Screen Height, Speaker Placement And Seating Locations

[CAVX]

I think the ITU-R was designed to provide a world wide standard for multichannel audio. From what I have read, there is little to no mention of a display. At the time it was written, a large screen was a 35" CRT. Placement of L and R need to change when sound accompanies a picture as some people can pick sound to picture mis-match (horizontally) by just 4 degrees. About 50% of the public become annoyed when that sound/image mis-match excceds 15 degrees, even if they lack the vocab to desribe the upset they have. So yes using 45 degrees instead of 60 degrees works.

[50mxe20]

The Dolby site talks about 22 (44) to 26 (52) so I guess we should try all of these until we are personally happy!

[CAVX]

The Dolby site talks about 22 (44) to 26 (52) so I guess we should try all of these until we are personally happy!

No doubt there I've been progressively moving my speakers in for some 19 years and today they are less than 40 degrees apart which works extremly well for me with my AT Scope screen. 40 degrees is the width of the 16:9 portion so my actual viewing angle is closer to 52 degrees from the front row (2x the Image Height). This speaker angle decreases from the rear row (3x the Image Height) yet stereo imaging and more importantly, sound to picture match remains intact.

[Guest]

we are building a new house shortly it will have a room that will be approxx

4.7m in length X 4.1 in width

i am trying to work out what screen size i should go have read through this thread numerous times trying

to work it out but havent really come to a conclusion plus the link in the first post is not working.

i am think of going a 120" fixed 16:9 screen?

some Q's for all also,

how high off the floor should the screen be?

and approx distance should seating be?

and how far back should the projector be? it will be mounted on cieling

if anyone can help me out that would be great

thanks

[CAVX]

we are building a new house shortly it will have a room that will be approxx

4.7m in length X 4.1 in width

i am trying to work out what screen size i should go have read through this thread numerous times trying

to work it out but havent really come to a conclusion plus the link in the first post is not working.

i am think of going a 120" fixed 16:9 screen?

some Q's for all also,

how high off the floor should the screen be?

and approx distance should seating be?

and how far back should the projector be? it will be mounted on cieling

if anyone can help me out that would be great

thanks

So based on post 1, take your room length and divide that by a number between 3.68 and 5.18 to find the screen height.

4700 / 3.68 = 1277mm.

The 120" 16:9 screen you were thinking about is closer to 1450mm, so not ideal. You should consider a slightly smaller screen.

Screen height off the floor is said to be about 1/3 of the room height, so for a 2400mm ceiling, 800mm off the floor.

You want you seating to be no closer than 2x the image height and no further then 4x. In your room of just 4.7m, another reason why you might want to reconsider the screen size.

Unless your projector (Sorry which projector are you using?) has a 2x zoom, you might be hard pressed to actually fill the 120" screen in that room even if the projector is mounted right back against the rear wall.

[Guest]

thanks mark,

the is actually 5060 in length according to our plans we got yesterday. which going by your calculation 5060/3.68 gives me a screen hieght of 1375.

so i might be able to squeeze in a 120" screen, but a 110" or 115" screen would suit better?

projector is mistubishi HC7000

Edited April 11, 2010 by Guest

[CAVX]

thanks mark,

the is actually 5060 in length according to our plans we got yesterday. which going by your calculation 5060/3.68 gives me a screen hieght of 1375.

so i might be able to squeeze in a 120" screen, but a 110" or 115" screen would suit better?

projector is mistubishi HC7000

You should be right. I'd need to check the exact sizes there, so don't me as being absolute.

Good to see you have your projector crossed off the wish list

[oztheatre]

thanks mark,

the is actually 5060 in length according to our plans we got yesterday. which going by your calculation 5060/3.68 gives me a screen hieght of 1375.

so i might be able to squeeze in a 120" screen, but a 110" or 115" screen would suit better?

projector is mistubishi HC7000

What if your room is 7 metres long? this would equate to a 190cm tall image which would look ridiculous.

I have never once based anyones screen size on the length of the room, simply because nobody sits on the back wall.

It should be based on where you sit. I have never got this wrong and never once had a single complaint apart from times when you can't tell people it's too big.

For example, if we used a 190cm tall screen for a 7 metre long room, but were seated at 4.8 metres it would look even worse than at 7 metres. (this 190cm high image is a 160 inch 16:9 screen, way too big and projectors for home cinema will not light up something that large at all well)

You also need to consider rooms that have 3 rows of seats, one or two of those rows is going to miss out on the perfect image because there is usually around 1.8 metres between rows. I always ask where you're sitting, the owner, and if the predominant seating position is the middle row then screen size is based on that and nothing else. If that room is 8 metres long and the middle row is 5.4 metres from the screen, image size is based on that row. Simply because if I used the room length into 3.68 it would again look terrible (that would be a 2.17 metre HIGH screen x 5.14 metres wide and would be unwatchable. HJ would have heart failure!)

For the last 3 years or so I have been using seating distance divided by 3.34 (sometimes 3.25 to 3.45 depending on what it's being used for. 3.34 is the average of the SMPTE and THX recommendations) and it works very well. For example, if your room is 5.06 metres long, you're seated say 4.4 metres from the screen, into 3.34 and you get 1.31 metre high image, which is a 106 16:9 screen.

If you went 4.4 into 3.25 the screen would be a 110 16:9. You could possibly go 115 'pending content'.

If you were to use the SMPTE 3.0 formula your screen (from seating position) would be 1.46 metres high which is a 117 inch image and quite possibly too big or atleast at the upper limit of what one should use based on where you sit within the room.

You then need to consider what you're watching, along with the idea of futureproofing your setup for what will become mostly 1080P in the years ahead.

If you look at the 3.0 and 3.68 formulas, room length into 3.68 and seating position into 3.0. 3 into 3.68 is a 19% difference. This is saying people would normally sit at 4 metres in a 5 metre long room, and many do. But I cannot tell you how many times I've asked the room length to get an answer of say 6.5 metres and then to ask the seating distance to hear 4.2 metres or similar figures. This is where room length formulas come undone. It is quite common for folks to sit more than 20% in off the back wall.

Between 2 and 4 is so vague you could pull this out of a hat and get within 2 and 4. These formulas are outdated and need a revamp.

Hope that helps.

[CAVX]

These formulas are outdated and need a revamp.

No they work. The room's length is used as you need a starting point. If your room is 7m deep (not too many people actually have a room this deep, and I am simply using your figure as the example to show why this works?), and you divide that by a number BETWEEN 5.18 and 3.68 to find the image height. Therefore you could have an image height between 1351mm and 1902mm. This means a horizontal viewing angle between 26 and 36 degrees for Scope. Given many HT projectors won't light a screen 1902mm tall, you will be forced to reduce the image size. This is a compromise of HT and one we must often except.

Seating distances MUST fit in the room. SMPTE's spec states no closer than 2x and no farther than 4x the image height. Therefore gain, you may be forced to reduce the image height in order to make the system work in a specific room if you want up to 3 rows. This takes the guess work out of the equation.

4.5 is a number (is a number between 3.68 and 5.18) that we have agreed on for use with the MK3 lens which works well because:

7000 / 4.5 = 1555mm

2 x 1555 = 3110

4 x 1555 = 6220

This means you are assured not to be seated on the back wall and you are within the SMPTE specs.

Many HT projectors are limited to smaller screens due to their inability to light them, however the idea stems from the fact that the longest dimension is usually the length of a room. If you follow the math in post 1, you will always be able to find a solution that works in any size room including cases where the projector must fire across the width of the room. This is tried and proven and I have spend countless hours looking for an example that would not work and so far I have not yet been able to do that.

[oztheatre]

No they work. The room's length is used as you need a starting point. If your room is 7m deep (not too many people actually have a room this deep, and I am simply using your figure as the example to show why this works?), and you divide that by a number BETWEEN 5.18 and 3.68 to find the image height. Therefore you could have an image height between 1351mm and 1902mm. This means a horizontal viewing angle between 26 and 36 degrees for Scope. Given many HT projectors won't light a screen 1902mm tall, you will be forced to reduce the image size. This is a compromise of HT and one we must often except.

Seating distances MUST fit in the room. SMPTE's spec states no closer than 2x and no farther than 4x the image height. Therefore gain, you may be forced to reduce the image height in order to make the system work in a specific room if you want up to 3 rows. This takes the guess work out of the equation.

With all due respect Mark, 2x and 4x shows a massive black hole in the middle. This is something you could 'pull out of a hat' and get right. All I am saying is seating distance ie the viewer is who is watching the movie, not the back wall.

If you put a 193cm tall scope screen in a 7 metre room, the viewers eyes 75cm off the back wall (chair hard up against the wall) the viewing angle is still 40 degrees.. Does this not tell you something?

4.5 is a number (is a number between 3.68 and 5.18) that we have agreed on for use with the MK3 lens which works well because:

I don't use that formula because again it shows a massive gap. The MK3 is set to a certain distance from the screen only because of the size of the front optic.

One third of the projectors zoom is the maximum that can be used for any screen size.

7000 / 4.5 = 1555mm

2 x 1555 = 3110

So you're saying it's ok to sit 3.1 metres from a 158 inch scope screen? I'm sorry Mark but that just doesn't work. Proof these formulas are too vague.

4 x 1555 = 6220

Sitting 2 times the image height does not work. Just because SMPTE state this does not mean you will be able to resolve the image. I have tried this before, sit 2.66 metres from my 135 scope screen which is 1330 high and you can clearly see pixels. 3 times image height or more looks far better.

This means you are assured not to be seated on the back wall and you are within the SMPTE specs.

Many HT projectors are limited to smaller screens due to their inability to light them, however the idea stems from the fact that the longest dimension is usually the length of a room. If you follow the math in post 1, you will always be able to find a solution that works in any size room including cases where the projector must fire across the width of the room. This is tried and proven and I have spend countless hours looking for an example that would not work and so far I have not yet been able to do that.

Let's do another example. A room of 6.5 metres long means, with the 3.68 and 5.18 formula which would be an image height of 1.76 metres down to 1.25 metres. The difference here is anything from a 125 inch scope up to a 180 inch scope screen. This is a massive difference and still hasn't taken into account the seating position because the most important question would not have been asked to begin with.

Now let's do this knowing the actual seating position of 4.6 metres. If we use 3 times formula we get 1.53 metres high and if we use 4 times we get 1.15 - still very vague and not to the point. However if we use something more realistic, let's keep 3 for the time being and go up to 3.45. This will give us an screen size of 152 inch scope down to 135 inch scope - closing the gap. Let's then consider what is being watched, in this instance let's say all blu ray, for me this enables a better sized screen, let's use 3 and upto 3.35. The screen size now is 152 scope and down to 140 inch scope which is going be a 110 inch 16:9 image. Let's say 150 down to 140 even 135 which will work beautifully (which would be using 3.45). Using seating distance nails the correct size every single time. Room length, whilst you may find a way for it to work only adds to the gap between screen sizes which makes it all the harder to find the correct size for the viewer.

My own screen is 135 and it looks best at 4.0 metres back to 5.3 metres. One can choose to sit closer but will not be able to resolve the image. (gees Im sounding like HJ here 3.99 metres is exactly 3x image height, 2x does NOT work period.

After hundreds of scope screens sold I've nailed the correct size for every single room setup and have never used the 2x to 4x or 3.68 to 5.18 formulas. I cannot tell you how many room layouts and PDF's I've looked over, I'd say hundreds more than yourself. I do this for a living afterall so I think I'm more than qualified to debate these rather outdated formulas.

Lastly, while the 2x and 4x methods might get you there in the end, I honestly believe these formulas are too vague for use when someone is about to spend thousands of dollars on home cinema gear and I don't know anyone else who would disagree.

[CAVX]

Maybe you should read the first post again.

Edited May 10, 2010 by MarkTecher

[oztheatre]

Maybe you should read the first post again.

I have read it Mark and the speaker placement section is very sound.

[900Newton]

what should one do when the L & R speakers are too tall to fit under the screen? Are you essentially saying that you can't have a large scope screen because the distance between the speakers will be too great? The distance recommended by ProAc for my speakers is between 2.13m (7ft) and 3.65m (12ft) so this indicates that it would be fine to place the speakers outside the scope screen?

[CAVX]

what should one do when the L & R speakers are too tall to fit under the screen? Are you essentially saying that you can't have a large scope screen because the distance between the speakers will be too great? The distance recommended by ProAc for my speakers is between 2.13m (7ft) and 3.65m (12ft) so this indicates that it would be fine to place the speakers outside the scope screen?

The distance is really an issue, it is the sub tended angle that forms from the speakers back to the listener. The reason I suggest placing speakers under a screen is to provide a better sound to image match. It does not mean the sound system will sound bad if the speakers are wider. Many people may not even notice the difference. For me, this is my 20th year combining sound with picture, so I have years of researching, experimenting and ultimately, listening and I've changed many aspects of my system in the pursuit of perfection.

[900Newton]

The distance is really an issue, it is the sub tended angle that forms from the speakers back to the listener. The reason I suggest placing speakers under a screen is to provide a better sound to image match. It does not mean the sound system will sound bad if the speakers are wider. Many people may not even notice the difference. For me, this is my 20th year combining sound with picture, so I have years of researching, experimenting and ultimately, listening and I've changed many aspects of my system in the pursuit of perfection.

Ok, so whilst the sound won't be bad, it just won't be specifically matched to the image staging? Even though my room is a dedicated AV room, for the purposes of the 2-channel audio listening I find I get a better sound stage having the speakers set to the distances recommended by ProAc. Unfortunately the height of my speakers is going to dictate that they have to sit outside of the screen anyway, but atleast I now understand that it's only a sacrifice in terms of matching the image stage. The overall sound for movies won't be afected and fpr 2-channel it will still be fine.

[CAVX]

Ok, so whilst the sound won't be bad, it just won't be specifically matched to the image staging? Even though my room is a dedicated AV room, for the purposes of the 2-channel audio listening I find I get a better sound stage having the speakers set to the distances recommended by ProAc. Unfortunately the height of my speakers is going to dictate that they have to sit outside of the screen anyway, but atleast I now understand that it's only a sacrifice in terms of matching the image stage. The overall sound for movies won't be afected and fpr 2-channel it will still be fine.

It may becomes an issue for smaller ARs of 1.78:1 and 1.33:1. In many cases, most people who listen to your system will not even notice, much less make comment.

If 2CH is important to you, then yes you want to have a nice wide sound stage. I don't listen to 2CH anymore, so have optimized my setup for MC.

[900Newton]

It may becomes an issue for smaller ARs of 1.78:1 and 1.33:1. In many cases, most people who listen to your system will not even notice, much less make comment.

If 2CH is important to you, then yes you want to have a nice wide sound stage. I don't listen to 2CH anymore, so have optimized my setup for MC.

Up until now it has always been a case of the picture not living up to the presence of the sound. The poor 50" Pioneer just couldn't match the sound I'm getting out of my full ProAc Response surround setup driven by my Arcam Pre-Pro electronics. Very soon I will have the picture to compliment the sound. Can't wait!!

[Ronsta]

^^^^^^^^^^^^^^^^^^^^^^

Spam Reported

[bbar]

Mark,

Carryover from other thread as discussion belongs here.

My premise is that THX and DD recommend L&R speaker placement at scope screen border based on 45 degree angle when sitting at 3 times the height which is about 9 degrees outside a 16X9 border.

This is based on Dolby And THX option for speakers at 45 degrees which is at the outside border of a scope screen when sitting at 3 times the height. See their sites for details.

DTS states 60 degrees and DD supports 60 degrees also. Don't think THX supports 60 degrees.

Here is a THX blurb on THX certified cinemas - http://www.thx.com/professional/cinema-cer...nd-baffle-wall/

Although not precise the image clearly projects the L & R speakers at the inside border of the scope screen

My premise is also that Cinemas have L&R at the inside border of the 16X9 screen which is also a CIW scope screen.

Your last post there " Cinemas have their L and R speakers just inside the 1.85:1 side masking because it is assumed that the masking is not AT.

At home, it comes down to them (Dolby DTS and THX) providing a placement solution that works for the majority (assuming the majority is 16:9 flat panel displays) for people that might not actually know where the speakers should be placed. This is more of courtesy than a rule and not everyone owns a 16:9 flat panel as their main display.

If you ever get the chance to read work from Tom Holman (I have his book Surround Sound 5.1 Up and Running and I consider it my Surrounds Sound bible), he talks about his research into "physco acoustics" (the way humans perceive sound). Remember, Holman is the guy George Lucas hired to design the THX stages at Skywalker Range which remain today as the very best sound facilities on the planet - so I'd say he knows his stuff. In his book, he talks about the results of tests where most people in the group could hear a horizontal shift of just 4 degrees and 50% of the test subjects became annoyed once sound was more than 15 degrees off the picture. So based on that, you really don't want your speakers outside the scope screen, especially since not everything you watch will be Scope."

1) RE " Cinemas have their L and R speakers just inside the 1.85:1 side masking because it is assumed that the masking is not AT."

You appear to be agreeing with me that Cinemas have speakers just inside the border for both scope and 16X9. In other words they are at 44 degrees when sitting at 3 times the image height.

2) RE " At home, it comes down to them (Dolby DTS and THX) providing a placement solution that works for the majority (assuming the majority is 16:9 flat panel displays) for people that might not actually know where the speakers should be placed. This is more of courtesy than a rule and not everyone owns a 16:9 flat panel as their main display. "

Agree most are 16X9 but they still recommend placing speakers at 45-60 degrees from prime seating position which is way outside 16X9 screen! They could have said as close to border of screen as possible. Much easier than having people calculate angles!

3)Agree re horizontal axis shift of 4 degrees. I noticed a significant image change when I moved my speakers from 16X9 border at 36 degrees to scope border at 44 degrees which is 8 degrees.

Agree that placing speakers at DTS and DD (optional) recommendation of 60 degrees would put them about 15 degrees off picture for a scope encode and 24 degrees off picture for a 16X9 encode which seems excessive. Placing at border of scope screen is only 8 degrees off 16X9 screen which should therefore be acceptable. I much prefer the THX and DD option of 45 degrees.

So, difference between you and me is basically I support THX, Dolby and DTS ( well maybe not DTS) recommendations from their web sites and publications whilst you support the view that sound engineers mix for films with speakers positioned only for 1:78/ 1:85 screens rather than at border of screens to accommodate both scope and 16X9 encodes and hence speaker placement should be at the 1:78 border and not the 2:35 border.

If this is the case then most cinemas that use CIW and have their their speakers at the border for both scope and 16X9 encodes have incorrect speaker placement for scope encodes.

Went looking for speaker placement in theatres/cinemas and could find nothing more than at the inside border but they did not stipulate screen aspect ratio. Is the book you are referring to - Sound for Film and Television, Third Edition by Tom Holman and is it in this book that h he specifies film audio is engineered to a 1:78 screen even for scope encodes?

If so can you send me a copy of the page where he states that it would be a GREAT help as I can find nothing on the web that supports your theory. Happy for those guys to be wrong;but would like to see evidence as cannot find any material on net to support your theory. If not then would appreciate any links or content that supports your theory as there are numerous sites and articles that supports theirs even though I myself am Leary of the 60 degree separation recommendation. 44 degrees yes as that is at scope border.

Can send you my email address if you have a page from a book that states this.

One thing that is not clear from the Dolby, DTS and THX sites is the distance from the screen as that impacts the angle Angles at scope border range from 25 degrees to 47 degrees depending on distance from screen ( from 4 X height to 2 X height)!

Edit: Have found this paper on the International standard for speaker placement for audio mixing - http://www.genelec.com/documents/publicati...Interaction.pdf

This seems to be substantiated by the Audio Engineering society - http://www.ambiophonics.org/AES%20Munich/AES_Munich_1.htm

and here - http://hardforum.com/showthread.php?t=1170975

It states 60 degrees, so my preference for 45 degrees may be incorrect also.

Edited August 9, 2010 by bbar

[CAVX]

Mark,

Carryover from other thread as discussion belongs here.

My premise is that THX and DD recommend L&R speaker placement at scope screen border based on 45 degree angle when sitting at 3 times the height which is about 9 degrees outside a 16X9 border.

This is based on Dolby And THX option for speakers at 45 degrees which is at the outside border of a scope screen when sitting at 3 times the height. See their sites for details.

So is that 9 degrees total or 9 degrees per side? I'm more inclined to run with 9 total or 4.5 per side. Given that a Scope screen is 33% wider than a 16:9 screen, the speakers are therefore inside the frame of the Scope screen. The ONLY Scope stuff I could find on the THX site is in their professional side, not their consumer side which tends to be based on a large flat panel.

DTS states 60 degrees and DD supports 60 degrees also. Don't think THX supports 60 degrees.

It was the ITU-R that proposed 60 degrees separation for the L and R speakers. When sound accompanies a picture, 60 degrees is often too wide and 45 degrees tends to work better.

Here is a THX blurb on THX certified cinemas - http://www.thx.com/professional/cinema-cer...nd-baffle-wall/

Although not precise the image clearly projects the L & R speakers at the inside border of the scope screen

Which is why I do the same. Going AT from my blog

My premise is also that Cinemas have L&R at the inside border of the 16X9 screen which is also a CIW scope screen.

Cinemas can be both CIH or CIW so yes and in both cases, the L and R speakers will be inside the 1.85:1 area.

Your last post there " Cinemas have their L and R speakers just inside the 1.85:1 side masking because it is assumed that the masking is not AT.

At home, it comes down to them (Dolby DTS and THX) providing a placement solution that works for the majority (assuming the majority is 16:9 flat panel displays) for people that might not actually know where the speakers should be placed. This is more of courtesy than a rule and not everyone owns a 16:9 flat panel as their main display.

If you ever get the chance to read work from Tom Holman (I have his book Surround Sound 5.1 Up and Running and I consider it my Surrounds Sound bible), he talks about his research into "physco acoustics" (the way humans perceive sound). Remember, Holman is the guy George Lucas hired to design the THX stages at Skywalker Range which remain today as the very best sound facilities on the planet - so I'd say he knows his stuff. In his book, he talks about the results of tests where most people in the group could hear a horizontal shift of just 4 degrees and 50% of the test subjects became annoyed once sound was more than 15 degrees off the picture. So based on that, you really don't want your speakers outside the scope screen, especially since not everything you watch will be Scope."

1) RE " Cinemas have their L and R speakers just inside the 1.85:1 side masking because it is assumed that the masking is not AT."

You appear to be agreeing with me that Cinemas have speakers just inside the border for both scope and 16X9. In other words they are at 44 degrees when sitting at 3 times the image height.

I am agreeing that for CIH, the speakers are inside the 1.85:1 area. For CIW, they will also be inside the 1.85:1 area, however they will also be inside the Scope area as the both the Scope screen and the 1.85:1 screen are the same width for CIW.

[CAVX]

Continued:

2) RE " At home, it comes down to them (Dolby DTS and THX) providing a placement solution that works for the majority (assuming the majority is 16:9 flat panel displays) for people that might not actually know where the speakers should be placed. This is more of courtesy than a rule and not everyone owns a 16:9 flat panel as their main display. "

Agree most are 16X9 but they still recommend placing speakers at 45-60 degrees from prime seating position which is way outside 16X9 screen! They could have said as close to border of screen as possible. Much easier than having people calculate angles!

They could have except that when they did the original THX Home Audio system in 1991, a large screen TV was just 35". What needs to be remembered is that everything they do is also done with 2CH music in mind as well. So whilst I would tailor a system for Film Sound, many would not. THX, Dolby and DTS know this and therefore have done what they have for solution that does both film sound and music.

3)Agree re horizontal axis shift of 4 degrees. I noticed a significant image change when I moved my speakers from 16X9 border at 36 degrees to scope border at 44 degrees which is 8 degrees.

Cool. And what position did you prefer? I found for music, I wanted my speakers wider, yet for films sound, closer was better. I listen to way more film sound than music, so for me, the closer spacing for film sound wins out.

Agree that placing speakers at DTS and DD (optional) recommendation of 60 degrees would put them about 15 degrees off picture for a scope encode and 24 degrees off picture for a 16X9 encode which seems excessive. Placing at border of scope screen is only 8 degrees off 16X9 screen which should therefore be acceptable. I much prefer the THX and DD option of 45 degrees.

My first CIH system had the speakers at the edges of the Scope screen. Whilst I found it good for Scope and great for 2CH music, 16:9 and 1.33:1 was not acceptable. If you look at my plans in my blog link, you will notice that the baffle is made from three pieces of MDF. At one point I was tempted to just centre each of the LCR speakers in the middle of the baffles, however I am glad now that I ran with the precise spacing for this project. It just matches the image so well. A sound engineer once told me that when a sound system is working properly (equalized and calibrated), the audience will not make comment. He said they only comment when something about the system annoys them even when they lack the words to describe the problem. I have people listen to my system and no one has ever commented about the close spacing or that something didn't sound quite right. Last Tuesday night, I had the owners of Sunnybank Hi Fi over for a demo. Those living in Brisbane who have dealt with them would know they are fussy about sound. Their comments were all very positive.

So, difference between you and me is basically I support THX, Dolby and DTS ( well maybe not DTS) recommendations from their web sites and publications whilst you support the view that sound engineers mix for films with speakers positioned only for 1:78/ 1:85 screens rather than at border of screens to accommodate both scope and 16X9 encodes and hence speaker placement should be at the 1:78 border and not the 2:35 border.

That is not quite correct as by that, you assume the speakers move for Scope. Dubbing stages and Cinemas do not move their speakers for AR changes. The speakers are inside the 1.85:1 area even for a Scope mix, so the goal should (my goal was) be to hear what the sound mixers heard. Unless your speakers are in the same locations, you won't hear what they heard and may even question why they made the artistic choices they did.

If this is the case then most cinemas that use CIW and have their their speakers at the border for both scope and 16X9 encodes have incorrect speaker placement for scope encodes.

No. Most cinemas are CIH, not CIW. In Australia, only REDDING use CIW screens. All other cinemas BCC, AMC, Pacific Cinemas, Greater Union, Hoyts and V-max are all CIH. The only CIW cinema I've recently been into is the D-Cinema screen at Logan Hyperdome. It is CIW simply because the cinema is too tight to pay for the 12K for the 1.25x ISCO for their projector. If they did, they'd remain CIH.

Went looking for speaker placement in theatres/cinemas and could find nothing more than at the inside border but they did not stipulate screen aspect ratio. Is the book you are referring to - Sound for Film and Television, Third Edition by Tom Holman and is it in this book that h he specifies film audio is engineered to a 1:78 screen even for scope encodes?

That book is good (don't own that one) too as it explains film sound well. The book I have is Surround Sound 5.1 Up and Running and was first published in 1999. Yes it does talk about L and R speaker location behind an AT screen. Also talks about X-Curve and other technologies often scoffed (due to a misunderstanding) that found their way home as a part of the THX Home system.

If so can you send me a copy of the page where he states that it would be a GREAT help as I can find nothing on the web that supports your theory. Happy for those guys to be wrong;but would like to see evidence as cannot find any material on net to support your theory. If not then would appreciate any links or content that supports your theory as there are numerous sites and articles that supports theirs even though I myself am Leary of the 60 degree separation recommendation. 44 degrees yes as that is at scope border.

Can send you my email address if you have a page from a book that states this.

Will do.

One thing that is not clear from the Dolby, DTS and THX sites is the distance from the screen as that impacts the angle Angles at scope border range from 25 degrees to 47 degrees depending on distance from screen ( from 4 X height to 2 X height)!

THX published 40 degrees for HDTV. On the CIH forum at AVS, it is agreed that 33% wider (53.2) is acceptable as the said 40 degrees is based on a 16:9 image. SMPTE's 2x is actually 61.8 degrees. My front row of seats is at this distance and I quite like it.

Edit: Have found this paper on the International standard for speaker placement for audio mixing - http://www.genelec.com/documents/publicati...Interaction.pdf

This seems to be substantiated by the Audio Engineering society - http://www.ambiophonics.org/AES%20Munich/AES_Munich_1.htm

and here - http://hardforum.com/showthread.php?t=1170975

It states 60 degrees, so my preference for 45 degrees may be incorrect also.

Is that for sound only or for when sound accompanies a picture? Even Holman's book has 60 for music only.

[bbar]

So is that 9 degrees total or 9 degrees per side? I'm more inclined to run with 9 total or 4.5 per side. Given that a Scope screen is 33% wider than a 16:9 screen, the speakers are therefore inside the frame of the Scope screen. The ONLY Scope stuff I could find on the THX site is in their professional side, not their consumer side which tends to be based on a large flat panel.

Correct 9 degrees total and yes the scope stuff is in their professional area

It was the ITU-R that proposed 60 degrees separation for the L and R speakers. When sound accompanies a picture, 60 degrees is often too wide and 45 degrees tends to work better.

I fully agree and have mine at 45 degrees. ITU recommendation and THX may only support 45 degrees; but I am not 100 % certain. DD supports anywhere from 45 degrees to 60 degrees and DTS is 60%. So to me 45 degrees , which is just outside scope border or just inside scope border are best aligned with the recommendations (except for DTS).

Not sure what one should do with a 16X9 screen as that makes angle about 34 degrees if inside border and 36 degrees if outside border. Should the speakers still be at 45% or just inside/outside the 16X9 border. I think you prefer just inside or outside the 16X9 border and I suspect that is fine also as most commercial cinemas are implemented that way even though recommendation from ITU, THX,DTS and DD do not specify a lesser angle for 16X9 screens. .

Which is why I do the same. Going AT from my blog

Cinemas can be both CIH or CIW so yes and in both cases, the L and R speakers will be inside the 1.85:1 area.

Yes and NO, with CIW ( scope projected on a 16X9 screen) speakers are within the Scope 2:35 area; whilst for 1:85 encodes they are within the 1:85 area

I am agreeing that for CIH, the speakers are inside the 1.85:1 area. For CIW, they will also be inside the 1.85:1 area, however they will also be inside the Scope area as the both the Scope screen and the 1.85:1 screen are the same width for CIW.

Then I am in heated agreement that for scope encodes they are in the 2.35:1 area and for 16X9 encodes they are in the 16X9 area when a 16X9 screen is used and within the 2.35:1 area for scope encodes on a scope screen and outside the 1.85:1 area on a scope screen for 1.85:1 encodes..

[bbar]

Continued:

They could have except that when they did the original THX Home Audio system in 1991, a large screen TV was just 35". What needs to be remembered is that everything they do is also done with 2CH music in mind as well. So whilst I would tailor a system for Film Sound, many would not. THX, Dolby and DTS know this and therefore have done what they have for solution that does both film sound and music.

Not arguing there only that in doing so their audio dubbing for films is at 45 degrees (THX and possibly DD) and 60 degrees for DTS. In other words my understanding is that audio engineers who dub a THX certified audio do it with L&R at 45 degrees whilst film audio will be dubbed for DTS and possibly DD encodes (DTS HD-MA and TrueHD) at 60 degree separation.

Cool. And what position did you prefer? I found for music, I wanted my speakers wider, yet for films sound, closer was better. I listen to way more film sound than music, so for me, the closer spacing for film sound wins out.

Music wider for sure and wider for films also, though to be fair I moved my speakers wider when I went from a 90 inch 16X9 screen to a 102 inch scope screen. To me the imaging is excellent now though I had no issues with it when I had the 90 inch 16X9 screen and had speakers at the outside border then also (36 degrees).

So, I have not done tests, double blind or not to compare audio imaging with L&R speakers at the 1:78 border (34 degrees) on a 2.35:1 scope screen (44 degree angle) to see if audio imaging is as good or better than having speakers at the 45 degree mark on a scope screen with 44 degree viewing angle.

It may be one of those things of personal preference and yours is to have the L&R speakers recessed inwards by 4.5 degrees on each side on a scope screen whilst mine is not.

I can only say that audio engineers appear to mix audio for film at 45 degrees for THX and possibly DD and at 60 degrees for DTS and possibly DD and that the ITU, DD, THX and DTS all recommend L&R speaker placement of either 45 degrees or up to 60 degrees.

My first CIH system had the speakers at the edges of the Scope screen. Whilst I found it good for Scope and great for 2CH music, 16:9 and 1.33:1 was not acceptable.

If you look at my plans in my blog link, you will notice that the baffle is made from three pieces of MDF. At one point I was tempted to just centre each of the LCR speakers in the middle of the baffles, however I am glad now that I ran with the precise spacing for this project. It just matches the image so well. A sound engineer once told me that when a sound system is working properly (equalized and calibrated), the audience will not make comment. He said they only comment when something about the system annoys them even when they lack the words to describe the problem. I have people listen to my system and no one has ever commented about the close spacing or that something didn't sound quite right. Last Tuesday night, I had the owners of Sunnybank Hi Fi over for a demo. Those living in Brisbane who have dealt with them would know they are fussy about sound. Their comments were all very positive.

You may be right re 16X9 and 4:3 images however the majority of encodes are scope and if you like music videos then the wider soundstage is great. I can no longer make comparative comments on 16X9 encodes with speakers at the 36 degree mark as I have moved my speakers and re-calibrated. Can only say the imaging seems perfectly fine with speakers at 45 degrees and no worse for 16X9 encodes thatn when they were at 36 degree mark. Now, imaging might be slightly better at the 36 degree mark for 16:9 titles but can not in fairness make a learned comment either way.

That is not quite correct as by that, you assume the speakers move for Scope. Dubbing stages and Cinemas do not move their speakers for AR changes. The speakers are inside the 1.85:1 area even for a Scope mix, so the goal should (my goal was) be to hear what the sound mixers heard. Unless your speakers are in the same locations, you won't hear what they heard and may even question why they made the artistic choices they did.

From the links I provided and other research film dubbing appears to be done at 60 degree separation; however THX audio dubbing appears to be at 45 degrees. Nowhere can I find reference where dubbing is at 34 degrees or inside the 1.78:1 frame. Again I use the angles based on 3X height whilst dubbing studios have 45 degrees (THX) or 60 degrees for the sound engineers regardless of image height.

No. Most cinemas are CIH, not CIW. In Australia, only REDDING use CIW screens. All other cinemas BCC, AMC, Pacific Cinemas, Greater Union, Hoyts and V-max are all CIH. The only CIW cinema I've recently been into is the D-Cinema screen at Logan Hyperdome. It is CIW simply because the cinema is too tight to pay for the 12K for the 1.25x ISCO for their projector. If they did, they'd remain CIH.

I think I have used CIW in a different way to you or I frequent different cinemas to you. I refer to CIW as 16X9 and 2.35:1 encodes being presented on a 16X9 screen with scope not being projected at the same height as a 16X9 encode ; and CIH as them both being presented on a 2.35:1 scope screen with the same image height but different image widths. Anyway all the theatres I have frequented recently, maybe 3 theatre houses and 5-6 theatres they have all been 16X9 screens and hence my reference to CIW. Might be a geographic thing or we are using the terms for different meanings.

That book is good (don't own that one) too as it explains film sound well. The book I have is Surround Sound 5.1 Up and Running and was first published in 1999. Yes it does talk about L and R speaker location behind an AT screen. Also talks about X-Curve and other technologies often scoffed (due to a misunderstanding) that found their way home as a part of the THX Home system.

Will do.

THX published 40 degrees for HDTV. On the CIH forum at AVS, it is agreed that 33% wider (53.2) is acceptable as the said 40 degrees is based on a 16:9 image. SMPTE's 2x is actually 61.8 degrees. My front row of seats is at this distance and I quite like it.

THX may have published 40 degrees for HDTV but has 45 degrees for HT and for Film dubbing. I can live with 53 degrees though I prefer 45 degrees and SMTPE's 2 X = 61.8 degrees is the same as 3 X = 45 degrees which is the THX recommendation.

So, again, you appear to be saying yes all recommend 45-60 degrees but I prefer 36 degrees because of 1.78:1 encodes though you are happy with music ( 2 ch and multi-channel?) at 45 degrees or higher as well as scope film encodes at 45 degrees. It is just 4X3 and 16X9 encodes you prefer 36 degree separation (i.e. find it superior ). Do I understand you correctly.

Is that for sound only or for when sound accompanies a picture? Even Holman's book has 60 for music only.

It is for multi-channel mixing which includes both I believe. In THX and the other link I provided it specifically states film whilst in another it just states and explains the ITU recommendation for multi-channel audio mixing. Basically THX recommends that fronts be placed in such a manner as to form a 45 degree angle from the listening position (22.5 degrees for each speaker on a radial plane). THX insists that this results in a “wide sound stage and precise localization of individual sounds”. They also insist that surrounds be placed two feet higher than the listening position or higher.

There are other recommendations about all speakers being the same in the ITU standard I believe. Not related to this debate but I have even come across recommendations that L,R and Centre speaker tweeters are at the same height being ear level of the primary seating position.

Edited August 11, 2010 by bbar

[CAVX]

I am at a loss as to the source of your claims. Having actually visited a THX dubbing stage, I was shown all of the mixing rooms including behind the screen of the main THX certified dubbing stage. This sound facility was the very one responsible for film soundtracks like THE MATRIX, MOULIN ROUGE, AUSTRALIA (and the list goes on).

I need you to forget what DOLBY, DTS and even THX have on their web sites for HT for just one moment. The reason they do have this published for the people with NO CLUE at all (This is NOT US), not those of use wanting to get better results (This is US). By NO CLUE, I mean about people who set their front speakers in the corners of their room (and I have seen this many times and my telling them to move the speakers in has caused more than the occasional upset) which could make the front stage as wide as 130 degrees. This is wrong - even or 2CH music. Therefore 45 ~ 60 is needed to at least bring these people closer to the intention. From there it is up to the individual to research and experiment. A part of my research was to visit an actual THX certified dubbing stage. If I can duplicate their environment at home, then my AV experiences will be closer to what the studio intended.

The main mixing room's screen is approx 2.39:1 at 36 degrees wide - subtended triangle from centre of the back of the room to the edges of the screen. The L and R speakers are inside the 1.85:1 width, so they are well and truly less than 60 or even 45 degrees apart.

The ARD mixing room used a direct view monitor with the L and R speakers physically touching the sides of the case. Again, well and truly less than even 45degrees apart. This is done so that when they interchange program from the stages, they are hearing relatively close sound staging. No direct view monitor will allow perfect speaker placement, however this is not such as issue as they don't pan dialogue that often.

The key point I have made many times is that if I want to hear sound locations in relation the on screen visuals at the same locations the sound mixers that created the work heard them, then my speakers need to be at the same locations that they were in the dubbing stage. It may seem to go right against the grain so far as wht limited information available to HT enthusiasts and I can appreciate that. More so if you have had a good 2CH music system before getting into HT.

[bbar]

I am at a loss as to the source of your claims. Having actually visited a THX dubbing stage, I was shown all of the mixing rooms including behind the screen of the main THX certified dubbing stage. This sound facility was the very one responsible for film soundtracks like THE MATRIX, MOULIN ROUGE, AUSTRALIA (and the list goes on).

I need you to forget what DOLBY, DTS and even THX have on their web sites for HT for just one moment. The reason they do have this published for the people with NO CLUE at all (This is NOT US), not those of use wanting to get better results (This is US). By NO CLUE, I mean about people who set their front speakers in the corners of their room (and I have seen this many times and my telling them to move the speakers in has caused more than the occasional upset) which could make the front stage as wide as 130 degrees. This is wrong - even or 2CH music. Therefore 45 ~ 60 is needed to at least bring these people closer to the intention. From there it is up to the individual to research and experiment. A part of my research was to visit an actual THX certified dubbing stage. If I can duplicate their environment at home, then my AV experiences will be closer to what the studio intended.

The main mixing room's screen is approx 2.39:1 at 36 degrees wide - subtended triangle from centre of the back of the room to the edges of the screen. The L and R speakers are inside the 1.85:1 width, so they are well and truly less than 60 or even 45 degrees apart.

The ARD mixing room used a direct view monitor with the L and R speakers physically touching the sides of the case. Again, well and truly less than even 45degrees apart. This is done so that when they interchange program from the stages, they are hearing relatively close sound staging. No direct view monitor will allow perfect speaker placement, however this is not such as issue as they don't pan dialogue that often.

The key point I have made many times is that if I want to hear sound locations in relation the on screen visuals at the same locations the sound mixers that created the work heard them, then my speakers need to be at the same locations that they were in the dubbing stage. It may seem to go right against the grain so far as wht limited information available to HT enthusiasts and I can appreciate that. More so if you have had a good 2CH music system before getting into HT.

Mark,

First let me thank you for your continued support here on the forum and my intention is not to disparage you but to gain the knowledge necessary to have the best HT setup possible in my configuration and to provide accurate advice to other forum members.

As you say there is not much information up there other than the ITU, DD, THX and DTS Web pages which may over simplify so all can set up a reasonable HT environment.

Now, again, you may be correct but here is a paper on the setup of a THX certified PM3 authoring studio for audio and DVD/Blu-ray. Note this is not for commercial theatres.

http://www.ibs.org.uk/files/LU88-6_Getting...rce_THX_pm3.pdf

As you will see/read they state recommendation for music is 60 degree separation and for DVD's a45 degrees separation in a PM3 THX certified mixing studio. Now, I cannot state that it must be 45 degrees only that the THX PM3 studio appears to recommend 45 degree separation of fronts for multi-channel audio/video mixing for DVD's ( and Blu-Rays I assume) and where possible these fronts should be recessed into a baffle wall behind the screen.

Now this is for a THX mixing studio and not a HT room; but as you say you want to mimic the sound mixing studio as best as possible for the best results at home.

Here again is an ITU recommendation mixing studio for multi-channel. So does not specify DVD just multi-channel and has front speakers at 60 degrees. Could be audio only as it is not clear what is accommodated in an ITU multi-channel mixing room. - http://www.genelec.com/documents/publicati...Interaction.pdf

This poster has highlighted some of the complexities and re-states THX at 45 degrees and ITU at 60 degrees and says majority of mixing houses follow one or the other. -http://hardforum.com/showthread.php?p=1030797190&highlight=itu#post1030797190

Here again is a THX Certified Cinema, not a HT though so it may/could be different that shows speakers behind a scope screen at the border (ala about 45 degrees) - http://www.thx.com/professional/cinema-cer...nd-baffle-wall/

Note: If behind the screen at 45 degree approximately then it appears to assume a 2.12 viewing distance ratio to height for a 16:9 encode and a 3 to 1 viewing distance to height for scope encodes given speakers are placed at inside/outside border of screen given both projected on a 16X9 screen.

As you have seen a studio with an alternate speaker configuration for DVD and Blu-ray audio mixing there is clearly latitude for front speaker placement in the THX specification. Then again you reference the film soundtracks which may be different to the mixing done for DVD and Blu-ray releases. They are re mixed/mastered for DVD and Blu-Rays I believe.

I suspect this discussion may have run it's course for as you say there is not enough detail info on the net to conclusively confirm if there is a mandatory separation for L and R speakers in a THX PM3 certified audio and video mixing room for Blu-ray and DVD's as you have seen one at 36 degree separation (though could have been mixing room for theatrical releases) and I have found documentation on one that states 45 degrees and others that suggests 45 degrees for DVD's and Blu-rays.

Forum members can make up their own minds and possibly try both as part of their HT set-up. I can't do much anyway as I cannot fit speakers below my scope screen anyway.

Edited August 12, 2010 by bbar