Setup guide

Dirac Theater Setup Guide Version 1.01
Document # 9301H40300V1.01
5
• Set the Fader to 7.0, which is the standard reference level.
• On the laptop with the Dirac Live proxy software, run Pink Noise on the first channel.
• Using the calibrated SPL meter in the auditorium, adjust the gain of the amplifiers to produce
a nominal 85dB level.
• Repeat for each channel.
2. Dirac optimization
2.1. Microphone placement – a discussion
Cinema room tuning is traditionally done using a four-microphone multiplexer system in which four mics
are placed in fixed locations in the theater, then audio samples are taken at each mic. From the samples
an average is calculated for the channel, and the technician can then make corrections to that channel’s
third octave settings. Dirac Live
®
is different, using a single mic to record audio from multiple locations
in the auditorium. The Dirac Live
®
software then produces coefficients from the combined audio samples
for the various channels, which are in turn used to build an audio profile for the room.
In large venues such as cinema auditoriums, multiple measurement positions are needed to cover the
listening region; typically 9 to 18 different measurement positions are used.
(Recommended) Locate an AC outlet for possible use if your laptop will require AC
power during the setup.
1. Put the microphone at a typical listening position with the microphone capsule pointing vertically
towards the ceiling. Make sure that it is silent and that no obstacle is placed between the
microphone and any loudspeaker.
2. Click on the Take new measurement button in the Dirac Live
®
screen. A test signal is now
played back on each of the loudspeakers.
Do not move the microphone during a measurement!
Do not change playback or recording levels during the output of a test sequence! If needed,
adjust the levels when the test sequence is shut off.
If the software reports that the recording level for a particular speaker is too low, then increase the
playback level and/or recording level and redo that recording.
If the software reports that the recording level for a particular speaker is too high, the reason can be
that there was a temporary disturbance during the recording (such as the sound of a door closing, or
the sound of a loud vehicle passing nearby). Then just redo the recording. If the problem persists, try
lowering the output level on the AP20 or lower the microphone level on the soundcard.
After a successful recording, the PC software synchronizes the recorded data to ensure that sampling
discrepancies in playback and recording devices are eliminated. This process may take a while. Then,
impulse and frequency responses are computed. It is possible to view the magnitude response of the
most recent measurement by clicking the button View last measurement.
3. When the recordings are done for all speakers, move the microphone to a new position and make
a new recording in that position.
4. When at least 9 recordings have been made, you can move on to the Optimization step, but in a
large venue such as a cinema theater you should normally use 18 measurement positions before
starting Optimization.