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105.2 clone with T33 tweeters?
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SaSi
Senior Contributor 200+


Joined: 24 Aug 2008
Posts: 236

PostPosted: Tue Jul 10, 2018 9:33 pm    Post subject: Reply with quote

Intrigued to read you are adding ferrofluid to the T27. It was not designed to use ferrofluid. The addition may spoil the sound or may tame it a bit, as many complain it's rather bright.

For the 105.2 KEF have published (I suppose) the schematics for an active crossover so that would be my first and only choice to turn them into active. As for amplifier, a single LM3886 would not have enough juice to drive the B300. There are bridged versions available but when it comes to bridging the chipamp, the tolerances of the various components, especially the current limiting resistors at the output, become very critical and I would not trust an un-named chinese PCB for that.
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audiolabtower
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Joined: 06 Jan 2009
Posts: 587

PostPosted: Tue Jul 10, 2018 10:12 pm    Post subject: Reply with quote

I investigated that active crossover and got in touch with Laurie Fincham at THX and Siegfried Linkwitz who did the Wireless World active design with his 4th order crossovers and neither could remember anything about an active 105 circuit, so it is probable that circuit did not originate from Kef... unless Speakerguru knows otherwise?
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Nimo_jon
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Joined: 21 Feb 2011
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Location: Singapore

PostPosted: Wed Jul 11, 2018 1:20 am    Post subject: Reply with quote

Yes, the ferrofluid is meant for the T33 I am fixing, not for the T27.

The B300 is to be replaced by the Peerless 12in. I am driving it with a 200W class D amp.

SaSi wrote:
Intrigued to read you are adding ferrofluid to the T27. It was not designed to use ferrofluid. The addition may spoil the sound or may tame it a bit, as many complain it's rather bright.

For the 105.2 KEF have published (I suppose) the schematics for an active crossover so that would be my first and only choice to turn them into active. As for amplifier, a single LM3886 would not have enough juice to drive the B300. There are bridged versions available but when it comes to bridging the chipamp, the tolerances of the various components, especially the current limiting resistors at the output, become very critical and I would not trust an un-named chinese PCB for that.
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speakerguru
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Joined: 18 Nov 2005
Posts: 1007
Location: Green Hut, Tovil

PostPosted: Sat Jul 14, 2018 12:17 pm    Post subject: Reply with quote

audiolabtower wrote:
I investigated that active crossover and got in touch with Laurie Fincham at THX and Siegfried Linkwitz who did the Wireless World active design with his 4th order crossovers and neither could remember anything about an active 105 circuit, so it is probable that circuit did not originate from Kef... unless Speakerguru knows otherwise?


No. I heard rumours too, while I was at KEF, but I've never seen an active 105 design, official or unofficial ever.
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SaSi
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Joined: 24 Aug 2008
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PostPosted: Mon Jul 16, 2018 6:46 pm    Post subject: Reply with quote

I have a circuit diagram of an active xo for the R105.2 and also a graph of the frequency response printed on KEF "stationary" naming circuit EE28/A/1 issue 2 with a date of 6.1.82 and signed by "EC".

The actual active xo circuit isn't drawn on KEF "stationary" - just a drawing.
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audiolabtower
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PostPosted: Mon Jul 16, 2018 9:13 pm    Post subject: Reply with quote

That is the one Fincham or Linkwitz has no knowledge of, thus not a Kef design and most probably sent in by an owner or third party.
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