As an Architect of high end residential, I've had quite a few opportunities to design/ build and research the room issues. Two years ago my client spent quite a bit of money ($15,000) having an acoustics expert calculate his $200,000 home theater needs. This guy designs home theaters, small scale preforming arts facilities, movie houses and churches.
In home audio our needs are unique in that the scale is very small, reverberation rates, sound enhancement and echo are nominal issues. This could possibly be what Everest is discussing. Our issues are mostly side wall and floor/ ceiling first order reflections (slap echo) and frequency exaggeration.
A very small splay (narrower at the front) will alleviate most of these frequency nodes, but some thought could be put to the amount of splay. Too much could reinforce the projection and act as a "horn" and not enough will not achieve the intended goal. Ceiling and floor sloping can be more dangerous, in that the sound angles off a sloped ceiling (in the same fashion as the walls) could end up directing the reflection bach to the listener (especially with multiple seating locations). Think of a dome, it reinforces all sound to the middle, very bad in our situation. A slope down the axis of the room however could disperse the reflections very well.
The consultant we used had a very elaborate computer program that he was able to model the full spectrum of possibilities for the best solution. He was able to produce an audio track for any position in the room to determine what every seat would hear. There are cheaper programs available that could do some of the same things, just not quite as involved.
The rule of thumb I would use is the ratios spelled out in Everest's books or Robert Harley's book to determine the best ratio and size. If you did splay the side walls, I would use the width recommended as the average (mid point) of the splayed wall. I have been using a 2 ½ degree angle on my designs with very good results. The ceiling I would vault if possible.
As to how important this is, it completely depends on how far your willing to go. If your intending to get every ounce from your system with power conditioning, cables and tweaks, then this makes sense. If your happy with 80% of perfection, skip it, it's not worth the hassle. If you do however pursue this I would recommend you look into what wall materials your using. One layer of drywall over wood studs can give a soggy base response compared to a more rigid construction. You might consider building in a true base trap in the design, what acoustic treatments are you willing to live with, if non then these issues become extremely important.
"Acoustic treatments are a band-aid for problems not addressed during design, not the answer" according to this expert.
In home audio our needs are unique in that the scale is very small, reverberation rates, sound enhancement and echo are nominal issues. This could possibly be what Everest is discussing. Our issues are mostly side wall and floor/ ceiling first order reflections (slap echo) and frequency exaggeration.
A very small splay (narrower at the front) will alleviate most of these frequency nodes, but some thought could be put to the amount of splay. Too much could reinforce the projection and act as a "horn" and not enough will not achieve the intended goal. Ceiling and floor sloping can be more dangerous, in that the sound angles off a sloped ceiling (in the same fashion as the walls) could end up directing the reflection bach to the listener (especially with multiple seating locations). Think of a dome, it reinforces all sound to the middle, very bad in our situation. A slope down the axis of the room however could disperse the reflections very well.
The consultant we used had a very elaborate computer program that he was able to model the full spectrum of possibilities for the best solution. He was able to produce an audio track for any position in the room to determine what every seat would hear. There are cheaper programs available that could do some of the same things, just not quite as involved.
The rule of thumb I would use is the ratios spelled out in Everest's books or Robert Harley's book to determine the best ratio and size. If you did splay the side walls, I would use the width recommended as the average (mid point) of the splayed wall. I have been using a 2 ½ degree angle on my designs with very good results. The ceiling I would vault if possible.
As to how important this is, it completely depends on how far your willing to go. If your intending to get every ounce from your system with power conditioning, cables and tweaks, then this makes sense. If your happy with 80% of perfection, skip it, it's not worth the hassle. If you do however pursue this I would recommend you look into what wall materials your using. One layer of drywall over wood studs can give a soggy base response compared to a more rigid construction. You might consider building in a true base trap in the design, what acoustic treatments are you willing to live with, if non then these issues become extremely important.
"Acoustic treatments are a band-aid for problems not addressed during design, not the answer" according to this expert.