7.1 in a 14'X18' Room? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 9 Old 04-13-08, 11:14 PM Thread Starter
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7.1 in a 14'X18' Room?

Hello, I an designing my home theater room and would like to use Dolby TrueHD 7.1 Suround Sound for BluRay Movies. The dimensions of the room are 14' W X 18' L. I would like to go with a 123" projector screen. My main concern is the 7.1 speaker placement, specifically the two rear speakers having enough room behind the seats. How far back do they need to be? Thanks for any help you can provide...
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post #2 of 9 Old 04-14-08, 03:46 AM
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Re: 7.1 in a 14'X18' Room?

mlacek , gooday , I have a 7.1 in an 18x14 room . no problem. your seats need to be 4ft from the rear wall . My screen is 106" . 120" may be a little on the large side . A small room that size needs to have have a lot of absorption in it . like carpet , rugs , drapes over the walls etc . Let us know how you go , Kind regards , Alan Monro .
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post #3 of 9 Old 04-14-08, 06:15 AM
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Re: 7.1 in a 14'X18' Room?

Agreed. Place your seats properly first and then set the screen size. Setting screen size first can result in lots of problems (and I'd agree that's a bit big for that room)


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post #4 of 9 Old 04-14-08, 11:22 AM
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Re: 7.1 in a 14'X18' Room?

Agree on the screen size issue as well.

I've seen a screen that took over the entire wall with only about 8" on each side. It looks incredible, however, the owner is stuck with using small speakers all around (which was fine at first, but now he wants to upgrade).

Get your seating right and then pick the size. There are a bunch of calculators online, or you can do the hand test. Sit in the listening/viewing position. Put your hands in front of you at full arms length, spreading your fingers. Touch your thumbs together. The pinky to pinky distance as seen on your wall is close to your ideal screen size. It gives good coverage, so the screen fills up most of your field of view, without having to turn your head to see everything.

A friend of mine from college who went to film school afterwards taught me that. It also works for computer monitors.
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post #5 of 9 Old 04-14-08, 01:02 PM
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Re: 7.1 in a 14'X18' Room?

I also have a 18 x 14 room, and have gone with a 92" (7.67') screen with the HD projector over my head. I sit back about 12 feet, and find it perfect for my viewing and speaker positioning.

Watch out for bass nulls in that area though... trust me.
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post #6 of 9 Old 04-14-08, 03:50 PM
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Re: 7.1 in a 14'X18' Room?

Placing your rear speakers about 4 ft apart and 4 ft behind the back seats is the best placement. I also echo the screen size recommendations I use a 96" screen and sit back 12 ft from it and find that size just right.

Home theater:
Onkyo 805, Yamaha YDP2006EQ, Samson Servo 600 amp
3 EV Sentry 500 monitors across the front, 4 Mission 762i's Surrounds, SVS PB13U sub, Panasonic BDT220, Harmony 1100, Nintendo WiiU
Panasonic PT-AE8000 on a 120" 2,35:1 fixed screen

Living room system:
Sherwood/Newcastle R972, Mission 765's, SVS SBS02's, A/D/S MS3u sub, Yamaha YDG2030EQ
Yamaha KX-393 Tape deck, CDC 805 CD changer, Panasonic BD60, Sony turntable PS-T20
Panasonic TC-P50ST60, HD-PVR & WDTV Live, Harmony 900

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post #7 of 9 Old 04-15-08, 04:01 PM
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Re: 7.1 in a 14'X18' Room?

They say the prime seating position is about 1.5 screen widths back from the screen. With a 123" screen you'd be sitting about 15 feet back. Any closer and it would start feeling like sitting in the first row at the movie theater. You'd end up having to turn your head to see everything and at the end of the movie you'd wonder why your neck hurt. You also can start seeing pixelization in 1080i projectors the closer you get. Size the screen to where you'll have your seats.

Here is a link to a good online viewing distance calculator

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post #8 of 9 Old 04-16-08, 05:54 AM
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Re: 7.1 in a 14'X18' Room?

PLEASE don't think of it that way. You don't move the seat to fit seating distance. You put the seat where it needs to be and then purchase the appropriate sized screen.

Also, the 1.5 width is a very rough rule of thumb. I prefer to use the 36 degree minimum included viewing angle. Where you go from there depends way too much on screen type and projector quality to make any other assumptions.


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post #9 of 9 Old 04-16-08, 04:45 PM
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Re: 7.1 in a 14'X18' Room?

Anyone is just posting what he likes.... Just place your seats then chose your screen size. My advice is big screens have a lot of WOW factor but PQ degrades with size as well. You should consider full definition and a good projector if you want anything bigger than 120" if you're about 13 ft-15ft.

THX recommends a max 40 degree and a minimum 36 degree. 40 degree make 150" from 15 feet....make the calculations for 36 degree.

I am having 106" from 10.8 ft and that makes about 39 degree viewing angle. Anything static and I feel the screen is too small. Transformers or Saving private Ryan make me feel I can't stand any bigger.... But sure I needed 1080p resolution ... Check my signature and decide

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Important HT proverbs:
- "You can never have too much headroom" (talking about bass)
- "you can never have too big a screen" (talking about still pictures)

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