More & more people are now starting to understand better how things work… which is good
Observe the pictures above, wanna take a wild guess what are the problem ?
Anyone ?
let me take a guess, assuming it uses acoustic screen in front of the speaker placed.
The sound can reflect off the screen and interfere with the sound quality, potential loss of clarity, detail, and imaging in the soundstage.
Frequency Response can be absorbed or attenuated potential uneven frequency response. This can potential cause imbalanced to sound panning or some frequencies over power each other.
This is something all will experience, depending on material, it can obstruct the sound and cause muffled or distorted dialogue reproduction. so one tends to turn up the C vol higher than usual
Screen will vibrate especially placing sub behind on first pic. It can cause vibrations in the screen.
The screen can also tends to introduce diffraction and reflection, which may interfere and can also result in less accurate and less convincing sound panning.
If the distance between the speakers and the screen are too close, it can also impact sound panning, the panning effect may be less pronounced since the sound sources are physically closer together.
Placing ALL LCR speakers behind the screen can also potentially narrow the soundstage, affecting the feeling of width and spaciousness of the sound as the sound pans from one speaker to another.
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Based on the previous posts, I think Bryan is referring to the height of the tweeter, probably too high in the upper half of the screen.
Bed layer and screen channels becomes too high, not enough separation from the ceiling layer.
But there are also sight lines and sound lines to consider. Usually rooms with multi row seating will have to ensure the screen channels tweeters are not blocked to the back rows. That usually makes results on a slightly higher placement.
Agree than LR speakers is too narrow, even with AT screen ideally only the center needs to be behind the screen. LR mains just outside flanking screen is about perfect from placement angle wise.
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Ah I see. That’s what desray/ronildoq is referring to.
Yes true also with regards to the use of acoustic transparent screen 
Spot on! This is exactly the problem some are facing now.
If we observe this image 
to the one before that, we will see that the tweeter location is about ear levels.
This allows the panning for bed channels to form that “phantom image” with surrounds and surround backs, hence completing the bubble for HT surrounds.
Not only that, because if there is enough height between bed and height channels, the user can then experience another layer, “phantom height”… which forms between the bed speaker and height/Atmos speakers . So it’s at 50% location, somewhere in between bed layer and height layer
Just think of it like a stereo pair. One left, one right, why is the image appearing in the centre ? Similarly for Atmos and bed Channel, u r experiencing another layer of phantom height. ( in between bed speakers and height speakers)
(You can imagine how much one is missing without the Atmos HT experience, if haven’t gone Atmos route, it’s about time)
Having it like this below 
is not ideal, for Homes with single layer seating capacity. It is more suited for cinema applications where u have multi rows with height and no height speakers used.
As we can observe the tweeter location is placed way too high up at the front stage. Sound that is suppose to pan across bed layer, is now appearing mixed with other height layers, the image will collapse . As the sound transitions from surrounds to mains, suddenly it gets elevated as it approaches the front stage… it won’t sound good. Will it have sound ? Yes it will have sound…. Will the image sound right ? U won’t know until u have experienced the full bubble of how image pans across the bed channels in a proper set up….
So don’t make this mistake when placing your speakers at home. Your home is not the cinema! It’s different
Placement for this below , is also not too bad . As we can observe the tweeter is at ear levels behind the screen
Thanks to this sact kit disc, people can make informed decisions on how to place the speakers in their room
PS://
How to solve it if you have already mounted ? No other way other than lifting the height of your seats and ensuring the surrounds and surround backs tweeters are all at the same height…
There is no shortcut to this, no way you can place it high up and tilted down to face your ears. Similarly for centre speakers, you can’t place them down and tilted upwards, it will not give you the best experience. Our brains will be able to process sound emanating from bottom or above. No way out …. Will u have sound ? Yes… it will come from bottom or top… Will it form the phantom image ? no ! <~ this is where u will be missing out ! (Just imagine left right speakers, one taller one shorter, how u think the centre image will sound ?) simple experiment
Conclusion, speakers at bed channels, must all be at ear level to complete the bubble and take the system up to the next level.
Level up guys !
Hope that helps
Oh yes, and these are the things that cannot be “measured” or “calibrated”
It is all down to the placement of the speakers
If your centre speakers are placed at the bottom of the screen , the image is going to pan like a “v” shape below
This is far from ideal, it’s a compromise due to limitations with space of using a non AT screen, or using a TV
Also a sacrifice of one over the other, as we know the video performance of a non AT screen vs AT screen…
so u will have sound from ear, going down then up again … our brains can pick this up… we cannot escape from this…
How much it affects the person? It really depends. If you have been exposed to having them aligned at ear levels and have been watching your movies this way for the past 5 years, the moment you switch to have them centre speakers at the bottom, you will be able to tell the flaw immediately… on the contrary, if you had been listening to that “v” way for the past 5 years or so… then you would probably not realise this flaw…
Do note, no matter how you rake angle the speakers, tilt it forward or backwards, your brains will be able to tell the source of the location of the tweeter high frequency sound… placing it high up tilted downwards or placing it low tilted upwards,… no escape… your brains will be able to distinguish this … no amount of expert calibration can help with this…
My center speaker is actually above the screen because of an installation issue, but it is toed down at the head of the listener. Speech seems to come from the center of the screen to me. When Alfie was here, he shook his head when he saw the center speaker so high up, but, interestingly, he was surprised that the dialog seemed to come from the center to him as well, rather than above. Wonder if you have tried toeing the center speaker up at the head of the listener?
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The further our MLP, the less issue we will have locating sound coming from top or bottom of our center speaker.
Those without center speaker is better to have a further MLP for better center imaging. Also lesser sound shift from position to position. Disadvantage is that less sound separation between speaker when we sit further. Speaker toe in definitely will help to get your center imaging more focus.
Most of our members here all have their center speaker on top or below i found they also don’t have issue.
I usually start with my left right speaker. Once i can setup a good Stereo image and soundstage… the center and surround is easier to integrate into my systems with lesser issue.
Having a dark room also help where you can’t see anything surrounded you… so we only focus on the movie and sound with no other visual distraction… Cheers 
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Hi Sammy,
For me, the position of Center speaker is very important. The tweeter must be in line towards ears.
Try to line up horizontally between C and L/R so when it is panning from Left to Right then they are sounding same level towards MLP.
I don’t believe towing towards MLP will help you as your position of C spk is high up there. Position is too far from your L/R. Panning will have a problem.
Try re-position your C, bring down same level as L/R, you will be amazed for the result.
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Many times thing doesn’t go according to our plan. 
. Ideally and theoretically we are some how all correct not until you try something differently and it work for you… 
HI Sammy
try this… https://drive.google.com/file/d/15PiK3XEAmV1nIIeeKB9cF_Vtz8D-N1wz/view?usp=sharing
Since your speakers are located way up above the screen, you will notice the voice is coming from above
In the above video, at about 40 seconds, the lion will stop and he starts panting… Observe his mouth, the panting of the lion, after running around in the jungle, should appear at the bottom of the screen…
If you have mounted the speakers above the screen, and if you listen to another set up with the centre speakers at ear level, you will get the point…the lions breath emanates from the bottom of the screen…
I picked this scene specifically because you mention your speakers are above the pj screen… so that is the reason i picked this scene… because the lion’s mouth is at the bottom of the screen
The other downside is that we need to understand the vertical dispersion characteristics from the speakers…when it is not placed at the centre or lower at ear level, the dispersion levels are different … we can see this on the heatmap of dispersion characteristics of that speaker
also the panning is affected as it transitions from left up then down to right speakers again, is a shape like this → ^
Now this scene above here, will not affect as much those who have placed their speakers at the bottom of the screen. Also it will track differently on screen when the guy speaks at 3/4 height location of the screen, for the guys having them at the bottom, it is much more challenging with another clip when the voice tracks above the screen. the bigger the screen, the easier to tell this discrepancy
I have had them below the screen in the past as well… once you have them placed correctly at ear levels, you will not go back to other options.
I do understand that sometimes most of us have limitations with space etc. No choice etc
But if you have the option and a choice, make sure all bed channels are at ear levels. that is the best…
Thanks guys, will try all the panning and Bryan’s clips when I am back in Singapore in mid-July. I actually don’t have a choice about the location of my center speaker, but interested in the effects that such a placement causes.