ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi everyone
Just thought id share some pics from my last few days of R&R.
After a painful trip to the dentist on Thursday I thought i'd pop past a seconds shop known for having some B&O kit. I wandered in and there in front of me was a pair of Beovox S75 in teak of all colours (most B&O speakers in Australia seem to be Rosewood which I really like). After confirming with the shop owner that they worked ok and agreeing on a price and return if they didnt work, I left with them in the back of my car.
They were in reasonable shape when I got them with a few scratches, a bit of rust on the stands and very dirty frets. The drivers all seem good, i'd say they have been stored in a garage as the stands have some rust on them and the tweeter fascia's have some white oxidation on the front which I have cleaned off with vinegar and then wiped down with an oily cloth.
I had a listen to them on my BM1900 when I got them, they sounded nice, lots of high end, slightly recessed mid range and decent low end, the BM1900 seemed to struggle a little to power them, it usually drives S45-2's. After a few days of clearning up the wood, drivers,etc I am having a listen to them now on my Marantz SR7002 amp which is a modern AV receiver with much more power than the humble BM1900 and they do sound quite nice, once again I am noticing lots of high end but the vocals are a little more relaxed/recessed than I am used to with my daily driver speakers or the S45-2, the low end is nice. They do image well which is pleasing. I would call their sound 'relaxed'.
I've sent the obligatory message to Martin for a cap kit and if I like them after recapping them, I might recover the frets in white cloth to match the rest of the decor in that room and use them for a while.
Enjoy the pics.
Here are the after shots.
Great job Andrew and I like all your pictures (LOP). So you managed to get out the scratches? Would be nice if you could show me or us how you did some of the restoration work.
Brengen & Ophalen
The re-cappeing will make big difference.
I have the similar M75 and love them dearly as my primary speaker now.The dometweeter in S75 is the famous Peerless KODT 10. I heard them the first time something 1973 and fell in love with its sound. , and later on in my life they were apart of many of my DIY projects
My re-capped M75 are my precious diamonds.
Hello Andrew,
Nice to see your S75's - the teak models are uncommon compared to rosewood, the most rare veneer is oak
My own S75's are enjoyed in my small apartment with a beosystem 8000, still going strong after 35 years in the family.
- Søren
Vinyl records, cassettes, open reel, valve amplifiers and film photography.
By the way, what did you put under the stands, screws?
Hi Leslie,
I dont have pics of the process but I can run you through what I did.
Cabinets; Spray isopropyl alcohol on the cabinets and use a cotton cloth to wipe all the years of junk off the veneer. I then used a product called Howards Restor-A-Finish to correct problems with the veneer, I used the Golden Oak colour for these particular units (for my Rosewood S45's and my mates M100's I used the cherry colour). Apply the Howards restore product using 0000 grade steel wool in long strokes, you can use it on the metal trims as well, pay particular attention to any scratched areas,etc. The 0000 steel wool is very mild on the surface but will allow you to pull any junk off the veneer as well as smooth out any deep scratches,etc.
Allow the product to stay on the cabinets for about 20-30 mins. Wipe off with a new cotton cloth and leave the cabinets to sit for about half an hour and give them another wipe down at that stage.
You can then use another type of wax product, I got the Howard Feed N wax product as I was in a hardware store getting the restorer so figured i'd give the other product a go. Leave the wax to sit on there as long as you can, the packet recommends at least 20 mins, I left it on for about 6 hours. Once you've let it sit, buff the cabinets up with a cotton cloth or towel.
For the frets, I used a product available in Australia called Nifty - its a basic spray cleaner which you'd use on your kitchen benches but it is ammonia free. I just spray it on the fret fabric and use a light brush to scrub the cloth and then rinse them down in the bath, usually the water which runs off is dark brown, then allow them to dry in the sun.
I used Iso alcohol and 0000 grade steel wool on the stands to remove most of the surface rust and then I used some 'stainless steel kitchen wipes' to take off the rest of the junk and then polished with a soft towel.
Hope this helps anyone wanting to rejuvenate their cabinets.
Drew
I got little rubber feet for them, they are clear and with the sunlight look like screws in the last pic. I did manage to get the scratches out as well.
Hi Soren and Christian,
Have either of you recapped your speakers? I think the M70 uses the same tweeter.
The midrange sounds a little vague in these and the higher range is a little over pronounced, does it sound like a recap might sort this out?
Have either of you had the issue of oxidation on your tweeters?
You really did a good job and spend lots of time to get results like this! I guess the aluminum trims were not affected by smokers poison (nicotine)? It's a horrible task to remove that. Congrats...
Andrew: Hi Leslie, I got little rubber feet for them, they are clear and with the sunlight look like screws in the last pic. I did manage to get the scratches out as well. Drew
Andrew, yes I recapped my M75, There is a thread of it with pictures
Its my opinion that recapping makes a huge difference to the sound.The transerance,fokus, details improves alot and the whole frekvuence spectra gets stability
I did a two slight modification to the filter and lifter the upper two domes a couple of dBs as it is my opiion that dome tweeters get a bit tired of age and loos abit of their power.
Eventually will I remove one of the mods but I really love the result.I have a pair of spekaers that have made me listen to music more then ever.
I believe that the tweeter is remade today as a replica, by a different factory then Peerless,but have no clue how good they are.
Could be good for you to know
Andrew: Hi Soren and Christian, Have either of you recapped your speakers?
Have either of you recapped your speakers?
Yes, did a recap with Martin's kit a couple of years ago - sounded like removing a towel from the speakers and I could not believe my own ears when I A/B-tested the original one vs. the one I just had recapped... Much better sensitivity too; played about half the loudness at the same volume on the amplifier.
Hi Soren (and all)
Do you notice the midrange is a bit less prominent than other speakers such as m100's or S45's?
Andrew,From a subjective point of view, yes. with my M75, yesBut what I experience with this unique 4 way design is that it is has a very very flat frequence responce.
Again I am talking about m75, not the same speaker but to design, similar.The human ear percieve frequence different depending on level of sound.
So people that listen to to music on low level might like a certain speaker.flat frequence responce is to some people "boring" but the advantage is that when you play abit louder, you wont have one single tone peak and scream in your ear.What I feel is the M75 is a very rare spekaer regarding this as playing louder just reproduce the music and I never get any anoying peaks that bites in my ear.I hope my neighbour will cope with me, but music is just fantastic in my apartment now. Equipment that is very flat in frequence responce have no personal "sound", "caracter"Personality of sound, which add something unique to the sound is common with musicinstrument equipment and microphones, when you want a certain colour to a specific sound.An equialiant regarding microphones is the Sennheiser MKH series, totally flat even off axis, some sound engineers dont like it because it doesnt ´"add" anything, but to me it just reproduce what comes into it.So yes in certain situations you want a specific coulour to your guitar amp, or a colour to the voice you record in the context of the rest of the music package, then you choose equipment with a cartain caracter, But when you reproduce the entire package at home..do you want to colour the entire package or not. ?This is very personal for people, but for me, I just love the neutral responce which basicly just reproduce the orginal music as it was recorded. I love the way the midrange is not prenouced in anyway.But listening only to music on low level, I could prefer a simple speaker like the little qute Beovox 1702 that is very "open" in the midrange, but that little spekaer is not able to play particular loud, neither dig so deep in the bass as the M75, but I propably would not like the 1702 how it sound if it could play loud.So, try listning also abit louder, and get your own personal opinion about the midrange.
Hi everyone,
So a bit of an update, after reading countless posts about people who have opened up their units to replace capacitors and found some damage inside, I decided to have a look inside my units this afternoon. (I have ordered a cap kit from Martin which will arrive in a few weeks as Australian post takes AGES!).
So this is what I encountered, very burnt and quite distorted foil cap with the bottom right-hand corner really damaged, some charred wires and a bit of a shock. The 3.3ohm 3w resistor was pressed hard against the foil cap which seems to be the reason the damage was so bad. All drivers work and the speakers sound pretty decent on my amp, I have been careful not to overdrive them and there was no smell in the cabinet so I expect this happened a while ago. None of the insulation was burnt. It seems the 3.3ohm resistor has melted the wires and the foil cap.
So whats the go here? Just replace all the caps and it will be fine? I dont believe Martin's cap kit includes a new foil cap (2.2uf 250v 10% tolerance Evox MMK), where would I get one of these or a suitable replacement from otherwise? The person I got them from offered that I could return them if I wanted for a refund if there was anything wrong with them, however they do 'work' as such and I dont mind throwing a few dollars at them since they are in good condition.
Is this a sign of excessive overdriving or are the crossovers in these units just a bit susceptible to doing this? it seems the 3.3ohm 3w resistor is a little under spec'd for the job? has anyone replaced this with something more substantial? say 5w?
Some help and info would be great.
Thanks
Andrew:I dont believe Martin's cap kit includes a new foil cap (2.2uf 250v 10% tolerance Evox MMK), where would I get one of these or a suitable replacement from otherwise?
You should have no problem finding a compatible replacement in your local electronics shop that sells components.
Andrew:Is this a sign of excessive overdriving or are the crossovers in these units just a bit susceptible to doing this? it seems the 3.3ohm 3w resistor is a little under spec'd for the job? has anyone replaced this with something more substantial? say 5w?
A resistor with a larger power rating would still produce exactly the same amount of heat (while probably occupying a bit more space doing it). I'm sure the original resistor is capable of dissipating whatever the designers expected it to do, but it was just installed too close to the cap. When you put the crossovers back together, try to locate & fix the components and wires so that hot resistors won't touch and burn wires or other components, even after the speaker is turned around a few times.
--mika
Looks familiar this
I insist that this is a flaw of those Beovoxes.
Jacques
Hi everyone.
The 3.3ohm 3w resistor isn't looking too good and I would like to replace it. I dont know what type of resistors B&O used (wirewound, wirewound low induction, metal oxide).
The options are
3.3ohm 5w generic brand ceramic wirewound (0.40c)
3.3ohm 5w MOX metal oxide low inductive ($1.50)
3.3ohm 10w MOX metal oxide low inductive ($2.50)
3.3ohm 10w Superes Wirewound low induction ($3.50)
Can you please advise which is the best one to get, 10w sounds risky as although they are physically quite larger which might help to dissipate heat, I dont want to run the risk of frying the tweeter. I was concerned the cheapest one which is not low inductive might cause issues.
Your advice much appreciated.
chartz: Looks familiar this I insist that this is a flaw of those Beovoxes.
If this is a common thing it indeed is a design flaw IMO. I had really wanted a pair of these, maybe what I really want is a pair of S45s?
That's the 2nd worst looking set of damaged speakers I've seen. The worst was back in college when I worked in a hifi store. I walked into the back and in the shop our tech had a big Cerwin Vega speaker on a stool. I looked at it, did a double take, as the rear mounted phenolic horn loaded dome had a crack in it. Look at the front he grinned. The big 12 inch woofer, with a large voicecoil, the dust cap was missing, and the voice coil was blown completely out of the woofer, and hung down off the front like a slinky. He said the compression horn tweeter was blown too, and when I looked every cap on the crossover board had exploded.
Turns out the guy had a Harman Kardon Citation 16 power amp, nominally 150 w/ch, but huge dual mono power supplies meant it could dump prodigious current. He had the stereo turned about all the way up, and dropped the tonearm onto the album, which produces a wonderful about 1/2 hz subsonic thump when the cantilever flexes. Booom! Heh...
I have to sheepishly admit to running a pair of Cerwin Vega subwoofers so hard I almost set the voice coils on fire...
Jeff
I'm afraid I'm recovering from the BeoVirus.
Andrew: Hi everyone. The 3.3ohm 3w resistor isn't looking too good and I would like to replace it. I dont know what type of resistors B&O used (wirewound, wirewound low induction, metal oxide). The options are 3.3ohm 5w generic brand ceramic wirewound (0.40c) 3.3ohm 5w MOX metal oxide low inductive ($1.50) 3.3ohm 10w MOX metal oxide low inductive ($2.50) 3.3ohm 10w Superes Wirewound low induction ($3.50) Can you please advise which is the best one to get, 10w sounds risky as although they are physically quite larger which might help to dissipate heat, I dont want to run the risk of frying the tweeter. I was concerned the cheapest one which is not low inductive might cause issues. Your advice much appreciated. Drew
Personally I would go for low inductanse, but thats just *"feeling". How about put a heatsink for resistor? Not hard and impossible. Anyway, even if, when, bigger resistor do make equal amount of heat, the more you have mass and surface for evaporation, the cooler stays surrondings.
blah-blah and photographs as needed
Unless the resistor they used originally wasn't low inductance, and they considered that when making the crossover. Of course, I also believe that's over thinking it particularly given the tolerances on most normal components used in crossovers. I'd get a low inductance, high power one. While contrary to the styling theme of Beovoxes, this is a speaker that seems to beg to have the crossover in an external box!
If that scares you, go check out the section Attention Attention Fire Danger here: http://www.oaktreevintage.com/B_and_O_Bang-Olufsen_Replacement_Speaker_Parts.htm
And specifically this picture; http://www.oaktreevintage.com/web_photos/Speaker_Parts/Bang_Olufsen_S-75_Burned_Crossovers.jpg
Resistors are designed to get hot under load (to dissipate heat and can operate up near 90 degrees celsius), my resistor was hard up against a plastic covered wire and a plastic capacitor so its pretty obvious what happened. All drivers are still working fine (as far as I can tell without a reference pair of s75) and the units in their unrepaired condition still sound fantastic, my plan is to ensure that the new resistor is located well clear of other components in the unit and that I leave a gap with the internal packing in the speaker to ensure it cant contact the resistor.
I believe after some info from Martin that the resistor used in original was a wire wound ceramic so I will most likely just use the cheap 5w ceramic wirewound and see how the results sound. The one I have has a much larger surface area than the B&O unit so more area to dissipate to heat should reduce the problem of having an intense concentration of heat in one place.
Chartz in another thread showed a post of a pair of s45-2 with a similar issue to this, I suspect if the crossovers were not located under a heap of packing and/or if the cabinet was a bass reflex design to allow a bit of ventilation, this may not have been such an issue.
It's possible that these were fine when new, but along the years the damping material comes loose or droops and covers the components. Whatever material is used, it is usually a very good heat insulator as well!
I have never liked the idea of constructing crossovers in slots along the edge of a piece of chipboard, though.
I used 7W Seta vitrified (green) wirewound resistors. I believe they are a French manufacture.
So Martin's cap kit arrived today and I am about to start the recap after a month of these being on the shelf as I didnt want to run them until they were sorted.
See the picture below, I have sourced two resistors to replace the 3.30hm 3w one which is burnt, a 10w Metaloxide MOX low inductance resistor (green on the left and 10w was the smallest available locally) or the 3.3ohm 5w old school wirewound ceramic, which should I use?
Similarly, to replace the damaged EVOX 2.2uf 250v poly caps, I went to my local audio parts store and got the yellow Suntan 2.2uf 250v poly caps shown on the left below, however yesterday a mate gave me the blue (Philips I believe) caps which are 2.2uf but only 100v (the originals were 250v - he didnt seem to think it would be an issue) which should I use?
Your help much appreciated.
I'm quite curious about how the S75 will look like using white cloths. Good luck with the crossover boards. Btw, I bought the green resistor. Can't explain why...
Shortly before xmas the cap kit from Martin completed its journey across the world and arrived on my desk at work. Just before xmas my friend and I kicked off the recapping job. I didnt have much time to take pics (he works very quickly with a soldering iron) but I did discover something pictured below.
The second cabinet (which I had not yet opened) had no damage to the crossover whatsoever. The 3.3ohm resistor was not installed against the poly cap and therefore nothing was burnt or damaged, the crossover looked pristine. This at least provided me with some hope that the previous owner had not given these speakers a very hard time causing the damage in the other cabinet as I have seen with others where they have burnt resistors and so forth.
So we replaced all caps in the crossover and fitted the yellow poly caps I got from the local electronics store in place of the old EVOX 2.2uf as the one from the other unit (pictured in my post above) was quite damaged. I didnt need to replace the resistors as the one which had caused the burning in the first unit I opened was still perfectly undamaged and tested fine.
Put them back together after gluing a woofer terminal in place and plugged them into the Marantz SR7002.
The sound difference is quite astounding after the recap. The bass seems to have tightened up a little bit and sounds more controlled (you seem to hear 'less' bass in a way, however what you hear is more accurate and when bass is required it is there in bucket loads). The high notes seem a little clearer and seem to extend a little further than they did. The biggest difference - which was my criticism of these speakers in the first instance, is that the midrange is back. I found the mids in my pair to be very recessed before the rebuild, there was lots of low and lots of high but not enough in the middle to balance the speaker, since the recap this now no longer an issue, they sound very balanced and pleasant to listen to. I am quite happy, now the decision to leave on my Marantz in the living room or put them on my BM1900 in place of the S45-2's in the analog room :)
Now its on to the frets!