AVS Forum banner
Status
Not open for further replies.
1 - 7 of 7 Posts

·
Registered
Joined
·
69 Posts
Discussion Starter · #1 ·
Hi all,


After lurking for months, finally going to build a home theater! Renovating the an old basement room that is 15x14ft. Question I want to ask is about optimal screen size and viewing distance in relation to proper audio listening position.


Read an article in S&V HT about locating proper listening position at around 2/3 or 5/7 of the room. People on this forum usually talk about 1.5 - 2X screen width. My question is how are people basing their decision on screen size - is it based on acoustics or video or are they usually quite close together.


Question 1:

My calculations are that with 15ft length, audio position should be around 10 - 11ft. In order to follow THX/SMPTE guidlines, that should mean I should have a screen size roughly 98" diagonally for 16:9. This would place me at 1.25 screen viewing. Does this make sense and is this an appropriate screen?


Question 2:

Also, would this seem sort of small on a wall that is much more wider than the 85" width? Should I just max out the size or is that just a bad temptation as it will leave me with too wide a screen for my eyes. I guess I could sit farther back but then will it be acoustically poor?


Question 3:

I haven't decided on a projector yet... looking at a DLP HD2 at this point. I need a pull down screen because the room will have other uses (so my wife tells me :) ) I haven't chosen the screen type yet, but is there a mounting bracket that I should prepare for during the construction phase so as to leave room for it? I am thinking that it will be recessed into the ceiling. I guess the other calculation will be for the screen height relative to the ground and projecto off set... sheeeshh... this is not as easy as I thought............. :confused:


Sorry if these are dumb questions. Thank you in advanced.


Respectfully,

Wooe
 

·
Registered
Joined
·
645 Posts
Wooe,


deciding screen size, viewing distance and angle plus listening distance and speaker position is indeed tricky.


The rules you cited are correct but don't solve all the problems.


This might get confusing but I'll try anyway.


If you are a stereo buff and do serious stereo listening on the same components as you do HT then I'd optimize for speaker/listening position first. Even if not, your speakers might still need to be pulled away from the srceen wall to give you a good soundstage depth. That has an effect on the incoming light path, of course. You also need to determine where they will be inrelation to your 14' width. Usually, at least two feet in from the side walls is a good point to start for decent size speakers (floorstanders). That would mean a distance between speakers of around 8'. The equilateral triangle rule would therefore set you at around 8 or 9' into the room. Add another 2' for clearance from wall behind speakers. Now you are at 11. Sounds good, maybe like me you prefer to sit just a little further than the triangle point, so make that 12' just in case.


If your audio position is around 11 or 12 you can recalculate for the SMTPE 35 degree viewing angle. My guess is that'll be around 90" width. Multiplied by 1.5 that gives you 135" which is quite exactly your 11 to 12'.


Cool so far. Now there are two things to consider: Throwing distance and pixels. Your projector is about a foot long, i.e. from lens to wall you have maximum 14'. Try to find out in the manuals of your prospective PJs which size picture they can project at a distance of 14'. The manual will also tell you the vertical offset. I suppose you will ceiling mount the PJ. The ideal solution is to have the lens straight so you don't need keystone correction. For ceiling mount that usually means the lens is lower than the upper edge of your screen. I would guess by something like 10 inches or so. If you integrate the screen into the ceiling and give a little drop your 50x90 screen (that's presuming you use a 16:9) will end around 40 to 45 inches above the floor. That's great because it will allow you to place the center's tweeter at the same height as the main speaker tweeters.


Theoretically, with your 8 foot=96 inches (derived from space between main speakers) you could go a little larger but you have to account for the position of the mains away from the backwall. The main reason I wouldn't go larger is that even with a DLP HD2 you might still see pixels if you are closer than 12 feet. The more you blow the picture up the more you'll see the pixels. So maybe an 86 inch wide screen would still give you the better picture even if slightly smaller.


Experiment with speaker placement first, then get throw distance and offset data, then adjust screen size. You will also want to leave some room behind you as this is good for stereo listening and allows you to mount a 7.1 system with rear surrounds or even another row of seating directly behind you. I could bet you end up with an 86 or 90" screen. I use a 92 or 94" screen (don't even remember exactly, what a shame!) and an HD2 at 13' viewing distance I can see the pixels in bright scenes if I wear my glasses, but only in bright scenes. I have 20/20 vision so the glasses are only ever so slightly corrective but it does make a difference.


By the way it sounds better when you wear the glasses, too. I read an interesting article about the brain having to work less for vision correction and therefore being more sensitive or having more capacity for acoustic signals. Crazy, no?


Hope that helps, the first stages are always exciting and difficult but it's worth it, believe me.


Till
 

·
Registered
Joined
·
69 Posts
Discussion Starter · #4 ·
Thanks Till,


Now I gotta do some more thinking... It does seem frustrating ... but fun


:D


Wooe
 

·
Registered
Joined
·
2,537 Posts
Good advice from Till.


I think most of us thought first about video, and second about audio. I have a 92" wide 16:9 screen in a room 11.5 feet wide. I sit 12' from the screen and use an XGA projector with MLA (LC76u). In my opinion I am just a little too close to the screen, but barely. If I had it to re-do I would put in an 86" wide screen. This is just my opinion, but my wife is of similar opinion.


On the audio front we have a constrained space, about the size of yours, but with a down staircase in the back. I have 2 side speakers barely above our ear level, and a rear speaker 3 feet behind our heads. The front mains are high bookshelf units in the corners of the room and we have a center at the bottom of the screen and a SUB on the floor below the screen.


This is awful for stereo listening, but works surprisingly well for movies ( I was surprised, I didn't expect it to be that good). If I were working with your space, I would place the seats (back row?) about 13' from the front wall, use an 86 to 92 inch wide screen, use tower speakers for the mains, place a center channel just under the pulldown, and use wall mounted (or in wall?) speakers for the surrounds and rears mounted as close to the THX reccomended location as possible.


Moving the towers around a little, and this should give you both decent stereo and great video/sound in one room.


This is just the approach I would take, YMMM.
 

·
Registered
Joined
·
645 Posts
Lespurgeon,


you read all my rambling? I'm flattered, thanks. You are very right that getting a good stereo sound from an HT system is not easy, especially if it's a little satellite system although there are good ones of those, too.


I've tried out different heights for my wall mounted tri-polar surround and back speakers. I ended up with c. 3 ft above ear level and ever so slightly angled down (I just put a rubber doorstop between the top backwall of the speaker and the wall. This will work like a lever combined with the screw in the speakers keyhole and it prevents all rattling of the speaker against the wall and leaves some room for cables).


Now, what is MLA? I suppose the 75LCu is a Panasonic unit with LCD chip?


If it works acoustically I think it's a good idea to place the sub below the screen and not in the corner because at least I can locate sub above 50 Hz. It's strange when all explosion rumble always comes from the left corner.


Till
 

·
Registered
Joined
·
2,674 Posts
Quote:
Originally posted by Wooe


My question is how are people basing their decision on screen size - is it based on acoustics or video or are they usually quite close together.
FWIW, I have one nice sized room and listen to music more than I watch movies - so it fills two roles.


I set my subtended field of vision based on video, and maximum width on audio.


In a dedicated theater you might do things differently.

Quote:


My calculations are that with 15ft length, audio position should be around 10 - 11ft. In order to follow THX/SMPTE guidlines, that should mean I should have a screen size roughly 98" diagonally for 16:9. This would place me at 1.25 screen viewing. Does this make sense and is this an appropriate screen?
I think an 80" wide (91" diagonal) 16:9 screen is ideal at 10', 87" wide (100" diagonal) at 11' (seating at 1.5X screen widths). Most people quote screen width because it makes the math easy enough to do in your head.


Projector choice will _drastically_ change what works well due to digital projection artifacts. For me, LCD projectors

preclude sitting at an immresive distance - YMMV.

Quote:


Also, would this seem sort of small on a wall that is much more wider than the 85" width?
With the lights on, an 87" screen looks large on a 13' wide wall - you'd have another 6". With a movie on you don't notice.

Quote:


Should I just max out the size or is that just a bad temptation as it will leave me with too wide a screen for my eyes. I guess I could sit farther back but then will it be acoustically poor?
If you care about acoustics, 2-3 feet from any walls is a nice minimum distance from the walls for the speakers. More is always nice.


An 87" wide screen is going to be 8' accross with the borders, which gives you 2-3' on either side depending on how far into the room you pull the speakers and how much you care about off-axis viewing.


I have 8' between my tweeters (if you stand in line with the edge of the screen, the speakers and border overlap), 2.5' out to the side walls, and 4' to the screen wall. I'm 11' from the screen wall, so I'm at the apex of the defacto standard stereo equilateral triangle.

Quote:


Question 3:

I haven't decided on a projector yet... looking at a DLP HD2 at this point. I need a pull down screen because the room will have other uses (so my wife tells me :) )
I'd want a tab tensioned screen if I didn't have a wall mounted unit - waves are real anoying. These are usually electric (Stewart has a manual screen, and Draper has a crank operated model).

Quote:


I guess the other calculation will be for the screen height relative to the ground and projecto off set... sheeeshh... this is not as easy as I thought............. :confused:
SOP is to have eye height (about 42" for me with my seats) 1/3 of the way up from the bottom of the screen. There's a little flexibility here especially if you're trying to accomodate additional rows of seating. I have my 87x49" screen 32" off the ground. Note that you may need to order a different drop than stock to get the height you want.
 
1 - 7 of 7 Posts
Status
Not open for further replies.
Top