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Discussion Starter #1
Hello,

I'm brand new to your forum and to the home theater crowd, so please excuse my "neophyte" questions. I'm into this because watching DVDs on my 32" Sony TV isn't too great!

I just purchased a Sony G70Q projector and a Quadscan Elite quadrupler, but I haven't yet seen either. But I have the Sony installation manual and I'm trying to figure out exactly wher to mount the projector. My screen is a Da-Lite 92x52 (16x9). My room is 18' deep and plenty wide, with an 11' slanted (to the left) ceiling. My "viewers" will be about 12' from the screen. I would like to mount the projector from the ceiling as high as possible to hide it as much as possible.

Although I don't yet have the projector, I do have the installation manual, and on page 11 it provides distances and heights, but it assumes a 4x3 screen, while mine is a 16x9 screen. Since my screen is 92" wide, I would assume I need to use (for calculation purposes) a 92" wide 4x3 screen, which would be 92x69, or 115" diagonal. Is this correct?

If this is correct, could I then interpolate between the 100" and the 120" screen size in the chart to get the correct distances and heights for my screen?

Also if this is correct, this will put my projector height, relative to the top of my screen, higher than for a 4x3 screen. Is this correct?

Finally, If I use the Quadscan Elite, is it possible to move the picture higher, assuming I had a normal 4x3 screen, than centerline? If this was possible, I could mount the projector even higher than that shown in the page 11 diagram. Would you recommend this?

Do you have any other suggestions for me as a beginner?

Thank you very much!!!!


Ray Kawal

Sequim, Washington
 

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Ray,


Spend some time getting the know the projector before you throw it up on the ceiling. I'd run it for a few weeks (even months) floor mounted until you're 100% comfortable with it and have figured out what distances to use (the manuals aren't always perfect).


When ceiling mounting, it's ESSENTIAL that all distances be perfect, so get all the learning out of the way first. No amount of adjustments can fix an inproper physical install.


Kal
 

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Discussion Starter #3
Kal,

Thank you for your reply. I will floor mount the projector and try it out first, but I really do need to get it out of the way and up on the ceiling. I can play with it a few days, but I'd be divorced if I had it in the middle of the room for any longer!! :)

If my thinking is correct on my first question, and mounted the projector, assuming the dimensions for a 115" diag 4x3 screen, and used the same horizontal centerline, wouldn't I have enough adjustment to later fine tune it?

Thank you,


Ray

Sequim, WA
 

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Ray,


I'm assuming you shouldn't have a problem centering the projector properly in the left/right axis relative to the screen. That shouldn't be a problem.


There's some adjustment that can be done for projectors that are a bit too high or too low relative to the screen. Though your're best off using the suggested values from the manual or from sony's PJCalc software program (available from their site I presume).


The one thing you have NO adjustments for is throw distance (screen to CRT distance) - CRT's have lenses with fixed focal lengths. PJCalc will give you a recommended distance for a given screen size (doesn't matter if it's 16x9 or 4x3), but once you get good at adjusting these things, most people end up moving their projectors (not just Sony's) a bit CLOSER to the screen then the manufacturers recommendations in order to use more of the phosphor area in order to give you a brighter image. This is a physical adjustment. You can't adjust it electronically.


Kal
 

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Discussion Starter #5
Kal,

Thank you again for your quick reply. Your experience sure helps a beginner at this. I downloaded the PJCalc program and the throw distance comes out 122" for a 92" wide screen, which is very close to what I interpolated from the Page 11 charts.

But in the manual, there appear to be adjustments for the RGB size of the image. Since I believe I will be feeding an RGB image from the Quadscan, it would seem that there is SOME adjustment in image size, even if the throw distance is fixed. Is there not SOME adjustment as well for focus?

Also, I will be building this ceiling mount myself (I'm an engineer and fabricator) so I could also provide some adjustment in the mount to allow me to move the projector closer than the 122" calculated distance, if I later choose to do so. From your experience how much in general should I plan on for moving it forward - a couple of inches maybe?

Finally, if one moves the projector closer to the screen to get better coverage as you describe, is a bit of the image lost in the edges?


Thank you again,

Ray
 

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Kawal,


I too just bought a Quadscan Elite, G70 and Da-lite 52X92 screen(cinema vision/cinema contour) sight unseen. After much calculation and concern, I went ahead and mounted the projector to the ceiling as my initial installation because I didn't want to have to reconfigure the projector, etc. I am currently working on convergence, but it appears everything is going to properly converge. If you send me an email, I'll be glad to share the measurements that worked for me. In any event, the G70 has a 0 - 5% tolerance for throw distances, and you should err on a longer throw distance. You want to make sure the picture will fill the screen and (I believe) the installation manual provides the minimum throw. You can reduce and shift the image sufficiently to compensate for a couple of extra inches in your throw distance. With regard to mounting height and hiding the G70, I suggest keeping it simple by mounting the projector parallel to the ceiling and using the default -15.2 projection angle. Further, the G70 is huge. You are not going to be able to hide it, so you may as well show it off. With a low profile mount, such as the one from Precision Mounts, the mounted unit is not bad to look at.



Ben Withrow
 

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Quote:
Originally posted by kawal
Kal,

Thank you again for your quick reply. Your experience sure helps a beginner at this. I downloaded the PJCalc program and the throw distance comes out 122" for a 92" wide screen, which is very close to what I interpolated from the Page 11 charts.

But in the manual, there appear to be adjustments for the RGB size of the image. Since I believe I will be feeding an RGB image from the Quadscan, it would seem that there is SOME adjustment in image size, even if the throw distance is fixed. Is there not SOME adjustment as well for focus?
Yes! Maybe I picked the wrong words... What I meant to say is that there is no zoom feature on CRT's as you have on most (all?) LCD/DLP projectors. What this means is that a CRT projector must be installed PRECISELY the right distance away from the screen for the given screen width. If you go too close, you'll try to expand the image on the CRT phosphor surfaces to fit the screen and you may run out of phosphor area before you fit your screen. Conversely, if you install the projector too far back, you'll have to shrink the image size on the CRT phosphor surfaces to the point that you're not making efficient use of the phosphor.


The trick is to use as much phosphor width as possible, but leave approx 1/4 inch on the L/R sides for breathing room as the phosphor surface will get hot from all the electron excitement.


PJCalc may tell you to install 122" from the screen, but many people ignore the throw distance recommendations and do this backwards by simply increasing the image size to almost fill the entire CRT phosphor area and then move the projector back & forward until it fits the screen. Make sense? Odds are you'll end up around closer then what PJCalc tells you to use.

Quote:


Also, I will be building this ceiling mount myself (I'm an engineer and fabricator) so I could also provide some adjustment in the mount to allow me to move the projector closer than the 122" calculated distance, if I later choose to do so. From your experience how much in general should I plan on for moving it forward - a couple of inches maybe?
I'm not really sure as I'm not familiar with the G70 and how pessimistic the PJCalc recommendations are. In terms of inches, it's in the single digits ... it won't be 2-3 feet or anything. Maybe 2-6 inches? I'm guessing here.


An easy way to build your own mount is to use Unistrut (sometimes called Channelstrut or Superstrut). It'll give you something that's completely flexible in terms of projector movement. Try searching for 'Unistrut' around here. Lots of good hints. I have some great unistrut mounting instructions I stole off a web site (that no longer exists) if you're curious... just send me your email address.

Quote:


Finally, if one moves the projector closer to the screen to get better coverage as you describe, is a bit of the image lost in the edges?
I think I've pretty much covered this... the trick is to get close, but not too close! By edges, I'm assuming you mean the edges of the phosphor in the CRT's right? (When you move the projector closer, the image get smaller on the screen so you have to increase the size of the image on the phosphor).


Try doing a search on "G70 throw distance".... you'll probably get some good ideas on how much closer (in terms of % of what PJCalc recommends) to go as compared to PJCalc's recommendations. Just be aware that throw distance is a function of screen width so don't go using someone else's values!


Enjoy the G70 - great unit!


Kal
 

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Sony's PjCalc program gives a throw distance of 121", screen surface to front of green lens, for a 92" wide screen and a G70. But please do NOT install it at this distance! With a 16x9 screen, I would move the projector at least 6% closer. You'll get more light output and better resolution, and the G70 can easily do this. (I'd move a G90 some 9% closer, but the G70 doesn't have the G90's lenses). So I'd start at 114". If you want to try moving it closer you can experiment but 114" should get you pretty close to optimum.


I would NOT shift the image off center to get a higher mounting position, I think this is a bad idea. You'll get uneven heating in the deflection circuits, and less stabilty, mostly convergence.


William
 

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Discussion Starter #9
Thank you all for your great help. I do appreciate it!

But I'm now getting a bit of conflicting information. William suggested an initial throw distance of only 114". Another fellow (not in the forum discussion) suggested I use the factory figures for a 120" 4x3 screen exactly, which comes out to a throw distance of 126" - longer than the 122" I got using PCCalc.

So I'm still in a bit of a quandry here.

Thank you so much, and I would appreciate some more suggestions.


Ray Kawal

Sequim, WA
 

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Hi Ben,

Glad to see you out here and already giving advise to new owners of G-70's. That's great and the power of this forum. Guess you got everything up and running the other evening and are starting to finish up your registration of the unit. How's the picture looking??

Ray. I use the PJCalc distances for a 16:9 screen and then put it back and inch or so to err on the right side. Like it's been said before, once it's mounted you don't want to move it. I've installed 3 G-70's and this works perfect for me giving be an innch of so of horizontal picture beyond the actual screen. I'm not sure I understand the 6% closer that was suggested by William for a 16:9 screen as PJCalc accomidates a 16:9 screen??

One thing I will tell you on setup that in my opinion lends to a great picture is to make sure that after you get a very basic geometry (registration) you spend your time getting the mechanical and electronic focus's as perfect as you can. Once that is done, you will have a clean small dot (except for the blue CRT) and the convergence lines will line up better.


Terry
 

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Ray,

Listen to William, he knows his Sony pj's. He has installed countless G70's and G90's and is highly sought for his expertise! He also recommended the same distance for my G70 and 52" x 92" screen. It has worked beatifully with a sharp bright image.

Just my $.02.

John
 

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If we're going to start talking number of installs, I have to point out that 'wm' is William Phelps.


Yes, this is the same Mr. Phelps that flies around the world doing professional installs for hundreds of customers including setups featured at trade shows such as CEDIA (Faroudja booth), and magazines such as 'Audio Video Interiors'. I believe his current number of Sony G90 installs sits somewhere in the high 200's. More installs of the high-end G90 then anyone else in the world.


Please listen to him! :) Better yet, hire him to set up your G70!


Kal
 

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Ray,


Congratulations on you G70 purchase. I've had mine for about 2.5 years and have been very happy with it. I see you're in Sequim. I'm not terribly far from you, just accross the puddle down in Fife.


Here's a thread from the archives. Look for the posts from William that explain the benefits of moving the projector closer with a 16:9 screen.


Steve
 

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Discussion Starter #14
This forum is great! You folks have an amazing amount of useful information, which I, and I'm sure others really appreciate!

I certainly didn't mean to start a "war" here on Sony's throw distance, but it sounds from reading the thread referenced above, that the "war" was ongoing before I brought it up again. It sounds like a number of experienced people with high credentials have a different viewpoint than William, who obviously also has high credentials.

Since I haven't even seen my G70 yet, I'm trying to soak in some knowledge on this subject, which is obviously difficult to explain, even for William. But in reading the past comments in the subject thread, I think I understand where William is coming from, and his comments make theoretical sense to me. As I understand what he is saying is since the CRT's are angled down towards the screen, in order to create a 16x9 rectangle, the image on the CRTs cannot be a rectangle, but a trapezoid - this makes sense - and therefore the image on the CRTs is wider for a full 4x3 screen than a 16x9 screen where all of the CRT is not used - or something like that - this also makes sense. So I can see in theory why the adjustment for a 16x9 screen might be different than for a full 4x3 screen.

And I can see that moving the projector closer will provide more brightness, which William finds a logical advantage.

What I cannot know of course is what in practice works for a Sony G70. Most of William's comments are for a G90, but apparently he (and his supporters) found similar results for the G70.

But I noticed a comment or two from users who said they could move the G70 a few inches closer, but it seemed not the 7 or so inches William recommends, or other problems (focus?) resulted.

What I seem to be able to conclude from all of this discussion however, is that the throw distance is not so fixed as I was told by one of the discussion group. It sounds as if there is a brightness advantage to moving it closer than the 4x3 table would suggest, but how much closer is not clear. I guess I don't quite understand the comments of some folks that say I need to move the projector FARTHER than the specs say. As I try to digest this, maybe my best best would be to move the projector initially a little closer than "spec", say 3-4 inches, then play with it. Since I am going to build my own ceiling mount, I can make it adjustable such that I can move the projector farther or closer from the screen - my original thought of building a fixed mount doesn't sound flexible enough.

If I move the projector closer, as William suggests, for those who do not agree with this idea, are there any issues that would hurt the projector? It would seem that if I can focus and make the other adjustments adequately with a closer distance, I see a net gain, unless I am missing something. Obviously William sees the gain, and to me (a complete beginner), his ideas seem sound, but if there is something in practice that I will lose, I would like to hear those arguments.

Thank you all very much for the very enlightening comments you all make. I look forward to further comments if you have any.


Ray
 

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I do not know of any reason why you should not put your projector at my recommended distance. I am not aware of anyone who has done this and found it to be detrimental to the picture, and I am not aware of any problems caused by doing this.


William
 

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Discussion Starter #16
I have thought of a couple of questions for all of the fine gentlemen who have kindly given me there thoughts:


Especially for William: I think I understand your reason to move the projector closer is to increase brightness and therefore a better picture. So I would therefore conclude that if I had the projector at "spec" distance, I would not lose anything, but the closer the more brightness I will gain. If that is the case, then I would conclude that anything between "spec" distance of 121" and your recommended 114" will work just fine, but the main gain will be brightness as I move closer. It therefore sounds like I have a lot of "safe" room to play with - about 7". Do you agree?


Especially for Kal: Your original comments I understood to mean that I had to have the throw distance exactly right because I would have "NO adjustments" for throw distance because of the fixed focal length of the lenses. But your later comments praised William's experience and knowledge. If William is correct, wouldn't you have to agree that all of the throw distances between the 121" spec distance and the shorter 114" will satisfactorily work with the G70? It would seem from all of the comments above, that there MUST be sufficient adjustments (focus or whatever) in the G70 to accommodate a reasonable range of throw distances. If I build my mount to be able to move the projector closer or farther from the screen, it would seem to be a safe approach. Would you agree?


Especially for Chuchuf: I don't know how you feel about the logic behind William's comments, but I think I would conclude from your previous comments that there must be a satifactory RANGE of acceptable throw distances in which the projector can be successfully adjusted. Apparently you have found that using "spec" distance or an inch or two more, you get a very nice picture. Maybe we can conclude that the G70 will give a great picture at a number of distances? Or have you found problems with setting up the projector at closer distances as William recommends?


Finally, again for William: Being brand new at this, I don't know for how long this discussion about closer throw distances for the G70 has gone on. But if Sony is aware of these stated advantages, why haven't they taken a stand and provided new calculations for 16x9 screens? It would seem that if there are no disadvantages, and there is a gain in brightness, they should provide a better guideline for the popular 16x9 screens.

They must have developed the published throw distances they recommend based on empirical data. Wouldn't they also have empirical data for the 16x9 images? Or is this too new of a subject?


I sincerely thank all of you gentlemen for your comments. If I have absolutely concluded nothing else, I know I will at least make my ceiling mount adjustable! :)


Ray
 

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Discussion Starter #17
After reading a number of other threads on this subject, I have another question for William:


It sounds like the main benefit for moving the G70 closer to the screen is to increase brightness, and therefore picture quality. But from reading some other comments, it sounds like most people have their brightness settings for the G70 far below the maximum capability of the projector. If that is the case, why is brightness a real issue? If one wanted a brighter picture, couldn't he just turn up the brightness a bit? I'm sure I'm missing something, but unless the projector's brightness capabilities are exceeded, why is this an issue?


Thank you again for your thoughts,


Ray
 

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The question is not just brightness, but resolution as well.


If you mount the PJ so that you are only using 90% of the available phosphor, then you are giving up 10% of the resolvable resolution as well a bit of brightness.


My recommendation is that once you get the PJ, mount it at the PJCalc recommended distance (or a few inches closer to screen). While the white ‘warm-up’ image is displayed, see how much of the light is spilling to the sides of your screen at that distance. If it’s several inches worth on either side, then move the PJ a tad closer.

What I look for is for the full phosphor white image to light up the edges of the screen frame (that is ~2†on either side of screen material).

This gives you enough range of adjustment to work with and still uses most of the phosphor. If you try this, I think you will find your final measurements closer to what wm suggests.


My G70, after some fine-tuning like this yields an awesome image on my 80†wide screen
 

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A war? No just a difference of opinion. But I do stand corrected to a degree.

In my case here at my house, PJ calc ver 3.21 says that the distance to the frony of the lens should be 139" for a 16:9 screen 122" diagonal with the exact relationship between the screen top and projector mounting height determined.

That said, I must admit that when I installed it last weekend, I didn't even use PJCalc, but rather had the unit on the floor with the same relationship between the bottom of the screen and the projector base as what it would be when it hung. The reason I did it this way is I was alone and didn't have anyone to hold the tape for measurements. (nor anyone to help me raise it which I did alone using straps and rachets) I set it up so that the warm up screen overlapped a total of 1" horizontally (1/2" either side)

Well I just and measured the exact distance from the screen to the projector and it is 135". This is about 2.8% closer than PJ calc called for and still yields the 1" total screen edge overlap (1/2" per side) that I was looking for.

Could the projector be a bit closer, yes.....but not much.

I believe that I accomplished what I was trying to do and that was to cover as much of the raster as possible.

So from now on I won't be as concerned with being an inch or two beyond what PJCalc says.

Hi Jonathon

Terry
 

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You have to remember that the distances given by manufacturers contain the Idiocy factor.

This applies to all Crt manufacturers. If you want the most resolution and the biggest amount of linear screen brightness it is absolutely "Vital" to get your CRT as close as possible to the screen regardless of what the spec sheets say.

Take the manufactures distances with a grain of salt and only use them as very rough guide. Even if you are setting up your CRT for a ceiling mount, first do all the physical working out on the floor then measure the distances and transfer them to the ceiling for your mounting.


First up get the rough starting distance from the manufacturers specs. I also like to see a new projector get fully burnt in by playing 75-100 hrs or so before doing a set-up. This stabilizes the new electronics and tubes. Then using an aspect ratio test pattern (from VE or Avia) look into the green tube which is the tube that everything is referenced to (turn down brite/contrast before looking otherwise you will damage your eyes). Get the image as close to the max width that the face of the phosphor can handle (without going off the face of the phosphor).


You do this by using the horizontal sizing (master and pre-set adj.). You must remember to leave just a little room on the edge of the phosphor for horizontal expansion which you need for a safety margin. Once you have it all set for maximum phosphor usage, move the projector as close as possible to fill your maximum chosen screen width. At this distance you should have none to very little over scan (remember you have a little left in your pre-set Horizontal sizing as a safety margin).

Transfer the distances to your ceiling mount and you will now have the maximum possible use of your projectors phosphor.


There is no point having 6.5"of phosphor if you are only using 5.75" of phosphor. Its like a fixed pixel device having 1024x768 and then only using 800x600.



Colin
 
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