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KEF 105/3 Restoration
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Headrush
Junior Contributor 10+


Joined: 10 Nov 2012
Posts: 18
Location: Nottingham

PostPosted: Thu Mar 07, 2013 2:37 pm    Post subject: KEF 105/3 Reply with quote

There is an original NT25 SP1240 tweeter for the 105/3 currently on eBay if anyone is interested. It's mine so rest assured it works ok Wink
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Tue Jul 30, 2013 6:35 am    Post subject: Reply with quote

WELL... I finally got my arse in gear and finished my 105/3 restoration! Let me preface that I was very happy with them before, albeit the treble seemed a little dim.

The first words that come to mind now are: night and day! Total transformation. This is not a biased reaction to justify the time and effort: I did one speaker at a time, so I was able to do a kind of before and after between left and right. HUGE difference!

I think the biggest impact is due to the new tweets and replacing all the seals. I also replaced the woofer donuts and the capacitors in the high-end section with ones from Wilmslow, although I can't say just how much the caps are contributing since I changed everything at once. I can say that the imaging is back to the holographic sensation I remember when I first heard these gems back in the day! What I find interesting is that I did the re-sealing of the front baffles after I had installed the new tweeters (forgot to do it initially and had to remove the baffles again) and I swear that seemed to make the imaging even better (maybe due to preventing any leakage from the top bass compartment?).

Also, I think the donuts made more of a difference than I thought they would, but not in a sonic sense. I think they might be for more than just keeping dust out of the VC gaps.
The fabric was nothing remarkable. I was told by the previous owner (who was probably told by the shop who did the work) that they were some kind of special woven fiber... Nope. Just some crappy, albeit thicker than usual, cut-up speaker grill cloth. Thankfully, they do seem to have done the job of keeping dust out gaps, but that's about it. With the new foam donuts, I noticed there is far less movement of the cones at higher volumes, including when the KUBE is engaged. Can't say the bass is tighter or if there's more or less of it (I've read some stating the bass gets slightly louder/boomier when the donuts have rotted away), but things seem much more "stable" now.

Also, for anyone interested, I needed to get 2 M5-.8 x 30MM machine screws for the new tweeters.
The original screw was an M5-.8 x 16MM flat-head, which was no where near long enough (the original tweeters had long, threaded stand-offs mounted to their backs).
The longest M5-.8 flat-head machine screw any local hardware store had was 25MM, which didn't reach. The only M5-.8 x 30MM machine screws I could find were pan-head.
Thankfully there was enough clearance to accommodate the slightly taller pan-head screw and they worked out fine.

OF COURSE.... I wound up with a leftover part that has me scratching my head. For anyone who's taken these apart, you will know that there are 2 bolts that hold the force-canceling rod in place between the 2 bass drivers. To my knowledge, there is one black washer and one (brass?) machine screw per driver (I've done donuts on a pair of 104/2's as well). When I disassembled the first cabinet, I only remembered seeing 2 washers. As I was flipping the first cabinet over to put the bottom cover back on, I heard what could only be a small metal part fall down into the cabinet. What I fished out was another washer identical to the ones I mentioned above. The only place I could imagine it would go is between the bottom of the force-canceling rod and top side of the plastic cup in the center of the bottom bass driver. When I disassembled the 2nd speaker, I again only found 2 washers. Either the shop who did the previous work forgot to put one back, or an extra washer fell in between the foam and the cabinet at the factory...

Does anyone know how many force-canceling rod washers there should be per driver?
I know it's a fairly tiny detail, but I'd like to confirm if possible. Leftover parts irk me....

Anyway, more details and maybe some pics to follow, after I finish cleaning up the mess I left in the dining room/test-lab (the wife is away thankfully!)...

I've got probably about 6 hours on them so far and I swear they're sounding better each time I listen!
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Tue Aug 20, 2013 7:14 pm    Post subject: Reply with quote

Confirmed with Andy @ KEF that there should only be 2 x bolts and 2 x washers per speaker for the force-canceling rods, so a loose washer must have fallen into the cabinet during assembly...

My current dilemma is with the new tweeters & capacitors combo.
The high end is more upfront than previous, which I expected to a degree with the new tweets, but I feel it is now overpowering the mids. I find myself missing some lower midrange, which is even more pronounced when switching between the 105/3's and my Model 100 center (covered in another thread).

So, I've read that you should not replace electrolytic caps with polypropylene and vice-versa, as it can change the voicing. Mine were swapped with Supersound polypropylene caps from Wilmslow. I am wondering if I should try putting the original electrolytic capacitors back in (but they HAVE to have gone out-of-spec by NOW, haven't they?), or order new electrolytic caps.

OR....

Is it since ALL the caps on the crossover have drifted so far out-of-spec at this point and only the HF caps have been replaced, that now the other drivers are not at the correct levels?

Any suggestions?
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speakerguru
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Joined: 18 Nov 2005
Posts: 954
Location: Green Hut, Tovil

PostPosted: Tue Aug 20, 2013 8:42 pm    Post subject: Reply with quote

Have written about capacitor loss factor ad nauseum on this forum. Check out my posts and put in some series resistors or go back to reversible electrolytics.
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clubsport911
Senior Contributor 100+


Joined: 26 Aug 2012
Posts: 157
Location: Cheltenham, UK

PostPosted: Tue Oct 15, 2013 11:15 am    Post subject: Reply with quote

@{ Deckard - hows the listening with the 1414's going ? I'm curious to know if you managed to resolve the issues you had (or percieved)

Thanks

Steve
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deckard
Intermediate Contributor 25+


Joined: 10 Sep 2012
Posts: 32

PostPosted: Wed Oct 30, 2013 3:45 pm    Post subject: Reply with quote

Hi Steve -

Thanks for the info! I wound up putting 1 x .47 Ohm / 10 Watt ceramic resistor in each speaker, inline with the tweeter leads coming off the crossover. Now that I think of it, I wasn't sure which leg to put them on at the time, but ultimately decided on the positive lead (does it matter if it's the positive or the negative)?

It was totally worth it. While I don't like the idea of adding more components, this appears to have done exactly what I needed. The change is subtle, but noticeable. The mids are slightly more pronounced now, but the timbre of the tweets is unchanged and I haven't lost anything with imaging or transparency. I got some .5 Ohm resistors as well, but I did not try them because the .47 Ohm resistors appear to be just enough at this point. I do notice some harshness at high volume, but only with certain recordings, plus it's more likely due to my current amp than the speakers.

Part of me is curious what the sound would be with a new full set of electrolytics from Falcon: http://www.falconacoustics.co.uk/kef-105-3-replacement-capacitor-set.html, but for the moment I am very happy and want to spend some time just listening instead of tinkering.

Also worth mentioning, regarding my quest for an SP1258, I found a guy on a site similar to Craigs List in the Netherlands who bought a bunch of old stock from a Dutch KEF importer. I was able to purchase 2 x SP1258's from him for an extremely reasonable price! It took some work to run the site through Google Translate, create an account and get in touch, but once we started emailing, everything was fine. Super nice guy and very accommodating. He asked me to mention his page in case anyone else is looking for any hard-to-find KEF parts: http://www.marktplaats.nl/verkopers/262089.html. If you open with with Google Chrome, it will automatically translate it.

Cheers.
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steve59
Junior Contributor 10+


Joined: 14 Mar 2015
Posts: 17
Location: chicago il

PostPosted: Sun Mar 15, 2015 3:49 pm    Post subject: Reply with quote

Interesting thread. I bought my 105/3's new and couldn't understand why they sounded so much better in the showroom THERE was NO bass. by advice of other 'audiophiles' I went on an affordable upgrade quest, but, when I looked in the bass port I saw surround material bouncing along with the music on the bottom woofer!!. I took them to a kef authorized service shop where they replaced the outer surrounds with butyl, they packed the white wadding in the center port instead of the sealed enclosure, and left the center wholes open. we're 10 years in now and the buyers remorse is still chewing on me so I go shopping and bring home every speaker from $2-4000.00 and while a pair of dyna's rocked their mid's were less revealing compared to the 105/3's. I ended up bi-amping with a krell kav 300il on top and a B&K 4420 with kube on bottom and something like 10 years later I got that showroom sound.
Fast foreward to 2015 my krell has crapped the bed for the 4th and final time. I bought an anthem 225 to replace it and while the sound is immediate redicilious exciting begging to go louder, something's different! I think the gain maybe because the bass is a little lower in level than it was with the krell. After 25 years I just may be moving on. I have a pair of 107/2's w/kube in the house and a pair of Revel f52 and honestly if I could put the 107's deep bass with revel's deep to mid bass handing off to the 105/3's uniQ and... The 105/3 is a bit colored in the midrange tipping up voices a little and sometimes it doesn't have quite the layering in the soundstage but they always have me reaching for another disc.
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clubsport911
Senior Contributor 100+


Joined: 26 Aug 2012
Posts: 157
Location: Cheltenham, UK

PostPosted: Thu Mar 19, 2015 10:52 pm    Post subject: Reply with quote

That's interesting Steve

My understanding is that the foam surrounds on the 105/3's - whilst a faff -are there for a reason and to change them for butlyl might well lead to a bass response that is far from optimum.

Also...stuffing the Cavity section.. That's a new one on me. Have you heard "native" 105/3's ? They are not big on bass, but accurate.
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