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B139 and T15 crossovers

 
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MGM
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Joined: 13 Nov 2014
Posts: 36
Location: Witney Oxon

PostPosted: Fri Jan 02, 2015 9:58 pm    Post subject: B139 and T15 crossovers Reply with quote

I am hoping to buy a pair of loudspeakers which utilise the Kef B139 anf T15 drive units, with a DN8 crossover.
Do any forum members know of an upgraded crossover circuit designed for these particular drivers ?

Thanks
MGM.
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M G Miles
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speakerguru
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Joined: 18 Nov 2005
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Location: Green Hut, Tovil

PostPosted: Fri Jan 02, 2015 11:16 pm    Post subject: Reply with quote

The only way to improve that combination is to add a B110 midrange unit and use the Cantata crossover.

Necessity and unbelievable optimism made KEF combine those two units in the early years before they had developed any midrange units. The B139 breaks up above 150Hz and barely makes it to 900Hz via some large and highly variable peaks in response.
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SaSi
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PostPosted: Sat Jan 03, 2015 1:13 am    Post subject: Reply with quote

I always wondered how this combination would work, when the B110 was considered "ill behaving" with breakups before the crossing frequency. Nice to have this riddle answered.
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MGM
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Joined: 13 Nov 2014
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Location: Witney Oxon

PostPosted: Sat Jan 03, 2015 8:31 am    Post subject: Reply with quote

speakerguru wrote:
The only way to improve that combination is to add a B110 midrange unit and use the Cantata crossover.

Necessity and unbelievable optimism made KEF combine those two units in the early years before they had developed any midrange units. The B139 breaks up above 150Hz and barely makes it to 900Hz via some large and highly variable peaks in response.


The Radford BSL used a lighter weight B139 and a Celestion HF1300 tweeter.
Not a true comparison, but listening to my restored pair I feel the midrange is a little recessed, but not 'missing' as you imply. The crossover is much more sophisticated than the Celeste, helping the B139's upper range to be covered with the HF1300's lower range.
The BSL sounds remarkably good.
The Celeste is brighter, but to my ears less natural . Arthur Radford tried many combinations of B139 and a tweeter before he decided on the HF1300.
It is an exceptionally good tweeter...
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