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Bringing the 105.2 back to life

 
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golanr
Junior Contributor 10+


Joined: 06 Jan 2012
Posts: 17
Location: Chesterfield, MO USA

PostPosted: Fri Sep 20, 2013 7:52 pm    Post subject: Bringing the 105.2 back to life Reply with quote

Hello everyone.
Few weeks ago, I had the opportunity to buy a pair of 105.2, SP1118 S/N 1921A and 1921B.

The seller mentioned that the voice quality is not good and I figured the issue was with the old caps, so I ordered a new set from Falcon Acoustics and replaced them even prior to connecting them to my receiver (Sansui G-9000DB)







Surprise surprise, they still sound bad, which ended up being rubbing voice coils. I tried turning them 120 degrees and even 240. Waited a day after every turn with no luck.

So, I have taken them to a local shop (PM me if you want more info) and today I have learned that both voice coils are in bad shape due to the rubbing and needed to be replaced, together with the spider. since he has no similar voice coils, he is shipping them to California to someone who can create new ones based on the size measured. the Bextrene membranes will not be replaced.

Questions to the experts on the forum. Any info I can provide these guys on the type of materials to be used for the new coils, number of wraps, thickness of wire, or should I just trust them to do their job?

I will continue to update when I get them back in 2-4 weeks.


Last edited by golanr on Sat Sep 21, 2013 12:32 am; edited 2 times in total
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T.O. Chef
Senior Contributor 100+


Joined: 31 Aug 2007
Posts: 150
Location: Toronto Canada

PostPosted: Fri Sep 20, 2013 9:43 pm    Post subject: Reply with quote

Ouch!
Well, if they are on the way to California I suppose you can now only hope & pray that they will be fixed up right.
You would think that if it's a reputable repair / rebuild facility they would match the VC wire type & gauge to original spec.
I considered doing this once but shied away when the cost was quoted. They said they would be re-gaussing the magnets too!
Since the B-300 spec's are readily available it's a fairly easy matter to test them on return and assess their work. WT-3 is a simple, inexpensive device with software to accurately measure woofer parameters.
My bet ... you'll get a decent job done, But pay dearly. Regardless, if done up right you should be over the moon pleased with your 105.2's. And that's priceless isn't it? Absolutely, mine were about the finest speaker I've owned. Only wish my room was big enough to do them proper justice!
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golanr
Junior Contributor 10+


Joined: 06 Jan 2012
Posts: 17
Location: Chesterfield, MO USA

PostPosted: Fri Sep 20, 2013 9:55 pm    Post subject: Reply with quote

I wouldn't be able to buy dirt cheap plastic speakers with the price he quoted me. I assume that shipping a voice coil only from St. Louis to California, is not that bad. I see this as an excellent investment so I can enjoy them for the next 30 years Very Happy
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speakerguru
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Joined: 18 Nov 2005
Posts: 958
Location: Green Hut, Tovil

PostPosted: Fri Sep 20, 2013 10:55 pm    Post subject: Reply with quote

I designed the B300 and wound all the prototype coils myself. The coil is 0.5" longer than the magnet top plate thickness. The pole piece is 2.0" diameter and the coil former i.d. is 0.020" smaller than that radially. i.e you use a 20 thou shim to centre the v.c. in the magnet gap. The coil was wet wound using a high temperature epoxy and a high temeprature polyamide/polyester coated wire. The coil former was split anodised aluminium with a nomex top tube to stop the heat getting to the bextrene cone. I don't remember the wire gauge.
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proffski
Über Contributor 1000+


Joined: 22 Aug 2003
Posts: 1297
Location: Tewkesbury UK

PostPosted: Sat Sep 21, 2013 10:55 am    Post subject: Reply with quote

Good luck with these magnificent classics!
There is a little information on these here.
Link: http://www.hifiloudspeakers.info/Anatomy/KEFDocuments/KEFGermanGallery/pages/p42.htm

Just needs translating but the units are obvious! Very Happy
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golanr
Junior Contributor 10+


Joined: 06 Jan 2012
Posts: 17
Location: Chesterfield, MO USA

PostPosted: Fri Nov 01, 2013 9:02 pm    Post subject: Reply with quote

After about a month both B300s came back home and boy was it worth waiting Very Happy
The Spiders, Voice Coils and Dust Cups were all replaced.
The tech had to manually wind them, but now has all data in his computer, in case someone else will need the same service. He also stated that it will take the new spiders about 100 play hours to break in.

I am attaching photos of the old voice coils.






Last edited by golanr on Fri Nov 08, 2013 4:33 am; edited 1 time in total
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audiolabtower
VIP Contributor 500+


Joined: 06 Jan 2009
Posts: 544

PostPosted: Fri Nov 01, 2013 10:03 pm    Post subject: Reply with quote

Interestingly, that German data sheet agrees with my Kef copy except they say the equivalent volume of compliance is 130 litres whereas the kef says 250 litres.
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