After having bought this really nice 115S cab nearly two years ago, I've finally found a great speaker for it. It didn't have the original in it when I bought it, but had a nice, and somewhat rare, 1978 CTS with the bronze frame and white dust cover. After looking and looking and looking some more, I've ended up with a few years old Electro-Voice DL15ST in excellent condition. It got here Saturday. I spent Sunday afternoon enlarging the speaker opening a bit for a proper fit. This afternoon, mounted the EV and hooked it to a '79 Beta Bass head (the closest head available) for a test run. I made a perfect choice. Sounds excellent. I can only imagine it will be even more impressive with a stouter head, since this speaker is a 400 watt RMS monster. For fun, I added a second 1x15 cab that I've recently acquired, a 1974 Music Man. It is nearly the same dimensions as the Sunn 100S, and it's loaded with a JBL K140. This gave me the use of the full 100 watts of the Beta. The smile got even bigger!
Anyone interested in the CTS, it's now available.