L/C/R all below non AT screen

You only need to do one simple thing to eliminate hearing the position of the speakers..

Mount an acoustic sound absorption panel on the ceiling halfway between the speakers and the listening position. This will block the primary reflection which is the mind's audible sound positioning cue. The auditory system calculates the delay between the direct sound from the speaker and the longer-distance reflected sound from the speaker to triangulate the position of the sound source. If you block that reflection with sound absorption, you'll not hear the vertical position of the speaker under the screen. I have a 150" screen and my center is on the floor and it sounds like it's in the picture.

You'll also gain audio clarity because you'll not hear the reflection, so the soundstage will open up giving you a more accurate and vast sound space.

And you'll also block floor to ceiling standing waves. The floor-to-ceiling distance typically equates to standing waves which create resonance in the lower human vocal frequencies. Blocking the standing waves with sound absorption panels will make male voices sound more clear, less boomy, and no more smoker's voice effect. These lower frequencies would require a 4" thick panel to absorb, preferably rock wool.

These three reasons are why all sound studios use acoustic panels at the primary reflection points. Over the past 15 years of major upgrades to my theater, by far the biggest improvement was sound absorption panels at the primary reflection points. This includes the side walls, but the ceiling is critical.

This always brings up the issue of ATMOS, which the industry came up with the ridiculous method of reflecting the ATMOS sound off the ceiling from the fronts. This gimmick is counter-productive to the direction home theaters should be evolving. You always want to block that reflection. When using ATMOS, use dedicated speakers on the ceiling. If you can't put ATMOS speakers on the ceiling, you're much better off going without ATMOS and blocking the reflections with sound absorption acoustic panels.

Mr. Neverbicker said:

You only need to do one simple thing to eliminate hearing the position of the speakers..

Mount an acoustic sound absorption panel on the ceiling halfway between the speakers and the listening position. This will block the primary reflection which is the mind's audible sound positioning cue. The auditory system calculates the delay between the direct sound from the speaker and the longer-distance reflected sound from the speaker to triangulate the position of the sound source. If you block that reflection with sound absorption, you'll not hear the vertical position of the speaker under the screen. I have a 150" screen and my center is on the floor and it sounds like it's in the picture.

You'll also gain audio clarity because you'll not hear the reflection, so the soundstage will open up giving you a more accurate and vast sound space.

Click to expand...

Eliminating the ceiling reflection, as well as other early reflections, is indeed beneficial, but your description of how humans perceive sound directionality is not correct. The first reflection is not the primary "sound positioning cue". The primary cues that allow the ear/brain to determine the direction are all contained in the direct sound. The arrival time/intensity differences between the two ears are what the ear/brain use to determine directionality. The process is described by:
1. The Head Related Transfer Function, (HRTF),
and;
2. The Law of First Arrival, or "Precedence Effect."
Precedence effect - Wikipedia

Both are well documented in the acoustics and psycho-acoustics literature. The point is that reflections do NOT determine sound directionality, and the cues that do determine it are in the DIRECT sound. The only thing reflections can do is impair the directionality and decrease the ear/brain's ability to determine the actual direction of the direct sound.

In any event, the rest of your post is spot-on, and I totally agree with your recommendation of acoustic absorption at the first reflection points.

Craig

Most modern receivers support some sort of height channels. I have 3 speakers below the screen with the tweeters at 34" from the floor and two speakers above the screen. Using Auro 3D or DTS Neural X processing pulls the audio location up into the screen area very nicely. Screen is a DIY 52" x 144" 2.76:1 curved screen using drapery liner as the screen fabric. Primary viewing distance is about 7.5 feet.

These pictures show the screen and a peek at the construction methodology.

Craig John, I'll have to agree to disagree. The studies I've read which were centered more so around studio sound and definitely my own experience have a key difference. The transfer function and first arrival both work differently in the horizontal plane vs vertical. Between the two ears determine directionality in the horizontal plane but the timing and intensity differences between ears don't assist with perception of vertical directionality which is the issue with speaker placement under the screen. The difference between the timing and intensity of the ceiling reflection comprises the majority of information we receive for vertical placement in an enclosed space. Twice I've removed the acoustic absorption panel when changing up my theater and my critical listening friends and I could clearly hear the vertical placement of the center channel on the floor again, along with the blurred and boomy sound. Then all three dynamics were again gone when re-adding the panel.

In the horizontal plane, the side wall reflections do impair horizontal directionality and adding acoustic absorption panels on the side walls also fixed this, as well as eliminating the audible blurring of the reflection timing differences and standing waves, which all contributed to a very noticeable opening up of the soundstage and articulate perception of sound placement in the recording with the side panels. This is more noticeable with better resolving speakers and components, but in my experience it's still a very noticeable improvement all around even with lower end components which I'd started out with.

I can directly relate to the OP's struggle with hearing the speaker under the screen, as I've struggled with this issue myself and my center is even much lower than his and I was more than pleasantly surprised to learn how well the issue resolved itself when adding the acoustic panels. I would at least suggest the OP would save himself a lot of hassle and also gain the two other audible attributes if he were to first add acoustic panels at the primary reflection points.