Projector distance.... What's normal vs to close.

Discussion in 'Projectors, Screens & Video Processors' started by DuncanFisken, Jun 14, 2015.

  1. DuncanFisken

    DuncanFisken
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    I've posted this in my main build thread but thought I'd start a separate one as it's a burning question for me right now.

    Okay so I'm having a bit of a dilemma today.

    Been outside measuring where I estimate the front speakers and screen will need to be seated.

    Based on the monitor audio website the speakers need to be placed around 20 cm from the wall. This plus the actual depth of the units means the screen will be about 70cm into the room.

    The front row of seating will have a viewing distance of around 290cm to the 120" screen.

    My question is is this to close? Should I reconsider and mount the screen on the wall and place the speakers to the side and underneath? Thus giving me a viewing distance of 360cm.

    Another option would be to place the speakers closer to the wall.

    I'm starting to get a little nervous when trying to picture me looking at the screen from the different distances.

    Thanks for any advice and help.


    Cheers

    Duncan
     
  2. kutsanagi

    kutsanagi
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    Personally I would say that's a little close. I've a 106" screen and sit approximately 3.75m aware from the screen and that's massive from the sitting position...if you have the projector I'd project the image (120") on the space where the screen is to be put, should give you an idea...
     
  3. dhts

    dhts
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    Not quite sure I fully understand. Are you planning on a 2.4 or 16:9 screen and are you looking at putting the speakers behind it ?
     
  4. dhts

    dhts
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    Ah, just found your main build thread which also explains why you were outside measuring !

    If you're doing 16:9 and using large floor standing speakers I think there's somewhat less advantage in going AT. As you've spotted the screen will come forward a fair bit to accommodate the depth required but also the L and R will be closer than is ideal. When I did my cinema I stuck with a non-At screen while I had floors standing speakers then moved to At when I was swapping my speakers.
     
  5. Peter Parker

    Peter Parker
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    THX recommend a eating range of 2.4 to 3.68 x the image height. 2.4 is optimal, 3.68 is the back row.

    SMPTE recommend 2 x the image height as the closest recommended and 4 x IH for the furthest.

    The geometric center of the seating area of THX theatres built to their recommendations is around 2.4 x IH.

    A good way to see what will work for you is to experiment by projecting onto a wall and see how close you can comfortably sit when watching movies for long periods. When you have done that, you can then determine the best screen size and seating distance.

    Your seating distance of 2.9m to a 120" diagonal 16:9 screen is around 1.95 x the image height - a tad closer than SMPTE recommends as closest, but from personal experience of a 4k projector with upscaled 1080 material, I found it a very immersive experience and fine for watching movies. Scope will be shown smaller in your case with a 16:9 screen (ideally scope should be the biggest format), so will be easier to watch (less vertical height and excessive vertical viewing angles can cause discomfort) but less immersive. You will be sat at around 2.5 x IH for scope. But what works for me, may not be ideal for you.

    What projector will you be getting?

    Gary.
     
  6. razy60

    razy60
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    One thing to consider is the height of the viewing area, I have similar speakers to yours and originally had my set up so that the screen came down and touched the top of the speakers but the viewing angle proved to be uncomfortable, the only practical solution's were move speakers to the side (not ideal as it meant moving a door and loosing an arm chair) or turning the sides upside down which worked fine. Although An AT screen would have been ideal the cost wasn't.
     
  7. Peter Parker

    Peter Parker
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    Forgot to ask - have you tried the speakers against the wall? If the speaker crossover has been designed for the box edge diffraction (baffle step correction), then having them where recommended away from the wall should work best, but placing the speakers against a wall is almost like having them in a baffle and can increase the bass response by a few dBs, so it may be worth trying different locations and see what sounds best for you.

    Gary
     
  8. DuncanFisken

    DuncanFisken
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    Thanks so much to all for your responses. The above helps me formulate some ideas and also answers a number of questions I had.

    Gary I'm like the idea of placing the speakers closer to the wall for added bass.
    I'm going to have a proper read through the posts on the train home.

    Projector I'll be using is an Epson tw9000

    Screen will be a 16:9 ratio.

    Thanks again everyone.

    Cheers

    Duncan
     
  9. Peter Parker

    Peter Parker
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    The Epson is an LCD projector so you may see pixels if you sit close enough with that size screen. Can you get a demo or have you already bought it?

    Gary
     
  10. DuncanFisken

    DuncanFisken
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    Hi Gary

    I already have the projector.... As I've seen bits come up for a decent price I've bought them over the last 12 months to put in the room.

    Now in reality had money not been a factor I would probably have chosen a slightly different route.

    When considering the floor standers I made the error of not factoring in the gap between unit and the wall.

    I've had another thought I could place the centre channel speaker behind the screen and then make a frame even side of the screen for the floor standers covered with speaker cloth to hide them behind. This would probably save about 20cm.... But then the question is will that 20cm make all the difference.

    Currently everything is boxed up in storage. Will go down and get the projector out at the weekend to test it.

    Cheers Duncan
     
  11. DuncanFisken

    DuncanFisken
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    Another question not completely screen related so may be better asked elsewhere....

    How deep should a baffle wall be?

    Been trying to come up with some options. I think these are them.

    1. Place current speakers against the wall and live with the sound. Could I block the bass ports? Would that reduce any unwanted reflections from the bass port?

    2. Scrap current idea, sell speakers on ebay and build a baffle wall with in wall speakers. How thick should a baffle wall be?

    3. Buy some smaller footprint speakers and put them behind the screen selling the current ones on ebay.

    Thanks for your help.

    Duncan
     
  12. Peter Parker

    Peter Parker
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    If you want to prevent sound leaking through to the room behind the baffle wall, there seems to be a recommendation of around two feet, with plenty of insulation within the cavity on the surfaces (so not stuffed). This doesn't sound like an option as you want to save space.

    1. The bass port is part of the speaker design and how the speaker achieves it's bass response. Blocking it will reduce that, so probably not a good idea. Measuring the speakers frequency response would be one way to find out by how much if you have that facility.

    2. How thick or how deep? Depending on the speakers you buy, the wall can be as deep as it needs to be (taking into account soundproofing if necessary). A 4" stud wall with normal in wall speakers attached directly to the plasterboard would be one of the shallowest options. One of the least deep and cheapest options is to use car speakers and the baffle would be around 2.5" deep, but not many people would be that adventurous. The better approach is to build the baffle wall, and fit the (normal box) speakers on isolated platforms in holes that are the same size as the speaker. This makes sure the wall doesn't vibrate with the speaker and colour the sound. The baffle itself should be quite thick. The first layer of the wall can be OSB and the second (and maybe third) can be plasterboard. Using green glue in between layers helps. Then cover the wall in (black) acoustic insulation.

    I think No 2 is the best approach as it can potentially take up the least amount of room and ideally would be used with an acoustically transparent screen with the three identical speakers placed correctly in a line behind the screen. Building a stud wall is easy and relatively cheap if you don't mind a bit of DIY. How deep and thick will depend on the speakers you use and how rigid you want the baffle to be.

    Gary
     

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