The easiest way (though not as aesthetically perfect as some require, but my personal favorite) is a 6-7 foot tall black metal grid shelf in the back of the room. You can get them at Walmart for under $100 (at least the 6' ones), or the larger ones they sell online. The shelves are fairly sturdy and do not need to be bolted to the wall, and they can hold a tremendous amount of weight as well because they are metal (500+ pounds). Some people also call them bread-rack shelves. You will find these same shelves often used in Data Centers in areas where they have tower servers instead of rackmounts. The reason DC's use them is for maximum cooling, easiest wiring, heaviest weight capacity, adjustable shelf heights, and lowest cost.---I will post my image later after I get a chance to take it, but for now...---Note:
The 6'+ ones actually have 5 shelves instead of 4 as the picture shows.Eye Sore?
The shelves are NOT an eye sore unless you have a very fancy room, so once you have your components on the shelves they actually look very good as they blend in sort of invisibly. Of course if you have a real fancy room, you'd probably want an in-wall installation with duct-work cooling paths instead of these shelves, but this works in most cases. This works great for mounting a single projector, or mounting 2 projectors, or even 6 projectors! You just fill in the extra shelf space with Bluray Storage (see pic at end of post), or decorative plants and items (I have some bluray storage and some decorative items).Projector Beam to Head Clearance and Maximum Shelf Height
One consideration, if you have a very long room, you will need to be careful of how you setup the height to clear peoples heads when sitting. The 6' tall version of the shelves works as far back as about 17 feet from the shelf to the screen, given that people are not sitting closer than 1.0x screen width. The 7' shelf gives you a few more feet (about 20' to 22'). The exact height depends on how tall you are when sitting, how high above the floor your screen is mounted, and how far back from the screen you sit. Rooms longer than that, you will either need to find taller shelves or you will need to secure a "printer-esque" stand or similar to the top shelf.Why are these shelves preferred overall?
Because the shelves are adjustable in 1-inch increments, and the wiring is cake. You can put all your components (Cable Box, Bluray Player, Stereo, HDMI Switch, UPS, whatever) on the bottom two or three shelves, and then put the projectors on the top two shelves. Also, since these shelves are swiss-cheese, it maximizes cooling for all your components. To hide the wires, simply use black cable ties and run the wires on the back side of each pole putting each wire behind the other as to not create too much thickness. Make sure you run the power cables on one pole, and the video cables on the other as to not create line interference. You can likely find these shelves in different depths, so even very long projectors should fit with enough clearance, or even if you need more depth clearance, the simple solution is to just place a black board or metal as an extension lip and then move the projector forward (it still looks fine actually). For your remotes, get an IR repeater or RF convertor so that you can still use them (though if the shelf is directly behind you, some remotes might still work without the repeater).How to use these shelves for double stacking two units?
You place the 2 projectors at the same horizontally centered position but place one underneath (shelf below), since all shelves are adjustable, the second projector will actually be right underneath the first one, and then just use a little V-SHIFT to get the images close, and then finish off the vertical alignment by adjusting the projector's wheels as your final precision adjustment. The horizontal alignment isn't all that difficult, since you just nudge each PJ a tiny bit until you get it perfect. Every time you do the horizontal adjustment, you will need to repeat the vertical adjustment and keep going back and forth until you are finally lucky enough for the alignment to come out correctly. I have found that it is far easier to use the projector's wheels to vertically align two images than to try to adjust a ceiling mount.Why not Ceiling Mount for a Double Stack?
Though ceiling mounting arguably looks cleaner for one projector, for double stacking I'd recommend against it. It is easier to make precise adjustments on a shelf instead of one or more ceiling mounts. This is also a ton easier when you have to troubleshoot something, especially given the swiss-cheese open nature of the shelves so that you can change the cabling configuration instantly if needed, and everything is always within arm's reach. It also saves a lot of money in cabling costs, and allows for the shortest HDMI cable runs (all cables under 12 feet).How is my setup?
I am not actually using it for double stacking (but it serves the same purpose), but I use it for A/B comparisons. So my current configuration is Top Shelf = Benq w7000, next shelf = JVC, then a wide gap, then bluray player on middle shelf, then second to bottom shelf I have my Blurays and an HDMI Matrix Switch (to do dual output), then on the bottom is my UPS and HTPC. In less than 5 minutes, I can easily add another 2 projectors for comparison or swap them out.Bluray Storage
To further enhance the shelves, you can convert one of the shelves to an open Bluray Disk Storage area to hold your commonly used disks by installing multiple wire storage units horizontally and wire tying them to the shelf (works great). Since the main shelves are adjustable, you simply buy whatever height you want the mini-storage grids to be. Then you just wire tie them all at the bottom and top and they will be as sturdy just as if they were part of the shelves. Below is an example image of what I mean, and you can find these online in all different heights and widths or chain multiple ones together. You could also add a regular Bluray storage cabinet and just place it on the shelf, but this method here generally matches to the aesthetics of the shelf better.Note:
I decided to add this post to my signature, because so many people make such poor shelf mounting decisions.