Vintage Bang & Olufsen Penta Restoration “Project Twins” – Part 2

This is the second part of the Bang & Olufsen Beolab Penta restoration. For the first part, see:

Vintage Bang & Olufsen Penta Restoration “Project Twins” – Part 1

For the first big task, I stared by removing all the dry-rotted foam from the midrange speaker drivers. This is a tedious process since the speaker cones are paper and can’t be damaged during the removal and cleaning process.

Quick picture of the wiring so I remember how to hook everything up:

The sad condition of the original foam:

Initial foam removal:

Showing the residue that needs cleaning:

Very clean drivers:

Another picture of the clean drivers ready for new foam:

Gluing the foam to the speaker cones:

Jig to apply light pressure for glue to dry properly onto the paper cones:

This was a lot of work since a pair of Pentas have 8 midrange drivers, but things are starting to progress.

Next: Vintage Bang & Olufsen Penta Restoration “Project Twins” – Part 3

  • eGoh Jan 31, 2015, 8:48 am

    I used a ton of cotton swabs that had a very small amount of isopropyl alcohol on them. It’s not difficult, but extremely time consuming and tedious. Good luck!

  • Kent Jan 30, 2015, 2:31 pm

    What did you use to clean the old rotted foam off the edges of the cones and the baskets. I just started preparing mine for new surrounds and I’m having a hard time getting them as clean as I would like them to be.

  • Olivier Aug 15, 2013, 12:52 am

    Bonjour Eric,
    La restauration de mes Penta III est terminée. J’ai changé tous les condensateurs (ampli et filtre) des enceintes par des condensateurs de qualité sauf les 2 de 10.000µF des amplis que j’ai conservé. Un peu déçu par les nouvelles suspensions en mousse qui n’ont pas les mêmes dimensions que celles d’origines. En effet, le diamètre extérieur est plus petit de deux millimètres ainsi que le diamètre intérieur. La lèvre intérieure est trop large et recouvre trop largement la membrane papier du haut parleur. Le soufflet est aussi trop large et on voit par l’arrière que le bord de la membrane papier arrive dans le pli en mousse. On perd 30% de la surface qui dissipe le son.
    J’ai aussi remis des tissus neufs. Je ne sais pas comment faire pour vous envoyer des photos sur le site.
    Cordialement,
    Olivier

  • eGoh Jul 10, 2013, 1:57 pm

    On doit utiliser les mêmes matériaux pour les véritables caractéristiques acoustiques Bang & Olufsen. Je voudrais utiliser caoutchouc seulement pour la commodité. C’est un peu plus facile. Avec cela dit, j’ai utilisé la “foam”. Pardonnez mon, parce que mon français est très mauvais. Bonne chance et e-mail des photos des haut-parleurs.

  • Olivier Jul 3, 2013, 9:18 am

    OK, thanks.
    I ask this question because I am not sure that the sound will be the same with the edge foam and the edge rubber.Compliance and absortion is not the same.The sound of a médium is not a piston as a boomer.The power in less and the middle frequency can be stoped by the rubber.I am not sure, it’s an expérience and it’s also a question.When you go to the hight frequency (tweteer) you dont find rubber on the speaker.I think I prefer the foam to have the original sound and perhaps the new foam stay for more ten years. So, it will be a pleasure to change it again in ten years fot ten years again. The badest in this story is that I will be ten years hold in more! Sincerly, Olivier

  • eGoh Jul 3, 2013, 7:27 am

    I purchased replacement foam from http://www.goodhifi.com in the Netherlands. While the original speakers utilized foam, if I do another restoration, I think I’m going to use rubber. I really don’t like the idea of having to re-foam every 10 years or so.

  • Olivier Jul 3, 2013, 4:32 am

    Hi from France, I have the sama Penta 6631 and the same problem with the foam.I look on the web some seller who sold “foam” and others sold “rubber”. Origin is foam; could you please send me the link where you bought your foam? Thanks for your help, Olivier

  • eGoh Jun 29, 2013, 9:49 pm

    Rico,

    If you’re referring to the crossover, it’s accessed from the bottom of the speaker. If you’re asking about the specific circuit on the crossover, first let me know what version Penta you have. That info should be on the bottom of the speaker.

    Cheers,

    Eric

  • Rico Jun 29, 2013, 12:58 pm

    Hi,

    Very good work !

    I have the same speaker. I like this speaker b&o, event if that’s not the best hifi sound…

    Thank’s for the tutorial because that helped me to make speaker medium…

    But can you tell me where is the filter for the high speaker ? Because i’ve not sound into this speaker…

    Thank’s a lot for your answer,

    Rico