CRT question

Discussion in 'Projectors, Screens & Video Processors' started by m0v1em4n, Oct 1, 2001.

  1. m0v1em4n

    m0v1em4n
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    Hi all,<br />I am in the process of gathering as much info on CRT projectors, especially the Barco 801&gt;808&gt;? Due to the fact that are reasonably priced,<br />The problem I have is that due to my low roof I would like to install a CRT higher than recommended by the Barco lenses program, <br />I can get the distance, but to install at the right height would make it to low being near my seating , What I would like to do is install it above the ceiling hight and angel it down to the screen, no more than 12”.<br />My Cinema room is very small, and I understand that it would be difficult to install a barco due to its size,<br />Seen the Barco that Roland installed at the What HIFI stand at Live in Birmingham<br />Any info would be appreciated.<br />If you would like to see what I am up against you can visit my web at <a href="http://www.stevenmorris.co.uk" target="_blank">Steve's Cinema</a>

    Thanks<br />Steve

    PS sorry to Roland B4 for not replying to his private mesage only just found it
     
  2. Roland @ B4

    Roland @ B4
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    Steve<br />Nice room<br />Can you confirm what that ceiling is made off looks like a conservary. <br />The projector is a heavy piece of kit you would need to make sure it was strong enough to take the extra weight.

    But to answer you question yes you can angle the projector down I would say up to about an extra 5 degres the lens program will let you do more but the amount of keystone correction may be excessive.

    Did you do your calculation for a 16x9 screen because that makes a big difference. I would have thought it would be possible. You don't give the screen size so it is difficult to give the exact dimension.
     
  3. m0v1em4n

    m0v1em4n
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    Hi Roland,<br />Yes it as got a conservatory type roof, that's to avoid any planning,<br /> Most of my viewing is at night but when viewing in daylight I have roof blinds that I pull down<br />What I intend to do is to increase the roof height in the area where the Barco? Would go say to take the top part of the projector, also I intend to beef up the area to take the weight, Screen width is going to be around 64” wide screen and considering that the seating is around 11ft away I would say that’s ample, <br />Where are the fans situated? On the Barco, Would I need to had any sound deadening to the roof area above the PJ.<br />Roland going to do a bit of a tech drawing with room sizes etc, would appreciate it if you would cast your eye over it and give me you opinion will post it on my site and send you an e-mail if that ok?.

    If any one got any info sites etc feel free to post them or mail me.

    Thanks

    Steve Morris
     
  4. m0v1em4n

    m0v1em4n
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    <img src="smile.gif" border="0">
     
  5. Roland @ B4

    Roland @ B4
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    Sorry Steve<br />Having a bit of a kip<br />What you are trying to do is possible but it really pushes the projector to its limit due to the keystone. I think an 808 is out due to size. I would look at Barcodata 708 or Sony D50.

    When you push the projector that high you will have to limit its scan rate down to about 40Khz (line doubled) which on 5' 4" screen will look fine.

    It could get awefully humid up on that ceiling.<br />If it ever condeses on a cold rainy day say bye to the PJ.

    Could you not live with a coffee table in front of seat? or better still two seats either side of the projector and lift the projector off the floor.

    So to give you the distances.<br />64" wide screen<br />708 will be 90" to front and 111" to back<br />801 / 808 will be 94" to front and 123" to back

    Fans on a 708 at front and back<br />801 at back<br />808 front and back

    On a rainy night no problem but you will have to get close to one of these to say if they are too noisy.
     
  6. m0v1em4n

    m0v1em4n
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    Thanks Roland,
    Will do a little research
    would the 708 connect to a line doubler or a progressive scan DVD?, whish there was enough room for a coffee table, and only just got the lazy boy recliner seat,
    the roof height above the PJ is going to the increased so there should be lot of air circulating around the PJ and I have never had a problem with condensation, because the room is heated, what should the angle be set at in the Barco lens programme it seem to auto set to 10.5, also does , Thanks for your help would it be ok to fire more questions at you later.

    Steve
     
  7. stratman

    stratman
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    Roland,

    I see from one of your posts above that having a 16:9 screen makes a difference to the throw distance calculation, do you have a formula for this and does it place the projector closer to the screen or further away. I have aquired a NEC 9PG+ that I want to set up with a 16:9 screen but am limited to floor mounting.

    Regards, Simon.
     
  8. m0v1em4n

    m0v1em4n
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    Hi Roland,

    Looks like the Barco 708, might be what i need, looks like it weights a lot less than the 808,
    What kind of cost would a used 708 Barco be
    Do you have any Barco 708's, if not perhaps you might know some else who might have a stock :)

    Steve Morris
     
  9. squid

    squid
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    HAVE YOU TRYED THE BANNER ON THIS SITE .

    THEY HAVE A 708, 3500+VAT
     
  10. Roland @ B4

    Roland @ B4
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    Steve
    Yes I have 701's and 708s even a Cine 7
    I will send you a mail with prices. I will include a drawing with angles etc.

    The internal Line doubler from Barco is actually quite good and yes it will handle the output from a progressive scan DVD player (component or RGB) or any other progresive scan signal (ie computor) up to about 69Khz (50Khz for 701)

    As regards the 10.5 degree angle this is standardish for most CRT projects. It works roughly like this.
    In order to produce a 4x3 image from either tp or bottom ofthe screen the projector lens needs to be angled. this is done in the factory and comes out at 10.5 degrees.

    Industrial CRT projectors are very flexable and will allow some masive key stone correction without too much loss of quality. But the lenses will need to be shimmed and have spacers fitted to cope with this extra angle so that the image is sharp top to bottom.

    There is a restriction on scanning rates also because of the extra stress that is put on the circuits. But provided you do not go over 32Khz (line doubled), things will be fine here.
     
  11. Roland @ B4

    Roland @ B4
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    Simon
    The 9PG is a 7" tube if I recall and i'm sure uses the same lenses (HD145 or HD6) so you should find the throw the same as the Cine 7 from the BArco lens program but post all your dimensions and we will see if it will fit. I'm not an NEC expert but it has sensible amonts of correction.

    The reason that a 16x9 image puts the projector closer is that you can draw a slightly wider 16x9 image than you can a 4x3.

    The image produced on the face of a CRT tube is Keystoned (ie wider at the top than the bottom). There is a limit on how wide you can draw that on the surface of the tube. (If it gets too close to edge of the CRT you heat the seal too much and it fails - expensive)
    Imagine drawing a keystoned image on your monitor in front of you. Widest bit at the top, say 14" wide and 7" wide at the bottom. This is roughly how things would be drawn for a 4x3 image. Now for a 16x9 image the keystone is not so accute because the relation between width and hight are not as grate. Therefore you can write a wider image and your projector gets a bit closer.

    Many of us techies ignore the lens programes set the width and move the projector back and forth to get it right. Every millimeter of phospher makes a differnce.
     
  12. squid

    squid
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    i would guess you could get it rather a bit closer if you could get the tubes perfectly level with the screen center . this would help a lot in a rearpro setup .

    i personaly have my pj closer than recomended .i do have the projector tilted a bit up at the front (ceiling mounted) so i don't have that much keystone needed. my ceiling is not too high and my screen aint that low

    the ideal situation would be to get a pro like roland or gordon in . saddly when you aint got 2p to rub together this is'nt an option .

    i'm sure if you got the pj through roland he could do a good deal(if he can get out to your area ;)
     
  13. Roland @ B4

    Roland @ B4
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    The distance is not significant but the width on the phospher is.

    For an 8ft wide screen a Cine7 / 708 would be
    3170mm from the screen for a 4x3 image
    3130mm for a 16x9
    3080 for a 16x9 0n axis.

    I think the above proves how important it is to get the possition correct. These figures assume that the projector is in the centre line of the screen and at right angles to the screen.

    I've said it before this goes a long way to getting the best out of a projector.
     

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