KEF 104aB... one more time

[Martynka]

Hi,

I am new here. I read the forum anonymously for a long time, now it's time to write something.
I want to show my latest speakers and learn from you what to do to make them even better.

Here are my KEF 104aB:





The boxes were good, but for the look they were refreshed with veneer, and to protect the speakers from small fingers I made textile grills.



I am still waiting for the KEF logo to put them on textiles.

Visually, I've achieved what I wanted. Now I want to deal with the sound. Will you help me?

 

[slimecity]

Not sure if this model had a ferro-fluid tweeter or not - but re-fluiding the tweeter is where I would start, personally

 

[SaSi]

No, it's a KEF T27, dry tweeter.

The surrounds of the B200 look good. Veneer looks great as well. So, just about the only thing you need to consider is replacing the capacitors. Their age makes them long overdue for a recap.

 

[sax6]

You reveneered these ? Very nice job for very nice speakers.

I do think though that, the most important thing to do with them is.... enjoy them !

 

[Martynka]

Thanks ! Yes, it's new veneer. My wife said that these are the first speakers that look nice without the grilles

I checked crossovers visually. The capacitors and coil looks good, the resistors looks damaged.






I desoldered one pin from each element and measured it.





In crossover 1:
Resistor 10 Ohm - 10,2
Resistor 3 Ohm - 3,1
Cap 10 uF - 10,9
Cap 10 uF - 10,2
Cap 5 uF - 6,08
Cap 0,6 uF - 0,82
Cap 3,3 uF - 4,51

In crossover 2:
Resistor 10 Ohm - 10,1
Resistor 3 Ohm - 3,1
Cap 10 uF - 10,1
Cap 10 uF - 11,2
Cap 5 uF - 5,79
Cap 0,6 uF - 0,792
Cap 3,3 uF - 4,5

I ordered new Welwyn W22 resistors from England because the old ones are swollen. Is the exchange of capacitors necessary after these measurements ??

 

[SaSi]

Measuring capacitors with a multimeter is not the ideal way to find out if they are good. You already have two of them show 40% drift (3,3 read 4,5) but the rest should not be assumed to be healthy.

You should measure them with an LCR bridge that can also measure ESR and do the measurement at a higher frequency than what most multimeters use. As I've seen, many multimeters use a very low frequency (in the less than 20Hz range) to do capacitor measurement. As frequency goes up, capacitance may go way wrong. And as voltage goes up, same goes for ESR.

I have already recapped a pair of KEF Corelli, 104ab and Calinda. My Reference 105 is next in line. They are all from the same era and the capacitors are of the same type mostly. And half of them are in crap condition. The difference in sound was really audible after the recap, mostly in tonal balance.

 

[Martynka]

I'm sure of the measurement results. I use my multimeter at work. It is a professional device from an industrial line.
But you're right, the values exceed 10%. I will exchange all for new ones. I found the set, 3 days ago it was in stock, but now ...

https://www.falconacoustics.co.uk/kef-104ab-replacement-capacitor-set.html

... out of stock


New W22, 10ohm 5% tolerance and 3ohm 1% tolerance came to me (normally there are only 2.7 or 3.3 with 5% tolerance in the store, but this is a version for military use )




I'm going to look for a cap...

 

[Martynka]

I ordered capacitors made by Solen - Factory Manufacture Audiophile 2% tolerance. I wonder, will I hear the difference?

 

[slimecity]

Those red & black elcaps are definitely different to the Falcon electrolytics used in the KEF reference line- the types that last forever and dont need to be replaced.

Im not sure if the red & black types are in the same league or not.....

 

[faber12]

Excellent work sir. Those are simply beautiful.

I bet they will sound as good as they look when you are finished.

 

[Martynka]

Right now, KEF's give the perfect sounds that Shibata plays...

...and they do it better than my other wonderful speakers - Beovox M70.

 

[Martynka]

I have almost everything...



... almost because Falcon Acoustics mistakenly sent 2 x 1 uF instead of 4 x10uF. Problem solved and I am waiting for the next package from FA.

I changed all the old wires (very thin) inside KEF's to new ones. Here, the comparison, old and new on the speaker:



And crossovers before and after change.




I changed the resistors and caps, but the photo will be when I get and change the rest of the capacitors.

In the meantime (because I like it when everything is fine) I changed the fuse housing because one old one was damaged and did not stay in place.




I know, it's not original, but looks much better and I can open it and change fuse if I need.

After changed caps and wires my KEF's sounds much beter. You were right !!!

 

[Pete B]

Is there a crossover schematic out there for the 104aB?

 

[Martynka]

For crossovers ??

 

[Pete B]

Yes

Found it here, this is actually how the OP built it with better parts:
https://www.diyaudio.com/forums/multi-way/189530-kef-104-kef-104ab-mkii-spice.html

This seems to be the actual KEF crossover with a tapped inductor for the contour switch:

 

[Martynka]

Yes, the scheme and values are original. He only changed the components and made measurements before and after.
Interesting website, I have not read it before. I invented the change of these wires myself, because they were very thin (bravo me)
It was originally 26 ga. ( 0,4 mm2 ) steel , I used 12 ga. (2 mm2) copper.

I measured the distance between the bass driver and crossover in the original place and in his place. It does not make a difference.

I left the original board first for aesthetic reasons, secondly, the board paths are really solid compared to the capacitor legs.

As I wrote above, I chose new elements:
- original W22 resistors (5% and 1%),
- Solen 2% capacitors but from the Falcon Acoustic line "Factory Manufacture Audiophile 2% tolerance" - I have note from FA that "each capacitors are measured and individually hand selected out of batches to match the actual value of the capacitor to the ordered tolerance"

My KEF boxes were rebuilded and sealed. Now, after all my change I sealed it one more time with foam seal and silicone.

My drivers were in speaker workshop ( old man with long practice works for reocord studios ). All checked, one T27 repaired ( coil was good but was cleaned and mounted in correct position ).

Now I only wait for missing caps from FA and KEF's logo to my textile grills.

 

[Martynka]

I got it!!
Ups... it is huge. It will be tight on board.



Maybe better disconnect crossover from front plate with switch and fuse?? Because it's tweeter circuit I can use thin wires and put crossover board deeper inside box.

What do you think about this??

 

[Martynka]

Yes, Yes, Yes. I finished my KEF's visually.



If someone does not see it, I am talking about the KEF badge on the grilles.

 

[Martynka]

... and I finished crossovers too.



I left it in one piece. It fits freely inside.



... and I think this is the end.

My "new" 104aB looks and sounds poerfect ( for me ). After recap music scene is wider, LH is little bit more powerfull but HF is much better.

Now I do the same with another Bang Olufsen M70 (I bought second pair yesterday)... because the point is not to catch the bunny but to chase him.

 

[Pete B]

Did you use a Solen for the .6 uF also?