What the content on an LFE channel ought to be is bandwidth limited. Unless I am told differently - in writing - I will always, always add an 80Hz LPF at a 48dB/Octave slope to all LFE channels at rendering the mix time - the 80Hz is lower than Dolby's recommended 120Hz, but bear in mind Dolby's 120Hz is a brickwall filter - 120Hz will pass, 121Hz will not so we use the 80Hz on steep slope to make the transition smoother and avoid lumpiness.
NON filtered LFE run a very real risk of an MLP Lossless encoding failure - especially if a downmix coefficient is encoded (and unless the 5.1 is going to a PGC-Block group in the Audio_TS then you really do want to include downmix values or else some silly sod will certainly try to play it & then whine relentlessly in another forum I will not mention that his disc is somehow 'flawed' and isn't he oh, so clever to have found this) but that is not why you called (thanks to Alex Belfield for that phrase).
A bass managed subwoofer is an entirely different animal and one we should never even attempt to second guess, as I have seen sub crossover points from as high as 500Hz and suspect there are plenty that go even higher than this. When preparing for DVD-Audio (and Blu-ray & even SACD) we must follow the RPGA 5.1 guidelines so that means doing things the correct way - the .1 is a .1 because it is not full bandwidth. Period, otherwise the mix would not be 5.1 it would be 6.0.
Treating the LFE as full bandwidth is quite simply wrong. To finish off, I will quote a section from the RPGA 'Recommendations For Surround Sound Production (also attached here)
As noted in section 1, the LFE ("Low Frequency Effects") channel was originally introduced by the film industry because early theatrical speaker systems were
unable to generate loud low frequency signals without clipping. Sometimes referred to as the "boom" channel, it is used in film applications to add dramatic
effect, almost exclusively carrying the rumble of volcanic eruptions, spaceships thundering into view, and bombs and planets exploding.
In terms of multichannel music production, however, there is some debate as to whether the LFE channel is necessary at all. One can argue that the home
theater experience is heightened by having the walls shake whenever rocket launchers are fired, but is there really that much value in having the listener feel
every bass drum hit in such a similarly dramatic fashion?
There is no clear-cut answer, but the mere presence of the LFE channel almost dictates that it be used. The danger lies in overuse, because too much reliance
on the LFE channel to carry bass information can result in the loss of low end altogether on incorrectly configured or poorly designed home theater systems. In
addition, the LFE channel is discarded by most matrixed encoding systems (such as Dolby Pro Logic; see section 1.1) and downmixing algorithms (see section
5.5), including those used for HDTV broadcast. Therefore, the LFE channel should never be used to carry the bass content of the main speaker channels —
that is the job of bass management. Because bass management is employed by almost every consumer home theater system, placing too much information in
the LFE channel will effectively result in double management — total bass overload and probable distortion.
Instead, the LFE channel is best approached with caution. Only modest amounts of signal from specific instruments with significant low frequency content — kick drum, tympani, bass guitar, acoustic bass, low organ or piano notes — should be routed to the LFE, and in all instances those instruments should also be printed full range to the desired main channels as well. An experienced mastering engineer can help in correctly assessing the relative level of the LFE channel as compared with the main channels.
