The 209 mid is very problem prone, too. You need find some 209Bc mids and some 200 Zc tweeters and re-build the crossovers .
Yes, correct. To clarify, that is the original paper-cone B-209 midrange. It has no suffix.
Avoid the B-209A at all costs. This was the first generation of the aluminum cone drivers.
It requires a special damping ring which has long since a shriveled and hardened lump, or turned to dust, or some combination of the two. Without that damping it rings and causes distortion.
Conclusion: do not buy the A version.
The B-209B, Bc, and C use a different surround to damp the driver. The B and Bc are rear-mount, the C is front- or rear-mount. The B is alnico, while the Bc and C are ceramic magnets.
The B-305 is different from the B-302 because it
nearly always uses a 16 Ω mid-range, so be sure you don't buy the 8 Ω. The 8 Ω B-199 woofers are series-wired to form 16 Ω. So the midrange is 16 Ω as well. This is
not guaranteed to always be true, as Bozak made a 16 Ω B-199, so two of those in parallel would be 8 Ω allowing an 8 Ω midrange to be used. In theory. I do not know of any of these B-305's, but there are a lot of Bozaks created by third parties or modified, so check what you need before buying drivers. I know of other dual B-199 configurations which used 8 Ω or 16 Ω configurations.
An AK member posted in BT that he has a pair of the 16 Ω drivers for sale, as he requires the 8 Ω variety for the B-302. No connection with the seller, just noticed them up there and mentioned it if you want to go that path.