Is the noise really disruptive while watching movies?The answer is yes and no.
If your projector produces a lot of fan noise, then that will be what you hear during the quietest parts of a movie. This reduces the overall dynamic range that you hear, because the very softest parts of the soundtrack will be drowned out by the projector. This problem gets worse as you sit closer to the projector. You may need to engage the dynamic range control (DRC - "night listening" mode) on your receiver. It compromises dynamic range, of course, but that damage has already been done by your projector noise. At least with DRC, the dialog won't be too soft to hear.
On the other hand, fan noise will mask sounds coming from outside your HT, reducing the need for soundproofing. It's like turning on the AC in a hotel room to mask traffic noise. A small amount of projector fan noise will reduce dynamic range by a few dB. But at least it will be constant, masking the spin cycle of that washing machine on the other side of the wall, and perhaps not enough to seriously cut into the quietest parts of a movie.
On the third hand, if your HT acoustics are not great (too much/uneven reverb, loud early reflections, boomy bass, etc.), all of the above doesn't matter too much. You've got other audio reproduction problems which will remain even after you've solved the noise issues.
I'm out of hands! How much projector noise you want to tolerate ultimately depends on how much of a purist you want to be. How accurately do you want the soundtrack to be reproduced, compared to a high quality commercial movie theater?
Regards,
Terry
