7.2.2 or 7.2.4 for a room with a sloped roof (1 Viewer)

[Krotar]

Hello everyone,

The past month I have been lurking on these forums and Reddit to get inspiration about my future home theater build. This summer I will start building the walls of the different spaces in my attic including the home cinema. The space has been claimed after convincing the wife in regards to the remaining space that she will have .

While doing the walls I already want to prepare the cabling as best as possible and here starts my question, on one side of the room I have a sloped roof. Buying the actual hardware will probably be for in 2 years when 4k projectors with a shorter range become more affordable that support 140 - 150 inch.

My main seating position will be the back row (a family of 4), the front row is for the occasional situation when more then 4 seats are needed. In my case I could move the front row even more upfront which would of course not be beneficial for the potential visitor's experience.

Because of the sloped roof I am doubting between a 7.2.2 or a 7.2.4 setup, would it make sense because the overhead atmos speakers behind the back row would be really close to the surround boxes?

Due to the sloped roof I'll probably also need to take into account extra acoustic panels for the back?

Audi advice: link

3D render 1 with measurements


3D render 2 with measurements


Audi advice 7.2.4 render


Audio advice 7.2.2 render

 

[JohnRice]

Interesting challenge. I would move the back row forward, since it’s the main viewing location. How often will the front row be used?

 

[Krotar]

Interesting challenge. I would move the back row forward, since it’s the main viewing location. How often will the front row be used?

Only if friends / family come to join so it definitely is not a primary goal. Maybe I could consider a setup where I put the platform on rails just like the sofa for when people join the sofa and back row can be moved more back (and only then not have the ideal audio positioning)

My kids are still young (3 and 1 years old) so from their perspective it could be they would prefer the sofa but at the end I'll be the main consumer with the wife.

 

[Krotar]

Been doing some more research and most home theater setups do seem to have the front row as their main row so that they can position Atmos in the best way, for me personally I would like to go for a maximum immersive visual feeling and the audio should be the best it can but definitely not perfect. This video convinced me to get my first row as the main row to get the most immersive feeling:


This video gave me more information about the best position of Atmos in regard to angles:


Layout of Atmos and rear speakers:

(the yellow circles could be a future upgrade to 6 atmos channels, for now I'll go with 4 but provide wiring for 6)

Any feedback?

 

[DaveF]

If you can pre-wire for future easy upgrades, that’s a good idea. It’s relatively low cost now. If you never use it, it’s minimal money wasted. And if you do use it, you’re saving big money and effort later.

I also suggest considering conduit and fish wire to the front wall (screen area) for potentially changing from projector and screen to direct view in the future.

 

[DaveF]

As for viewing: standard is 45º I think? I set my front row a bit closer. If you have your projector, turn it on and demo some seating positions and find what you like. I did this, playing PS4 on a wall in a folding chair months before we really got serious about the theater build.

 

[JohnRice]

Been doing some more research and most home theater setups do seem to have the front row as their main row so that they can position Atmos in the best way, for me personally I would like to go for a maximum immersive visual feeling and the audio should be the best it can but definitely not perfect. This video convinced me to get my first row as the main row to get the most immersive feeling:


This video gave me more information about the best position of Atmos in regard to angles:


Layout of Atmos and rear speakers:

(the yellow circles could be a future upgrade to 6 atmos channels, for now I'll go with 4 but provide wiring for 6)

Any feedback?

The spacing of the overhead speakers looks good. Just make sure they aren’t too far toward the walls. People tend to put them too far to the sides. Wiring for 6 overhead is fine, but current home Atmos doesn’t make good use of more than four. That’s a little known limitation I can explain further if you want.

Making the front row the primary one is a very good move.

 

[ManW_TheUncool]

As for viewing: standard is 45º I think? I set my front row a bit closer.

Not sure what's "standard" (unless we're talking SMPTE or THX recommendations), but that's roughly what I currently use as well -- mine apparently calcs to ~47º for 120" 16x9 screen w/ ~10ft viewing distance.

_Man_

 

[Krotar]

The spacing of the overhead speakers looks good. Just make sure they aren’t too far toward the walls. People tend to put them too far to the sides. Wiring for 6 overhead is fine, but current home Atmos doesn’t make good use of more than four. That’s a little known limitation I can explain further if you want.

Making the front row the primary one is a very good move.

Thanks for the tip, will probably place the overhead speakers above the 2 outer seats of the row of 4 seats.

Not sure what's "standard" (unless we're talking SMPTE or THX recommendations), but that's roughly what I currently use as well -- mine apparently calcs to ~47º for 120" 16x9 screen w/ ~10ft viewing distance.

_Man_

With a 150" screen (2:4:1) I will now have a viewing angle of ~54º with a ~11ft (3.4m) viewing distance. Could be this is to much so I will first install the projector and try some different aspect ratio's on the blank wall before purchasing (or building) the screen.

 

[Wardog555]

https://www.dolby.com/siteassets/technologies/dolby-atmos/atmos-installation-guidelines-121318_r3.1.pdf

Here you go for what the angles are supposed to be! I'd normally suggest 55 and 125 degrees for the 4 atmos front to back. but if you going with six you could have a larger spacing between

 

[JohnRice]

Thanks for the tip, will probably place the overhead speakers above the 2 outer seats of the row of 4 seats.

Just an additional comment. Dolby recommends spacing the Atmos speakers at +/- 35 degrees from the main viewing area, but implementations in the real world haven't produced good results using that. That ends up spacing them too far apart. So, I've revised my general recommendation to be more like +/- 15-20 degrees, which looks pretty close to what you have in the illustration. Plus, you have the sloped rear ceiling, which limits your side surround speakers.

Also, regarding the possible middle Atmos speakers, current home Atmos implementation results in little to no sound coming from middle Atmos speakers, unless additional processing is used. Yeah, processors have outputs for 16 channels or more, but the way home Atmos soundtracks are mastered, there will be, at most, minimal sound from them, and most of the time, none. There's no harm in wiring for them, but at the moment, they're not worth installing. I can explain in more detail if you want, but it gets pretty techie.

 

[ManW_TheUncool]

With a 150" screen (2:4:1) I will now have a viewing angle of ~54º with a ~11ft (3.4m) viewing distance. Could be this is to much so I will first install the projector and try some different aspect ratio's on the blank wall before purchasing (or building) the screen.

Yes, probably best to play w/ the ratios some from actual experience to find what's best for you.

I'd note that a 16x9 image inside a 2.4:1 screen would lose roughly 1/4 the width of the screen to pillarboxing, so it'd look roughly like a 120" 16x9 image on that 150" 2.4:1 screen.

Based on the calculator I used, your planned viewing distance of ~11ft would then yield ~43º viewing angle for 16x9 images, which is a pretty good size view.

I did a quick rough test myself. And if I were going for a 2.4:1 screen w/ ~11ft viewing distance, I might go for 150" if I had the space. As it is, I probably woulda gone for a 135" 16x9 screen for my current viewing distance of ~10ft if I could actually fit it (and that would yield ~52º angle) -- and then, go w/ a smaller window-boxed 16x9 image for most 16x9 (including 1.85:1) or narrower content, except for some that demand bigger like IMAX formatted ones, 3D, maybe some old Academy ratio classics (that might feel too small otherwise), maybe some sports, etc, as I already do to some extent now (to still make wider AR content look/feel larger scope as intended)...

Actually, based on my quick calc, 135" 16x9 w/ ~10ft viewing distance would yield about the same ~52º (full-width) viewing angle as 140" 2.4:1 w/ ~11ft viewing distance, if you're wondering -- and that was the other (smaller) screen size you were considering.

Do also realize that going bigger likely means a (modestly?) dimmer image in practice (per unit area anyway... although maybe not necessarily perceptually given the greater immersion), which may be an undesirable downside given PJs are generally already challenged for light output and dynamic range, especially if you want good HDR and/or 3D performance. All that plus you still have the issue of throw range that your dedicated HT room seems to limit (due to the sloped ceiling/roof?)...

_Man_

 

[Doug2000]

This video gave me more information about the best position of Atmos in regard to angles:

This video was very helpful!