Vintage Bang & Olufsen Penta Restoration “Project Twins” – Final Reveal

This is the sixth and final part of the Bang & Olufsen Beolab Penta restoration. For the original post, see:

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

This project was completed before my first child was born. I have a few additional B&O projects I’d like to complete but time is more limited with the addition to my family. It was grueling to complete in my workshop which topped off above 110 degrees on many days. It was however extremely rewarding and I absolutely love the sound of these speakers. To the best of my recollection, they sound better than the new pair I auditioned in New York back when I was still in high school in the early 90’s. So, here are the pictures of my labor of love:

Almost compete right speaker next to a Beolab 8000. Waiting for new closure before attaching final front panel:

Almost compete left speaker next to a Beolab 8000. Waiting for new closure before attaching final front panel:

Straightened out top speaker cap:

Groove between stainless steel was painted black to match the new black paint on the other plastic panels:

Fresh coat of stain black paint on all gray plastic parts. This shot is reflecting the color of the carpet a bit. The color presents darker in person:

New stainless panels revealed. Beautifully straight without a single fingerprint:

Final picture of the restored speakers:

  • eGoh Oct 19, 2015, 2:18 pm

    Are you looking for a B&O? The Penta 2s are compatible with much of the B&O equipment. Give me an idea of what you’re looking for and perhaps I can help some more.

  • Lisa J Sep 29, 2015, 9:17 pm

    I have a pair of BeoLab Penta 2’s and need a receiver which one would I need?

  • Peter Sep 19, 2015, 8:51 am

    Hi,
    Maybe this is an answer for Chan. This is what I found in the servicemanual for BeoLab Penta on the intrawebsite from B&O Denmark.

    Puffs or distortion occur in the loudspeakers
    Symptom:
    Puffs and/or distortion may occur intermittenly in the loudspeakers after a re-start within approx. 3 minutes.
    Cause:
    The supply voltagte in the amplifier has not reached the correct level.
    Solution:
    Insert a mute circuit, part no. 8002927.
    This modification will also be introduced in the production.

    Best regards
    Peter

  • eGoh Sep 10, 2015, 11:03 pm

    It sounds like an electronics fault. Sadly, I doubt changing drivers will help you in this case.

  • chan Jul 22, 2015, 5:28 pm

    I have a pair of Bang and Olufsen Penta I. The left speaker makes crackling sounds, sort of like listening to empty channels on the radio. It seems to be coming from some of the midrange speakers and some of the top woofers.

    This happens randomly, sometimes I can listen to half an hour of music and nothing will happen, but the next morning it will come up again, even when playing the same songs.

    Even after the Beosystem 5500 goes into standby, the speaker continues to make these crackling noises until the light under the speaker turns red.

    Will changing the midrange speakers and woofers help? Or is this an electronics problem (resistors etc).

    Thank you for any help you can provide.

  • eGoh Jul 15, 2015, 10:52 am

    Ed,

    I haven’t personally swapped the stock internals for an ICE amp. That said, those modules are quite small and a retrofit should be pretty simply given the amount of space inside the amplifier housing. Additionally, they are extremely clean and efficient amplifiers. Good luck!

    Best,

    Eric

  • Ed Resh Jul 14, 2015, 2:01 pm

    eGoh,
    Fantastic job you did on the Penta’s, I two have a pair and happen to live in Lewisville. One of my speaker Amps hums and I’ve been investigating taking out the B&O amp and replacing it wit an ICE 250 asx 2 power module. Right now I am using a Carver amp to power my Penta’s the Ice modules would replace the Carver as well as the B&O amp.
    Do you have any experience with this
    Thanks in advance Ed Resh
    972-579-1551

  • eGoh Jun 1, 2015, 8:25 am

    I purchased all the electrolytic capacitors from mouser.com. The 10,000uF caps I used were from Panasonic, but are no longer available. Mouser will likely have caps that will fit, but you’ll have to spend some time searching for ones with the correct specifications and dimensions.

  • Cypher May 25, 2015, 9:53 pm

    Egoh,

    Really nicely done! I just inherited a pair of these speakers from my father. One of them seems to work perfectly, the other however does not work at all. I disassembled the amp on the bottom and found a burned fuse, replaced the fuse and then the ELNA 80v 10000uF Cap Blew on me. That left an awfully stinky room for several hours. I am curious if you replaced these caps when you rebuilt your amps, if so where did you purchase them from? Also, where did you purchase the rest of the caps that you replaced?

    Thanks,

  • eGoh Mar 31, 2015, 9:13 am

    Tuong,

    The crossovers are located on the bottom of the speaker cabinet. You must remove any nuts and screws and remove the bottom access panel. Once open, the two boards just slide out. B&O may have used some hot glue on the board, so you might have to loosen that first. If you have more problems, feel free to email me some pictures at the contact info listed on my site.

    Good Luck!

    Eric

  • tuong Mar 30, 2015, 11:52 pm

    How can you take the crossovers? I did try it but can not

  • Marcus Dec 12, 2014, 8:39 am

    Great work, looking superb!

  • Brandyn Jan 2, 2014, 8:01 am

    Thanks for the quick reply Eric!

    Ill have a look at the Crossovers tonight. Just how can I tell if the electrolytic capacitors need to be replaced other than them being burnt out? Regarding the amps, I took the them to get looked at recently because one of them was overheating, he explained that it was oscillating, but not sure what exactly that means. The amps seem fine now other than the Auto/On/Off switch not working.

  • eGoh Jan 1, 2014, 11:17 pm

    Brandyn, Thanks! The crossovers are in the main speaker cabinet. If you have any amp or receiver around, you can try hooking it up to the terminals on the bottom of the speaker. If the bass is still lacking, it’s probably the crossover. Luckily, the woofers have rubber surrounds and are pretty durable. The crossovers have a bunch of electrolytic capacitors that tend to dry out with age and it’s common for them to fail, especially at this age.

  • Brandyn Jan 1, 2014, 9:59 pm

    Hi Eric,

    You did such an incredible job!

    Are the Crossovers located in the amp or in the cabinet ? I would like to take the amps apart and have a look to see if anything is burnt out.

    I get very little bass from these Penta’s and they are Penta 1’s so I would like to see if the crossovers could be the problem

    Thanks!
    Brandyn

  • eGoh Jun 29, 2013, 9:48 pm

    Mark,

    The stainless steel was bent on an industrial metal break: https://en.wikipedia.org/wiki/Brake_(sheet_metal_bending). You might want to try emailing B&O USA since I heard they still had parts as of a year ago. If you can’t find replacements, try looking for a sheet metal shop that does custom work.

    Good luck!

  • mark Jun 28, 2013, 8:52 am

    Hi,

    Very impressed with your work – just one question though – how did you form the aluminium – both getting those lovely creases and cutting the pieces to size.

    You can’t get the replacement metal from B&O in the UK any more :-<

    Thanks

    Mark.

  • eGoh May 4, 2013, 8:49 pm

    Thanks Alan!

    Unfortunately, I don’t have the parameters for the midrange drivers. Depending on when they were manufactured, the drivers might says Nokia, but I think they are the same. Since most of the drivers out there have likely changed due to age, you might want to get your hands on a new one before doing your tests. Last time I checked, B&O still had replacement drivers, albeit expensive.

    A tri-amp setup could be really interesting. I believe I read about someone who did that with some ICE amps a while back. IIRC, he was very happy with the results.

    Good luck and keep me posted as your project progresses!

  • Alan May 4, 2013, 8:42 pm

    Nice workmanship! The folks at B&O would be proud!

    I used to sell B&O when I was in college. I recently bought 2 pairs of Pentas (1 pr Mk1 & 1 pair MkII). The Mk1’s work great. The midranges in the MkII’s need new surrounds.

    Do you know the Thiele/Small parameters for the midrange driver? They can be determined using a $100 test kit like http://youtu.be/dARRX-tZpg4.

    I think SEAS makes the driver for B&O. Perhaps someone has obtained the T/S parameters for the SEAS model #? Any pointers/help is much appreciated!

    I’m considering a project to tri-amp one of my pairs. I have a high quality stereo active crossover and amps. This is probably looked down upon by true B&O fans, but I thought it would be an interesting project. Thoughts?

    Thanks,
    Alan

  • eGoh Feb 28, 2013, 11:06 pm

    Jim,

    Thanks so much! So nice to hear from other B&O fans in Texas. I gave up on vinyl years ago when I wanted to digitize everything, but I’ll take you up on the offer if I get back into it. The best glue is Aleene’s Original Tacky Glue. You can get it at craft stores anywhere in central Texas. I believe I picked mine up at Michaels, or Hobby Lobby. So are you saying that the Penta’s sound fine with music through the BS9000 but distorted from the Sony receiver? I’m just trying to understand the problem. Sorry for any delay in my responses. I’m in the middle of moving.

    Cheers,

    Eric

  • Jim Moore Feb 28, 2013, 10:46 am

    Hi Eric. I’m so glad I stumbled onto your website. WOW! Great stuff!!

    I have a pair of Penta IIIs that I am about to re-foam. What is the best glue to use? Your re-foams look so clean and professional. Beautiful work!
    My TV surround sound is connected to the passive side. Recently, I have had to turn them way down because of EXTREME distortion when any bass is present. I am using a Sony AV receiver.
    I run my BS9000 through the active amps and it sounds perfect so I’m thinking that it must be the sony amp.
    Your thoughts would be greatly appreciated.

    Best regards.
    Jim

  • eGoh Jan 25, 2013, 3:40 pm

    Monte,

    The 6603 is the Mk. I.

    On all of the Penta’s I’ve seen, the top cap is held in place with two strips of very strong double sided tape. I used a heat gun and lots of finesse to remove them without damaging them. Good luck!

  • Monte Jan 13, 2013, 1:52 pm

    Eric, what a great project and nicely doccumented!
    I have been searching all over and your project is just what I have been looking for.
    I am helping a friend redo a set of these but I am not sure what model it is. All I can find is the model number 6603. Would you know what Penta (MKI, II, or III) they would be similar to?
    I am haveing a problem with one of the amp lights staying amber. I cannot find any burnt components or hot spots on the board. I will replace all the caps/potentiometers and test the other components as your suggested earlier.
    Also, before I start with the top section, how is the top aluminum cap removed? Is it just stuck on with two sided tape? These speakers have been kept in very nice conditiona and I don’t want to mess up the beautiful look.
    Thanks and that is a very professional job on your speakers!

  • eGoh Dec 13, 2012, 9:43 pm

    Doug,

    First try switching the right and left channel to try to isolate whether or not it’s the receiver. Are you using the receiver’s speaker out directly to the Penta as a passive speaker? Or, are you using an RCA out from the receiver to the Penta amp?

    Eric

  • Doug Benbow Dec 13, 2012, 8:00 pm

    Hey Eric,
    Great restoration job by the way! I currently have 8 Pentas & only 4 are working properly now. I have 2 hooked up to a Pioneer Elite receiver as a part of a surround sound system and on just one side I have had 3 speakers start to pop & buzz & then shut down. Could it be the Receiver? Also, would you know where I could get them repaired in the Chicagoland area?
    Thanks!
    Doug

  • eGoh Nov 22, 2012, 4:48 pm

    Allan,

    To my knowledge, I don’t think B&O still stocks that item. I’ve bought a few spare Penta parts from: http://myworld.ebay.com/parts-bay. You might try contacting them to see if they have any, but I didn’t see any listed currently.

    Good luck and thanks!

    Eric

  • Allan Koch Nov 22, 2012, 4:31 pm

    Hi.

    I just must say: What a job. Your Beolab Penta looks like a million.

    I have a pair of Penta MK2 but I have a problem.

    I´m looking for the Display Glass Part number. 3320132 for both speakers.

    Can you please help me. I can´t finde them anywhere.

    Allan Koch
    Denmark

  • eGoh Nov 10, 2012, 6:02 pm

    Alejandro,

    Check http://www.hifi-manuals.com or http://www.beoworld.org/manuals.asp (subscription required)

  • alejandro Perez Nov 10, 2012, 3:55 pm

    hello I’m repairing the amplifier will have some diagram that I find the fault, thanks

  • eGoh Oct 16, 2012, 1:15 pm

    Thanks Roy, they were certainly a labor of love. Once things settle down, I’ll have a few more restoration projects posted, but sleep is quite limited with a new baby in the house. 🙂

    Ryan, You have to keep them stainless! It’s ok to paint the plastic parts, but the metal is what makes them so distinctive. I’d love to see the condition of the ones you found. Feel free to email me pictures: http://egoh.com/contact/

  • Ryan Oct 16, 2012, 12:53 pm

    Wow, I just found some in the garage of a house I bought. They are in bad shape, but nothing like what yours were. I wish I had the know how, to do what you’ve done. I wish I could just paint the whole things flat black.

  • Roy Oct 16, 2012, 1:08 am

    NICE JOB!!! You my friend are an Artist. Having built a few Fried Transmission line speaker kits I can see the fine work, attention to detail and love of the job. It was a pleasure to read your story and follow your processes.

  • Km Aug 7, 2012, 10:57 am

    Thanks A LOT LOT LOT!!!

    I tried doing research on this stuff but I have absolutely NO idea what’s going on with this(I did try to fix my cars before when I was in college a couple years back, because of lack of good tech guys in Tucson AZ, and I did ok hahaa) but this time I totally failed. Maybe, because of lack of time from work and stress. My brain seems not functioning haha. But yeah, like you just said I should take it to some local tech(way too expensive to send them back to B&O) to check them up with a full service since I am planning to keep them as long as I am still standing on this earth lol.

    Btw, I think I will kinda rebuild it with new mesh n stuff. I will send a couple of pictures of before and after to you, just to share the pleasure coz you look like a B&O fan like I am. hahah

    Again. I am appreciated with your precious time and reply!!

    Km

  • eGoh Aug 6, 2012, 7:12 am

    Km,

    Thanks for the kind words. The amplifier is going into protection mode, most likely because some of the components need replacing. The likely culprits are any (all) of the electrolytic capacitors which dry up with age and need replacement, the two adjustment potentiometers which also deteriorate with age, and possibly the transistors. At this age, the amplifier really needs a full service to bring it back to give it another 10-20 years of service. 🙂

    Oh, and don’t try using it any more since it can do more damage.

    Cheers,

    Eric

  • Km Aug 6, 2012, 5:37 am

    Hi Eric

    Your work is absolutely amazing!! I wish I could have your skill to get my penta 1 reborn like this. Sadly I dont have such skills, knowledge and space(since moved back to HongKong from states) to do that. By the way, I have been having trouble with one of the speaker.
    One of them stopped working. I put both of them on “AUTO” (whenever you connect your speakers to your ipod they automatically turn on), they usually turn to “GREEN” light when the speakers work but somehow one of them turned to yellow(orange?) and it doesn’t have any sound but only a “POP” and when I tried to turn it off by switching to “OFF”, it doesnt turn off and the light is still on “Yellow”.

    Now, sometimes it turns on but even if its on the sound would go totally off with no sound or some weird sound like sizzling. I heard it is about the amp or something.

    I hope you can help me on this so I know whats going on and take it (maybe both of them since they are old) to check. Or do you have any suggestion/advise for me?

    Appreciated!!!

    Km

  • eGoh Jul 26, 2012, 10:41 am

    Eddie,

    The resistors and coils likely burned out due to shorted electrolytic capacitors. You’ll need to likely replace all of them while replacing the other damaged components. I believe there are three versions of this crossover floating around. My Pentas are MKI but have MKII crossovers, so you might have to check all versions until you find the one that matches what you have.

    If you have the same crossover as I do,

    L6 on the bass is a 1.8mH air coil
    L3 on the midrange is 100uH air coil

    I believe you’re in Europe, but I’ve had good luck working with Mark at http://meniscusaudio.com for custom wound coils.

    Good luck!

  • Ed Jul 26, 2012, 10:27 am

    Hi Eric
    I just disassembled my Penta s , and discovered that I had the same promlem with burnt resistors and coils.
    Do you have the values for the L6 coil on the Bas and treble filter and the L3 coil on the midrange filter ?
    I have looked at other sites with the penta filter but they do not describe the same values of caps and resistors as on the filters i Have. I do not think that they are the same. But looking at your pictures your filters look alot like mine.

    Best regards
    Eddie

  • Ed Jul 21, 2012, 3:19 am

    Hi Eric

    Congrats with the newborn. Thats alot of work.
    I have ordered the Aleene’s Original Tacky Glue and also the cloth with some strech.

    Best regards
    Ed

  • eGoh Jul 11, 2012, 3:41 pm

    Ed,

    I’ll see what I can do, but it might take a little while since I have a newborn at home and things are a bit hectic. But, there isn’t a whole lot to see. Just rough cut fabric and some Aleene’s Original Tacky Glue residue.

    Cheers,

    Eric

  • Ed Jul 11, 2012, 3:20 pm

    Hi Eric

    Thanks for your reply.
    The jig sounds like a good idea.
    Would it be too much to ask to se a foto of the backside og the top and bottom grills?

    Best regards

    Ed

  • eGoh Jul 11, 2012, 12:13 pm

    Ed,

    There are two ways to deal with this: 1) Make a jig 2) Use stretch fabric

    I’ve done both for different B&O speakers. Method #2 is easier. In either case, you’re going to need a ton of clamps. Unfortunately, I didn’t take pictures of how I replaced the cloth, but I’ll try my best to explain.

    1) You’ll need to make a jig out of wood that will restrict the frame from flexing too much inward. This way, you’ll still be able to stretch the fabric while not making the frames into an hourglass shape. I usually build the jig to be slightly smaller than the speaker so that there is still extra tension once the grille is installed to take out any remaining wrinkles or creases.

    2) The easiest thing to do is to buy fabric that has a lot of stretch to it. In the US, fabric stores sell “dance fabric” which has some elastic to it. It’s available in many colors and finishes. I used matte black on these Pentas. Since the fabric is so stretchy, it’s much easier to get all the wrinkles out. The lower grilles are a breeze with this fabric. The upper grilles can still be challenging on the very top, but with some patience and a ton of claps, you can get it perfect.

    Good luck!

    Eric

  • Ed Jul 11, 2012, 11:11 am

    Nice work
    I have a pair of Beovox Penta with torn cloth
    How would one replace the front coth. I have tried with bad result as the cloth frame is very soft and bends.
    Best regards
    Ed