Looking at archived pics of the Model 20PLUS speakers I see that they have a different woofer basket in that the outer flange has been cut away on two sides to fit the smaller width of the cabinet. I see that same woofer on page 3 of the #59 Service Bulletin listed as "20+w" but there is no other technical info about it provided on that sheet. Maybe there's more on the missing page 2? I'm wondering if it maybe had a larger magnet assembly than the plain Model 20 as the volume inside that cabinet is considerably larger than the plain Model 20. Maybe other differences as well? It IS a 4 ohm part like the plain 20, correct? Did they really just hack off some of the frame on a plain 20 woof? I guess that would be in keeping ...