KEF 103/4 Drivers B160, recone

[TR6man98]

I've got a pair of KEF 103/4 on a garage sale with bass drivers shot.
Surrounds are all rotten and have to be replaced, for sure. I have tested
all 4 drivers, and only one voice coil is OK, others are open, pressumably shot.


I would like to get any data on these drivers. KEF model B160 Sp1302, 8 Ohm.
Those are fitted two per cabinet and connected with a steel rod.
I guess I should plan for worse case scenario, just in case and would need
complete recone with new coil and spider as well as surrounds.
What about foam dustcap? it's not traditional style, it's more like donate shape
made of the same foam material as surround.


What are my options? I would like to do this myself, but parts might be a problem.
where can I get those? I have never fix drivers before, just build some speakers and crossovers.
Refoaming looks easy but complete recone is unknown to me.

Any recommendation from you guys?
What are the opinions about importance of the donate-dustcap where the rod is passing through?

Thanks in advance.

Igor

[AndrewJ]

Hi Igor, I would suggest that you contact KEF for replacement woofers. If the coils as well as the foam surrounds are gone then they are your only hope for replacements.
The centre "doughnut" dustcap is actually a rolling seal because of the need to connect the two drivers with the force cancelling rod. You will not find aftermarket replacements for these.

Good luck

Andrew

[TR6man98]

Andrew,

Well, KEF doesn't have a replacements for some time now.
I guess complete recone is in order.
Voice Coils on all 4 drivers look OK and Cone is moveng, albeit with some scratching noise.
Does that mean VC former is shot and not the coil?
Also, the only working driver sounds bad, but with no surrounds and rolling seal (as you said) doesn't mean much, I guess.

What is that "rolling seal"? Is it necessary for the "sound"?
Does anyone know for sure?

Thanks

Igor

[AndrewJ]

Igor, if the voice coils are in-tact, ie measuring somewhere around 4-6 ohms resistance, then they should be OK. The scratching sound is caused by the coil rubbing against the top plate because of the rotted sourround no longer keeping the coil centered in the gap.
even if you find a repair kit for the surrounds you are still left with the problem of the rolling seal. I do not think you will find a replacement for this.
The only other solution is to forget about the force cancelling rod and just use a regualr dustcap. The force cancelling rod is used to reduce box vibration and clean up the sound. Without it the speaker will still work, though there will be more box colouration to the sound. Make sure if you do this that you adequately fasten the drivers into the box.
The driver parameters are critical to the performance. Not only do they determine the box tuning, but also the impedance seen by the xover. The xover is very complex, and the driver impedance is heavily conjugated in order for the xover to work correctly. If you change the driver for a substitute you will find that the xover response and impedance may go haywire!


All the best

Andrew

[TR6man98]

Andrew,

Thanks for your help.
I assume, rolling seal is there instead a dutcap, to prevent dust geting between the rood and a cone. Omitting it would be a bad idea.

Cheers,

Igor

[AndrewJ]

Igor, you are right about the rolling dustcap acting as a seal. It does this for two reasons. One is as you say to keep dirt out of the gap, but the other is to seal of the air leakage path. Coupled cavities are quite sensitive to leaks between the two cavities.

regards

Andrew

[RichG4PCE]

The surrounds are gone on my 103.4s.
The bits are falling out.
An obvious question to some, but how do I get into the cabinet to remove the drivers?
Rich

[RichG4PCE]

I got into the cabinet easily, so please ignore my previous post.

I got my AR6 drivers surrounds fixed about 15 years ago. Does anyone know a local repair shop here in Birmingham, UK?

[Allenr]

Hi RichG4PCE,

I just got a pair of 103.4 whose surrounds have gone becuase of the age. Would you please shed some light on me how to safely remove the woofer units from the cabinets? I would like to take these units to a local speaker repair shop to get new surrounds.

Thanks a lot!

[RichG4PCE]

Allenr,
Very easy. Take out the 8 screws holding the terminal plate at the back of the cabinet. The plate comes away with a little persuasion. Make a note of the wire colours and their connection terminals.
Remove the souns wadding, the top speaker is now accessible, remove the centre screw in the magnet, which holds the force cancelling rod in position.

Turn the cabinet over, remove the spikes and all the Posidrive wood screws, and take out the bottom wood piece. The bottom speaker is upside down, and the connections are soldered. You can either feed the wire connections through from the top, or just cut them close to the speaker and resolder them later when refitting. Again, remove the force cancelling rod screw.

I repaired myself, the inner, smaller seals were rotted too. I got the surrounds in UK, about 30 pounds, 60 dollars. Its not too difficult, if you are patient and precise in repositioning the speaker cone in the centre. It must'nt scrape in the magnet centre!

I can let you know the foam supplier I used, if you need.
Rich