Home theater projector installation

October 28, 2004

AE700UOf all the things a do it yourselfer is likely to have problems with, surely somewhere near the top of the list would be installing and aligning a video projector. In the immortal words of AC/DC, “For those about to rock, we salute you.” For the purposes of this article we’ll assume your projector will be a ceiling mounted DLP/LCD, but many of the same rules apply for floor mount applications. Hanging and aligning a video projector isn’t the most difficult task with one caveat, preparation. I can’t emphasize enough how important preparation is, not after the fact but before the screen or projector are even purchased.

Projectors vary in their throw distances and offsets. Throw distance is essentially the correlation between the size of the image projected and the distance of the projector to the screen, while offset is the drop from the ceiling in relation to the height of the projected image on the screen. I always start by determining what screen size best suits the room, once that is determined it’s easier to pick a projector. The key in this exercise is checking the recommended throw distance provided by the manufacturer for your particular model.


For example, let’s assume for your 100” diagonal screen you need to place the projector bracket 14’3” from the screen. Grab a tape measure and measure out that distance. Are there any obstructions that would prevent the bracket from being firmly attached to the ceiling at this distance? Is it possible to pull your cabling and AC power to this location? Hopefully now your beginning to get the idea that knowing exactly what you’re going to install and all the pertinent measurements ahead of time is critical in achieving a quality install.

All right, getting down to the nitty gritty of projector installation there are several schools of thought when it comes to which one to mount first, the projector or the screen. Many installers prefer to install the projector first, allowing joist location in the ceiling to be a known factor. I take a slightly different approach by getting a general range of where the studs are located, and then mount the screen. I like to be able to have the screen perfectly centered in the room, this isn’t a 100% must, but it surely makes for a more aesthetically appealing final result. Regardless of which approach you take understand that for the best results, the projector must be perfectly aligned with the screen (or as close as possible). Projectors with lens shift may not be 100% subject to this rule, but in general always try to maintain proper alignment.

projector_offset

Mount preparation
You might just have the luck of the Irish and pick a mount location perfectly centered with one or more ceiling joists, but if not there’s a workaround. Take a piece of MDF fiberboard and cut it in a rectangle just slightly wider than the two closest joists. Screw it into place with some heavy sheetrock screws and you’ll have a ‘span’ across the joists, giving you a much wider mounting platform.

Preliminary measurements
One critical measurement (not that they all aren’t) is center of screen or in other terms the absolute center of the screen in relation to where the projector is to be mounted. Alright assuming you’ve installed the screen first, one trick I’ve used time and time again without fail to determine center is a “straight line” made from a long piece of nylon string and a pencil. Take a length of string (you’ll need string that won’t stretch) and tie a knot toward one end. Take the other end and measure it off approximately to the recommended mount distance from the screen. Now tie the string around the pencil and have someone hold the other end at one corner of the screen.

Stretch the string tight and in an arc motion, with the pencil perpendicular to the ceiling, make a mark a few inches long. Then have your assistant move to the other side of the screen and make another mark on the ceiling. The (X) where the two lines cross is your absolute center in relation from screen to projector. Now if your projector of choice has it’s lens positioned dead center, your in luck because you can go ahead and install the mount. If the lens is offset left or right from center (as many are), you’ll need to calculate how far off from center and account for this in relation to your center mark.

lens_offset

The second most overlooked alignment is lens angle. Always aim for a perfectly paralell lens to screen angle, rather make sure the lens of the projector is flat in relation to the screen. Even a lens that’s slightly out of plane with the screen can result in keystone. This could appear as either the upper or lower portion of the image appearing slightly narrower than the other half. Word to the wise, never under any circumstance (if at all possible) use the projectors keystone adjustment. One could argue if it’s there it was meant to be used, but hopefully the same wouldn’t apply to a fire extinguisher. Sure in a pinch you can use the keystone adjustment, but the resolution of the video will suffer for it.

Installing the projector
Ok you’ve mounted your screen, installed the projector mount, and pulled your cables into position. Now take your projector and put it in place and snug up the bolts, fire it up and hopefully, if you’ve checked and double checked your measurements, all will be as planned. If not, don’t panic! Power it down and remove it from the bracket and take another look at your setup. Was your center line really centered? Was your overall offset the right height recommended by the manufacturer? And lastly, was the lens parallel to the screen? More times than not the last setting, gives more headaches than any other. Check to see if your screen is really flat in relation to the wall it’s mounted to and then very carefully, with a torpedo level, check the projector also, either by placing the level against the projector case or the lens shroud. If these two don’t resemble each other, try again.

One variable you may experience is line of sight issues. If you’re planning a tiered or a stepped riser platform, all you have to do is, well account for the head of the person in front of you. Start by getting the measurements of the theater chair you intend to use and estimate how high the average size person would be sitting in the chair. Better yet purchase your seats ahead of time and get an exact measurement of someone seated, then you’ll have a much more accurate representation of how high your rear riser should be.

line_of_sight



Posted by Bryan Greenway | | Filed Under Home Theater How-to


Comments

  • Brandon

    thanks for the info on not using the keystone function. I definitely was planning on using it.

  • Brandon

    thanks for the info on not using the keystone function. I definitely was planning on using it.

  • robert

    This is very useful. I am glad I read this paper before I started the installation

  • robert

    This is very useful. I am glad I read this paper before I started the installation