PRELIMINARY
miniDSP Ltd, Hong Kong /
www.minidsp.com
/ Features and specifications subject to change without prior notice
35
4.10.5
Rear channel synthesis
The
Invert
button in the matrix mixers is useful in applications such as generating a difference signal for rear fill.
This must be done in the Routing tab, not the Mixer tab. This allows Dirac Live to correct the response of each
individual speaker (correcting the response of two speakers at the same time does not work well). The signal
flow is illustrated here overlaid on the signal flow diagram from Figure 5:
The basic strategy is as follows:
1.
Create L
–
R and R
–
L signals as shown in the routing matrix below.
2.
Add a delay of up to 20 ms to the rear channel outputs (experiment to see what sounds best to you)
3.
Add high pass and low pass filters to the rear channels to limit bandwidth (experiment to see what sounds
best).
However, there is some interaction with Dirac Live. When performing a Dirac Live calibration, Dirac Live will
attempt to compensate for the delays on the rear output channels. The high pass and low pass filters will also
make calibration more difficult. Therefore, you will need to follow this procedure each time you run a
calibration:
1.
Turn off high pass and low pass filters on the rear output channels.
2.
Zero the delays on the rear output channels.
3.
Run the Dirac Live calibration.
4.
Set the delay and filters on the rear output channels again. Experiment to find out what sounds best.