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Kef Special Development Reference Series - 1973

 
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Caliente
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Joined: 05 Apr 2009
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Location: Leeds

PostPosted: Mon Jul 06, 2009 8:11 pm    Post subject: Kef Special Development Reference Series - 1973 Reply with quote

Ok, I was hoping to join this site to gather more info regarding my unique Kefs. But due to having a small listening room I have decided to let these go.

Pictures can be found at http://s301.photobucket.com/albums/nn63/Calientezx/Kef

They were produced in 1973 for the BBC but never went into commercial production - only 6 or so were made and these are possibly the only ones still in existence. They were restored by a well known and respected hi-fi fanatic - I obtained them last March, and despite trying various combinations of amp/cables I cannot avoid a degree of boom. I must admit that they give excellent results with modern jazz and world music, but don't cope too well with Led Zeppelin & Van Halen type of thing.

If interested please contact me premsyl@tiscali.co.uk I'm based in Leeds
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ColinR
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Joined: 31 Jul 2004
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Location: Staffordshire

PostPosted: Mon Jul 06, 2009 9:25 pm    Post subject: Reply with quote

I believe there were more than 6 pairs like yours which ended up in the hands of both KEF and BBC employees.

Numbers 5 & 6 are rebuilds, as my least favourite Norwich speaker stripper got there first, luckily ex-KEF man Malcolm Jones of Falcon had the plans, so Peter (another Speakertalk member), who bought just the boxes did an expensive rebuild.


Any chance of a listen Very Happy ?
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Caliente
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PostPosted: Mon Jul 06, 2009 10:34 pm    Post subject: Reply with quote

Colin - ah, you seem to know about these

These are sn 3 and 4

Are you aat all interested in looking after them as part of our speaker heritage?

Rob
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ColinR
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PostPosted: Mon Jul 06, 2009 10:55 pm    Post subject: Reply with quote

I know bits and pieces, but I really would like to examine them more closely as they're so "off the wall" but meant to be hung on one!
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proffski
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PostPosted: Tue Jul 07, 2009 6:56 pm    Post subject: Reply with quote

Utterly fascinating, were all the units directly driven or is there an ABR lurking in there somewhere?

Andy.
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Caliente
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PostPosted: Tue Jul 07, 2009 6:59 pm    Post subject: Reply with quote

proffski wrote:
Utterly fascinating, were all the units directly driven or is there an ABR lurking in there somewhere?

Andy.


? - dunno, come on someone must want to get their hands on these!!
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proffski
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PostPosted: Tue Jul 07, 2009 7:09 pm    Post subject: Reply with quote

Oh come on, take a peek inside, pretty please... Smile
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Caliente
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PostPosted: Tue Jul 07, 2009 7:39 pm    Post subject: Reply with quote

proffski wrote:
Oh come on, take a peek inside, pretty please... Smile


Look, you are asking the wrong person (believe me), I don't even look in my wallet for fear of what I will find - I'll try and ring the guy that I got them from...
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proffski
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PostPosted: Tue Jul 07, 2009 7:53 pm    Post subject: Reply with quote

I cant even afford a wallet!
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SaSi
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PostPosted: Wed Jul 08, 2009 9:09 am    Post subject: Drivers Reply with quote

My guess is there is one B139 active and two PRs.
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ColinR
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PostPosted: Wed Jul 08, 2009 10:07 am    Post subject: Reply with quote

Peter's rebuild of 5 & 6 used two SP1044s and a high power SP1333, unfortunately I've no information about the crossover points or series/parallel configurations.
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speakerguru
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Joined: 18 Nov 2005
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PostPosted: Fri Jul 10, 2009 8:27 am    Post subject: Reply with quote

1973 is before I joined KEF, so I can't help. I don't recall anyone talking about these, either, probably because they were busy selling LS5/1ACs to the newly formed commercial radio stations and installing the new 'computer' by '75 when I joined.

Looking at your photos, my guess is that they are basically Concertos in a custom box but with 2 PRs replacing the usual vent. PRs are better than vents for avoiding turbulent air flow.

The PRs may well be modified as regards moving mass to suit the box. You need to check out the thickness of the steel tube which links the diaphragm and the rear suspension. For prototype work the tube was sometimes filled with 'Plasticene' to vary the mass.
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