Me? Weigh in?... Dunno... I'm pretty shy.
1. The taller the array the more pronounced the "array effect" of widened horizontal dispersion and narrowed vertical dispersion.
2. Ditto for the narrower the aspect ratio. This is different than physical height.
3. Also in play here is the complicating fact that smaller drivers produce wider dispersion patterns than larger drivers.
Crazily, you could stack four two-foot speakers vertically and technically call it an 8-foot high line array. However, the aspect ratio of the array would only be 4:1. The array effect would be minimal.
Alternately, you could stack 48 two-inch (full range) drivers to get the same 8-foot array height. But, your aspect ratio would then be 24:1, and the line array effect would be as near-perfect as you'll ever achieve in real life.
In this case, "near perfect" means the top of the upper driver would define a horizontal plane above which nearly no sound was projected. The bottom driver would also define the lower limit horizontal plane, below which effectively no sound would propagate. And, to the sides, SPL drop at 180-degrees would be negligible -- virtually the same as dead center, on-axis.
With the first example -- four two-foot drivers -- mostly none of that occurs, and you'd still essentially have a point source loudspeaker system, with a spherical drop off pattern in SPL, generally the same SPL drop off vertically and horizontally.
So, given that array height and array aspect ratio impact the dispersion characteristics, those engineering decisions define the way the product eventually performs in real life.
Bose chose a super tall and very narrow aspect ratio approach, and the L1 behaves that way: a super tight array effect -- ultra wide, with eerily chopped output above and below the end drivers...
creating a 6-foot tall "slice" of sound going out at an audience. Anyone whose ears are within that vertical 6-foot space will hear a near-perfect 3dB SPL drop per doubling of distance effect of a line array. Anyone whose ears are above the top of the slice or below the bottom of the slice will hear virtually nothing. Really.
Go to store selling the L1, turn it on, walk away and stick your head above and below the "slice" and hear this for yourself. It's truly weird. Where'd the sound go?
Fishman chose to use a much shorter array with wider drivers, and then plop a tweeter in the middle that decouples the top three drivers from the bottom three drivers. While there's no published and agreed definition for this, I don't consider anything under an 8:1 aspect ratio as a line array, as the effect is minimal. The SA220 has a pair of closely located arrays (one above and below the tweeter) of about 2.5:1 aspect ratio -- very nearly a couple of simple point source loudspeaker systems. So, there is very little array effect at play. The wider horizontal dispersion of the product mostly results from simply using small drivers, not from an array effect. Go figure.
In deciding the physical approach to the BagAmp, I wanted to avoid the tunnel like effect of a near-perfect array (Bose), but still benefit from some substantial throw improvement that a line array can create. So, I compromised by using eight three-inch drivers, for an array height of about 26-inches with a width of 3-inches, for an aspect ratio of about 8.5:1 or so.
So, BagAmp is intentionally not a super aggressive line array design. Why?
I don't want people to have to "aim" my product in situations where some people may be a little above the top driver or below the bottom driver. I wanted a set it up and just use it sort of product. The result is much better than a point source speaker's throw, but without the sci-fi level tweekiness of the Bose array "slice." I consider the L1 effect too much of a good thing for most real-world small venues. There *will* be heads above and below that perfect six foot high slice of sound in many coffee houses, small clubs, juke joints, auditoriums, ballrooms, etc.
So, that's the poop on why and how on the line array effect with the three products in discussion. I left out the L1 Compact, as it twists (rotates) the drivers, breaking the plane of projection, and isn't a line array at all. It, like the Fishman, benefits in slightly wider than typical dispersion simply by using small drivers.
And, of course since I don't have a Ph.D. in acoustic engineering (by one poster's implications), you can accept or reject any of this as you see fit.
