A friend gave me a SWR Son Of Bertha 15+tweet cab, after he discovered it really did nothing for his sound in combination w/ his Hartke 4-10. He didn't care for it alone either, so I became the lucky recipient.
Turns out, it's not really my flavor either. My regular rig is a fEarful 15/6. I like a modern, and very "mid-forward" tone from my rig.
After reading on this cab, I found that the tweet is crossed over @ 5khz. No way that 15" is making it that high. Leaves a significant hole in the upper mid. What to do? I found a 5" mid driver made by Goldwood(PN GM/85-8), that goes as high as 15khz, and as low as 500khz. It's a closed back driver, so no need for a separate chamber. I removed the Fostex tweet, and had to make only a small notch to clear the terminals of the new mid, and it dropped right into the existing hole. I added a Dayton 2khz 2-way pre fab crossover and it sounds great.
The Fostex tweets are very common, and I figured someone else might not abandon a perfectly good cab, with this easy mod. Only cost $47.03 with shipping.