaker = -3dB in each speaker
something equally split to four speakers = -6dB in each speaker
and so on.

On Cubase which is in front of me now that is what happens:
If I make a quad group and send tone at 0dB to one speaker I get 0dB in that speaker
Pan to midway between front L and front R of that quad group I get -3dB in each
Pan to midway between front L and rear L of that quad group I get -3dB in each
Pan to the middle of all four speakers in that quad group and I get -6dB in each

With 6 channel outputs (e.g. 6.0 cine) equal levels in all channels gives me -7.8dB in each, which is still equal power.