Because of the variety of cinema processors in use, there are a number of things to consider when making RT60 measurements.
win|RTA uses the approach for measuring RT60 specified in ISO 3382. There are some differences due to the unique environment in cinema, but essentially
the pink noise signal is turned on, then gated off, and the decay measured.
Check the level for each channel to make sure it is at reference level, 85 dBC for the screen channels and 82 dBC (in most cases) for surrounds.
Also look at the frequency response to make sure it is generally OK. It doesn't have to be precisely tuned, but shouldn't have any major problems.
With all channels on at reference level, the SPL in the room should be 95-97 dBC.
Turn off HVAC if possible. This will allow the signal to be measured longer as it decays.
There are a number of options for gating the noise.
If you have a Dolby CP500 or CP650 (and some older Dolby processors), the noise gating feature can be used. By connecting pins 7 & 12 to the relay on the
D2 Controller, the D2 can control the cinema processor pink noise. This feature was removed as of the CP750.
Many USL cinema processors will allow the D2 to trigger the pink noise, but the action is reversed. The pink noise is on with the relay energized,
and off when the relay is open. The feature of reversing the relay action was included in win|RTA as of V2.2.
QSC processors have mic and line inputs that can accept the D2 pink noise. In this case, win|RTA turns the D2 pink noise on and off at the appropriate times.
If the cinema processor has 6-channel inputs, these can be used, but a distribution amp will probably be needed to feed all the inputs.
When connecting to the Dolby CP850, the optional AC3 encoder can be used to input pink noise.
Once the setup is done, click GO, and the test will automatically run.