Projector installation issue: Best way to resolve? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 12-22-2013, 03:03 AM - Thread Starter
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I just bought a Mitsubishi HC7900DW and, knowing this when making the purchase decision, I will have an installation issue.

The way I currently have my screen with my current projector is that the screen comes down just in front of my regular computer screen at the computer desk, this means I can't have my screen start under 33" (30" for the desk, 3" for the screen border) from the floor.

With this projector's height and throw angle, even if I mount the projector 1/2" off the ceiling with a plank of hard wood, the highest I can get the screen with lens shift is 14.5" from the ceiling, but my screen top ends up being at 8" from the ceiling, making a 6.5" difference.

The solutions I thought of:

1. Angle the projector, hopefully the distortion won't be enough for me to have to use keystone which ruins image quality . I tried angling my current projector for the image to be 6.5" lower and end up with a 1" width difference between the top and bottom widths. Since I will be making a much bigger screen with the new projector, the distortion should be significantly less.

2. I could install the screen 1 foot closer so that it can be lowered below the 30" height of the desk, but the way the room is made, I'd end up having to have the couch at least 1 foot off center from the screen, or deal with being even closer to the screen (with my original setup plan I'd end up 8 feet way from a 106" screen which is already close).

Thanks
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post #2 of 9 Old 12-22-2013, 12:21 PM
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I take it your PJ will be at the back of the room so why can't you just use a mount that will drop the PJ to the required height? my screen is a few inches from the ceiling and my mount brings the PJ down nearly 2 ft if required. if you angle the PJ even slightly you will need to use keystone correction
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post #3 of 9 Old 12-22-2013, 03:07 PM - Thread Starter
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The problem is that the projector needs to be above (not below) the ceiling for the top of the screen to end up at the right place due to its very steep projection angle (even with lens shift) and I obviously can't install it above the ceiling. My current projector is angled slightly sideways due to improperly aligned holes in my DIY mount and I've used it this way for 7 years and I think I only noticed it recently, this causes the left side of the screen to be slightly taller than the right side. The image looks better with minor distortion than the significant quality loss caused by using keystone, so I don't use keystone since the angle is so minimal.

I have 3 options:

-Angle the projector slightly

-Put the screen 1 foot closer allowing me to get the screen lower, but I'd end up sitting about 7 feet from a 106" screen

-Put the screen 1 foot closer and the couch 1 foot back and 1 foot to the left, this way I keep the same 8" sitting distance I was planning on but end up with the couch 1 foot off center from the screen

Which do you think is the best sacrifice to do? If I try it and see sitting 7 feet from a 106" screen isn't too close that will be the best solution

Thanks
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post #4 of 9 Old 12-23-2013, 05:22 AM
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tbh I'm confused with your configuration and having trouble seeing it in my head. I guess others are too which is why you haven't had much response.
can you do a quick diagram to illustrate it?
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post #5 of 9 Old 12-23-2013, 07:07 AM
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You pretty much know your choices on this one. I'm not sure how the Mits handles keystone correction so, you would want to test it to see how much it impacts the image and if YOU can live with it.

The offset of the 7900 is significant. With a 110" diagonal, the 'neutral' offset position is 18" above the top of the screen, which is unusable for most 'typical' setups. The offset can be reduced to 10" or up to a whopping 25".

I think that while it's great you are asking others for some options, it remains the fact that this will be your decision and none of use have to live with it.

My mentality says that you move the stupid desk so you can properly position the screen where it belongs. biggrin.gif

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post #6 of 9 Old 02-21-2014, 01:41 AM
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Does anyone know what the angle of the offset is for this projector? I realise it would change with the vertical shift. With my 90.5" ceiling I have a joist spacing of 23 inches and a depth of 9.8. giving me more room to use if I mounted it between the joists and managed to get the projected image to miss the joist closest to the screen to then hit my 110" screen.

 

Just trying to think of some solutions so I don't have to have the verticle shift at full and then still have the screen down too much.

 

Sorry this is my first projector so it has been a bit of a learning curve, especially the large offset this projector has.

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post #7 of 9 Old 02-21-2014, 07:03 AM
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Quote:
Originally Posted by Andy Sowden View Post

Does anyone know what the angle of the offset is for this projector? I realise it would change with the vertical shift. With my 90.5" ceiling I have a joist spacing of 23 inches and a depth of 9.8. giving me more room to use if I mounted it between the joists and managed to get the projected image to miss the joist closest to the screen to then hit my 110" screen.

Just trying to think of some solutions so I don't have to have the verticle shift at full and then still have the screen down too much.

Sorry this is my first projector so it has been a bit of a learning curve, especially the large offset this projector has.
If you can mount between joists, and get the lens up higher than typical, then I would expect the highest the image could be is 11" below the ceiling. Since the image is always projecting downward, you need to worry about the joist closest to the projector cutting off light, not the one nearest the screen. Angles are somewhat irrelevant as it changes not only based on lens shift, but on projection distance. But, the constant is how much shift is available for any screen size. 10" down to 25" down for a 110" screen. Trying to deal with angles will just make things very complex for no reason. But, if you want, you can draw it all out from the side to see how things will look.

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post #8 of 9 Old 02-21-2014, 10:14 AM
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Thanks AV Intergrated. If I can get the image 11" or less below the ceiling height I will be happy. I worked out the screen size, throw and seating on projector central calc but it didn't have the offset info for this projector there so this is the vital info I missed as a first time projector and screen buyer.

Not that I really would want to but I could always remove some joist height in front of the projector to allow the image to not hit it. Would have to strengthen it somehow if I did that though.
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post #9 of 9 Old 02-21-2014, 01:50 PM
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Quote:
Originally Posted by Andy Sowden View Post

Not that I really would want to but I could always remove some joist height in front of the projector to allow the image to not hit it. Would have to strengthen it somehow if I did that though.

the things we'll do for a larger screen....
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