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SpeakerTalk This forum has been set up to facilitate discussion of 1970s KEF speakers and drive units. The owner of the Forum has no connection with KEF Audio.
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pmcg Introductory Contributor
Joined: 11 Apr 2013 Posts: 1 Location: London
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Posted: Tue Apr 16, 2013 5:42 pm Post subject: 104ab repair - advice needed |
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Hi, I recently came into possession of a pair of 104ab speakers, having never owned a decent set of speakers before in my life. Unfortunately not really knowing what I was doing, I pushed them too hard at my birthday party, and blew one of the tweeters, one of the bass drivers and one of the capacitors in one crossover.
I need some advice on repairing them. I've managed to find a replacement b200 sp1039 on ebay, but I'm quite poor and can't stretch to the price of an original t27 (they seem to go for at least £50 from what i've seen) - so I was wondering if anyone could advise on alternatives.
I saw this advertised as a t27 replacement on ebay but wondered if anybody here had any thoughts on how good it is?
http://www.ebay.co.uk/itm/1-Silk-soft-dome-130w-flat-response-Hi-Fi-tweeter-KEF-T27-replacement-upgrade-/321088394391?pt=UK_Sound_Vision_Speaker_Parts&hash=item4ac25c1497
Also I need to replace the capacitors, as one of the ones in the crossover has visibly exploded...i found a replacement set on falcon acoustics site but wasnt sure what the difference between ALCAP 50V low loss 5% or 2% was, and which I should choose?
http://www.falconacoustics.co.uk/kef-104ab-replacement-capacitor-set.html
Many thanks for your help!
Paul |
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Richie Senior Contributor 100+
Joined: 06 Nov 2010 Posts: 108 Location: Northamptonshire
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Posted: Tue Apr 16, 2013 7:37 pm Post subject: |
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Hi Paul, this is what I did with mine.....
I was advised to replace all the caps in the crossovers as even if they weren’t leaking their values would have drifted after nearly 40 years, I did this with a kit of same value caps from Falcon Acoustics, I opted for the slightly dearer Solens (2%).
I then coated all of the inside un-damped parts of the cabinets with 2mm of floor grade epoxy resin (doesn’t go brittle). I rewired them internally with silver plated OFC and added some nice gold plated binding posts.
I by-passed the contour control switch and the fuse. There is a substantial brace holding the bass/midrange (B200) speaker at the back (inside) that had shrunk, so I made some wooden shims and reinstated the brace. I also removed the lose wadding inside to make the ABR (B139) work better and it did on my concrete floors but I’m not sure this would be a good idea on wood floors.
The results were very pleasing, if you want to keep them reasonably "true" I would try and find a T27, they do occasionally go cheaper than your quote on Ebay, also try Gumtree and preloved.
Best of luck
_________________ Still learning ...... |
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Garethwatkins Junior Contributor 20+
Joined: 18 Nov 2011 Posts: 22 Location: Tring, UK
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Posted: Tue Apr 16, 2013 9:04 pm Post subject: |
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That's bad luck blowing a tweeter. it sounds like the fuse was the wrong rating (or bypassed) I assume you have checked it! Even if the unknown replacement for the t27 works well it will be different in some respect so you will have a mis-matched pair. |
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proffski Über Contributor 1000+
Joined: 22 Aug 2003 Posts: 1297 Location: Tewkesbury UK
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Posted: Wed Apr 17, 2013 8:32 am Post subject: |
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Bad luck with the 104aB incident, I did the same to mine in a monitoring situation back in the late 1970s!
Gareth is quite correct, you will have mismatched loudspeakers so the best option is to change both if you can, I doubt if the crossover will be a proper match but better than nothing.
Also note that the machined rebated cutouts are for 108 mm diameter.
The replacements are 96.5mm... you would need to make a sub-plate mounting arrangement rather than butchering the cabinet.
T27 cutout for magnet is 84mm replacement is 71mm. _________________ I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill |
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