I am curious about the evolution of the 6321-6323-6343 series of speakers (C75, C75 and CX100 respectively).  I couldn't find a service manual for the 6321.  The service manuals on this website show the same, fairly simple cross-over for the 6323 and 6343, although Beocentral implies that the cross-over was simplified in the CX100 (in addition to other changes).  

When I opened my C75's for restoration, I found a more complex circuit with two capacitors 8 mF and 15mF respectively, rather than a single 6.8 mF.  Hence my discovery of the two types of C75. 

I thought I would re-foam the upper woofers - the lower ones have rubber surrounds , replace the capacitors, check the resistors and hope the inductors are fine (since this is a hobby and for my personal use I can be somewhat cavalier about some issues).  Is there anything else of significance or interest with respect to the 6321 as distinct from the other two?

Thanks,

JRW

Are you sure the n6321's you have are original? AFAIK the C75 had all-foam drivers apart from the tweeter in common with  all of that series.

Simon

Thank you for your interest and response.

I should clarify, the C75's that I bought are 6323's, but don't have the cross-over found in the service manual for 6323's on this site (which is identical to the CX100 cross-over found in the manual on this site).  I wondered if there was an earlier cross-over version which these speakers might share with the 6321's.

The information on the back of both speakers is C75 T6323 2080008.  The upper speaker which has rotted foam has 580236, 783 TNG, and Japan on it.  The tweeter has "1" Dome Tweeter, H216 6 ohm, 46/76, and made in Norway.  The lower speaker has rubber surrounds and on the back has B&O, 8480143, 6 (the symbol for ohm) OV012 (could be 0V012, with a leading number rather than a letter).  The inner edge of both surrounds is quite neat.  Some glue is visible around the outer edge of one speaker although it is not messy.  Both drivers have a dull gold dust cap which is different than the upper driver of the same size.

The cross-over consists of 3 inductors, 2 capacitors and a resistor.  Only the capacitors are labled, 8 and 15 uF.  The tweeter has the 8 uf in series followed by an inductor in parrallel.  The lower driver is in parrallel with this on a circuit consisting of an inductor in series and then the 15 uF capacitor and a resistor in parrallel. The upper driver is in parrallel with the lower, coming off between the inductor and the 15 uF capacitor and has an additional inductor in series.

I have no idea if these are original.  I was looking for some CX100's for my study when these came along.  The internet reports indicated that the C75's were if anything "better" and so I decided to make a project of them.  From a cosmetic perspective they clearly have had some use and I would assume been moved more than once, given a few nicks.  As I am a listener not a collector this isn't a problem, but if the rubber surrounds are not original and would alter the sound, I would go back to foam. 

Did any of the C75's have rubber surrounds on the lower driver?  If these are not original, is the difference between foam and rubber typically audible?

JRW