Hi "Harry".
Yeah, it's a long running thread, but that only shows how much we all seem to like this projector.
To your question - It sounds like your projector may be doing the "shake-rattle-and-roll" while you watch content with high sound pressure levels.
I've looked carefully at the
photos of your HT on your web page, and have some thoughts.
You've obviously given great attention to your setup there, and I especially note the effort to render excellent sound.
Some immediate feedback to offer is that I've got a "similar" room arrangement in that I too have a THX certified Receiver, Speakers and Sub and have worked to optimize it's sound and video performance. My projection surface is 84" wide and the projector is 140" from it, rigidly ceiling mounted [to the floor joists of the room above] "inverted" in orientation.
We differ in that I'm certain my peak sound pressure levels are at least 10db less than yours, and based on my next questions you may find I place more of a premium on the video performance than you have. Also my viewing area is unbounded on two sides, and the room volume is ~7700 cubic feet [41'x27'x7'] with the premium seating area being an 8 ft wide box 10 ft in front of the screen.
In my setup, I routinely monitor my system's electronic and mechanical "drift" over time. This includes not only the "focus" but the horizontal and vertical positioning of the projector lens' "shift" settings.
I can say unequivocally that it "does not change" mechanically of it's own accord. My raster image is aligned to sub-pixel sized marks I placed on the projection surface for that purpose .
If I do not physically "touch" the projector, it simply does not change.
No change in focus, nor in raster position. However, about a year ago, a 300 lb item fell off a shelf in the room above my HT, putting a huge impulse in the floor which is the ceiling of my HT. On this occasion only, I noticed the shift setting had moved. This is the first and only time since it was installed, and may have been partly due to the manner in which I loosely attached the mounting plate to the ceiling joists. [no longer]
So, on a showing-to-showing basis - my experience is different than yours.
Studying images of your HT, I see that the projector is not "mounted", but appears rather to be sitting on the floor of a cubby-hole in the vertial surface of an overhead beam.
- Is that correct? Is it just resting on it's rubber feet?
- How strong / rigid is the structure it's in? When performing SUB-Woofer level checks, have you touched this structure to see if it is effected? Perhaps it's resonating.
- Can you see any image disturbance [viewing a test pattern] while a troublesome movie / scene is playing?
I guess my suspicion is that you may have inadvertently created a situation where the projector is effected by your room's sound.
Having been so careful and meticulous with the optical alignment of my projector to the screen has given me a unique appreciation of just how stable it is. I have taken care to assure the field of pixels is as close to rectangular as I can measure, and the system delivers this better than I could have imagined possible. This was done by assuring the projection line was precisely perpendicular to the screen. Doing this makes all pixels at all extremes of the image, at maximum focus at the same time. Then use the "shift" to position the image on the screen vertically and horizontally.
Also, I do not change the projector's
zoom. It leave it alone. I have noticed there
is an interaction between focus and zoom in this lens. **
Does any of that help you think your problem through?