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Discussion Starter · #1 ·
I have my first projector coming this next week, I purchased it from AVS its the Enrich TC2000.

I already build a 74" diag. 4:3 screen and put it on a wall covered in black felt.

I want the image to fit exactly onto the screen, keep in mind that this unit has no keystone adjustment but does have a zoom feature.

Any tips, tricks or advise on how to obtain a PERFECTLY aligned picture would greatly be appreciated.

Perhaps a list of steps would be useful.


Also would I obtain a better picture if I do not use the zoom feature?





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James' DIY Speakers
 

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Hopefully you will get a manual with your projector which will give you the exact mounting location. Anyway my NEC VT540 came with a table of dimensions for both the ceiling and desktop mounting options, and the table dimensions were "right on". I use a homemade 72"X54" screen (90" diagonal 4:3 AR) with a black 2" frame border. I can zoom the projector to exactly fit, and my projector is tilted down less than 1 degree from optimum - resulting in approximately 3/8" wider image at the bottom than at the top. Given the crisp edge definition of the flat black painted frame, I can live with that much "overscan", without using the digital keystone correction.


I picked the screen size after using the projection calculator at: http://www.projectorcentral.com/

and plugging in my throw distance. You could also enter a screen dimension and work backwards to get a range of throw distance (because you have zoom) or simply use the manual. I picked a value midway between the "Full Tele" and "Wide" limits of the zoom lens. I never heard of Enrich, so you will need to know who the original projector manufacturer was, to look up the projector calculator. Alternatively, you could use the table of dimensions in your manual.


The dimension you need is actually an angle - the projector will produce a rectangular image at one angle measured between the lens centerline and screen centerline, due to an optical feature called "lens shift". This angle remains constant, and you use trignometry to figure the distance from screen center to lens center for each projector throw distance and screen size.


1) Determine maximum and minimum throw distance from the screen size and zoom range of your projector. Now you have a throw distance range and the distance from the projector to the screen should be in that range.


2) Choose either ceiling mount (high mounted projector with image inverted in projector menu) or desktop mount (projector sits on table, image is not inverted). Most people including me choose ceiling mount for a permanent install, because you don't want furniture and people casting shadows on the screen. Some people use the table mount option and portable screens - or project on painted room walls.


3) If using the ceiling mount option, figure out how to mount the projector. I used a commercial mount bolted to the top inside of a hushbox, and placed the box on top of a 7' tall bookcase, giving me an image that starts at 33" above the floor and ends 12" below the ceiling - a good choice, gives a "theater feel" and I am looking up just slightly from a seated position. Some bolt the projector to the bottom of a shelf, even a hinged shelf which allows tilting the projector. Some even suspend the projector below a shelf in the adjacent room, and project through a hole or glass pane. Common ceiling mounts like mine can also be screwed to pipes while running cables inside the steel pipe. Figure this out.


4) The one thing you have to get right, because almost no projectors allow you to correct it, is that a line perpendicular to the horizontal center of the projector screen must line up with the lens center. Some projectors have a "variable lens shift" but this is almost always only usable for vertical shifts, not horizontal. So the projector lens centerline must be aimed square at the horizontal centerline of the screen - as exact as possible.


5) Should you not be able to follow these steps for some reason or another, just play with the projector when you get it, and measure carefully image size and throw distance - it's simple geometry and carefull measurements that make the difference.


Gary


PS - I like your speakers. I'm using a Shiva passive radiator subwoofer (EBS alighnment) and 5 identical speakers from Adire's free GrandPop! design. I wanted 5 of the 281's but blew the budget on the NEC projector. I'm driving the projector and an Onkyo TX-DS575X with a HTPC for DVD playback and using DScaler for TV viewing off analog cable. Hoping for HDTV soon.


[This message has been edited by Gary McCoy (edited 09-04-2001).]
 

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Discussion Starter · #4 ·
Thanks for the reply.


and my projector is tilted down less than 1 degree from optimum - resulting in approximately 3/8" wider image at the bottom than at the top.

>>>>>>

Wow, 1 degree makes that much of a difference?


I guess getting some hands on experience with the projector is going to give me the best training, but now that you gave me some sort of steps to follow it will make it much easier.


Thanks for the comliment on my speakers, the entire reason I purchased a projector is because my newest speakers that I am building have very large magnets that will cause some interference with my direct view set, I looked into purchasing an RPTV but found out that these speakers will interfere with these sets as well so I chose an FP set.

These speakers will cost me about $3400 for 5 of them, but I am just building a pair for starters to make sure that these are what I want.

I am shooting for audio quality and SPLs well beyond what any theater can produce. Plus I have plans to build a larger sub than my 'Big Pig' , I will build two that use 3-4 18" drivers per enclosure.

You should build the Kit281s some day if you can find the means to do so , they really are fantastic speakers.

What is the point of having a 100" movie theater quality video if you don't have a sound system to match?

After being at this forum awhile I now realize I have been missing out by having such a small viewing screen. Now that I entered the world of FP I hope to have the best of both worlds. http://www.avsforum.com/ubb/smile.gif


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James' DIY Speakers
 

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The max SPL of course depends upon room size and shape as well as speaker design. I find the 5 GrandPop!'s are capable of driving to reference levels at partial volume setting in my 14X13 foot, cathedral-ceilinged room.


When figuring room layout and viewing distance, use a concept called "subtended angle" and plan your viewing distance from the screen so that the screen width subtends 25 or more degrees in your field of view, and the screen height subtends 15 or more degrees. This will give maximum emotional impact from the image. At whatever viewing distance this works out to be, you should not be able to discern the image structure (scan lines for CRT projectors, or pixels for digital projectors), or you picked the wrong projector. My viewing distance is 1.5 screen widths for my XGA-resolution projector, and I achieved my image size objectives without building a special room.


As for "theater sound", remember that a real theater starts with 3 full range front speakers and a subwoofer concealed behind the screen. The screen is really NOT acousticly transparent, so they use high efficiency horn tweeters to overcome the screen absorption of high frequencies. Good home theater speakers will actually sound better than this, with more even frequency response and lower distortion. The best way to generate a seamless front soundfield with front projection is to start with three full range, high quality, and IDENTICAL front speakers. Realize that the horizontal layout common with front center speakers is a compromise for RPTV and direct-view sets. For FP, use three vertical format front speakers mounted just below the screen, tilted slightly to beam the tweeters directly at your ears, and keep them away from rear and side walls for good imaging. (This works only for one row of seating of course but that is the most common short of a dedicated HT room.) Since virtually all of your directional hearing is in the horizontal plane not the vertical, you will not notice the speakers are actually below the screen when the room is dark. I like to set the RF and LF right below the screen corners, and the CF right between, for best coupling of image to sound. I try to keep the subwoofer either on that same wall or an adjacent corner.


The surround speakers are less critical but I still like the seamless soundstage of five identical boxes. I also prefer the way monopoles sound as compared to bipoles or dipoles in spite of what THX says. My present room sounds best with the surrounds on top of the bookcase where the projector is, well above ear level. Calibrate all speaker levels using a SPL meter, and measure distances for the digital delay settings in your receiver.


Do it right and you will prefer your home theater to a real one.


Gary
 
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