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B-110 sp1003 / sp1057 interchangability

 
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T.O. Chef
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Joined: 31 Aug 2007
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Location: Toronto Canada

PostPosted: Tue Dec 23, 2014 12:28 am    Post subject: B-110 sp1003 / sp1057 interchangability Reply with quote

Here's a question I'm not sure has been asked before,

Forgive me if it has and explanations lurks deep in the history here.
Perhaps Speakerguru can give insight or direct me to any posted material on the subject.

As I understand it, the B-110a (sp-1003) had inherent resonant challenges that made it "honky" in spots. This has been attributed by some to the cone material used, and or the surround design.
Regardless of this sonic characteristic it certainly was one of the absolute best mid frequency reproducers of the time, used not only in a large number of KEF products but by many other manufactures.

Then came the sp1057.
From what I read, this evolution seemed to have addressed many of the sp1033 drawbacks and I'm wondering about a few things here.
* were there other changes in the design aside from the surround?
* was the cone material the same?
* Most important (to me) were they interchangeable?

The reason I ask is ...
I have some wonderful R.101 clones (homemade cs1's), a pair of Cantata's, and have had R.105.2's (now gone to a larger home where they can sing properly) .... all using the later sp1057. There's only wonderful mid range reproduction from all of them.
I also have IMF TLS80's that use the sp1003, but those drivers have been modified by IMF with copious coating of some type of damping material painted onto the cones, apparently to address the resonance issues. These sound fabulous.

Now ..... I am considering swapping out the sp1003's in some TL-200's for sp1057's that I'm blessed enough to have on hand. Of course the ear will tell if this is advisable, but before I go to the effort I would love to have some insight into the expected results.
The spec's seem to be Very Close in all practical aspects. Would the crossover accommodate this swap without modification . I wonder?

Any thoughts here???
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audiolabtower
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PostPosted: Tue Dec 23, 2014 1:00 pm    Post subject: Reply with quote

The surround and voice coil are the main differences, the 1057 had virtually double the power handling of the 1003. The specs are quite similar, the mechanical damping the most difference. If you look at the various crossovers they do not look interchangeable without component and/or circuit changes if you are after the flattest response. There must have been a reason Kef designed the 1228 for the 3/5a replacement rather than using the existing 1057?
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speakerguru
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PostPosted: Tue Dec 23, 2014 10:26 pm    Post subject: Reply with quote

audiolabtower wrote:
The surround and voice coil are the main differences...

The rubber surround and the cloth dustcap for the 1003 were stock Kurt Muller items. The surround did not terminate the cone surround and the dust cap did not fit the cone profile as well as the later, in-house vacuum formed, Velbex items. So the 1003 had a more pronounced "surround dip" and a more variable dustcap cut-off peak at hf.

The voice coil of the 1057 was wet-wound using epoxy onto an aluminium former. Hence the higher power rating but induced currents in the aluminium former reduced the Qm of the driver. This would affect the LF alignment, if used as a woofer (compared to the 1003).
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T.O. Chef
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Location: Toronto Canada

PostPosted: Wed Dec 24, 2014 1:33 am    Post subject: Reply with quote

Ah, thanks for sharing that Speakerguru.
It's interesting indeed to note the dust-cap's effects on HF. Perhaps this why in the case of the Cambridge R-50 the Falcon upgrade that changes the mid to HF slope to 18dB is highly recommended.

So then is it fair to say that throughout the mid-band the sp1057 and sp1003 are very similar, and in fact the sp1057 even smoother possibly in the upper extremity?
And by extension assuming the use is as a dedicated mid-range driver the 2 are almost identical?
However there is the question of sensitivity. The sp1057 is slightly more efficient than the sp1003, (11.2V RMS for 96dB vs 12.5V). I wonder ... If substituted, would the 1057 require padding down, or would the difference be audible?
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speakerguru
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PostPosted: Wed Dec 24, 2014 10:15 am    Post subject: Reply with quote

Early KEF bextrene cones were coated front and back with a fixed number of coats by hand with a paint brush. It was remarkably consistent and a testament to the skill of the factory workers at that time. However, with the coming of Reference Series came the need to reduce variations still further. The 1057 was probably the fist unit to benefit from this. The cones were now rear coated to a specified wet weight , allowed to dry, given a second rear coat again to a specified wet weight. This reduced the variation in cone mass with paintbrush operator. The final front coat was very thin and for appearance sake only - to show that the cone was coated. This process trickled down to all coated cones at time moved on.
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