Don Stewart, Electrimask Question - AVS Forum
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post #1 of 11 Old 01-27-2002, 10:04 PM - Thread Starter
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Dear Mr. Stewart,

Hello! I am in the process of building a dedicated theater room and I have some questions about the greyhawk and the horizontal electrimask screen thingy. :)

I am getting a JVC G15 projector, and have painted my walls black and the ceiling a very dark grey, and will be matching the carpet to the ceiling color as well, all to reduce reflection. I have installed recessed and track ligthing that can be completely dimmed or turned off.

Anyways, my aspect ratio will be 4:3, and I will later upgrade to a panamorph so as to keep the width the same. Therefore, I want to use a greyhawk with the horizontal electrimask motorized frame to blackout the bars horizontally, whilst using my blackout curtains as the width blackout. That way, when I watch a letterboxed movie, I can simply use the remote to adjust the horizontal blackouts.

My issue here is that my screen needs to be 145 inches diagonal, and 86 inches high. The wall that the screen will be on is 192 inches diag. and 97 inches high. Can you make a screen that big and still have room for the electrimask frame??

I'm sorry if I sound like an idiot here Don, I only decided last week about the screen and have very little knowledge on how it all works!! :)

Thanks for your time!! :)

KING RYGAR
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post #2 of 11 Old 01-28-2002, 08:25 AM
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Welcome to the forum--I would strongly urge you to contact Stewart (the company, not the man) via e-mail or phone to answer your question...or a Stewart dealer. Although Don is a forum member and does oftentimes respond to questions, he can't possibly be expected to answer every question in a timely manner...he's got a company to run! :)

I have specs for a Horizontal Electrimask Screenwall in front of me--it's for a 100" wide 16:9 (starting point) screen. It requires 7.5" at the top and 7.5" at the bottom to house the screen masking system/motors. It is my understanding that ALL Horizontal systems add the 15" to the max screen height (their web site validates this)--in your case, 86" high + 15" is over your limit of 97".

As an aside, that's a pretty big screen--it will seriously impact speaker placement (I would hazard a guess that microperf is the only answer for proper imaging with a screen that large). Also, unless your room is HUGE, you might want to look at a smaller screen--depending upon who you talk to, your first row will need to be about 18'-22' back...and unless you have only one row of seating, you're going to have HUGE issues with sightlines for your other row(s)--if your goal si to have a screen basically covering your entire front wall top to bottom, you've really limited yourself to one row of seating.

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post #3 of 11 Old 01-28-2002, 10:32 AM
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Eagle,
The post above by Alex is right on and their is not much that I can add to it. Alex brings up some critical issues that need to be considered. Thanks Alex!
The largest screen height that can be achieved with a 97 inch floor to ceiling dimension is 81 inches. Your image would start at 8" of the floor and would also be 8" off the ceiling.
I have seen this done a few times with installations with one row of seating. It can work as long as the seating is not to close to the screen.
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Don
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post #4 of 11 Old 01-28-2002, 04:53 PM - Thread Starter
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Thanks Guys!

When I use the JVC throw distance calculator program, I use my dimensions, and it tells me I will have a 145 inch diagonal 4:3 image. Is the program telling me wrong? The G15 lens will be 19ft away from the screen. Will that projector output an image that big and does Stewart make a Greyhawk/Firehawk that would support a screen of that size? What is microperf and will it be neccessary for a screen that large? I could do without that Electrimask system but could I use a normal Stewart frame and have one that big?

Thanks Alex and Don, I will contact directly from now on!! :)

Thanks for your time!

KING RYGAR
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post #5 of 11 Old 01-29-2002, 09:20 AM
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If you use the throw distance calculator at Projector Central (http://www.projectorcentral.com/projection_calc.cfm) for the G15U with throw set to 19', it gives you the following ranges:

4:3 on a 4:3 screen: 97.3-150.8" diagonal screen
4:3 on a 16:9 screen: 119.1-184.5' diagonal screen

I can't verify that these values are the "real" answer, but at least it gives you hope that you're not locked into that 145" diagonal screen.

Yes, a G15 can light up a large screen--even a 145" one, assuming that you have excellent (if not total) light control. As for how that looks (a G15 on a 10' wide screen), I'll defer to others--I've never seen such a setup.

Stewart can easily handle a frame/screen that size--everything they do is custom cut, and their website has all the stats on max size, screen material options, framing options, masking options, etc.

Check it out...here's a sample page: http://www.stewartfilm.com/engineeri...creenwall.html

Microperf screens allow you to place your front speakers BEHIND the screen--microperf screens are essentially acoustically transparent (they do tend to roll off the high frequencies, but this can be compensated for). All commerical cinema screens are microperf--the front speaker arrays (e.g., left, center, right) are behind the screen. Some people hate microperf--it takes away 10% of your light output and it does require care in installation to ensure that no light "backsplash" pops up (it's not that hard, just make sure everything "behind" the screen is flat back or non-reflective).

The reason I alluded to the need for microperf is that having a screen essentiall the same size as your wall precludes placing the speakers around/below the screen--although you don't really have to have a 145" diagonal screen (it looks like you could get away with a 120" diagonal), doing so would easily eat up most of your front wall real estate in terms of speaker placement options.

I sent you a private message on this as well.

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post #6 of 11 Old 01-29-2002, 09:38 PM - Thread Starter
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Alex,

Thanks a Million!!! The information I have learned from this thread alone was priceless!!

Sounds like you have a sweet setup! :) With all the help you have given me, my vision has taken a new shape and direction, so again, thanks!

:)

KING RYGAR
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post #7 of 11 Old 01-30-2002, 07:38 AM
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Don't know if you saw this thread concerning screens and G11/G15s...

http://www.avsforum.com/avs-vb/showt...hreadid=112541

I didn't know that you can't microperf a Firehawk or that a Firehawk wasn't a good match with a DILA like the G15. If I were you, I'd do a search on "G15" and see what you can find out from current G15 owners on their screen preferences.

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post #8 of 11 Old 01-30-2002, 11:15 AM
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The calculations in that topic, which may or may not be useful, would suggest either a 9' wide GrayHawk or a 10' - 11' wide FireHawk as the maximums for 16:9 without a Panamorph, providing the screen didn't need to be MicroPerfed. With a MicroPerf, those calculations would yield a 8' to 9' GrayHawk as the maximum.

With a Panamorph, things change. The big variable is how much brightness increases when using the Panamorph. We've seen reports ranging from 4% to 22%. Assuming the number is closer to 20%, add about 1' of width to any of the numbers above.

However, I think we need far more comments about the calculations in that topic...

BTW, Kam indicated in that topic that the FireHawk would be an acceptable match with a D-ILA. Just stay aware of the reduced viewing angle on the FireHawk.

/jab
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post #9 of 11 Old 01-30-2002, 03:35 PM - Thread Starter
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Wow.

You guys have really got me thinking now. :) So what is being said here is that the FireHawk 'would' be a better match for the G15 with a really large screen? (145in. diag.) Or would the GreyHawk still be better?

I have read of hotspotting issues with the FireHawk, but this may be unfounded and disproven when Stewart finalizes the FireHawk for sale...?. Maybe this is only with really bright projectors maybe? Anyways, I have painted my walls black and the ceiling really dark grey, and my window is sealed! When I turn off the lights, my room becomes a black hole.... :) I am building all my furniture from oak, staining it dark cherry but with no gloss for even less light reflection. Will taking all these steps to reduce ambient light and reflections during movies and games have a small or large impact on coolness??

I also will buy or make a masking system for the screen, so that when I switch from 4:3 (which I will use more than anything else amazingly..) to 16:9 or other aspect ratios, it should look good right?? Does having a screen larger than any given aspect ratio degrade the image?? Or am I now the village idiot?

Thanks for listening!

KING RYGAR
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post #10 of 11 Old 01-30-2002, 09:52 PM
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With that size screen, I would think a FireHawk would be a better choice, but I'm basing that purely on calculations. I have seen neither a G15 nor a FireHawk, let alone a G15 on a FireHawk of that size.

Based on reports here, I doubt the hot spotting would be a significant issue.

Some questions:

* How wide is your seating?

* How far from the screen is it?

* Is it centered on the screen?

In the end, I think your best bet is to get in contact with someone at Stewart and see what they think.

/jab
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post #11 of 11 Old 01-31-2002, 10:44 PM
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Really the best way to tell is to see a sample for yourself. There will be some hotspotting with the Firehawk, that is unavoidable. Whether this is visible or objectionable is another question, many of the beta testers seem to think it's a fair trade-off and that the hotspotting it not really noticeable. In general I would say that if you have enough light output a Greyhawk would be the safest bet (not having seen a Firehawk myself), but a 145" screen is really pushing the limits and you may find that a Firehawk would be a good choice, especially at the end of your bulb life. As jab says, just be aware that hotspotting will be more visible than on a Greyhawk.

Regards,

Kam Fung
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