I've tried this Atmos "aim a speaker at the ceiling" idea with some Elac atmos speakers ( designed by Andrew Jones ) - They are a decent sounding speaker on their own, and I don't see any real resonance peaks in the measurements I made. So, the premise is that they are at least "OK" speakers, possibly better than "OK." They have this same angle built in to their cabinets. I find the sound doesn't appear to be coming from any kind of height dimension from these things. They just sound like off-axis bookshelves sitting on my towers, or even placed on shelves that are about 5 feet off the ground which flank my listening / viewing area. The Atmos height effect from these doesn't seem- well - effective. It doesn't seem like the sound is bouncing off the ceiling very much, most of what I hear is direct from the speakers.
Makes me wonder if any of these up-firing Atmos speakers will really do the effect justice. I have some small speakers I can attach to mouldings on the left and right side walls at about 7 foot height and aim them up to "splash" over the ceiling, I want to see if that gives a better effect. They haven't got any low end to speak of, but then I wonder how well low frequencies can be localized in a room by listeners....the wavelength at 200 Hz is 150 cm, which is 59 inches., so it would seem to me that a person ought not to be able to sense the location at that frequency any more precisely than ± 59 inches. Could I really tell if a 200 Hz sound was coming from Atmos "up" in my room or would I just localize the sound based on higher harmonics? I think the latter; makes me wonder why you'd need bass from an Atmos speaker.
It wouldn't surprise me to find that Dolby applies some filters to the Atmos "up" channels, reducing the low end. Information on what Dolby Atmos does is kind of sparse. I know it's an object-based surround paradigm, with the decoder deciding which sounds go where based on the sound mix and the number and type of channels in the configuration of the playback system; but I know nothing of what, if any, DSP is applied. Filters? Delays? I'd like to know.