Originally Posted by Drew Eckhardt
My Lexicon THX-preamp doesn't do that, and doing so at least violates Dolby's recomendations.
To answer another post, loudness plus isn't going to be an issue either. By the time you get to 100dB the equal loudness curve is flat like a ruler and no boost is needed. You only need to bring up the lower frequencies at reduced listening levels. Like Lexicon's loudness function circa 1994.
Why do THX unit owners make up rules about THX units conforming to Dolby recommendations? They do not seem to understand that THX units conform to THX specifications. THX specifications may vary from time to time, so maybe your Lexicon unit does not apply that extra 4 dB of DD gain. Then again, maybe your Lexicon does have this extra 4 dB of gain (as in the Lexicon MC-12).
Some discussion here (last update in 2001, so this is not a recent THX development):http://www.smr-home-theatre.org/optimode/page4.html
"In an effort to standardise the output levels of both Dolby Digital and DTS, some THX receiver and controller manufacturers (Denon being one example) are introducing a global 4dB gain to their Dolby Digital decoders, perhaps under instruction from the THX department of LucasFilm. This directly counters the 'standard' -4dB Dolby Digital dialog normalization bit and results in matched output volume levels between Dolby Digital and DTS source material. As manufacturers can reduce their internal calibration noise (against reference) by the same amount, output levels remain at the correct level unless the Dolby Digital signal carries a -0dB dialog normalization bit, in which case the outputs will have an artificial gain of 4dB."
If you own a Lexicon MC-12, then you should read your instruction manual again. The Lexicon MC-12 bases DD volume on DD source material that has a Dialnorm value of -27, not the Dolby -31 value. This is called THX reference level by THX.
The MC-12 dialog offset reads +4dB when a DD DVD encoded with a dialnorm value of -31 is used. That means that the Lexicon MC-12 will play back at the 4 dB higher level than it would have if it used the Dolby standard.
From the manual:
DIALOG OFFSET -27 to +4dB
Indicates the dialog normalization value applied to the input signal.
Dolby Digital input sources reproduce dialog at 27 decibels below
full-scale (-27dBFS). When the dialog normalization value of the
incoming signal is higher or lower, the DIALOG OFFSET parameter
indicates the amount of adjustment the MC-12HD makes to
normalize dialog to -27dBFS.
I can give you a list of DD DVD's and dialnorm values if you want to test this on your system. In a typical THX system, DTS and DD (DN -27) playback at the same volume levels. In a non-THX system, DTS and DD (DN -31) playback at the same volume levels. Perhaps THX units are not consistent, but that means you have to test your THX unit to see what how it handles "reference level".
It does not matter much unless you are comparing a THX unit with a non-THX unit, or if you insist that there is such a thing as "reference level" playback. Would that be THX reference level, Dolby reference level, or DTS reference level?