The surround speakers are supposed to be directly to either side of you (slightly behind you if they are monopole) and facing each other. They should also be 2-3 feet above your seated height, with at least a 2 foot gap from the tweeter to the ceiling. They should not be angled down so far that they are "aimed" directly at your seated height. The sound should "pass over" your head in order to create an enveloping sound.
There are experts that disagree with you.
The HT tracks already have the correct freq responses for ambient effects. If the height of surrounds is elevated that much relative to the ears, you now receive incorrect freq response. The best orientation of a speaker to the listener is on axis. If the speaker must be considerably above, then the speaker should be angled to be on axis. If one worries about multiple viewers to be on axis, at least someone gets to be on axis, otherwise no one is.
90 degrees for side surrounds is actually the accepted best orientation. The reason why people move them to more obtuse angles is if they prefer to straddle the rear stage somewhat.
Audyssey states at their site:
"The second tradeoff is related to the ITU recommended placement of the two surround channels at ±110°. Surrounds at ±90° were found to produce the most envelopment compared to other angles, while surrounds at ±135° produce better rear phantom imaging capability. Thus ±110° was selected as the best tradeoff between envelopment and imaging. This is another limitation of 5.1 surround systems because one must choose between better rear imaging or better envelopment."
Ethan Winer has on multiple occasions, in multiple threads, offered a pdf, Grammy Surround Standards, when the topic of surround height comes up:
"That's old school, and is derived from movie theaters years ago when the rear channel was mono. The idea was to put the rear speaker(s) up high so the sound bounces around the room before it reaches your ears to create more ambience that also has some stereo width. But what works in a large theater doesn't necessarily work in a home-sized room. More to the point, these days movies have all the needed ambience already embedded in the soundtracks. This PDF contains a more modern guideline from NARAS (National Academy of Recording Arts & Sciences), the technical vision of the Grammys:
Grammy surround standards
The emphasis is on rooms used to mix movies, but the same applies to rooms you watch in.
--Ethan"
http://www.grammy.com/pdfs/recording_academy/producers_and_engineers/5_1_rec.pdf
I have a question about that. What about speakers with side firing bass drivers? I would think one would just set them up to face away from each other but some speakers won't allow that. I'm specifically thinking of NHT speakers that have an angled front.
They are either bipole or dipole speakers. Bipoles will give you greater coverage, but I personally found that the effect wasn't as significant as I was hoping, and with dipoles, it's best to sit in the null. If mch music is important to you, monopoles might be ideal. I think monopoles are completely adequate for anything less than a multirow theater. And even then they're probably adequate, IMO.
