Yesterday I fixed up the 2441s. I put a new Radian diaphragm into one, and put the JBL one from that into the other. For some reason, the Radian diaphragms are a tighter fit than the JBL ones.
That’s the JBL diaphragm in situ. It has a circle in the middle, which the Radian doesn’t have, and the diamond pattern around the edge that is a 2441 thing.
The problem was caused by some distortion, perhaps from the diaphragm rubbing. In the end I fixed one simply by using the Radian replacement, and the other by only using three rather than eight bolts. Any more and it would vibrate.
I tested them by running fixed frequencies and sweeps from my phone and through a little class D amp. The Bink test CD is great for these sweeps and stuff.
I think that using the 2441 should really help reduce the distortion - running the Rectums so high is fine, but not through that horn with a sharp turn. I think…