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post #1 of 25 Old 01-30-2012, 10:40 AM - Thread Starter
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Getting my TV mounted over the fireplace this week, and in doing so, needing to rearrange my front soundstage. In order to maintain appeal of the room as the living room 1st, with home theater being a part of it.

As such, my fronts are going to be 17' apart, with the center dead in between. The speakers are JBL L880 towers. Is 17' going to be too far/wide?

Can audyssey correct for any detrimental effects of this spacing?
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post #2 of 25 Old 01-30-2012, 11:38 AM
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How far will you be sitting from them?
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post #3 of 25 Old 01-30-2012, 11:56 AM
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+1.

The usual starting point for speaker placement is an equilateral triangle, meaning each speaker is as far from the listener as from each other. If they are 17' apart and you are 17' from each speaker, no problem. If you are too close, there will be a "hole" in the middle; too far away, and stereo separation will suffer. Audyssey can correct for distance and EQ but cannot work miracles or re-arrange your room.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #4 of 25 Old 01-30-2012, 12:05 PM - Thread Starter
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GREAT! If that's the case, then I should be good! Thanks for the answers!
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post #5 of 25 Old 01-30-2012, 05:54 PM
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Quote:
Originally Posted by Docj04 View Post

Getting my TV mounted over the fireplace this week, and in doing so, needing to rearrange my front soundstage. In order to maintain appeal of the room as the living room 1st, with home theater being a part of it.

As such, my fronts are going to be 17' apart, with the center dead in between. The speakers are JBL L880 towers. Is 17' going to be too far/wide?

Yes.

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Can audyssey correct for any detrimental effects of this spacing?

No.

Take a look at Triad in-wall speakers with grills that can be finished to match your walls.
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post #6 of 25 Old 01-30-2012, 06:01 PM - Thread Starter
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^^^ Soooo, the equilateral triangle suggestion is bogus?
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post #7 of 25 Old 01-30-2012, 06:18 PM
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Originally Posted by Docj04 View Post

^^^ Soooo, the equilateral triangle suggestion is bogus?

I don't remember my trigonometry but what is that, a 15 foot viewing distance?
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post #8 of 25 Old 01-30-2012, 06:59 PM - Thread Starter
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Trig or Ge -ometry?

But yea--as is turns out, my primary seating area is about 16 foot from both fronts.
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post #9 of 25 Old 01-30-2012, 07:23 PM
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Originally Posted by G-Bull View Post

I don't remember my trigonometry but what is that, a 15 foot viewing distance?

Recall the formula for the hypotenuse (long side, c) of a right triangle:

c^2 = a^2 + b^2

Thus b = sqrt(c^2 - a^2)

Then sqrt[16^2 - (17/2)^2] = 13.6 feet perpendicular to the center point between the speakers.

Note the suggested viewing distance is from 1.5x to 2x the screen's diagonal, so this implies an optimal screen size (diagonal) between 6.8' and 9.1'. Hope he has a projector...

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #10 of 25 Old 01-30-2012, 09:21 PM
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I thought it was 1.5 to 2x screen height. Or am I thinking width?

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post #11 of 25 Old 01-30-2012, 11:38 PM
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Quote:
Originally Posted by Bigus View Post

I thought it was 1.5 to 2x screen height. Or am I thinking width?

How Far Should I Sit From My HDTV? have a table of distances that also depends on the resolution of the source format. The 576 in the article is for the European PAL that has higher resolution than NTSC that uses 480 lines.
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post #12 of 25 Old 01-31-2012, 07:41 AM
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Originally Posted by Bigus View Post

I thought it was 1.5 to 2x screen height. Or am I thinking width?

I have copies of reports from the HDTV testing done years ago. Unfortunately, finding said copies and retrieving them from the black hole masquerading as a basement storage room is beyond my means at this time. What I clearly remember (IOW I could be wrong but am not uncertain) is it was 1.5 - 2 times the diagonal (since that's the way most screens are measured they stuck with it) and for HDTV (not standard definition, which of course nobody has now anyway, right?) The primary criteria was pixelation -- can we (humans) distinguish individual pixels at X distance from the screen. What I have forgotten is whether it was for 1080p, 720p, or something in between. Back then there were huge debates about every aspect from pixels to aspect ratio to color gamut to refresh rates...

Still annoys me a bit that they did not just choose the movie theater ratio, and also how few realize that a X" diagonal HDTV screen is actually less area than an X" standard (4:3) screen...

If I get time I can dig up the references on-line (IEEE web site, hopefully).

Edit: Duh, allsop4now llinked an article that probably covers it...

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post #13 of 25 Old 01-31-2012, 01:23 PM
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Just an FYI, but I was curious so did a bit of quick (very quick) looking. Both THX and SMPTE refer to horizontal screen width when discussing screen size, whether in X.X times the width or a horizontal viewing angle. However, this is for a certain aspect ratio (couldn't quickly tell if it was 1.85:1 or 2.35:1 they were referencing), and all of the more recent discussion of this topic I have seen relate screen size/viewing distance considerations more to the screen height than either diagonal or width. I suppose that's because we have a much wider comfortable horizontal FOV than vertical (even though our total FOV is much closer to 16:9 or even 4:3, which is I think why this was the original aspect ratio, research over more recent decades has shown that we may have decent vertical FOV but it isn't comfortable to shift our eyes up and down, while horizontal scanning is quite natural and well within our comfort zone).

I wish I could find a handy reference link... I know I've seen them in months past but can't locate one quickly now searching through the CIH forum. I think the current recommendations are to sit (or size the screen) somewhere between 2x and 3x screen heights to the primary viewing position, regardless of aspect ratio.

I just don't think I've seen the diagonal used to make a recommendation, at least not anytime recently. I'm sure it's out there though. With the changing aspect ratios, using a fixed height does seem to make a lot of sense, and aligns better with the way we view the world.

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post #14 of 25 Old 01-31-2012, 04:59 PM
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My memory is not recent at all; these studies were performed back when the HDTV standard was being worked out and I was an interested observer (designing analog ICs meant to go into the broadcast systems). I can not dispute your argument; your information is definitely newer than mine (old dogs).

I did ping a friend (another anal design engineer) and he had the same guidance I had, from his search just a couple of years ago when he upgraded his TV, but like me couldn't remember the references. He may email them to me and if so I shall post here.

I do suspect the 2x - 3x height comes close to the 1.5x - 2x diagonal for HDTV, however. Just a guess.

No worries - Don

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post #15 of 25 Old 01-31-2012, 06:29 PM
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I'm sure all of the references work out close to the same. Interesting that they started with diagonal. Makes sense as that's how screens were and mostly still are measured. And now the references I see use width, which I think is a bit strange as the height more closely corresponds to comfort.

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post #16 of 25 Old 01-31-2012, 07:14 PM
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Quote:
Originally Posted by Bigus View Post

I'm sure all of the references work out close to the same. Interesting that they started with diagonal. Makes sense as that's how screens were and mostly still are measured. And now the references I see use width, which I think is a bit strange as the height more closely corresponds to comfort.

SMPTE and THX both recommend viewing distance based on viewing angle, that is to say how many degrees the width of the screen occupies in your field of forward vision. SMPTE recommends a viewing angle of 30 degrees (the width of the screen should occupy 30 degrees of your field of vision) and THX recommends 36 degrees. Again, these are based on screen width, taking into account the screen shape, and will calculate the width if given the diagonal size of the screen. Strictly speaking, height is not taken into account, at least not directly.

Such distances are much closer than most of us are used to viewing in a living room or bedroom environment. They are good guidelines for seat placement and projector placement when building a dedicated home theater, however, and this is before taking into consideration optimum and maximum viewing distances based on screen resolution.

http://myhometheater.homestead.com/v...alculator.html

This link provides a good graphical representation for determining minimum and maximum viewing distances based on screen resolution rather than on viewing angle. The optimum distance will take into account both viewing angle and screen resolution.

http://s3.carltonbale.com/distance_chart.html
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post #17 of 25 Old 01-31-2012, 07:40 PM
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Originally Posted by Will2007 View Post


SMPTE and THX both recommend viewing distance based on viewing angle, that is to say how many degrees the width of the screen occupies in your field of forward vision.

Yes. Just seems a bit behind the times.

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SMPTE recommends a viewing angle of 30 degrees (the width of the screen should occupy 30 degrees of your field of vision) and THX recommends 36 degrees.

Minimum, IIRC. There is a nice seating chart that depicts the thx and smpte min max and ideal distances based on width but I don't have the link handy. Maximum viewing angle is I believe closer to 60 deg.

Basing distance on resolution is a nice idea, but iy isn't something I've worried terribly much about since 1080p became common place. If you do the math and want to push the 60 deg size, then 1080 doesn't quite cut it. But few people push that limit, and even then with 4k pj's on the horizon I think its much easier to build a screenwall and room around viewing angles with perhaps a pj swap when feasible than to design and build around resolution and face a redesign and rebuild when higher res pj's become affordable.

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post #18 of 25 Old 02-01-2012, 12:10 PM
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Originally Posted by Bigus View Post

Yes. Just seems a bit behind the times.

Not at all. Both organizations have established standards so that home theater enthusiasts and installers can aspire to recreate the theater viewing experience. Width makes much more sense than height when discussing viewing angle and field of vision. It's also in accord with how predatory mammals' peripheral vision and central focus is oriented horizontally in order to detect horizontal motion of potential prey. That suits humans' physiology.

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Minimum, IIRC.

Good point.


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Basing distance on resolution is a nice idea, but iy isn't something I've worried terribly much about since 1080p became common place. If you do the math and want to push the 60 deg size, then 1080 doesn't quite cut it. But few people push that limit, and even then with 4k pj's on the horizon I think its much easier to build a screenwall and room around viewing angles with perhaps a pj swap when feasible than to design and build around resolution and face a redesign and rebuild when higher res pj's become affordable.

It depends. I've tried to use that chart, or at least information gleaned from it, to explain to friends and family members in the market for a new flat screen TV that below a certain screen size (e.g., 42", or possibly even up to 50"), there is no benefit to paying a premium for "full HD" (nothing but a marketing buzzword), a/k/a 1080p, vs. a comparable 720p TV. To the extent that some television manufacturers still produce some models at 720p, depending on viewing distance and eyesight, 720p makes more sense (saves $$$ at purchase time, even in 2012) over 1080p in the appropriate circumstances. Increasingly, this is getting to be a moot point as fewer and fewer 720p models are available, but smart buyers who actually listen and understand the point can save a few hundred bucks. I did when I bought my last two 42" plasmas.
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post #19 of 25 Old 02-01-2012, 01:42 PM
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If I'm not mistaken, "20/20 vision" is defined as the ability to resolve 1 arc minute . . . thus there is a limit to how much of your field of view can be covered by a screen with a given resolution (about 30 degrees side-to-side for 1920x1080). From this slide, we can also see that, when display resolution goes to 4096x2160 or 3840x2160, the placement of L|R Main speakers 'near 30 degrees' positions them conveniently just beyond each edge of the display.

Max display side-to-side field of view by resolution (if I did the math correctly!)
1920x1080 . . . 31.2 degrees
3840x2160 . . . 58.4 degrees
7680x4320 . . . 96.3 degrees



[Of course the good news for DSX|Neo:X fans is that when they replace|upgrade to 7680x4320 display resolution, their current LW|RW speaker pair can be 'reused' as the 'new' L|R edge-of-screen speaker pair?! ]

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post #20 of 25 Old 02-01-2012, 02:04 PM
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Originally Posted by Will2007 View Post


Not at all.

Different points of view I guess. I know the standards exist to try and recreate the cinema environment, I'm just saying even cinema standards that consider width as dominant may be behind the times. We have a wider fov horizontally for sure, but our comfort level is much more dependant on vertical fov. Thus we tolerate much wider aspect ratios than our actual fov which is closer yo 4:3. Your statement that we have horizontally oriented eyes is actually an argument in favor of using vertical angle as the limiting factor. Again just a different perspective buy one I believe is correct. Not exactly intuitive though.
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but smart buyers who actually listen and understand the point can save a few hundred bucks. I did when I bought my last two 42" plasmas.

Good point. I was thinking about the large, not small end of the spectrum. I saved just as you did with my bedroom plasma purchase using that logic.

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Originally Posted by Docj04 View Post

^^^ Soooo, the equilateral triangle suggestion is bogus?

No. It's correct. A simple answer to a simple question, once again being turned into a complete fustercluck. You sit around 17' from each speaker at the point of a triangle, 17' spacing is fine. Enjoy.

cheers,

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post #22 of 25 Old 02-01-2012, 10:02 PM
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Wouldn't be avs without 14 sidebars.

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post #23 of 25 Old 02-02-2012, 05:46 AM - Thread Starter
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No. It's correct. A simple answer to a simple question, once again being turned into a complete fustercluck. You sit around 17' from each speaker at the point of a triangle, 17' spacing is fine. Enjoy.

cheers,

AJ

Well, I was able to briefly listen to some 2 channel music yesterday. I actually set my AVR to "5 ch stereo" mode, but only had the front 3 speakers hooked up. It seemed "fine". Mind you, I have not ran audyssey, and have not placed my acoustic panels. As it turns out, Seating is 15' from each speaker--here's to subtle differences.
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post #24 of 25 Old 02-02-2012, 06:13 AM
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For audio you are fine. The diversion is about optimium viewing distance to a TV screen, and life is about compromise. Or living with the sub-optimal...

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #25 of 25 Old 02-04-2012, 04:59 PM
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trig--> geometry --> formulas --> dead stupid simple: try it and see how you like it. You'll likely find it will be fine. In fact, I've found that 90 degree angle placement enhances movies, as you will still have the center to fill in, and anchor, the front stage. As for music, your ears will conclude immediately, what a threadful of calculations can only suggest.

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