Here again is an ITU recommendation mixing studio for multi-channel. So does not specify DVD just multi-channel and has front speakers at 60 degrees. Could be audio only as it is not clear what is accommodated in an ITU multi-channel mixing room. - http://www.genelec.c...Interaction.pdf
I am sorry if I appeared to come across as short before. The truth is, there is not enough freely published information about this for enthusiasts to use a reference.
THX PM3 PDF is a good find. I don't think I've read that before.
Film sound for a cinema Vs film sound for DVD/BD should be the same, however they are not. Most of the differences lay in channel levels (Surround levels are pulled 3dB for home or packaged media), so there may be some slight variations between what one heard at the cinema compared to what the DVD/BD sounds like.
So far as L and R speakers placement is concerned, film sound is about providing auditory clues to match an on screen visual. Mixing for MC music is not as critical as very seldom does the sound actually match the picture - I am talking about a studio version not a live concert.
Reading the PDF and yes it does state 45 degrees. Again, in my case, what I have done is simply copy a real example dubbing stage, so by defaut, the speakers have to be closer. This topic was beaten half to death at AVS when many new to CIH started to question the speaker placement. One suggestion was even mount the L and R speakers on the same rig that controlled the side masking, so as it opens, so the L and R speakers move out. It kind of got squashed when Vern Dias posted a photo of his LCR array with his VERY wide 2.66:1 screen. Here were the three LCRs in what looked to be the centre 1/3rd of the screen, however as Vern explained, their location was based on his 40 years of projection experience, and who was game to challenge that? Several members lfrom this forum like Tukkis (he has a very nice cinema BTW) have also found that this placement of the L and R just inside the 16:9 portion works best.
When seated in the back row (3.2x IH), my eye line is centred vertically to the screen and because the speakers are some 6 feet apart, stereo separation is clearly heard even though the angle is quite tight. A apart of this is the fact that my speakers do have tight control over the vertical directivity. I don't think it is still on the THX site, however there was a time when it explained why speakers with controlled vertical directivity can be placed closer than conventional loudspeakers. I've certainly taken advantage of that fact with my system.
Another reason why I choose to move the speakers in (apart from a better relation ship with smaller ARs) is that my current room has the screen going from wall to wall. This just would not work if my speakers were wider than they are. I need to make a covers for above and under the screen and therefore havn't really posted any good shots of the front of the room.