Some time ago, I got a pair of Beovox S45-2 for a very fair price: DKK 150 / EUR 20 / USD 30 with the original stands. That was a fine day!

The speakers looked somewhat neglected in many ways – but worked. And they played well – actually more than well: They sounded really good! So a lot of records/CDs were played – and a lot of Watts were put into the small speakers (from a 2 x 110 W Luxman amp.). And even though the 8 inch bass really was busy – everything went well

Or so it seemed…

Because when I – just out of curiosity – opened one of the boxes, this is what I found: The heat from one of the resistors in the cross over network had melted the isolation on one of the wires – and was well on its way through the next wire (see photo). One more millimetre of melted plastic, and the speaker would have been dead - or at least the tweeter and midrange/phase link unit. My curiosity seemed to be a good thing. 

The damage had – of course – to be fixed.

And since the speakers were doing so well, I thought it was worth taking some extra steps to make them sound the best possible (within sensible economic limitations).

So here is the story of what I did – maybe it’ll inspire others to give their small Beovox S45s (or the like) some TLC.
Please feel free to copy any ideas and/or suggest alternatives and further improvements. 

Cross over network:
Capacitors: Two problems with the capacitors: They are 30+ years old – and they’re the “Bipolar” type. Neither things are good, so all 3 capacitors were changed to an audiophile type (though an inexpensive such): Jantzen Cross Cap. (Haven’t tried Martin/Dillen’s kit – only read about it after I had bought the components)

Resistors: Well - they got too hot so all 6 resistors were changed to higher wattage type (10 and 20 Watt). The two in series with the tweeter and phase unit is also low-induction types. 

Coils: The 4 coils are of a good quality – so no need to change here.

All the new components got a 5 mm thick bead of Silicone underneath (to dampen vibrations) and a cable strip to fix them to the board. Silicone was also put on the ferrite core in two of the coils to avoid vibrations against the back side of the cabinet.

Wires: They are rather thin. I could – and maybe should – have changed the wires to the units and the DIN connector.

Tweeter
When you take out the tweeter and knock on it with your knuckles, you notice some resonances. This can colour the sound when playing, and should be dampened (or eliminated). So the units were dismantled and Silicone was filled into all the small “holes/rooms” on the backside – see photo below under "Cabinet". Even it out with a wet finger (water or acetone). Be careful when you put the dome/coil-part back into the magnetic gap.

Midrange/phase link unit.
No modifications – except a drop of Silicone to seal the small hole for the wires (so you’re sure it’s airtight).
By the way: When mounted the midrange-“chamber” is connecting the front and back of the cabinet – an thus stabilizing it. Very clever design detail by B&O here!

Woofer:
Two beads of two-component glue (epoxy-based – in Danish: Araldit) on the upper and lower edge of the magnet. This should prevent it from getting loose – and make the unit useless/un-repairable. See photo.

Cabinet:
Almost all speaker cabinets could be made stiffer and/or more “sonic dead” – also the Beovox S45-2: When you knock on the side of the cabinet the sound change a lot depending on where you knock (it sounds more “dead” near the top and bottom).

So a 12,5 x 40 cm piece of Bitumen based sound-dampening material (for automobiles) was glued on each cabinet side (inside of course…). And a piece of wood (15 x 25 mm) was places between these across the cabinet just under the midrange.
On the photo below you should be able to see the black Bitumen inside (a bit shiny) and the piece of wood (as well as the tweeter w. Silicone).

Also a small Bitumen piece was glued on the front baffle (inside) to the right of the tweeter/midrange (where the tweeter front is on the photo above). New grill cloth was also mounted, so now they’re black again – not gray…

The result:
First of all: The speaker has put on some weight – app. 1 kg (Bitumen, Silicone, new components etc.) and the cabinet is far deader when you knock on it.

Then there is the sound:

The bass is more accurate and better controlled. It sounds cleaner and e.g. a bass drum stops and starts more precise. It’s not an enormous difference – but easily audible even on “non-audiophile” materiel. E.g. The Beatles “Abbey Road” (remastered) track 16: On Ringo’s drum solo, the attack on the bass drum much more “punctual” (where it sounds more “boomy” without the modification).

The treble and upper midrange sounds a lot clearer – really a lot! There is much more air around the instruments and voices, hi-hats sound crisper and you hear a lot of small details that were masked. Even on an old – but very well made – recording like Dave Brubeck Quartet “Time Out” (1959) it’s very easy to hear the difference. On newer high quality records the difference is even bigger.

I made a near-field measurement of the tweeters performance from 2 kHz – 20 kHz. The microphone was placed 6½ cm in front of the tweeter. Blue curve is the non-modified speaker, red is the modified speaker.
The unmodified speaker is much more “peaked” and looses level above 7 kHz. This matches the audible difference but looks worse. (First I didn’t trust the measuring – but when repeated they were all identical).

Conclusion – is the modification worth the effort?
Well, if you look at it from an economic-rational view: NO!
It took me app. 5 hours to fix one speaker and cost around DKK 250 / EUR 30 / USD 50 for components (a side). I’ll most likely never get this much for the speakers – if I ever sell them.

And this is just the point here:

I really like my modified Beovox S45s. I “know” them better than before, I enjoy listening to music through them – and enjoyed the time I spend under ways. It’s is really a great, little speaker and even more so than before I - almost - killed them.

So: YES – it was well worth the effort!

Good luck with yours! 

Claus,

Thank you for a very informative, well written post on one of my favorite BEO! 

thanks claus for your interesting guideline. i did my beovox 2400/2500 restored with support from frede and dillen... my first soldering work and they sound really hi-fi now. ;-) the improvement in sound is hearable and it was fun to work on it.

are the jantzen cross caps good?

best regards

p.s.: araldit is a swiss product: http://en.wikipedia.org/wiki/Araldite

Thanks for sharing

I only got as far as soldering one of martin's capacitor kits and some cosmetic work on the cabinet with mine. I don't think I will touch my main pair but I am tempted to use my spare pair as a project!

Simon

A very interesting post with plenty of good ideas for speaker refurbishing.  Pity that my ears cannot tell the difference but your graph never lies.  Well done

Regards

Geoff

Thanks for the comments

Geoff:
I think the difference from changing the capacitors (which I belive is the single most influential modification) will be audible to everyone. One doesn't need to have "goldens ears" og high end equipment to spot and enjoy the improvement. I A/B-tested mine - that is of course the easiest way to tell. Try it out!

Superdario:
Yes - the Jantzen Capacitor are (to my knowledge) considered to be very good for audiophile purposes. Jantzen (no afiliation) specializes in audiophile components - have a look at http://www.jantzen-audio.com/index.html.
There are several types - I've only tried the cheaper ones ("Cross Cap").

And I made another measurement of the speakers (se below). This time more near field (4 cm distance to tweeter) and shown w. a lower resolution (to focus on the more the overall difference).
However the big picture is the same.

There is a third curve (green) on the graph. This is with the grill mounted on the unmodified speaker (the others are with grill off). The green graph should be compared to the blue - and shows that there is only minor differences with the grill on/off. Good - since it looks so much nicer w the grill

(Please ignore the small "scratches" on all three curves - they're caused by the PC sound card beeing used)

Excellent write up - and as said above, on a wonderful and much loved speaker. You certainly flatten the midrange beautifully. It is interesting how if anything the bass drops. I suppose you lose some of the cabinet resonances due to the damping which will actually give more control. I imagine that the increased treble peak would no longer be audible to me! 

Are you going to do the same to your M75s? How do you feel the two speakers compare?

Peter, the frequency curve starts at 2KHz so is not showing the bass response
but merely the lower range of the tweeter.
But I agree that it looks a nice result and I'm sure that we would all
hear a 3dB increase in treble amplitude, not to mention the 11dB increase around 4,5KHz.

Having said that, the Beovox S45 would not be the first one I would have looked at improving as it is
quite good as-is.
I think, it could be fun to see how good a X25/X35 could become if some fairly undrastic modifications,
like these, were tried on it.

Martin

Not sure just how much improvement you will get with the drive units provided! Would be interesting though! You would probably spend more than B&O ever did though!

And you are correct; I didn't see the scale properly on the frequency response.

A thing I've often found a bit funny is, that whereas the Beovox X35 generally
is considered a quite poor low-end speaker, the Beovox S30 (type 6317) is
often considered to be a fairly accepted speaker in its own right.
The S30/X35 cabinets are of the exact same size and build, only difference being that
one is veneered and the other has grey'ish black foil.
The drivers and crossovers are exactly the same.
One wonders...

The same goes for the Beovox S2002 which is also exactly the same speaker.
It is not rated very high either but is so rare so I suppose noone ever notice. 

Martin

Claus:

Superdario:
Yes - the Jantzen Capacitor are (to my knowledge) considered to be very good for audiophile purposes. Jantzen (no afiliation) specializes in audiophile components - have a look at http://www.jantzen-audio.com/index.html.
There are several types - I've only tried the cheaper ones ("Cross Cap").

thanks for the link. interesting website, did you tried the speaker-kits? the midbass drivers JA-5006, JA-6006 - JA-6012 looks very simular to the dynaudio drivers... a carbon case would be nice. ;-)

Dillen:

I think, it could be fun to see how good a X25/X35 could become if some fairly undrastic modifications,
like these, were tried on it.

Martin,
I do have a pair of S35 (type 6311) that could be used for this purpose: To see what can be done to a mediocre speaker w. some DYI effort and a few new components.

What is your (and others) opinion on using the S35 as the target for this?

Personally I wonder if there might be to many issues w. the S35:
- the Cross Over is primitive
- the Cabinet is “thin”/light (and made from an other type of wood than e.g. S45-2 an others – looks and sounds more like “cigar box” wood…)
- the front is very “loud” when you knock on it
- the woofer has foam surrounds (mine are OK though. I’ve tried to preserve them my "miracle rubber conditioner" - seems to work.)
- the tweeter is (correct?) one of the “least good” B&O have ever used (but it’s a dome though)

Opinions welcome!

Peter,
Measuring the low frequencies is difficult due to room resonances (and I don’t have access to a sound-dead one…).
I’ve made a near field measurement of the woofer – but no important difference is visible (see graph below - colour as before. "Scratch" at 600 Hz is the sound card - again...).
The measuring was done at low level – the enclosure resonances will only be audible at higher SPL. Got to get a mike attenuator...

I’ll be back on the question of M75 vs S45 after I’ve done more serious comparison.
My first impression is that they are alike in many ways and fine speakers (but more bass in M75 of course).
Upgrading M75 will be somewhat more expensive – it’s a much more sophisticated cross over.

Superdario,
No - haven't tried any of Jantzens speaker kits (but I suppose they are of good quality too). 

Claus:

Measuring the low frequencies is difficult due to room resonances (and I don’t have access to a sound-dead one…).

I’ve made a near field measurement of the woofer – but no important difference is visible (see graph below - colour as before. "Scratch" at 600 Hz is the sound card - again...).
The measuring was done at low level – the enclosure resonances will only be audible at higher SPL. Got to get a mike attenuator...

Ear plugs would come in useful here. And neighbours that go on holiday often!

Out of curiosity, what kind of amplifier did you use for the testing here?

I still need a few 'damping' tricks myself, but that's for my system cabinet. It's made out of hollow veneer board, with the Beogram on top of it. When that's playing, it's almost an enormous membrane microphone, so I need to add a ton of dead weight.

Actually, the Beovox S35 is slightly better rated than the X35 and S30(6317).
Even the smaller Beovox S30 (6301) sounds more balanced than the larger S30 (6317).

Martin