Originally Posted by leedesert
Dolby Atmos recommends ceiling speakers because effectively, not theoretically that's not true. It's much easier and does not require special mixing to create an over head sound when the speaker is actually overhead. The wider the seam is between the speakers the less believable the sound is as it passes from one speaker to the next. To create an overhead sound it requires a mix between the front height and rear height to fool your ears into thinking its overhead. If you have an actual top height speaker on the ceiling the transition is audibly much shorter and more realistic. The distance between the speakers (the seam) is shorter so much closer to seamless.
Using height speakers only on the opposing walls is a set up of necessity because of room limitations. If your able to mount ceiling speakers it is always more desirable when it comes to Atmos.
This is one of the common misconceptions of those newer to Atmos. It's a misunderstanding of the geometry and the prevailing importance of ceiling height. There fundamentally is zero physical
difference between a "top" and a "height" speaker. The speakers are one and the same in 99.9% of all home theaters
. In rooms with tall ceilings, this may not be the case.
This so called "seam" that you've created is referring to the space between front and rear speakers it sounds like. Let's assume you have a 10' deep room with 8' tall ceilings, which is fairly close to a standard non-dedicated room. The front top/height speakers will be 56" in front of you and the rear top/height speakers will be 56" behind you if you shoot for 45° and 135° respectively....That equates to ~10' spread between front and rears, or the exact depth of the room. So the speakers could be in-ceiling at the wall/ceiling junction or they could be on the wall....Physically they are in the exact same location within just a few inches based on mounting method. Placing them further apart (or increasing the "seam") simply results in your speakers being at the edge or even outside of specifications. In this example if your room is deeper, it does not mean that you can just throw the speakers on the wall and call them FH/RH. Specs must still be maintained.
The thing you are not understanding is that the angles for tops and heights are essentially identical.
This means that most rooms cannot accommodate all 5 pairs of top speakers. Even in my 16' deep room with 7.5-8.5' tall ceilings, each of the 5 pairs would only be separated by about 18" due to the ceiling height, the critical determining factor. I've even gone so far as to try to figure out how to install FH/RH pairs to maximize speaker count, and it's physically impossibly to place them in spec as they would be right on top of my TF/TR or require all pairs to be installed nearly touching each other or installed out of spec. Simply put, the angles are identical and therefore the spacing (or seam as you call it) between proposed heights and tops is identical. You may not believe this despite angle specifications being identical. Spend a few hours drawing and measuring everything in your room. Break out tape measures and create spreadsheets with arcsin, arctan, arccos formulas. Or even grab a laser angle finder. You can validate this in a multitude of ways, all of which I have done extensively for over a year.
Furthermore on the "seam"...Currently my top front and top rear speakers have about a 12' spread between them. I actually run my speakers to the extreme angles of spec to achieve the largest spacing between pairs. You seem to be indicating that this large "seam" is unfavorable. But this allows for a better distribution of TF, TM, TR and results in a much more spacious Atmos panning effect. It also helps to accommodate 2 row seating areas. This wide "seam" is actually a wonderful thing and results in extremely large sound stage. Imagine placing your FL and FR speaker right next to each other to minimize the "seam" and you will immediately comprehend this, as left-right panning will be extremely minimized and the stage extremely compressed. The majority of the sounds I hear are perfectly phantom imaged between the front and rear pairs (where my unconnected TM speakers are installed). Most people think they are on and being used, but for now they are just bare speaker wire hanging in the AV closet until 13 or 15 ch prepros exist. When installed correctly, this "seam" does not even exist. It's a seamless panning from the front to back of the room, and in between.
Now on the processing of the height vs top speaker layout, that's a completely different story. Nearly anyone can reassign their tops as heights and vice versa. Again this is due to the fact that the speakers have the same angle specifications. And within any given room the ceiling height is going to dictate where those speakers can be installed. 99% of the time, the speakers can be labeled as either/or. You will see that most people have done just this and have swapped between height/top designations due to the recent release of DTS:X; all without physically moving the speakers. Many of us prefer to use "top" amp assigns vs "height" amp assigns and think the processing sounds better. We all also realize that while the speakers are physically the same, the processing is different.
I can easily prove this to you with dimensions of your room. But at the end of the day, I'm telling you that this "seam" is non-existent and that height/top speakers are the same physical speaker in most every home theater. If you want to debate the processing, well that's another story that we can't even really dive into since we don't know HOW the processing is being affected in any great level of detail (since Dolby hasn't released that information).