SpeakerTalk

ebf · Intermediate Contributor 25+ Joined: 08 Jun 2020 Posts: 25

Hi,

Im looking at:

https://reconingspeakers.com/product/kef-sp1215-10-aftermarket-recone-kit-kef-107-b250/

Im woundering if anyone has tried this particular recone kit, or any other recone kits from them? Experiences?

speakerguru · Posted: Thu Jul 16, 2020 11:17 am Post subject:

No, not tried it and have no systems with SP1215s , so not likely to.

A word of warning, if the stated vc i.d. is correct then the clearance is insufficient. KEF 2" drivers had a 2.000 dia magnet pole piece and a 20 thou (0.020") shim was used for assembly. That means the vc should have been wound on a 2.040" dia mandrel. I would expect it to be next to impossible to avoid coil rubs using this recone kit.

ebf · Intermediate Contributor 25+ Joined: 08 Jun 2020 Posts: 25

On my question to them on "How close are the coils measuring from the original coils", they answered:

speakerguru · Posted: Fri Jul 17, 2020 8:43 am Post subject:

10% of two inches is 0.2" or 200 thou Exclamation

The person who told you that knows nothing about designing speakers. With only 6 thou clearance (that's 3 thou radially !!!) you'd have to be super careful in assembly and hope that the spider stayed flat and did not have any internal stresses. It might work, but for how long before something drifted or relaxed and moved 0.003" I wouldn't like to say. I can't see a 3 thou clearance being maintained over a 0.5" cone excursion either!!! Cloth spiders are just not that linear. Good luck with that, you'll need it.

ebf · Intermediate Contributor 25+ Joined: 08 Jun 2020 Posts: 25

I think they are talking about Ohms - 10%, not the size of the cone. But will ask about the size issue...

speakerguru · Posted: Fri Jul 17, 2020 4:09 pm Post subject:

To clarify further; KEF's ancestry is from the older British school. Raymond Cooke came from Wharfedale, Laurie Fincham from Goodmans. In the days before cheap Chinese forgings, magnet pole pieces were mass produced by turning from standard Imperial diameter steel rod. It was cheaper to use standard stock bar for production but this meant that the factory voice coil winding machine mandrels had to be custom made. Woofer diameters were 1" + 14 thou clearance for B200, 2"+ 20 thou for B139, B300 and B250.

With the advent of Chinese pole/backplate forgings, any diameter pole could be mass produced. I suspect that the kit you've found was designed for a woofer with a metric 50mm pole diameter. 50mm is 0.8mm (32thou) smaller than 2" giving the about the required 0.020" radial clearance with a 2.006" vc i.d. (actually about 18thou if my calculations are correct)

Huba Buba · Introductory Contributor Joined: 09 Sep 2020 Posts: 6

Hi,

Are there any updates on this? Did you try the kit?

All the best,
- K

ebf · Intermediate Contributor 25+ Joined: 08 Jun 2020 Posts: 25

I received the wrong parts. They have resent the parts that I actually ordered, but have to wait a long time for them to arrive I guess.

Will keep everyone posted.

ebf · Intermediate Contributor 25+ Joined: 08 Jun 2020 Posts: 25

@Huba Buba, you tried the kits right?

It went well ?

Huba Buba · Introductory Contributor Joined: 09 Sep 2020 Posts: 6

Hi, everyone,

I actually ended up sending two drivers to Belgium for professional rebuilding, so I'm not likely to try this kit after all.

All the best,
- K