I am seeking some advice on how best to go about refurbishing a pair of
speakers.

I have a pair of Bang & Olufsen S40 speakers from my college days, circa 1980.
These are a two-way sealed-enclosure design, medium in size. I have a room in
my home where a pair of small speakers like these would be perfect, and the
price of "free / close to free" is the right price. Being B&O speakers, they
are finished in a pretty rosewood veneer that is still in good shape. The
enslosures are likewise in good shape: tight and solid.

But they don't sound so good; something is blatantly wrong with the lows. I've
checked the drivers and they appear to be in good shape -- no obvious rot on
the surrounds. So I am guessing that the capacitors in the crossover, which
are 30+ years old, have gone bad.

I figured it would be an easy job to replace the crossover components. So I'm
trying to find a schematic for the speaker that would show the values for the
resistors, capacitors & inductors. I haven't been able to find one.

- It's pretty easy to reverse engineer the topology of the circuit, and
- the caps will probably be clearly marked
- but the coils won't be marked with values, and
- resistor markings are sometimes readable and sometimes not.

I really need the actual values spec'd for the design. Then I can go to
a company like Madisound, Digikey, Parts Express, or Mouser, get the
parts I need, and do the work.

www.beoworld.com has an access-protected page with service manuals. Since it's
protected, I can't tell if there is an S40 manual behind the paywall. I'd be
happy to pay for a membership, but it would be annoying to do so and then
discover there's nothing for the S40.

My technical skills are a mixed bag. Here's what I know and what I don't
know.
- I know a lot about software.
- I know some about electrical engineering -- impedance and the frequency
  domain, R/C/L circuits, transistor models, opamp circuits: this I can hack.
  Plus the basic soldering skills you pick up in a lab. I also know a bunch of
  digital EE which is completely irrelevant to this task.
- I know almost nothing about speaker design and acoustics. 

For this particular job, I'm pretty comfortable with a simple upgrade task. If
I was going to, say, try to mess with the *design* of the speakers, by
swapping in different drivers or altering the crossover -- that I would not be
competent to do, without a lot of study.

Any advice?

By the way, I'd love to find a set of stands for these speakers
    -Prof. Olin Shivers

Here are more specs on the B&O S40:
    Gross volume                    22.2 litres
    Dimensions W x H x D            26 x 48 x 18 cm
    Weight                          6 kg

    Woofer                          20cm / 8 in
    Tweeter                         2.5cm / 1 in dome

    Impedance                       4-8 ohms
    Frequency response +4 -8 dB     49-20,000 Hz
    Sensitivity                     2.5 W
    Power at 96 dB SPL            2.5 watts
    Sensitivity 1W            92 dB
    Crossover frequencies        3000Hz

Welcome to Beoworld !

I'm surprised to hear that you feel the Beovox S40 are not up your needs.
They are widely recognized as being some of the best two-way speakers around.
Maybe you are right, that something is wrong.

Capacitors could be a problem, but that can be solved.
The woofers themselves, are you sure that they are the originals ?
It's quite common, unfortunately, to see that the original woofers got replaced
by some cheap run-of-the-mill types because they suffered from foam rot.

Martin

Dillen:

I'm surprised to hear that you feel the Beovox S40 are not up your needs. They are widely recognized as being some of the best two-way speakers around. Maybe you are right, that something is wrong.

Capacitors could be a problem, but that can be solved. The woofers themselves, are you sure that they are the originals ? It's quite common, unfortunately, to see that the original woofers got replaced by some cheap run-of-the-mill types because they suffered from foam rot.

Oh, I'm not criticising the S40 speaker in general or saying it's not up to my needs. I'm saying something is wrong with *this* pair of speakers -- something that wasn't wrong when I was listening to them in 1980, or 1985, or 1990. I didn't buy them used on eBay in some unknown state. I've owned them since they left the store -- they were a Christmas present to me in 1980. They used to work fine; now they don't -- so I want to fix them.

So, my question remains:

Can anyone tell me if an S40 schematic or service manual exists behind the beoworld paywall?

    -Olin

 

There's currently not a Beovox S40 schematic in there but that can easily be arranged.
The Beovox S40 service manual is basically just an update to the Beovox S35.
Merely a parts list, exploded view and schematics.
I will have Peter put them both up in there.

Martin

 

Olin Shivers:

Can anyone tell me if an S40 schematic or service manual exists behind the beoworld paywall?

I just checked, there is aparently no manual for S40, but it may be hidden in some manual together with other types.

The crossover in S40 will be a simple one as its a 2 way speaker, my sugestion will be, first check if both speakers are bad, if yes, check them with another source, just to be sure that its a speaker failure and not amplifier. Open one speaker, check driver for foamrot, check all connections and solder points, check resistors, coils and caps, change the caps, they are old and if not bad now they will go bad within short time. If only one speaker sounds bad use the good one as reference, I would open both speakers and use one for reference and cross check and when one is repaired and tested, do the reference speaker.

I did a pair of S45s myself, new sorrounds and 1 cap in each crossover, a simple and easy job.

Thank you for your fast reply, Søren.

 

Søren Mexico:

The crossover in S40 will be a simple one as its a 2 way speaker,

Yep.

Søren Mexico:

first check if both speakers are bad, if yes, check them with another source, just to be sure that its a speaker failure and not amplifier. Open one speaker, check driver for foamrot, check all connections and solder points, check resistors, coils and caps, change the caps, they are old and if not bad now they will go bad within short time. If only one speaker sounds bad use the good one as reference, I would open both speakers and use one for reference and cross check and when one is repaired and tested, do the reference speaker.

Yep -- I'm pretty much past this point. The amp is known good. The speakers are definitely bad. The drivers have no foam rot. These are speakers that have been sitting in storage for the last ten years; during that time some parts must have aged out and failed. I just moved to a new, larger home and have a room where I can use them, so it's time to fix them up and deploy them.

It is a very easy job to replace the crossover. But as long as I'm going to do it, I think I'll upgrade *all* the parts, not just the caps. I'll upgrade the resistors to nicer resistors rated for higher power, and I'll chuck in some Goertz foil inductors. I'll probably also stick a cross-brace into the cabinets to stiffen them up, as long as I've got them open. This is all easy.

The only thing that is blocking me is knowing the spec'd values for the handful of parts in the crossover. In particular, the coils. They almost certainly won't be marked. Thus: I need the service manual. Or, at least, I need someone who has access to one to tell me the specifics of the crossover.

Olin

There's one coil in each cabinet.
It's listed as 0,26mH but I wouldn't replace anything apart from the capacitors.
I would certainly replace them though. Put in a good quality electrolytic type, bipolar of course.
The rest will be fine unless electronically failing.
Replacing the coils, in my opinion, would be overkill, a waste of money and completely unnecessary.
The dimensions of that coil is more than adequate as-is, it's not as flimsy a thing as it may look.
Don't throw 500 US Dollars in an upgrade attempt, you won't hear any difference.
That's my advice, anyways.

Martin

Welcome, Olin, to Beoworld.  Have you tried the search function in the forums yet?  There's at least one S40 refurb project detailed on the forum, and probably many more.  If B&O made it, chances are someone on this forum has fixed it at least once.

Here's my S40 refurb project.  Do the refurb.  You won't regret it.  The people here will walk you through it whether you have a schematic or not.

Rich:

Welcome, Olin, to Beoworld.

Thank you, Rich. People here are amazingly friendly. As I remarked in a private message to Dillen earlier today, I was browsing around this forum yesterday and stumbled over a thread started by this disgruntled guy in Florida who had decided that B&O gear was complete crap, worse than useless, an outright scam, for which, fortunately, he was too clever to fall. Etc., etc. Aggressively hostile, and pretty relentless. I was astounded at the universally courteous way everyone else on the forum responded to such blatant trolling. I've never seen anything like it, anywhere else on the net (and I've been using the net since 1979). If you pulled a troll like that on any other forum, you'd get flamed to a crisp.

I guess B&O fans just do things a little differently.

Have you tried the search function in the forums yet?  There's at least one S40 refurb project detailed on the forum, and probably many more.  If B&O made it, chances are someone on this forum has fixed it at least once.

Nope! There's exactly one s40 refurb writeup: yours. Or at least that's what my search turned up -- searching this forum was the first thing I tried.

Here's my S40 refurb project.  Do the refurb.  You won't regret it.  The people here will walk you through it whether you have a schematic or not.

Dillen has already provided me with the one hard-to-determine spec, the coil inductance (however, he also recommended leaving the coils as-is), and he went on to say that he can probably get a full schematic up on the download section behind the paywall pretty soon, so I'm going to wait for that and get the whole picture before proceeding.

Thanks for the encouragement -- not only your email but for taking the trouble to do a project writeup of your refurb.

    -Olin

Schematic now on site - good luck!

Peter :

Schematic now on site - good luck!

And now on my hard drive; thanks!

    -Olin

Olin Shivers:

Dillen has already provided me with the one hard-to-determine spec, the coil inductance (however, he also recommended leaving the coils as-is), and he went on to say that he can probably get a full schematic up on the download section behind the paywall pretty soon, so I'm going to wait for that and get the whole picture before proceeding.

"Do what thou wilt," of course.  But listening to Martin (Dillen) is Never A Bad Thing (tm).

I've refurbed M70s, S45-2s, and S40s, and I've never replaced an inductor.

The best upgrade is to buy some S45-2 speakers! Same frontal aspect but a superior speaker. Available for usually little money - I gave a pair away not long ago! Still kept one pair - I must do the cross overs some day but they still sound great!

Peter :

The best upgrade is to buy some S45-2 speakers! Same frontal aspect but a superior speaker. Available for usually little money - I gave a pair away not long ago! Still kept one pair - I must do the cross overs some day but they still sound great!

I'd love to get a pair and fix them up. They usually pop up on eBay for more than "a little money," though. All I really need is for the veneer to be in good shape, and the drivers to have nothing wrong that a refoam of the woofer couldn't address; I'm perfectly willing to deal with crossover fixes.

While on the subject of S45.2's... can someone explain to me why the *later* model S45.2's dropped the phase-link driver? I thought the Baekgaard crossover & phase-link unit was the central tech behind this speaker's claims to excellence. So why'd B&O punt on it?

    -Olin

It can be quite confusing, really;
The original (1970's) Beovox S45 (Type 6302) had a slight mid-production upgrade and
became Beovox S45-2 (Type 6312).
The main difference being the type of tweeter (and a slight modification to the crossover accordingly).
Actually, to add to the confusion, the new tweeter was already introduced in the latest Beovox S45, that is before
the model name and type number change.
The Beovox S45-2 was never changed, but was discontinued when the new series of speakers were introduced.

The new series of speakers had the S45 (Type 6427) as the smallest model, you can easily tell them
from the earlier types by the front grills. The earlier types had fairly sturdy one-piece grills where the later type
has rather flimsy two-piece grills.
Where the good old Beovox S45 (and S45-2) was a well performing three-way medium-range system, the
later (1980's) Beovox S45 was a two-way bottom range speaker. Not the worst sounding two-way speaker really,
not at all, but there were better ones available, even in the earlier range (f.e. Beovox S40).
A direct comparison from the later series to the earlier is not very easy but the old Beovox S45 (& 45-2) would
probably fit in somewhere between Beovox S55 and Beovox S80 range-wise as they are both three-way
speakers and fairly good performers for their size.

So basically we have three different Beovox S45 speakers.

Martin

Where the good old Beovox S45 (and S45-2) was a well performing three-way medium-range system, the
later (1980's) Beovox S45 was a two-way bottom range speaker.

 

So, this leaves the issue that I don't understand: why would a company make a given product *worse* -- why *change* the design of the S45 in a manner that clearly makes it less good? Very weird.

 

    -Olin

Since it is a completely different product, I think the question should be more like
"Why did they use the same model name?"

The earlier Beovox S45 was a popular speaker so maybe that's why they wanted to ride
on using the same model name but on the other hand, using the same model name
doesn't make the launching of a brand new product really stand out.
Strange indeed, but not the only time we see this from B&O.
There are several other model name clashes.

Martin

In the UK at least, the S45-2 was sold alongside the new shape Uniphase range. I imagine the newer range were cheaper to make - the fit and finish is certainly not as good though the actual sound can be excellent. The S120 took over from the S45-2 as the best sounding speaker in the range.