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CAVX

Screen Height, Speaker Placement And Seating Locations

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Hmmm ... for a cinema scope i could potentially even go right up to 150"??

It has the following specs

  • Overall size including frame: 3646 X 1625
  • Viewing area: 3496 X 1475

If the border is symmetrical i calculate that to be a drop of 1550. Still within my 1650 tolerance level? How far from the ceiling does it need to be? I am assuming you can't place the border right up to the top of the ceiling? There needs to be a gap between the ceiling and top border of the screen?

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A 150" scope screen will probably fit, the three considerations you may want to take into account are:

1. Whether your projector is bright enough. The JVCs and Pana AE8000 will be bright enough on a new lamp, but I expect the JVCs would need lamp replacement before nominal end of life (putting aside any risk of early dimming).

2. Whether viewers are comfortable watching an image that extends so high.

3. If there's enough side room for your L&R speakers to image correctly.

If you have any cornice, the screen will need to sit below it. Also, the closer the screen is to the ceiling, the more sensitive it will be to reflections off the ceiling. Painting the ceiling a darker colour for a few feet in front of the screen will help.

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A 150" scope screen will probably fit, the three considerations you may want to take into account are:

1. Whether your projector is bright enough. The JVCs and Pana AE8000 will be bright enough on a new lamp, but I expect the JVCs would need lamp replacement before nominal end of life (putting aside any risk of early dimming).

2. Whether viewers are comfortable watching an image that extends so high.

3. If there's enough side room for your L&R speakers to image correctly.

If you have any cornice, the screen will need to sit below it. Also, the closer the screen is to the ceiling, the more sensitive it will be to reflections off the ceiling. Painting the ceiling a darker colour for a few feet in front of the screen will help.

And would add that if zooming then best to zoom the black bars on the wall and not ceiling or on speakers/equipment below and this needs to be considered in determining best scope screen size.

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Thanks guys ... looking at other peope's setups and reading through all the reviews etc i have decided i want to go with an AT screen. I think my room is long enough to build a false wall and put all my gear behind an AT screen which may allow me to go even larger than a 150" screen. Given that i already have an all "Adam Speaker" setup i will just permanently place them behind the AT and the others in their relevant position and will look at acquiring another set of dedicated 2ch speakers in the future to use when i only want 2ch.

This is going to be an exciting project .....

First i will need to treat the front wall then build a frame along the front wall to house the 3 front speakers then the screen etc ... Not being hindered by speakers etc so as to maximise screen size i think is the way to go ... the AT setups look awesome.

cheers Jeff

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Excellent choice! Was going to suggest this yesterday as a way around having the screen too high up the wall, but didn't think you'd be keen from the way you've described the room and the emphasis on 2ch. At 8m deep you'll have plenty of depth still even if you build the false wall out 1m. Happy building :)

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If you're going with the AT screen then to do the whole setup justice you might want to consider:

1. Aspect ratio masking - see here. Chris (Prior) the designer is one of our members here. Note it's available with AT masking as an option.

2. An anamorphic lens so you're not wasting 25% of the projector's brightness on the black bars when in cinemascope (you'll lose a few % in transmission losses, but it's still a lot brighter than zooming). A lens will help you light up a really large screen. There's a couple of local offerings that are both very good, the Aussiemorphic and the Crystalmorphic. I'm running a Mk4 Aussiemorphic (same optics as the Mk5) and am mightily impressed.

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Using an "A" lens will result in a loss of sharpness (MTF), increased distortions and chromatic aberrations for an insignificant increase in brightness.

A good high gain screen will provide much more brightness than a lens could ever provide without the down sides.

If visible pixel structure is a problem a 4k or sudo 4k projector is a better option IMHO.

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Using an "A" lens will result in a loss of sharpness (MTF), increased distortions and chromatic aberrations for an insignificant increase in brightness.

A good high gain screen will provide much more brightness than a lens could ever provide without the down sides.

If visible pixel structure is a problem a 4k or sudo 4k projector is a better option IMHO.

Quite correct Owen, you would know because you use one (A-lens) every day. I don't use my HT anymore because the PQ through my A-lens is so poor. Thankyou again for pointing this out.

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Using an "A" lens will result in a loss of sharpness (MTF), increased distortions and chromatic aberrations for an insignificant increase in brightness.

A good high gain screen will provide much more brightness than a lens could ever provide without the down sides.

If visible pixel structure is a problem a 4k or sudo 4k projector is a better option IMHO.

By an "A" lens i am presuming you are referring to an Anamorphic lens? And therefore you are both suggesting that Anamorphic lenses are not good?

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By an "A" lens i am presuming you are referring to an Anamorphic lens? And therefore you are both suggesting that Anamorphic lenses are not good?

No, only Owen is saying he prefers without.

Quark and Minty have an anamorphic lens and are very happy with it.

I don't use a lens as I zoom. Some prefer an A-lens. Not sure there is a right or wrong, just preference.

If you picked a JVC projector then it has lens memory and will zoom back and forth with a single touch of the remote.

If you pick a PJ without this feature or a PJ with manual zoom...etc and you want a scope screen then an A-lens is the best solution.

Owens preference is to pick something like the JVC ( or maybe only JVC) and zoom as he thinks it is better than using an A-lens.

Edited by bbar

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The optics on the two local A lenses are in some ways better than you'll get in mainstream projectors. Most projectors have some visible chromatic aberration (due to convergence limitations it's harder to pick on 3 chip tech like DILA and LCD, but it's usually there). The local A lenses have no visible chromatic aberration.

The two local A lenses will have some minor grid distortion (invisible to the naked eye, but measurable with equipment) and depending on throw, may have some minor pincushion, which is not visible with a few mm of overscan. With your deep room and a large screen, pincushion would be very minimal.

Edited by Quark

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You will loose brightness with an AT screen, but with the appropriate projector that can be addressed.

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You will loose brightness with an AT screen, but with the appropriate projector that can be addressed.

Compared to what? Some AT materials have a positive gain so where is the loss? unless you're comparing against negative gain materials?

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Compared to what? Some AT materials have a positive gain so where is the loss? unless you're comparing against negative gain materials?

Each perforation is a non reflective area, hence the non returning light is a sum of those.

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You will loose brightness with an AT screen, but with the appropriate projector that can be addressed.

The perfs of an AT screen will let sound pass one way and light pass the other. Yes there may be some light loss, however I don't consider the 3~5% surface area that holes combine to make to be significant and why I was able to get FL readings as high as 33 from my own system.

Edited by MarkTecher

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Each perforation is a non reflective area, hence the non returning light is a sum of those.

True, but if the rest of the material has a positive gain, it negates the losses from the perf holes to give an overall positive gain.

See here for an ISF test on our acoustic vision. It ended up having the same gain as 2 other leading screen manufacturers non woven vinyls'.

http://www.ozts.com.au/acousticvision_test_results.pdf

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I did these diagrams to hopfully better explain parts outlines in Post 1.

The link is to my Blog.

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On 05/03/2013 at 5:47 PM, CAVX said:

I did these diagrams to hopfully better explain parts outlines in Post 1.

The link is to my Blog.

mark, perhaps just a point of note. and perhaps a tad unclear in your diagrams is main listening position location vs depth of room. perhaps am misreading the diagram but it looks like the main listening position is a long way back close to back wall of the room. this is usually not idea due to reflections off back wall causing coherency issues and also not great given room gain for bass tend to get there. In moving between rooms and houses I've always found sitting at 2/3rd room depth to work out ideal. not near the back wall not in middle of the room where there is usually a null.

this would ofcourse place a 2nd row in a compromised location behind...but usually it owed leave enough room behind in most rooms id suggest with 1/3 rd of the room behind the main listening position. also i think works on the principle can make one seat ideal in a setup. rather than have all just a compromise. 

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I based the primary seating at 2x the image height (as I would for CIH) and that places the listener closer to half way of the depth of the room.  Given more people prefer 2.5x to 3x, then they are closer to where your suggesting.  

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6 hours ago, CAVX said:

I based the primary seating at 2x the image height (as I would for CIH) and that places the listener closer to half way of the depth of the room.  Given more people prefer 2.5x to 3x, then they are closer to where your suggesting.  

yeah half way is not a good place to be as guaranteed to be sitting in a natural null for any room. something not even EQ as bandaid will be able to fix unfortunately. but yeah 2.5x-3x even sitting closer i.e. 2.2x comes closer to the 2/3 room length than ending up in the middle :) and all too the benefit of the audio

its always a balance of compromises these things I guess.

 

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The end goal is to get a flat response and the path to the final result differs from room to room.    
It will be interesting to see how the sweeps come out in the latest project I have been involved in.  One thing I have changed since this thread was first posted is the way I find maximum screen heights.  

My own room is based on most of this and I just checked my in room response with the RTA and found that I have rid of my 30Hz peak and now have a fairly uniform bass response from 30 to 80Hz.  This was done by a combination of sub placement, medium density foam cylinders in the back corners and level matching.  My system does not offer EQ for the SUBs so I cheated slightly by playing with the only adjustments I had - the crossover on the plate amp and it the final level controls.      

 

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Post #1 is now revised.  Thank you Mods. 

 

Edited by MarkTecher

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You should now be able to edit the post.

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56 minutes ago, Marc said:

You should now be able to edit the post.

Done.  Thank you.

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what about basing it on image width? 1 x image width for scope works out to be 2.35 x image height.. I found with 4K in particular, even 'fake 4K' on the epson and jvcs that 1 x image width seems to be the sweet spot. Or at least it's very immersive for me. I wouldn't change it any time soon put is that way. And if you stay in the same spot for 16:9 material, you're still 2.35 x image height away too. I guess it's the same as what you're saying Mark but looking at it on the horizontal plane instead of vertical.

 

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