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Projector Screen Help

Discussion in 'Projectors, Screens & Video Processors' started by armxz02, Apr 29, 2004.

  1. armxz02

    armxz02
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    Recently purchased the ae500, now need to decide on which electric screen.

    Need some advice from you guys.

    My loft conversion will be 6.1 metres in lenght by 4.3
    Ideally I would like a 7ft screen, would this be too big for my room considering the seating
    postion should be 2.5 the width of the screen??

    I was considering purchasing one these screens (is the size ok or too big, please

    recommend)-

    1. 90" NexNix 16:9, 1.2
    2. 7ft Owl Othello Electric Homevision 16:9 (seem expensive even with powerbuy)
    3. 92" Draper Baronet 16:9

    Which of the above screens would you guys purchase considering picture quality, build

    quality and overall reliability.

    Do you lose picture with larger screens or is it based on the output from the projector?

    I will also purchase an LMP ceiling mount (3 axis) for my projector.

    I'm confused on which specific ae500 mount to order with regards to size/drop from the
    ceiling??......how do you work this out?
    Standard lengths are from 100mm to 500mm in increments of 50mm

    Do I install the screen or projector first?.....the projector screen then measure the drop

    for the LMP mount??
    (ceiling to base of projector)

    And finally, I will be using a 12v trigger from the Ae500 to automate the screen drop.
    Is better to wire the 12v trigger with my amp or ae500 (anyone tried this?)
    Where can I purchase a 10metre 12volt trigger cable from????

    I would really appreciate your help with the above

    :lease:
     
  2. Gary Lightfoot

    Gary Lightfoot
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    Will you be sitting at 2.5 times screenwidth, or is that a figure you *think* you should sit at?

    Most projectors still give a good image when sat at 2 x, and the higher res pjs when sat slightly closer (i.e. 1.85 screen width), though the recommended viewing is around 2x which is approx 30degrees viewing angle and easier on the eyes. There's a very useful calculator here:

    http://www.myhometheater.homestead.com/viewingdistancecalculator.html

    I'm sitting 12.5ft from a 7ft wide (viewable) screen in my loft (smaller than yours) and the image is very pleasing from my xga DLP. Your pj has comparatively bigger gaps between the pixels, (but smaller pixels thus smaller gaps) so you should be fine with a similar set-up. Get the pj first, and project it from a table onto the wall and try various seating distances to see what you are happy with. Then buy a screen accordingly.

    If you're buying a matt screen with unity gain, then they will all be about the same. When it comes to adding gain, some do it better than others. A good matt white paint is comparable. The electrics etc are another matter, but hopefully someone with a good electric screen can help you there.

    With screen size, the key number you are looking for is ft lamberts (reflected light). You want more than 12 if you're after something similar to the cinema, and you get this figure from the screen size and *genuine* lumens of the pj - the lumens will reduce over time as the bulb ages, and the manufacturers figures are normaly precalibration, so you could end up with less than this. Therefore it might be prudent to aim for at least 16 to 20ft lamberts initialy.

    Divide the lumen output of the projector by the surface area of the screen, then multiply by the gain, and you will have how much light is reflecting back, and give you an idea of what kind of screen you would need:

    I.E 7ft wide 16:9 screen:

    84" x 47.25" = 27.56 sqr feet. Divide that into 850 (IIRC) lumens of the AE500 and you get 31ft lamberts. Factor in bulb wear (they dim after a few hundred hours) and misleading lumen figures by manufacturers by reducing by 30 to 40%. You then end up with around 20ft lamberts at unity.

    A 7.5ft wide 16:9 screen is around 17ft lamberts.

    Both will appear brighter when new, and end up closer to those figures after a few hundred hours. Adding a lens filter will dim it further if you want to colour correct it later (LCDs can appear a bit green sometimes).

    You'll need Panasonics info for mounting the pj height wise unless another 500 owner can help. Is there anytyhing in the manual or downloadable pdf?

    I installed my screen, then installed the pj, though you can do it the other way round. You can get the pj central to the screen by using string to measure from the top corners of the screen to where the center of the ceiling where the pj lens will go. When both measurements are the same, make a small mark on the ceiling and use a plumb bob to get the center of the lens in the right place. You'll know it's about right then.

    I put my first pj up where it looked about right, but found I had to move it to the right a couple of inches due to a small geometry problem (I hadn't used string). It wasn't too tricky, because I had put a piece of wood between the joists in the ceiling so that fixing was merely a case of screwing through the plaster of the ceiling and straight into the wooden board. Moving it left some small holes that were easily filled and painted.

    Having the pj further back and zoomed in is slightly better than closer up and zoomed out because the optics are better in the middle, and you get less internal scattered light that way. It's only a marginal improvement but you might want to take that into consideration.

    HTH

    Gary.
     
  3. armxz02

    armxz02
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    Hi Garry

    Thanks for the prompt reply to my questions

    I was considering sitting 2 times the screenwidth for optimum viewing.

    Tried the viewing calculator on the website you provided -

    Distance to main viewing location - entered 14ft
    16:9
    Diagonal Size - 90"

    Maximum SMPTE recommended viewing distance (Result) was = 12.2ft

    Does this mean the projector needs to be 12.2ft from the screen (based on 90" screen)?

    Come on guys....recommend a good electric screen based on Garry's response (would like a
    7.5ft screen)

    Guys - can I purchase a 12volt trigger cable from the web anywhere (10m preferably)

    I'm still a little confused on getting the projector and screen aligned central with strings.

    I was reading your posts regarding soundproofing (excellent info), my main problem will be the new loft ceiling.

    If I get the loft conversion company to add another layer of plasterboard to the ceiling only (or even full second layer

    overall), will this significantly reduce sound going out the ceiling from my detached house?
    Should I get the company to install a different insulation material,
    you mentioned soundblock or 35mm rockwool (for ceiling).
    Will try sealing the plasterboard joints with silicon seal.

    I need to limit the costs but be efficient on the soundproofing ideas.

    Worried about noise and my neighbours.

    I'm a noobie, be gentle.
     
  4. Gary Lightfoot

    Gary Lightfoot
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    The projector doesn't have to be 12.2ft from the screen but it's suggesting that's how far you should sit. As the pj has a particular 'throw' which depends on the lens, it can be situated anywhere within it's throw range. The zoom function can also adjust this so you can fit the pj somewhere more convenient or just place it with it's zoom range and adjust the zoom to fit the screen. Looking here:

    http://www.projectorcentral.com/projection-calculator.cfm?part_id=2315

    Gives some info which (if accurate, sometimes they're not) looks like that the pj can be 12.3ft away from the screen to give the size you want. It has a zoom so you can vary this to have it further behind. Best to get the pj and/or manual to be sure. The coffee table test will help a lot to get a feel for the size etc.

    SMPTE is based on movie viewing and doesn't take into account the projection technology - if you're using a low res LCD you could be seeing a lot of screendoor. Using a small CRT could mean not enough light, so you may have to sit either closer or further away. 14ft seems a good seating position though.

    The string idea is to make measuring easier - if the distance from the top r/h corner of the screen to the lens is the same as that from the top l/h corner, then the lens is in the correct place. Only a little orientation of the pj to make sure it is straight needs to be done then. If the lengths are different, then the pj is closer to one side than the other, and the image will be a little distorted (smaller on one side, or the top or bottom may run off a little).

    I only used a single layer on the roof joists so as to not add any extra weight, though if you're getting a proffessional install, they may be able to advise on this. I used insulation and a single layer on the ceiling though for the small width a double layer would have been OK. I didn't put the insulation up close to the halogens due to the heat they produce.

    Plasterboard is very effective on reducing sound - around 3db attenuation per layer (IIRC) provided you have no holes - a 25mm hole (again IIRC, it's late. :) ) lets in around 15dbs so can negate any sound proofing - hence the need to seal all edges with silicon. My soundproofing seams to have worked quite well as the audio is barely perceptable when playing at normal levels. You have to know what to listen for when in the garden front or back to hear it.

    I used 2" rockwool slabs in my roof joists which allows 2" of air space behind for ventilation of the wood (they should also fit a vapour barrier between insulation and plasterboard). I use the HD slabs in my rear studd wall, and 4ins in the small ceiling. One thing I didn't do but probably would do now, was to use the plasterboard that comes with insulation and reflective foil on it for the south facing part of the roof. It gains a fair bit of heat in the summer and the loft is 3 degrees centigrade warmer than the landing area.

    If you have vents, try to route them in an 's' configuration to reduce sound travel.

    Plasterboard and Wickes HD slabs are cheap and effective. If you go to the US forum www.avsforum.com you'll find the majority go the 4x2 stud wall with 4ins of insulation and 2 layers of plasterboard. Look for posts by Dennis Erskine for proffessional input.

    If you have a sound pressuer level meter, you can use it to see what the noise level is now using just a stereo as a base reference, and then see what it's like after each stage of soundproofing is done. If you get on with the neighbours, you can do the tests from their houses.

    HTH
     
  5. Techno Freak

    Techno Freak
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    Hi armxz02,

    I have an owl othello 7ft electric.

    I am very pleased with it.

    It's quiet when dropping / retracting and I really like the black velvet finish on the casing. Cuts out any reflection from the PJ.

    The only thing I will say to it's detriment is that the vertical edges where the black border meet the white screen are always curled up when I initially drop it. Within 5 - 10 minutes they straighten up though so you never notice it through the film.

    I have had mine about 8 months and watch 1 to 2 films per week and it still looks like new. No rippling or curling ( other that the curling mentioned above ).

    All in all it is a quality product.

    Paid around £700 ish from www.av-sales.com

    I have a PT-AE300 and they seem well suited - I have no complaints.

    Check my website link for some pics of the screen during install.
     
  6. armxz02

    armxz02
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    You guys are great!

    Special thanks to Garry and TechnoFreak

    I will show this post to the installers and let them order the relevant material.

    ps. I'm looking into the Owl screen now

    TechnoFreak - any ideas on the 12volt trigger...need to order a 10metre from somewhere

    :thumbsup:
     
  7. Techno Freak

    Techno Freak
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    Sorry, don't know anything about the triggers.

    I just used the standard - wired, switch that came with the screen.

    Just means that I have to get my arse up to raise and lower it.
     
  8. armxz02

    armxz02
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    I'm a little too lazy to get off my @rse

    I liked your site and homecinema pictures (cool centre speaker placement)

    Many thanks
    Moh
     

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