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Old 18th June 2007, 10:59 AM   #1
pshead is offline pshead  United Kingdom
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Default KEF B200 drivers

I have a pair of much loved KEF 104ab speakers which have been in regular use for many years. Sadly, one of the B200 drivers has been damaged recently due to a fault in my amplifier (which has now been fixed).

These speakers use B200 drivers type SP1039, and I am having difficulty in obtaining replacement units. However, I can get a pair of B200 SP1054 units. The question is: can the SP1054 units be used in place of the SP1039 units in this speaker?

I have downloaded the spec sheets for both drivers and notice that there are subtle differences in their electrical and mechanical characteristics. In particular, the inductance of the SP1054 is greater than that of the SP1039. The impedance characterisitics of the drivers are therefore likely to be different, meaning that the SP1054 may not be well matched to the 104ab crossover circuit leading to a degradation of performance.

Does anyone have any views or experiences in this matter?
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Old 18th June 2007, 11:17 AM   #2
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Location: Norlane; Geelong: Victoria: Australia
Question B 200 Kef

Do you not have anyone in the UK who can repir the drivers and return them to original spec's?/
Iwould have thought that would be the best cheapest solution.
i like the B200 driver although I am not sure which one I have sitting in my garage at the moment ( unsuitable for your purposes sorry, but it has been reconed Kevlar as a Mid-base )
I wish you luck,
Regards ted
QUOTE" The more I know, the more I know, I know (insert maniacal laugh >here<) NOTHING"
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Old 18th June 2007, 11:48 AM   #3
Did it Himself
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Your thoughts are correct, it won't be suitable. About all I can suggest is keep an eye out for a drive unit or damaged speaker on ebay.
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Old 18th June 2007, 12:13 PM   #4
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Hi pshead. There is a v.good site in the UK that will be most useful. Without getting my old files out, as I understand it from memory, the two drivers are quite different. The B200 from the 104 or 104ab had a big magnet and a v.short voice coil compared with the one used in the infinite baffle systems. I'll try and find the site. Back in a minute.

Right, back again. Put "" into google and you'll get the site with a couple of useful threads with all sorts of helpful people. Its entirely about KEF speakers and drive units. Hope its helpful.
"It was the Springtime of the year when aunt is calling to aunt like mastodons bellowing across primeval swamps." P.G. Wodehouse.
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Old 18th June 2007, 04:52 PM   #5
AMV8 is offline AMV8  United Kingdom
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If you want to have the speaker repaired wilmslow audio will do that for you.

If you want to keep the same speaker I think that might be the only way as I think you may wait a while for that particular model of B200 to appear for sale. The usual ones you find for sale are the earlier models with the smaller magnet.

Having said all that I have tried replacing the later B200 with one of the earlier ones and it does work and is hard to detect a difference by listening. However I have found that the best replacement for the later B200 is the Wharfedale 5" unit that is currently being sold in lots of 4 or more on e bay for only a few pounds ( I have found this a good speaker ). It gives a slightly changed mid balance but offers more detail than the B200. You may need to add a resistor - 1 to 3 ohm 10 watt - in line with the tweeter to reduce the treble slightly.

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Old 20th June 2007, 10:18 AM   #6
pshead is offline pshead  United Kingdom
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Hi All,

Thanks for the comments and suggestions. I am considering the idea of having the unit re-coned, but suspect that it may be expensive. Also, it would probably be necessary to have both units re-coned to ensure matching, even though one of the pair is undamaged.

I guess I will just have to look out for a pair of SP1039 drivers!

The SP1054 unit did look attractive as it is more sensitive than the SP1039 and also has a higher power rating.


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Old 21st June 2007, 01:45 AM   #7
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fwiw, there's a pair of the appropriate drivers for sale on the 'Bay at the moment -- search under KEF.
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Old 21st June 2007, 03:23 AM   #8
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It's all starting to come back.......there were at least three B200's There was a small mag' version for the 20 litre infinite baffles(Chorales) Then two versions with larger magnets. One was in the Cadenza and the other was for the 104/104ab. As I understand it although both the 104 and Cadenza were ABR types the two units are not the same. But I think a B200 out of a 104 would be compatible with the 104ab as the latter differed only in the cross over. The "ab" refering to the Acoustic Butterworth nature of the tweeter's output after the cross over mod.
AMV8 I wonder if your reference to five inch Warfedales are really replacements for the B110 and not B200 which is a bit over 8" in diameter?
"It was the Springtime of the year when aunt is calling to aunt like mastodons bellowing across primeval swamps." P.G. Wodehouse.
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Old 21st June 2007, 05:49 AM   #9
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Originally posted by Jonathan Bright
.there were at least three B200's
5 as of the late 70s and more since -- i've seen at least 1 version with the triangular bezel that i don't have listed here

community sites,, ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
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Old 21st June 2007, 06:06 AM   #10
qwad is offline qwad  Australia
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yea dave knows his b200's
we all have problems only some people have more than most....
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