SpeakerTalk

golanr · Last edited by golanr on Sat Sep 21, 2013 12:32 am; edited 2 times in total

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.

T.O. Chef · Posted: Fri Sep 20, 2013 9:43 pm Post subject:

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!
_________________
Music is food for the soul.

golanr · Posted: Fri Sep 20, 2013 9:55 pm Post subject:

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

speakerguru · Posted: Fri Sep 20, 2013 10:55 pm Post subject:

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.

proffski · Posted: Sat Sep 21, 2013 10:55 am Post subject:

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

_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

golanr · Posted: Fri Nov 01, 2013 9:02 pm Post subject:

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.

audiolabtower · VIP Contributor 500+ Joined: 06 Jan 2009 Posts: 686

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.

golanr · Posted: Tue May 15, 2018 9:31 pm Post subject:

4.5 years later and they still sound amazing Smile

audiolabtower · VIP Contributor 500+ Joined: 06 Jan 2009 Posts: 686

Good story, well worth doing. In their day they were one of the finest speakers you could buy, and even today unless you need 110 dB to go deaf quickly they are still one of the best ever.

speakerguru · Posted: Fri May 18, 2018 4:30 pm Post subject:

SaSi · Senior Contributor 200+ Joined: 24 Aug 2008 Posts: 256

I brought back to life a pair of 105 original version. They sounded like I'd never put them aside. But then came the 107. I like the tightness and richness of the upright bass more on the 107. But the 105 are now in the living room, in full glory.