It seems to me that here on this forum most agree that a speaker with a wide dispersion pattern is a good thing. Why is this? If one was to do their stereo listening from the same spot (like a listening chair), and have the speaker toed in to be facing them, wouldn't a wide dispersion pattern be... sort of wasted?
Also lets say that in this hypothetical listening room that one speaker is near a corner. A foot away we will say. Wouldn't having a wide dispersion create an early reflection problem? A problem that a more narrow beaming speaker would not have.
A wide dispersion pattern does not equal a wide sound stage right? If you had a beaming speaker pointed right at the you listening on axis would this not give the best imaging? The best frequency response?
I only can see two problems with a beaming speaker. Having you "head in a vice" is one problem. Maybe you don't want to sit static is one position to get the best out of your speakers. The other is if you wanted to listen with another person. If they were sitting next to you they would not get the same imaging and frequency response. (This is not a problem for me as all my friends think I am an A hole for the money I spent on my system )
So, why is it wide dispersion is preferred?
So you are talking about a few different things here. Wide directivity speakers can have a wider sweetspot, but not necessarily. Placement and toe in can make a narrow-directivity speaker have just as wide a sweet spot, and in some cases even wider.
But you asked "a wide directivity speaker does not equal a wide soundstage right?" Actually, that is quite literally the primary effect of a wide directivity speaker, all else being equal.
To oversimplify and generalize, let's imagine two pairs of speakers that are identical in every regard except for dispersion, placed in a good room. One has rather wide directivity, one has rather narrow directivty. The narrower speaker will have more pin-point imaging, in which sources appear more focused. You can pick out exactly where each sound is coming from. You could probably point to the sources with a laser.
But the wider directivity speaker will sound, well,
wider. Hard-panned instruments are less likely to sound like they are coming directly from your speakers and may instead seem to occupy the space between your speakers and your walls. The soundstage and instruments appear larger than on the narrower design. But as a consequence, the image may appear 'fuzzier' and you may lose some of that pinpoint instrument placement.
The reason why is fairly intuitive once you understand that our brains use information from both the direct and early reflected sound to create our impression of music
With wider horizontal directivity, you get louder sidewall reflections. Though the direct sound is still dominant, your brain allows the sidewall reflections to contribute information about the sound as long as they are not delayed by too long. As a result the image gets broader and/or shifts in the direction of the reflection. So wide directivity quite literally equates to a wider soundstage in most cases.
It might help to think of the opposite scenario. The narrowest directivity speakers are headphones. Without reflections, it's hard for the sound to feel particularly spacious. For the same reason, I've often heard listening to speakers in an anechoic chamber (again, no sidewall reflections) described as being somewhat akin to wearing open back headphones.
However, it's not black and white, as things can vary depending on the recording and room acoustics. Some recordings contain a lot of spatial information already, for instance, or use special tricks to provide a wider soundstage.
Research into both sidewall reflections(in the context of room treatment) and the directivity of speakers seems to suggest that the presence of louder sidewall reflections is
generally preferred.
But this should not be conflated with the idea that wide directivity is *always* a good thing, in the way aiming for a flattish frequency response is pretty much always good. Some people have a strong preference for a narrow sound, and there is nothing wrong with designing a narrower speaker. It can also be handy for dealing with particularly bad room acoustics.
Blue is overwhelmingly the world's favorite color, but plenty of people much prefer red.
Also keep in mind the discussion is more useful in a comparative sense. Most mainstream speakers aren't extremely wide or narrow, after all, so it's best to compare on a case by case basis. In the real world, there are no completely identical speakers with different directivities, so you have to figure out your own tastes.