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New member restoring a pair of 105.2
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Thierry
Intermediate Contributor 50+


Joined: 02 Sep 2010
Posts: 72
Location: France - Outskirts of Paris

PostPosted: Fri Sep 03, 2010 9:25 am    Post subject: New member restoring a pair of 105.2 Reply with quote

Hi there,

I am Thierry and I am new to this forum.

I recently bought a pair of Reference Series 105.2 loudspeakers which were in a sorry state : previous owner had coated the speaker cones with sort of gold coloured goo Shocked

Aside from this there were other flaws : the B300s had their rubber gaskets removed ( !!! ) leading to air leaks around the chassis. The mid/highs enclosures connectors had been bodged with adhesive tape also, with the result of erratic bad contacts. Also the rear input connectors were loose, I suppose some rubber gaskets are missing. All in all I said to myself : what a mess Evil or Very Mad

How on earth can someone do this to such a refined piece of equipment, I can't understand Sad My luck was that I got the speakers for very cheap.

Those 105.2 are such amazing beasts, probably amongst the best 2 or 3 systems I have ever listened to, along with the elusive KM1 that I have been lucky enough to enjoy for a few days back in 1988. I am currently using the 105s with a Quad 33 and a Quad 405 that I have both restored and modified (do a google search with the words "quad 405" and "Bernd Ludwig" to find out what has been done) and I am very happy with this.

Let's get back to topic, I intend to restore those sorry 105s to a mint condition and to their original beauty and perfection. After a long and patient work I got rid of the paint (what a hassle) but I still have some minor repairs on my to do list and I need your help for the following :

- Although I removed most of the horrible "gold stuff" from the cones, those do not have their original black satin finish anymore, particularly the B300s . There are some dull areas, a few tiny gold spots are visible here and there and all this disturbs me. Is there any specialized paint or coating I may use to restore this ? Initially I thought I could spray a very thin layer of black satin acrylic (water based) paint with an airbrush but I am not sure how the cone material will react in the long term.

- the front grilles found on the 105.2 bass cabinets were of course missing. I am in the process of rebuilding them from scratch. Would someone be kind enough to describe them precisely (or even send some pictures of them) to help me understanding how they were made ? I have built two frames with MDF and got hold of black cloth along with male plastic clips but I haven't been able to see anywhere on the web how the clips are attached to the frames.

- my 105.2s have quite ugly castor wheels : they are grey in colour and look very cheap. What kind of wheels did Kef install ?

- although they sound wonderfully I am guessing about rejuvenating the crossovers. I have read here that the capacitors and inductors were precisely matched to the drivers by KEF but would it be advisable to replace selected capacitors with, let's say, modern metalized polypropylene ones such as SCRs ? I don't believe in "capacitor's magic" as some audiophiles do but I rather believe in parts bad aging. Any hint of feedback would be greatly appreciated.

I apologize for such a long post and I thank you in advance for your precious help.

Long live to KEF fine loudspeakers!

Thierry
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audiolabtower
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PostPosted: Fri Sep 03, 2010 11:36 am    Post subject: Reply with quote

I would forget the casters, on mine I simply removed them and the spigots they sit on are as good as spikes on carpet floors because the cabs are so heavy. The originals were double wheel types.

The crossover is more of a problem. The components have tolerances and the factory computer matching effectively negated the effect of tolerance variation. So the actual value may be some way off the printed value by deliberate design, ie high caps were matched with low inductors wound to suit etc. The inductors are fine iron core and have more than adequate saturation performance.

The caps were all selected into 1% bands at the factory and computer matched to the values of the inductors and the selected by measurement drive units. This means that the only way to get to design frequency response is to measure each cap on a bridge and build the exact value by new parallel caps. This is what I did many years ago.

Two things... by now the reversible electrolytics may well have drifted with age, but by comparing the measured values for each channel might give a better clue as to the original design values.

Secondly polyprop, polycarb or polyester caps have less dissipation factor than even low loss reversible electrolytics, so direct substitution even of the exact original values will give rise to a very bright or hard sounding result, something these speakers should never have! To compensate you need some resistance in series with the drivers, I found around 0.5ohm for the mid and 1ohm for the treble about right in conjunction with my selected speaker wires (mine are tri-wired with the crossovers out of the cabs at the amplifiers). Without these you need tone controls to boost bass by about 2dB and cut treble by about 2dB, all this room dependant of course.

Don't let me put you off, they are great speakers and respond magnificently to tri-wiring and tri amping so well worth persevering. I hope someone can give you an answer on cleaning the drive units.

It also saddens me when you see such classic designs where so much effort was made to get them as perfect as possible originally, treated so badly by idiots Evil or Very Mad
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Thierry
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Joined: 02 Sep 2010
Posts: 72
Location: France - Outskirts of Paris

PostPosted: Fri Sep 03, 2010 12:22 pm    Post subject: Reply with quote

There is already a lot of useful information in your post, thanks for this.

So I'll stick to the original and leave the crossover alone as the speakers sound wonderfully as they are, really among the best I have ever heard in terms of clarity and smoothness.

Beside the 105s I own a top-notch active multi-amplified system. My goal is only to enjoy the KEFs exactly like they were meant, perfectly designed and engineered with ultimate refinement.

Thierry
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Lee in Montreal
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Joined: 22 Aug 2009
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PostPosted: Fri Sep 03, 2010 1:30 pm    Post subject: Reply with quote

Hi Thierry

I redid my 105/2 crossovers last year and replaced all capacitors with high quality Solen units. Are better parts always better? Not necessarely. These caps have much less resistance than the original ones and kinda upset the original balance. I find I have two much mids, perhaps because there are also more caps in this section of the cross-over. and these were not cheap. For the price of the Solen caps, I could have purchased a Behringer active crossover and a used amp. If I had to redo it all over again. I would simply remove the crossover, and tri-amp the 105/2. Which is actually what I did on my other set of 105/2 and will apply to the initial set.

As for the gold paint, well, remove as much as you can, but please do not spray any paint on the membranes. Perhaps spending more time with a clothed wet with alcohol will help remove whatever is left. For the plastic heads, the best you can do is to buff/sand them with very fine sand paper (1000/1200 grit) under constant flow of water. That will polish them.

BTW - Your choice of Quad 405 is excellent with the 105/2. Especially if they have been modified. If set-up as dual mono with a 4 PSU capacitor assembly, they will sound very, very good. Then you will hear the 105/2 with a Qad 606 and the sky will open up, a beam of light will bath you, and you will hear angels sing. Yes, the 606 is that good. Faster, punchier, more present than the 405. Indeed it has 6 power transistor vs 2 for the 405.



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Kef Calinda - since 1979
Kef Cantata - since 2009
Kef 105/2 - since 2009
Evo 105/2 - in the build
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Thierry
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Joined: 02 Sep 2010
Posts: 72
Location: France - Outskirts of Paris

PostPosted: Fri Sep 03, 2010 1:52 pm    Post subject: Reply with quote

Hi Lee,

Thanks for your contribution.

Lee in Montreal wrote:


As for the gold paint, well, remove as much as you can, but please do not spray any paint on the membranes. Perhaps spending more time with a clothed wet with alcohol will help remove whatever is left.



So I have go the answer : I will have to live with this. Fortunately there is not enough paint left on the B110s to be seen through the grilles when they are in place. The T52s are immaculate (although they were also painted!) so no issue with them. That's one more reason to restore the bass cabinets grilles, they will hide the sad vision of the B300s.

Would you happen to have a picture of those grilles, on how they are built ?



Lee in Montreal wrote:


For the plastic heads, the best you can do is to buff/sand them with very fine sand paper (1000/1200 grit) under constant flow of water. That will polish them.



I will keep them as they are : as weird as it may sound they were intact, appart from one with a broken spigot, easy to repair.



Here's a pic of the setup after I cleaned the mess :





And now ladies and gents, here is the vision of horror, be prepared these are real tear-jerkers :










One B300 after a lot of cleaning :



One of the B110s, you can see what's left on the cone :




I had warned you....

Thierry
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Lee in Montreal
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Joined: 22 Aug 2009
Posts: 203

PostPosted: Fri Sep 03, 2010 2:48 pm    Post subject: Reply with quote

Why would somebody spray paint membranes? And why gold? Hmm...

Your wheels/caster are obviously not stock. I thought the heads were painted gold too. My mistake. You did a great job at removing the paint from the membranes. Perhaps scrubbing the remaining flakes with a tooth brush could help.

Lee
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Kef Calinda - since 1979
Kef Cantata - since 2009
Kef 105/2 - since 2009
Evo 105/2 - in the build
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Thierry
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Joined: 02 Sep 2010
Posts: 72
Location: France - Outskirts of Paris

PostPosted: Fri Sep 03, 2010 6:39 pm    Post subject: Reply with quote

Okay, I will try to find some better looking wheels.

Here are the frames I have built for thre front grilles. I tried my best, using the scarce pictures I found on the internet to determine the shape and the dimensions. I didn't have a clue on how the original were made.

The top of the frame has an angle in order to align with the cabinet's top. I determined all the dimensions by carefully examining the pictures and trying to find out by dividing the known dimensions (referring to specs) by the apparent length of selected places on the grilles; e.g. the top "lip" of the grille is 6.25 times smaller thant the cabinet top etc...

I came to the conclusion that the top edge has a depth of 52mm and the bottom 26mm, that is to say a bit more than 2" at the top and 1" at the bottom.

I also rounded the vertical sides angles. I hope it's not too far from the real things.

At this step I really would like to know how KEF attached the plastic pegs onto the frame Question I decided to use MDF bits in the corners to gain some rigidity and allow fitting the plastic bits in a simple way. The inside corners are centered onto the cabinet holes.

I still have to rectify some bits, sand them down, coat them with two layers of black paint and attach the cloth with stapples. I'd also like to find KEF logo's but this is really unimportant detailing.







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Last edited by Thierry on Fri Sep 03, 2010 7:36 pm; edited 1 time in total
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audiolabtower
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PostPosted: Fri Sep 03, 2010 7:04 pm    Post subject: Reply with quote

excellent job. How did you remove the paint? That must have been a delicate job on the tweeter? I would be very wary of solvents on the drive units, you don't want to upset the glue on surrounds or dustcaps.

VERY stupid to paint the some of the best drivers ever made, but you have done a great job in cleaning them up.

When I did my caps many years ago, I measured on a professional bridge and values were all very close L to R, so replaced the mean values to accuracy of better than 0.1%.

I have Mk1s and the look of the full frames was too imposing, so made some half frames for the bass cabinet to look the same as the Mk2 with the lower frames. It needed a 3 sided frame of simple high density board cut to match the side angles, sprayed matt black, and black grill cloth stapled to inside edges. The top wood spar was made as small as possible to avoid refections but accept a row of staples, and thus joined to the sides with tiny metal brackets.

The Mk1s also had foam on top of the bass cabinet which mopped up some mid freq reflections spoiling the lower crossover. This rotted away over the years, so I replaced with new black foam on a very thin base and covered that with black cloth - it looks better than original.

Once again, great job Very Happy
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Thierry
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Joined: 02 Sep 2010
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Location: France - Outskirts of Paris

PostPosted: Fri Sep 03, 2010 7:53 pm    Post subject: Reply with quote

audiolabtower wrote:
excellent job. How did you remove the paint? That must have been a delicate job on the tweeter? I would be very wary of solvents on the drive units, you don't want to upset the glue on surrounds or dustcaps.


I have used ispropanol (a.k.a. isopropyl alcohol) and a soft brush, and A LOT of of patience.

audiolabtower wrote:

VERY stupid to paint the some of the best drivers ever made, but you have done a great job in cleaning them up.

At first I thought of punching him in the face

Quote:
When I did my caps many years ago, I measured on a professional bridge and values were all very close L to R, so replaced the mean values to accuracy of better than 0.1%.

Will leave'em alone, these 105s sound soooo good Very Happy


Quote:
Once again, great job Very Happy Evil or Very Mad


Thanks ! I really hope to get all the info I need to complete the restoration job.

Thierry
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speakerguru
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PostPosted: Sun Sep 05, 2010 6:55 pm    Post subject: Reply with quote

Thierry wrote:
how KEF attached the plastic pegs onto the frame Question


The original pegs had an integral moulded "christmas tree" whose sloping branches all bent to make entry into the grill frame easy and exit very hard without ripping the wood.

What sort of replacement pegs did you manage to get?
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Thierry
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Joined: 02 Sep 2010
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Location: France - Outskirts of Paris

PostPosted: Sun Sep 05, 2010 7:07 pm    Post subject: Reply with quote

speakerguru wrote:
Thierry wrote:
how KEF attached the plastic pegs onto the frame Question


The original pegs had an integral moulded "christmas tree" whose sloping branches all bent to make entry into the grill frame easy and exit very hard without ripping the wood.

What sort of replacement pegs did you manage to get?


Thanks for the description.

I bought these, they fit exactly in the original receptacles, same diameter :


Yesterday I have finished stapling the cloth onto the frames after the paint had dried.








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Lee in Montreal
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PostPosted: Mon Sep 06, 2010 3:04 pm    Post subject: Reply with quote

Good job!
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Kef Calinda - since 1979
Kef Cantata - since 2009
Kef 105/2 - since 2009
Evo 105/2 - in the build
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Thierry
Intermediate Contributor 50+


Joined: 02 Sep 2010
Posts: 72
Location: France - Outskirts of Paris

PostPosted: Mon Sep 06, 2010 3:41 pm    Post subject: Reply with quote

Thank you Lee, it encourages me keeping up with the project.

Yesterday evening I took care of the bass cabinets finish and detailing.

I completely removed the original varnish with lots of enamel thinner, then sanded down all the little scratches and repaired a few dents.

Then I applied a very thin touch of "British Red" colour in order to get a slightly warmer colour than the original oak finish. I'm pretty happy with the result.


Removing the old varnish





This goo is the melted varnish... yuk..





Clean wood, just like new




Freshly coloured woodwork







Now here is what's left on my To Do List :


    * thoroughly check cabinets for air tightness
    * apply two thing coats of satin clear varnish on the wood
    * replace the caster wheels with the new ones I bought
    * refit crossovers : I soldered the wiring for the inputs and woofer outputs directly on the PCB rather than using connectors as the previous owner had replaced them with Faston types ones but waaaayyy too big (6mm, and the lugs are only 3mm) hence many bad contacts there. This dumb ass was complaining about a sometimes fizzly sound ! What an a**hole !
    * fit new terminals on the back side. Here I will use rubber gaskets to ensure that there is no air leak like the ones I found.
    * refit the B300s with their new airtight foam gaskets (the originals had been removed by the geezer)
    * try to find and fit KEF badges on the grilles (ePay ? KEF themselves ?)


Thierry
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Thierry
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PostPosted: Mon Sep 06, 2010 6:11 pm    Post subject: Reply with quote

The first coat of satin clear varnish has been applied. Will apply finish coat tomorrow after overnight drying. In the end it is supposed to look like an oiled or waxed finish, here I took the picture right after applying the varnish, hence the glossy aspect.

New caster wheels have been installed.

Thierry




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audiolabtower
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PostPosted: Mon Sep 06, 2010 7:58 pm    Post subject: Reply with quote

wow, the cabinets look great. Can you come over to the UK and do the same to mine Laughing Laughing Laughing
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