Originally Posted by Breau
Wider dispersion gives better stereo imaging and soundstage... and a larger sweet spot.
Let's start with the imaginary scenario of listening in an anechoic chamber. In this scenario, only the sound arriving at our ears from the two speakers is heard. This means you need about 2 inches worth of sound waves at your ears. Anything else just doesn't arrive.
We have two ears, and they're not on our chin and forehead, so we need wider horizontal dispersion in an anechoic chamber for the sound from the speaker to be registered by our ears, but still only about, what, a foot worth of dispersion? Though to be honest you may not want the stereo cross talk and might choose to divide the sound for true ambiophonics.
This will give you the so called best imaging. You might consider it "headphone" imaging and maybe it's not your preference, but it's truest to the souce. It's not my preference either, mind you.
Anyways now leave the anechoic chamber, and put yourself in the room. Now you've got reflections
. Reflections do many things
1) Change stereo imaging
2) Change sense of spaciousness
3) Change tonality, especially on sustained notes.
Now the thing to pay mind to, is the delay of the reflection.
The first issue, is that in most rooms we hear vertical dispersion as a VERY early reflection. The floor is almost always the first reflection out of all "first reflections".
VERY early reflections are damaging to timbre and detail.
Now let's return to the concept of our two ears. They hear reflections off the side walls as imaging cues. With wider dispersion speakers they give the illusion that the sound is coming from "outside the stereo triangle".
Now if you're doing a waveguide build, you've already sacrificed those horizontal reflections. You want imaging that's on the recording, not imaging created by the room.
That's a personal choice. The main advantage is the plus to timbre and detail.
The problem is this:
Our two ears are a lot less sensitive to these "created by the room" imaging cues when they from above or below.
So what you get if you increase vertical dispersion, is very little of the "good" of dispersion (reflections creating a wider soundstage) and a lot more of the "bad" of dispersion (damaging detail and timbre).
So all dispersion isn't good dispersion.
You want enough vertical dispersion to cover a zone. But i've never seen any reason to advocate more ceiling reflections.
Now you've said something about treatments.
The problem with treatments is this:
Reflections are what creates spaciousness.
Every time you absorb an early reflection, you're also killing late reflections.
So the deader the room, the less it feels like we're in a "huge place" and the more it seems like we're listening to loudspeakers.
Absorption is just about never the solution.
And I agree with Noah, what's the point of a speaker producing more wide angle output (dispersion), only for it to be directed into an absorption panel? It's a waste of time
That's just nonsense.
"Just diffuse it then"
Actually, that's probably the best thing to do with vertical reflections on the ceiling. But not realistic for the floor. =(
Finally after all that, there's the issue of center to center spacing.
The decision for the 60 degree coverage angle reduces it. That reduces destructive interference (more bad and unpredcitable vertical reflections) while also making the crossover easier (driver acoustic phase is less mismatched)