Interesting discussion, lots of great practical information flying around here. 👍🏻
I heard this line array (in a stereo pair obviously) and it was a surprising and wonderful experience. It is based on 25 Visaton FRS8M drivers, unshaded and some fairly basic passive filtering to balance the frequency response. It was crossed to a sub, but I don't remember at which frequency or what the subwoofer was. Anyway, it was at a diy-meet and I could play my own music and I chose Mahler, 5th symphony, the opening minutes with the powerful trumpet phrases. A recording of an orchestra I know well, a trumpet player I have heard many times, recorded in a concert hall with a famous and characteristic acoustic signature (Concertgebouw in Amsterdam). The scale of the sound was very good and the sort of lazy and dark dying off of the reverberation in the hall was absolutely perfect. There were many excellent loudspeakers there that day and in many ways they sounded more detailed, special, etc. But this basic line array absolutely slayed overall. So I attributed this to its dispersion characteristics and, basically, the total cone area of a 15 inch driver with the midrange and treble of a 3 inch fullrange driver.
I looked into the concept but the sheer number of driver and resulting cost were prohibitive. A bit later, I heard a 4 driver array crossed over fairly high in the midrange, which gave some of the effect. I wanted to limit vertical dispersion due to harsh reflections off the floor and ceiling of my living room, so gave the smaller line array a go. 6 drivers.
By that time, Visaton had recently released the FRS5X:
SD is a mere 12.5 cm^2, it has a beautifully extended treble, good dispersion. Too small for a sub-sat system by itself, but it worked very well in a short line array. Definitely offered enough vertical beaming to get rid of those nasty reflections. But still a limited cone area, so sounded a bit tame on dynamics.
If I ever would to a full floor to ceiling line array, I would prefer to use this driver. But because it's even smaller, I would need even more than 25. Yikes.
I heard some really long ribbon "tweeters" (something like 1.8 meters long) crossed at 200Hz to woofers. I guess that would be a suitable proper line source. It sounded really good, but.... Not sure if it sounded any better than the Visaton 25's.
Hmmmmm I should have a point in sharing this... 😉
Ah, yes, I strongly feel that it matters why you are building speakers and what you want to get out of it. For me, it started out of curiosity for "different sound" by which I mean: what do people mean by horn dynamics, what effect do different dispersion patterns have etc etc etc. I know what a civilised consumer audio two-way sounds like, but what else is out there?
I think that small fullrange drivers in a large line array offer that big cone area/small driver midrange and treble experience, and the special dispersion characteristics. As such, they are highly involving and enjoyable. I have heard an open baffle system, a 3-way based on consumer level drivers and a very brilliant crossover (designer has a PhD in that stuff, he takes no prisoners and doesn't need exotic components to achieve that) that was obviously superior, by far. Definitely the drivers working together optimally, the front and rear radiation patterns flawless and identical. I also heard a horn system with a coaxial compression driver in a round tractrix horn that had that same coherence, but a very different experience.
I believe very much in the 80-20 rule, getting 80% of the result with 20% of the effort. A bucket load of fullrange drivers in a line array are definitely in my top 3 of 20% effort for lots of quality. Perhaps number one if you're someone like Wesayso and can take that long path of DSP optimisation. Wesayso, I have followed your work for years, big respect!
OP, I would do more work with regards to driver selection. The driver used determines so much about the character of the resulting line array. The driver under consideration is old and still OK, but there may be others more suited in the price range by now.