Originally Posted by BeeMan458
I distinctly recall stating THX reference (standards), not DD or DTS with any mention of CODEC's.
If the boss (THX) says up to 120Hz,...
THX??? What makes you think THX is the "boss" of the LPF of LFE? THX neither specifies the inclusion of an LPF of LFE, nor do they make a recommendation on the setting. The only LPF THX specifies is the LPF of the subwoofer crossover, where they specify an 80 Hz crossover frequency, a 4th order roll-off on the LPF of the subwoofer, as well as a 2nd order roll off on the HPF of the speakers. Nonetheless, these have nothing to do with the LPF of LFE, or with THX.
The LPF of LFE is a Dolby
requirement, not a THX requirement. Dolby started requiring a LPF of LFE in their decoders when they stopped brickwall filtering of the LFE channel at 120 Hz on encoding. That happened when Dolby introduced TrueHD and the other lossless codecs. The LFE channel became a full range, 3 Hz to 20 kHz, channel. Since it was no longer filtered on encoding/recording, the filtering had to be instituted on decoding/playback. The playback filter is not a brickwall filter, so a lower setting can be more effective. Take a look at this graph:
(originally posted by Roger Dressler)
There is significantly more higher frequency energy above 120 Hz allowed to pass by a 120 Hz LPF than an 80 Hz LPF. Nonetheless, this has NOTHING
to do with THX.
Originally Posted by BeeMan458
...what do I care and it sounds like those who LPF their subs at 80Hz are being ego bound (stubborn) as opposed to being flexible as 80Hz or 120Hz, what does it matter if the LFE channel (the subwoofer) is set to 120Hz? Sounds more like Rodger is digging in his heels to support his "personal" thesis as opposed to trying to get along with THX reference standards.
Roger Dressler's "personal thesis"??? Do you mean THIS Roger Dressler who:
"Helped Dolby launch its first Dolby Surround technology, and every one since, including Pro Logic, Surround EX, PLII, PLIIx, Dolby Digital, DD+, Meridian Lossless, TrueHD."
Roger Dressler's "personal thesis" would have been developed in his position as the Director of Technology Strategy for Dolby Labs for 26 years, (now retired), http://www.linkedin.com/pub/roger-dressler/b/879/336
If you mean THAT Roger Dressler, then yeah, I'll accept his "personal thesis" that the LPF of LFE should be set to 80 Hz. I've been doing that in my system for a long time.
Then there is what Mark Seaton had to say:
I think many have a gross misconception as to the real difference between a 120Hz vs. 80Hz low pass. Personally I always have found I prefer an 80Hz setting. This isn't the difference of having a low pass or not having one. This is just setting the filter lower. If instead we look at the difference between a 120Hz vs. 80Hz low pass, we see it is in fact a shelf filter. Assuming a 4th order filter, moving to 80Hz has no real effect below 40Hz, reduces the 80Hz level by ~4dB, 100Hz by ~7dB, 120Hz by ~9dB and ultimately reaches -14dB somewhere above 200Hz. If the low pass filter is 2nd order, cut those differences in half.
If you have your subwoofers rising to say 3-6dB above the main speakers, the lower crossover point would have the 80-100Hz range pretty much in line with a flat calibration and a smooth rise below there, which many like the sound of.
In addition, FilmMixer, (Mark Fischman) http://www.imdb.com/name/nm0279892/
has stated that he always filters the LFE channel at 80 Hz, as do many other recording engineers. I can't find that quote right now, but you can ask him.... he's a member of the forum.
So... there ^^^ you have 3 real experts recommending an 80 Hz LPF of LFE, and THX, making NO recommendation whatsoever.
Edit: While I was looking for the above quotes, I see that you were also looking. You found the localization issue, and that is good information. The graph I posted above shows why it is important to reduce the content above 80 - 120 Hz to reduce localization. In addition, realize that any info above 80 Hz in the LFE channel will also be replicated in the main channels. Playing it back through BOTH the speakers and sub(s) will accentuate that content and make it sound overly prominent, and boomy, muddy or inarticulate.