Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Cinema / Discrete / 10dB - definitive answers required!

Ok, here's what I think is going on... (subject to improvement over time!)

At the mixing desk:

1a) The sub is calibrated for a flat response with the other speakers given the same input level.

2a) For movies, the LFE channel is calibrated for a +10dB response vs. the other speakers.

3a) For movies, the soundtrack will actually be recorded at -10dB vs. the other channels for the same SPL.

4a) in their "5.1-Channel Music Production Guidelines", Dolby says:

As discussed in Section 2.2, bass content can easily overload a recording system. This is the historical reason for the creation of the LFE channel and the practice of recording to tape 10 dB below reference level and boosting the playback 10 dB to achieve a flat response. In this way, plenty of bass can be included in the recording without causing tape saturation or distortion.

Because lower frequencies require more energy than higher frequencies to be perceived as the same level of loudness, recording energy-sapping deep bass on a separate track at a lower level to allow for a wider dynamic range is still good practice. For these reasons, plus the added bonus of legacy cinematic recording playback compatibility (both in the studio and the home), the +10 dB practice is still recommended.

This implies that the LFE channel for music should also recorded at -10dB.

At home:

1b) The sub is calibrated for a flat response with the other speakers giving the same input level.

2b) For movies, the LFE channel must actually be played back at +10dB to sound the same as when it was mixed. As this corresponds to a net 0dB gain (recorded at -10dB, played back at +10dB), it is correct for the "Cinema" DSP preset to display "0dB".

3b) Given (4a), for music the LFE channel must also be played back at +10dB. Assuming that multi-channel "music" soundtracks are always decoded in the DVDA/SACD player, this means that the DVD player must add 10dB to the LFE channel on decoding.

Cinema
The Cinema preset is recommended for listening to multichannel
movie soundtracks when no further processing is required.

Discrete
The Discrete preset is similar to Cinema, except that it uses the
Music speaker layout and sets the LFE level to -10dB.

In summary, I reckon that "Cinema" boosts the input LFE signal by 10dB (displaying the LFE level as 0dB), and "Discrete" does *nothing* to the LFE signal (displaying the LFE level as 0dB). What this means is that "Discrete" should not be used with a DD/DTS soundtrack decoded in the processor without the risk of losing 10dB of LFE. In other words, "Discrete" should only be used with multi-channel PCM, MHR or analogue inputs.