User manual

miniDSP Ltd, Hong Kong / www.minidsp.com / Features and speci fications subject to change wi thout pri or noti ce 45
If, on the other hand, the DDRC-88A is to be “aware” of the need for LFE alignment gain, then choose the 5.1
Speaker System or 7.1 Speaker System configuration. In this case, Dirac Live will calibrate for 10 dB higher
acoustic output on the subwoofer channel by adjusting its internal trim on the subwoofer channel. This does not
necessarily mean that the DDRC-88A will apply 10 dB of gain to its subwoofer channel – that is determined by
the calibration process.
6.4.2 LFE effect on gain structure
In the gain structure optimization procedure on page 42, we recommend that for the 5.1 Speaker System or 7.1
Speaker System configurations, the target level of the subwoofer be set 6 dB higher (*1) than the speaker
channels. This will push the bulk of the 10 dB LFE alignment gain into the subwoofer amplifier, which will in turn
result in an input-output gain on the DDRC-88A subwoofer channel of about unity. (Assuming the input
sensitivity is the same as the output gain setting.)
Purely in terms of gain structure, this is better than applying the extra gain in the source equipment. This is
illustrated in Figure 6.4 below. At the top, with 10 dB of gain applied in the source/processor, the subwoofer
signal is 10 dB higher than the speaker signal at the DDRC-88A inputs and outputs. At the bottom, with the 10 dB
extra gain applied in the subwoofer amplifier, we still have the required 10 dB greater subwoofer output, but
the subwoofer signal at the DDRC-88A inputs and outputs is aligned with the level on the speaker channels.
Figure 6.4. Illustrating signal levels depending on where LFE alignment gain is applied
(*1. The suggested 6 dB higher target level is only an approximation—the resulting input-output gain of the
subwoofer channel depends on the bandwidth of the subwoofer and its measured in-room response. A more
precise setting would require measuring the electrical output of the DDRC-88A after calibration, but this is
unlikely to be necessary nor it is something that can be covered in this manual.)