116 replies to this topic

[MarkTecher]

bbar, on Aug 12 2010, 12:11 PM, said:

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.u...rce_THX_pm3.pdf


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.c...Interaction.pdf

I am sorry if I appeared to come across as short before.  The truth is, there is not enough freely published information about this for enthusiasts to use a reference.  

THX PM3 PDF is a good find. I don't think I've read that before.  

Film sound for a cinema Vs film sound for DVD/BD should be the same, however they are not.  Most of the differences lay in channel levels (Surround levels are pulled 3dB for home or packaged media), so there may be some slight variations between what one heard at the cinema compared to what the DVD/BD sounds like.

So far as L and R speakers placement is concerned, film sound is about providing auditory clues to match an on screen visual.  Mixing for MC music is not as critical as very seldom does the sound actually match the picture - I am talking about a studio version not a live concert.  

Reading the PDF and yes it does state 45 degrees.  Again, in my case, what I have done is simply copy a real example dubbing stage, so by defaut, the speakers have to be closer.  This topic was beaten half to death at AVS when many new to CIH started to question the speaker placement.  One suggestion was even mount the L and R speakers on the same rig that controlled the side masking, so as it opens, so the L and R speakers move out.  It kind of got squashed when Vern Dias posted a photo of his LCR array with his VERY wide 2.66:1 screen.  Here were the three LCRs in what looked to be the centre 1/3rd of the screen, however as Vern explained, their location was based on his 40 years of projection experience, and who was game to challenge that?   Several members lfrom this forum like Tukkis (he has a very nice cinema BTW) have also found that this placement of the L and R just inside the 16:9 portion works best.      

When seated in the back row (3.2x IH), my eye line is centred vertically to the screen and because the speakers are some 6 feet apart, stereo separation is clearly heard even though the angle is quite tight.  A apart of this is the fact that my speakers do have tight control over the vertical directivity.  I don't think it is still on the THX site, however there was a time when it explained why speakers with controlled vertical directivity can be placed closer than conventional loudspeakers.  I've certainly taken advantage of that fact with my system.

Another reason why I choose to move the speakers in (apart from a better relation ship with smaller ARs) is that my current room has the screen going from wall to wall.  This just would not work if my speakers were wider than they are.  I need to make a covers for above and under the screen and therefore havn't really posted any good shots of the front of the room.

[bbar]

MarkTecher, on Aug 12 2010, 03:20 PM, said:

I am sorry if I appeared to come across as short before.  The truth is, there is not enough freely published information about this for enthusiasts to use a reference.  

THX PM3 PDF is a good find. I don't think I've read that before.  

Film sound for a cinema Vs film sound for DVD/BD should be the same, however they are not.  Most of the differences lay in channel levels (Surround levels are pulled 3dB for home or packaged media), so there may be some slight variations between what one heard at the cinema compared to what the DVD/BD sounds like.

So far as L and R speakers placement is concerned, film sound is about providing auditory clues to match an on screen visual.  Mixing for MC music is not as critical as very seldom does the sound actually match the picture - I am talking about a studio version not a live concert.  

Reading the PDF and yes it does state 45 degrees.  Again, in my case, what I have done is simply copy a real example dubbing stage, so by defaut, the speakers have to be closer.  This topic was beaten half to death at AVS when many new to CIH started to question the speaker placement.  One suggestion was even mount the L and R speakers on the same rig that controlled the side masking, so as it opens, so the L and R speakers move out.  It kind of got squashed when Vern Dias posted a photo of his LCR array with his VERY wide 2.66:1 screen.  Here were the three LCRs in what looked to be the centre 1/3rd of the screen, however as Vern explained, their location was based on his 40 years of projection experience, and who was game to challenge that?   Several members lfrom this forum like Tukkis (he has a very nice cinema BTW) have also found that this placement of the L and R just inside the 16:9 portion works best.      

When seated in the back row (3.2x IH), my eye line is centred vertically to the screen and because the speakers are some 6 feet apart, stereo separation is clearly heard even though the angle is quite tight.  A apart of this is the fact that my speakers do have tight control over the vertical directivity.  I don't think it is still on the THX site, however there was a time when it explained why speakers with controlled vertical directivity can be placed closer than conventional loudspeakers.  I've certainly taken advantage of that fact with my system.

Another reason why I choose to move the speakers in (apart from a better relation ship with smaller ARs) is that my current room has the screen going from wall to wall.  This just would not work if my speakers were wider than they are.  I need to make a covers for above and under the screen and therefore havn't really posted any good shots of the front of the room.

Cool and thanks again.

Agree there really does need to be more published info and the waters become muddied as the audio mixing studio doesn't really care about video per se, all they are doing is mixing audio. As such it is probably impossible to tell separation angle from pictures as one cannot assume the mixer is sitting at 3 times the height from the screen. They could be closer or farther away when mixing so looking at L & R speaker positions may not give one a true understanding of the L&R separation used for mixing in that studio.

Also, if they mix films, games and music then they may move the L&R speakers according to the source, ala 60 degrees for music.

Question please. You say - " Another reason why I choose to move the speakers in (apart from a better relation ship with smaller ARs) is that my current room has the screen going from wall to wall.  This just would not work if my speakers were wider than they are. " . Are you saying you have a 16:9 screen and speakers are already at the inside border so they have nowhere to go?

Lastly, accept your analysis that non music BD's/DVD's with smaller AR can sound better with L&R at the 16:9 border ; which raises another issue - Is it better to get towers at side of a scope screen at 45 degree separation or place bookshelves below a scope screen though I guess I know the answer - a better quality bookshelf below screen is better than a lower quality tower beside the screen.

Also, appears advice could be if music and majority scope encodes then placing at border of scope screen is probably best; however if not listening to music or watching majority scope encodes then placing at the 16X9 boundary may be the best solution. If playing games on the HT system then this further supports the 45 degree solution I believe.

I suspect most scope users are like me and have their tower L&R speakers at the border of their scope screen as they don't fit under the scope screen so debate is probably moot for the most unless one goes AT with speakers behind.

[MarkTecher]

bbar, on Aug 12 2010, 07:08 PM, said:

Cool and thanks again.

Agree there really does need to be more published info and the waters become muddied as the audio mixing studio doesn't really care about video per se, all they are doing is mixing audio.

Correct and for music only sources, wider is better - up to a point.

Quote

As such it is probably impossible to tell separation angle from pictures as one cannot assume the mixer is sitting at 3 times the height from the screen. They could be closer or farther away when mixing so looking at L & R speaker positions may not give one a true understanding of the L&R separation used for mixing in that studio.

I'd say about 2.5x the image height allowing studio execs to sit behind.  The mixer doing the dialogue was virtually right in front of the monitor, so even with the speakers as close, he would have still heard decent separation.  

Quote

Also, if they mix films, games and music then they may move the L&R speakers according to the source, ala 60 degrees for music.

The ONLY multi channel "music studio" I've been in was a part of the Griffith University's "bachelor of popular music" where there was no monitor, so yes the speakers were set up in accordance to the ITU-R.

Quote

Are you saying you have a 16:9 screen and speakers are already at the inside border so they have nowhere to go?

No I have a curved AT CinemaScope screen and my speakers are just inside the 16:9 portion.  This means that even though my screen is wall to wall, my speakers are not near the wall or about 30cm away from the closes wall.  And I have treatments on those walls.  

Quote

Lastly, accept your analysis that non music BD's/DVD's with smaller AR can sound better with L&R at the 16:9 border ; which raises another issue - Is it better to get towers at side of a scope screen at 45 degree separation or place bookshelves below a scope screen though I guess I know the answer - a better quality bookshelf below screen is better than a lower quality tower beside the screen.

My philosophy is to find the best centre speaker your budget will allow and buy three.  I've combined audio and video since 1990 and I've never had towers.  Even my first system was a sub/sat even though the sub was passive.  

Quote

Also, appears advice could be if music and majority scope encodes then placing at border of scope screen is probably best; however if not listening to music or watching majority scope encodes then placing at the 16X9 boundary may be the best solution. If playing games on the HT system then this further supports the 45 degree solution I believe.

That was my initial thought process too, then I listened to Scope soundtracks very carefully.  Films like T2 are still reference quality and the fight in the steel mill is one such example where correct speaker placement is paramount.  

Quote

I suspect most scope users are like me and have their tower L&R speakers at the border of their scope screen as they don't fit under the scope screen so debate is probably moot for the most unless one goes AT with speakers behind.

You do the best with what you have.  As I said above, I've never owned towers, so speaker placement for me has never been an issue.  The ONLY "rule" I know I've broke in regards to the AT screen is that my 3 LCR speakers are below the centre line.  I did this based on the fact that my seating arrangement would need the speakers lower to work for both rows.

[bbar]

MarkTecher, on Aug 12 2010, 10:33 PM, said:

Correct and for music only sources, wider is better - up to a point.



I'd say about 2.5x the image height allowing studio execs to sit behind.  The mixer doing the dialogue was virtually right in front of the monitor, so even with the speakers as close, he would have still heard decent separation.  



The ONLY multi channel "music studio" I've been in was a part of the Griffith University's "bachelor of popular music" where there was no monitor, so yes the speakers were set up in accordance to the ITU-R.



No I have a curved AT CinemaScope screen and my speakers are just inside the 16:9 portion.  This means that even though my screen is wall to wall, my speakers are not near the wall or about 30cm away from the closes wall.  And I have treatments on those walls.  


My philosophy is to find the best centre speaker your budget will allow and buy three.  I've combined audio and video since 1990 and I've never had towers.  Even my first system was a sub/sat even though the sub was passive.  



That was my initial thought process too, then I listened to Scope soundtracks very carefully.  Films like T2 are still reference quality and the fight in the steel mill is one such example where correct speaker placement is paramount.  



You do the best with what you have.  As I said above, I've never owned towers, so speaker placement for me has never been an issue.  The ONLY "rule" I know I've broke in regards to the AT screen is that my 3 LCR speakers are below the centre line.  I did this based on the fact that my seating arrangement would need the speakers lower to work for both rows.

Thanks and love the screen  

[MarkTecher]

bbar, on Aug 13 2010, 10:15 AM, said:

Thanks and love the screen  

I like it.  I just want a bigger one some day - screen that is  

[MarkTecher]

Ronsta, on Jul 15 2010, 04:15 PM, said:

^^^^^^^^^^^^^^^^^^^^^^
Spam Reported

And again...

[PMG5]

MarkTecher, on Jul 1 2007, 10:50 PM, said:

Over the past few months, I have been asked to start a thread on Constant Image Height.  Given that not everyone is into CIH, I thought this thread might be more useful if aimed at general HT front projection (but will include some CIH tips).  



The diagram in THIS LINK is based on cinema viewing angles.

Any chance that link could be reposted? It appears to be dead.

Very interesting topic also - am about to have a house built with a dedicated HT room and the amount of information out there is taking some getting used to and is taking time to digest all the terms...

[MarkTecher]

PMG5, on Mar 8 2011, 09:29 PM, said:

Any chance that link could be reposted? It appears to be dead.

Very interesting topic also - am about to have a house built with a dedicated HT room and the amount of information out there is taking some getting used to and is taking time to digest all the terms...

The guy that drew the diagram pulled the link.  If I could attach it as an image, I most certainly would.

Please post away and I will happily answer any questions if I can.

[hufflepuff]

just pulled the trigger on my first projector and am just tweaking my setup .

read this in a review :

'If you’ve never setup a front projector, the optimal position is near the longest distance recommended by the distance calculator and centered on the screen.'
[http://www.digitalho...tre-projector/]

firstly ...is this true ....and why ?

secondly .... doesn't being further away from the screen decrease brightness , color saturation, and contrast  ?

[Quark]

hufflepuff, on Apr 12 2011, 01:24 PM, said:

just pulled the trigger on my first projector and am just tweaking my setup .

read this in a review :

'If you’ve never setup a front projector, the optimal position is near the longest distance recommended by the distance calculator and centered on the screen.'
[http://www.digitalho...tre-projector/]

firstly ...is this true ....and why ?

secondly .... doesn't being further away from the screen decrease brightness , color saturation, and contrast  ?

Longest distance mostly applies to use of an anamorphic lens, so as to avoid vignetting and to minimise pincushion.  Some people may also want to mount a projector behind them to minimise noise.

Without a lens it's often better to have the projector as close as possible to the screen for the reasons you mention, but this may vary with the model and any foibles around lens shift, room placement etc.  For example the Infocus SP8602 has a large variation in brightness depending on the amount of lens shift used.  Placement extremes (closest or furthest) may also highlight other limitations like chromatic aberration.  Close placement is also likely to highlight any uneven focus issues a projector model has between the center of the screen and the edges - this is quite common.

Centered on the screen to avoid horizontal lens shift is the best option in every example I'm aware of.  This is another common cause of aggravating any chromatic aberration in the internal lenses.

Reviews don't tend to evaluate the optics of projectors - when they were expensive, not so many comprises were made, but now the optics are an area where corners are often cut.

In summary, there tends to be a trade off on any placement option - best to understand the foibles of your intended projector, what compromises will annoy you the most and then work through what's best for your preferences.

[hufflepuff]

Quark, on Apr 12 2011, 01:54 PM, said:

Longest distance mostly applies to use of an anamorphic lens, so as to avoid vignetting and to minimise pincushion.  Some people may also want to mount a projector behind them to minimise noise.

Without a lens it's often better to have the projector as close as possible to the screen for the reasons you mention, but this may vary with the model and any foibles around lens shift, room placement etc.  For example the Infocus SP8602 has a large variation in brightness depending on the amount of lens shift used.  Placement extremes (closest or furthest) may also highlight other limitations like chromatic aberration.  Close placement is also likely to highlight any uneven focus issues a projector model has between the center of the screen and the edges - this is quite common.

Centered on the screen to avoid horizontal lens shift is the best option in every example I'm aware of.  This is another common cause of aggravating any chromatic aberration in the internal lenses.

Reviews don't tend to evaluate the optics of projectors - when they were expensive, not so many comprises were made, but now the optics are an area where corners are often cut.

In summary, there tends to be a trade off on any placement option - best to understand the foibles of your intended projector, what compromises will annoy you the most and then work through what's best for your preferences.

ta

the 4000 isnt the worlds brightest projector....especially on the better modes ....ive put it right behind my seating position [its very quiet] but i could have put it back further but wanted to keep the brightness up

[MarkTecher]

hufflepuff, on Apr 12 2011, 03:17 PM, said:

ta

the 4000 isnt the worlds brightest projector....especially on the better modes ....ive put it right behind my seating position [its very quiet] but i could have put it back further but wanted to keep the brightness up

Generally the closer the projector to the screen, the brighter the image at the expense of CR.  Further back gives a better CR at the expense of brightness.  IMO, digital projectors don't struggle to produce bright whites, they do however need help with their blacks, so why further back is preferred.  Also as Quark stated, if you intend to upgrade to CIH with an Anamorphic Lens at some point, you will want a decent TR and it is better to mount the projector just once.

Edited by MarkTecher, 12 June 2011 - 06:00 PM.

[petetherock]

I am considering coming back to projectors (last one I used was an old Infocus 4805).
I will be seated about 3m from the screen, which is a hand me down manual 82" Da-lite. This will be suspended from a 3m ceiling, and the bottom of the screen will be about 90cm from the floor.

I intend to use the HD 20 on a coffee table, placed in front of my sofa.

So
How high should the table or more accurately, the HD 20 be?
If I use if on a shelf behind my sofa, is that ok and how high should it be?

Any issues with using such a temporary kind of placement?

Thanks mates.

PS: since I am considering a 65" TV, will using such a small 82" screen be moot and I should just stick to the 65" pocket the change and simply sit a tad closer?

[MarkTecher]

petetherock, on Oct 31 2011, 10:57 AM, said:

I am considering coming back to projectors (last one I used was an old Infocus 4805).
I will be seated about 3m from the screen, which is a hand me down manual 82" Da-lite. This will be suspended from a 3m ceiling, and the bottom of the screen will be about 90cm from the floor.

I intend to use the HD 20 on a coffee table, placed in front of my sofa.

So
How high should the table or more accurately, the HD 20 be?
If I use if on a shelf behind my sofa, is that ok and how high should it be?

Any issues with using such a temporary kind of placement?

Thanks mates.

PS: since I am considering a 65" TV, will using such a small 82" screen be moot and I should just stick to the 65" pocket the change and simply sit a tad closer?

I just looked up the HD20 and it appears it down not have any lens shift and only 1.2x zoom.  If you were ceiling mounting and was able to suspend the projector at or just above the top of the screen, you would be OK in regards to no lens shift.  Sitting it on a coffee table which is way lower than your screen is going to result in key stone error.  

A smallish book shelf behind the seating might be a better alternative?  

Otherwise you might want to consider the larger flat panel.

[petetherock]

MarkTecher, on Oct 31 2011, 03:03 PM, said:

I just looked up the HD20 and it appears it down not have any lens shift and only 1.2x zoom.  If you were ceiling mounting and was able to suspend the projector at or just above the top of the screen, you would be OK in regards to no lens shift.  Sitting it on a coffee table which is way lower than your screen is going to result in key stone error.  

A smallish book shelf behind the seating might be a better alternative?  

Otherwise you might want to consider the larger flat panel.

Thanks Mark
I am looking at using the Ikea "Freden" shelving for this, which goes up to a height of 90cm.
I am vacillating (yes, now I am a convert to this word... ) on the VT30, I almost pulled the trigger today, but the vendor was not budging on price, and my own renovations won't end until end November or so.

The coffee table should go up to 50cm, but I guess that's too low?

[MarkTecher]

petetherock, on Nov 1 2011, 01:30 AM, said:

Thanks Mark
I am looking at using the Ikea "Freden" shelving for this, which goes up to a height of 90cm.

900mm should be OK so long as you don't cast a shadow.  How high will the screen be off the floor again?

Quote

I am vacillating (yes, now I am a convert to this word... ) on the VT30, I almost pulled the trigger today, but the vendor was not budging on price, and my own renovations won't end until end November or so.

The coffee table should go up to 50cm, but I guess that's too low?

Unless you had a really short throw and could put the projector in front or slit the seating to be at the sides so not to cast a shadow, that is probably too low.

[MarkTecher]

Having a quick read back over this thread and the diagram I linked to was blocked, so I have attached it below.

ALLSCOPE diagram by Erik Garci

[kopthat]

I can't get to that attachment.

We have just moved from a 90" at about 3m
to a 120" at about 3.2m and I am loving the big screen feel.

The expert at Todd's Hi Fi said I would get headaches and get motion sickness
even going to a 100" at that seating distance, I must have a strong stomach and thick head
because I feel none of those effects.

[:)]

shows how peoples tolerance varies. I wouldnt want to go any bigger than my 92" at 3.3m I suppose this is why they created multiple rows in a theatre I guess. for those that like sitting in front row. those that like sitting in the middle and those who like the back row. am more of a middle to back person. beauty with pjs that still means you can fully resolve hd at those distances. and yet be a decent distance so that the not so best sources...eg standard definition dvd or fta tv doesnt end up looking like pixel city !

I wanted to add, screen technics include in their brochure re screen size vs placement viewing distance for single and multiple rows etc. which might help as another point of reference
http://www.screentec...csCatalogue.pdf

[SDL]

:), on 09 January 2012 - 04:17 PM, said:

shows how peoples tolerance varies. I wouldnt want to go any bigger than my 92" at 3.3m I suppose this is why they created multiple rows in a theatre I guess. for those that like sitting in front row. those that like sitting in the middle and those who like the back row. am more of a middle to back person. beauty with pjs that still means you can fully resolve hd at those distances. and yet be a decent distance so that the not so best sources...eg standard definition dvd or fta tv doesnt end up looking like pixel city ! I wanted to add, screen technics include in their brochure re screen size vs placement viewing distance for single and multiple rows etc. which might help as another point of reference http://www.screentec...csCatalogue.pdf

While agreeing with most of what you are saying in that we all want different screen size to seating distance, I think the reason for multiple rows in the cinema is an economic one. It is the only way to fit enough seats to pay for the cinema and the film.

Edited by SDL, 09 January 2012 - 05:48 PM.

[MarkTecher]

:), on 09 January 2012 - 04:17 PM, said:

I wanted to add, screen technics include in their brochure re screen size vs placement viewing distance for single and multiple rows etc. which might help as another point of reference
http://www.screentec...csCatalogue.pdf

Interesting info.  Note that both the 2x (SMPTE min) and 3x (SMPTE preferred) the image height are used.  The distance I have to querry is the 6x for the multiple row set up and the reason I have to querry this is because when THX formed TAP (Theatre Alignment Program), they made a point of stating that viewinng angles of less than 26 degrees would not pass certification.  They even went so far as to say "no bowling allies" because they want everyone hearing stereo.  Unless your speakers are well outside the screen (something I do not agree with), that 6x distance is quite a bit less than 26 degrees.

[oztheatre]

kopthat, on 09 January 2012 - 04:04 PM, said:

I can't get to that attachment.

We have just moved from a 90" at about 3m
to a 120" at about 3.2m and I am loving the big screen feel.

The expert at Todd's Hi Fi said I would get headaches and get motion sickness
even going to a 100" at that seating distance, I must have a strong stomach and thick head
because I feel none of those effects.

Not much of an expert then. Motion sickness? What's next? A stroke from using a lens? Block arteries from going DLP? Bird flu with an epson perhaps?

Had a client in yesterday for a CIH demo. He came from some 'expert' store in brisbane. They tried to tell him he needed a curved screen and told him it's because anamorphic lenses are 'bad' and 'faulty' but couldn't really tell him why or why he needed one, which he didn't. His room is 8 metres long so a long throw will all but eliminate pin cushion, but the experts didn't ask him about his room...

[bbar]

kopthat, on 09 January 2012 - 04:04 PM, said:

I can't get to that attachment.

We have just moved from a 90" at about 3m
to a 120" at about 3.2m and I am loving the big screen feel.

The expert at Todd's Hi Fi said I would get headaches and get motion sickness
even going to a 100" at that seating distance, I must have a strong stomach and thick head
because I feel none of those effects.

Strange as a 120" scope screen at 3.2 metres is just over 2.7 times screen height which is not that close and at 47 degrees viewing angle is only 3 degrees off optimum as per FOX and SMPTE recommendations.

[kopthat]

As Richard mentioned these so called "experts" don't really know their stuff.

They had an ae7000 that was supposed to be calibrated, and the settings they had were
poor watching 3D Avatar compared to my Optoma HD33, which was selling that projector short.

I should have known by looking at their screen in their premium cinema room, it didn't even have the
black velour on the frame

I think they are pushing the plasmaled home theatre experience to the masses.

Although I did see someone has an 80" plasma for around $US 6500 at CES,
but I love the whole feel of projecting an image, and you may need to crane in a 100" + plasma
when they eventually come down to a price that you don't need to sell a kidney,
my 55" was heavy enough.

Edited by kopthat, 11 January 2012 - 11:51 AM.

[MarkTecher]

oztheatre, on 10 January 2012 - 10:23 PM, said:

but the experts didn't ask him about his room...

They never do and that is a problem because the room itself (the forgotten component) is what contains all the gear.