Hello.  Me again.

Should one worry about the diaphram and surround material when buying, let's say, a pair of S-45s?  That's always been a concern when I consider "used" speakers.

Yes, we discuss that all the time here (search the forums for "foam rot"). If you're after the S45-2 (the -2 is important), you don't have to worry since the woofers have rubber surrounds. I don't know about the plain S45 (there are actually two distinct models of those) but I believe it's susceptible.

My parents have a pair from 1979 and no foamrot yet.

The Beovox S45 and S45-2 with one-piece frontgrills have rubber surrounds and will not rot. The woofer magnets tends to losen in transport though, freezing the coil and cone so pack with great care.

The S45 with two-piece frontgrills will have foam rot if not already repaired.

Personally I prefer the older (one-piece) models because of their compact size, the difference from S45 to S45-2 soundwise is practically non-existing.

The newer (two-piece) version will be somewhat inferior soundwise but comparing this 2-way speaker with the older 3-way as some people like to do, however unfair this seems, it's not too bad either. The foam rot can be repaired and they usually come cheap simply because of the rot.

The design differences is a matter of personal taste, I suppose. I actually like both.

Martin