lausvi wrote:

 "Perfect centered by under laying spider". Is it really that easy?

I'd say no.
Of course, you can get lucky... or you could get unlucky.
I have seen several cases of both...

The spider only holds the cone (and with that the outer end of the voice coil) at one point.
The surround holds the other end - the end farthest from the voice coil.
The inner end of the voice coil is not supported.
The spider is rarely touched when doing a refoam job, leaving the placement of the surround responsible for a perfect axial movement of the voice coil in relation to the magnet pole piece.

Sellers of new surrounds often seem to play the replacement job down, refraining from showing the shim'ing process and/or telling/showing what to do when things don't work out right - thereby encouraging more DIY-buyers to try their luck.

Martin

Good HiFi in the Netherlands has a set of 8 foam surrounds for Beolab Penta. They cost 23€. I have bought several foam surrounds for CX50/CX100 at Good HiFi and been satisfied with the quality.

/riis

Ok, I went on and bought a replacement kit from GoodHifi. The surrounds seem to fit fine and while tedious, it wasn't too bad to do them (I have now done one of the two speakers, ie. 4 midranges, took me about two evenings to finish).

I found that the Penta midranges (mine were ITT branded, Made in Western Germany :)) actually didn't need much centering at all, they were pretty easy on that part. The new rings are perhaps a 0,5-1mm smaller, so there is room for adjusting. I glued to new foam first to the cone, and after it had dried, to the outside rim of the speaker. Simply pressing in the cone and listening for any scraping I figured they were centered good enough and used cloth-pegs to hold them in place while the glue hardened.

The old ones were looking pretty bad, all had cracks and they were all around sticky and spotty. Still holding in though, and still sounding very reasonable.

Login to view image

Here one can also see how the elements are in different levels, the tweeter is deep inside the mounting and the two outer mid-ranges re slightly higher than the inner ones that are flush with the mounting bracket.

 

And here is the after-shot:

Login to view image

I might have used a bit too much glue, but I'd say they look Ok, will do a final clean before re-install.

Now that I have done one speaker, it'll be interesting to listen if there is a notable difference.

Hi!

Thanks for the thread! I have recently refoamed my Penta mkIIs but for some reason one midrange produces an audible buzz. Its most easily heard while playing piano music. Do you think the buzz could be a result of a badly aligned foam surround? Should I re-do the foam fix or try to find a replacement driver?

 

Dillen wrote:

Not sure if the rubber rings in question was from Audiofriends as I wasn't the one who fitted them - I only replaced them with foam.

Has anyone confirmed the performance of the Audiofriends rubber surrounds? Like the OP I am hoping the rubber surrounds will last longer than the foam surrounds without a huge negative impact to the sound quality. I don’t want to have to change them again in 20 years, during my retirement.

One other thought I had was how the sound will shift over the years as the foam degrades. That must surely impact the sound quality as well, right? Or will there just be minimal change followed by a sharp drop off at the end of their operational life?

I have purchased both rubber and foam surrounds from them, and have just been waiting to complete the project. So anyone with personal experience to share? If not, I might just stick with foam as Dillen wisely suggests.