Hi nikeyboy.  The foam degradation on the penta mid ranges is a very common problem.  Although the sound will be affected, the speakers will still work until the degradation is bad enough that the cone is no longer supported and starts to rub on the inner coil as it moves.  The foam ring is a suspension, that supports the cone while still allowing the cone to vibrate and thus produce sound.  When it breaks down it can then no longer support the speaker.  The foam also has to be air tight, so the degradation ruins that also.

Refoaming them isn't just a matter of whether it'll improve the sound.  It's downright necessary or you will slowly damage the speaker as you use it more and more.

Austin 

It is possible to refoam these but the easy solution would be to buy new drivers which are still available from B&O.

Chris.

With the gracious help of this board...we fixed the amp sections on both penta 2's...and they had the foam rot too..

We bought the foam rings from GoodHiFi...for $42 for all 8 rings....but i also had a set of 8 midranges that were rotten left over from some penta 1's...

Strange thing...in South America...they re-foamed all 8 speakers...including labor and foam...(did not use the goodhifi rings) for....$3.50 usd per midrange.....

They look like and sound as good as the penta 1's with brand new midranges.....

I'd try the re-foam first....

Please note these 'new' replacement drivers are also 10 or more years old. They may have been stocked on the shelves, so the foam rot didn't go that fast, but even in stock the foam rots! It's best to replace the rotten rings with new rings that have been pressed recently. If you replace your units with the ones by B&O you will suffer foam rot again in a few years.

Good Hifi