I'm also into very high-efficiency loudspeakers, and my hat's off to you; you're a true sound artist. Are you Japanese or Korean? I'm from Montreal Quebec and the former designer at Oracle audio. Bravo!
According to those who I trust explicitly say the 13 and 12 were the pinnacle of WE sounding reproduction, with the 13 being the top dog in their esteemed opinion. I’ve heard quite a few WE speakers, but never these two.
The system consists of two WE555W, two GIP 555mesh, two GIP 597 Tweeters, and two WETA4181.The 12a, 13a are equipped with 555 drives and need a subwoofer because they can't play less than 80 hertz. It is extremely difficult to position all eight drives.
