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Which B139 in the C80 ?

 
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hans 67
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PostPosted: Mon Jun 05, 2006 3:56 pm    Post subject: Which B139 in the C80 ? Reply with quote

Does anybody know?
Somewhere I read the SP1212, but I do not know that one.

Thanks in advance, Hans
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ColinR
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PostPosted: Mon Jun 05, 2006 10:29 pm    Post subject: Reply with quote

C80 - T33 tweeter (SP1210), B160 midrange (SP1203) and B139 woofer (SP1212).

The crossover schematic is still lurking somewhere on diyaudio.com.
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hans 67
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PostPosted: Wed Jun 07, 2006 11:25 pm    Post subject: Reply with quote

Thank you ColinR.

I had never heard before of the SP1212.
Does anybody know if it is used in other speakers than the C80?

Hans
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ColinR
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PostPosted: Thu Jun 08, 2006 12:01 am    Post subject: Reply with quote

Quote:
if it is used in other speakers than the C80


No, as the SP1212 is another 4 Ohm unit to compliment the other two 4 Ohm drivers.

So don't blow them, as rewinders of broken 4 Ohm units are less common and tend to charge more for their services.
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django
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Location: Walsall West Midlands UK

PostPosted: Sun Jun 18, 2006 8:24 pm    Post subject: KEF C Series Reply with quote

On the subject of KEF C Series;
What do KEF C80's perform like?
Are they appreciably better than KEF B200 based units?
On another matter,
Does anyone have ideas on re gluing centre dust cap cover on KEF C40 units SP1205?
I have three SP1205 units in my C40's where the dust caps have become loose and vibrate on certain guitar music.
Looks like a rubber (inner tube repair?) adhesive may fit the bill?

Any Help Greatly appreciated.

Best Regards,
Nick Mellor
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ColinR
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PostPosted: Sun Jun 18, 2006 9:13 pm    Post subject: Reply with quote

Quote:
Looks like a rubber (inner tube repair?) adhesive may fit the bill?


Nooooooo Cool . A bit of water soluble PVA wood glue is what you want Smile .
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django
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PostPosted: Mon Jun 19, 2006 12:41 pm    Post subject: KEF C Series Reply with quote

Colin,
That's great I'll give it a try

Many Thanks

Nick Mellor
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django
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PostPosted: Mon Jun 26, 2006 11:59 am    Post subject: KEF C80 Reply with quote

I recently bought a pair of KEF C80's, they have been owned from new by a guy in Yorkshire.
He put them away, fully working a ‘few’ years ago, don’t know exactly how many years.
They’re in great condition. I Plugged them in at the weekend, in place of my C40’s.

Very strange, HF and Mids are working but no output from B139/SP1212’s

I quickly unscrewed one from the baffle board and checked dc resistance, the coil appeared to be open circuit. At the time the leads to the crossover were still connected, they are soldered.
I didn’t have my iron plugged in to remove the leads, so I need to investigate further by disconnecting the x-over leads and check again, there may be a charge in one of the capacitors that is upsetting my readings?

Normally I would have expected a low ohm reading, the SP1212 should have a reading of approx. 4 Ohms.
Is there anything else in the x-over that would give no bass output at all from either speaker?

I unscrewed the other B139 and got the same open circuit reading.
The guy assures me they were fully functional when he put them away, he went to great lengths to explain the ‘contour’ settings, influenced by speaker wall placement, adjusted by using the sockets on the back of the speakers.

The B139 units look perfect, no sign of discolouration or damage to the voice coil or connections.
Am I missing something?
If both B139's have damaged voice coils, where do I go to get them repaired, any idea of cost?

Nick Mellor
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ColinR
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PostPosted: Mon Jul 10, 2006 9:41 pm    Post subject: Reply with quote

The 4 Ohm B139 units used in C80's have a "materials science" problem.

The voice coil is so thin that it breaks under mechanical stress (shock), at the point where it is joined to the lead-out wires.

If you're lucky you may be able to rejoin the broken ends - I've met somebody at Tonbridge who's done it at least three times on his pair.

Otherwise it's Richard Allen, Wembley or Boultons, but at £50 each plus shipping it might be easier to bin the midranges and make your money back by selling the T33mkII SP1210's.
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django
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PostPosted: Thu Jul 20, 2006 1:51 pm    Post subject: KEF B80 Reply with quote

Colin,
Thanks very much for the info.
I removed the Magnet assemblies on both B139 units again and checked the connections to the voice coils. Sure enough, on close inspection both units had broken connections to the lead out wires.
I managed to pick up enough of the existing wires to tin and solder back together. Result is two working units again.
Thank you very, very much.
T33 are no hopers, gone very dull, Mids are fine.
I've replaced both T33's with a pair of Mission Type 700 HF units.
I bought these new in 1988 for another project but never used them.
They are round, the diameter being a good fit in the space left by the T33.
With a small gasket and three new screw holes, the result is, to my ears anyway a good working pair of C80 speakers.
I know the Mission units are .75 compared to the T33 1 inch units but they seem to give out enough HF to make a presentable sound.

Nick Mellor
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