Kef Corelli SP1051 - possible fix and servicing. [Archive]

Edward

29-01-2018, 23:17

So from eBay I got a pair of Kef Corelli (type SP1051) speakers for the grand sum of £12.50. It was sold as spares or repair with one of the tweeters being mentioned as suspect.

I started a chat with Geoff (walpurgis) over on the ebay bargains thread which basically starts here (http://theartofsound.net/forum/showthread.php?33544-Bargains-on-ebay-(Part-2)&p=942069#post942069). Geoff essentially gave me some tips on testing the drivers (e.g. coil resistance to roughly 5/6 ohms etc).

Since those posts I have plugged the speakers into my system and to my surprise it sounds wonderful. Nice and open with lots of detail and, as expected, quite laid back with warmth. Very 70s sound. :)

However, there is quite a lot of distortion on one of the tweeters. Initially it was fine but then playing different music it became very evident. Playing one of my reference albums (Fiesta (https://www.discogs.com/Dallas-Wind-Symphony-Howard-Dunn-Fiesta/release/4846911)) which without fail always shows up the strengths and weaknesses of systems (esp. speakers) the Kef tweeter failed miserably. Amp being used here is a 60w EL34 PP.

When I lightly touch the suspect tweeter dome the distortion largely goes away - but of course the upper range dies as well.

The seller mentioned that about two years ago he replaced the tweeters with standard T27 Kef units and that worked for about a year then developed same fault. So he suspects it is the crossover.

I have not done any testing or swapping over yet. But I thought I would open up this thread to see if anyone has any ideas as to what may be going on.

I'll try grab some time tomorrow to open up the speakers, see what is there and perhaps swap the tweeters over.

I got these speakers as a fun project only. Perhaps will recap the crossovers. I need some desoldering and soldering practice after all. :cool: I've already found a schematic for the xover - I guess I will have to first learn to understand what a schematic is. :doh:

walpurgis

29-01-2018, 23:32

Possibly a failing cap affecting the tweeter. I'd change them ASAP. Could be too much low frequency info is getting through and overloading the T27. That could blow it. Fortunately the T27 version used in that model is fairly plentiful, if a bit overpriced these days..

If you have trouble locating 0.56uF caps. I've got a bunch of them. The rest are easily available.

The Corellis are pretty easy to work on. Just handle the tweeters with care. Don't touch the domes, they are extremely thin Mylar/Melinex.

You won't need the schematic if you're just substituting components. Just do them one at a time.

Oh. And my Class A 15 watt EL34 monoblocks drive them just fine. Despite the low sensitivity, the Corellis don't seem too demanding on amps.

Edward

30-01-2018, 11:08

Thanks Geoff

I've now opened both up. The speaker that is giving grief seems to have had some dodgy wiring going on. Also one of the caps on the xover for that speaker has leaked, although to be fair similar but not as much has has occurred on the other xover.

I rather expect I need to get both out and replace all the caps and tidy up the wiring with better soldering and heatsleeves rather than the tape someone's used.

Also one of the wires on the outside of one of the tweeters looks very suspect. I'm reluctant getting a soldering iron near that.

The first three pics are of the wonky speaker, the next three of the better speaker and the last of one of the main drivers. Will need to find a non invasive way of cleaning the main deivers up.

https://uploads.tapatalk-cdn.com/20180130/97d09ca6baa43d4c3768fb0e9d31f7ef.jpghttps://uploads.tapatalk-cdn.com/20180130/61c493ffbc4286555a638aca1cbf4161.jpghttps://uploads.tapatalk-cdn.com/20180130/71f90320436c265931d76f90916e743a.jpghttps://uploads.tapatalk-cdn.com/20180130/c24ab870a4441e3bd1462114b470afb1.jpghttps://uploads.tapatalk-cdn.com/20180130/bc60e225c9494f0c5bdc9e7fd455bce0.jpghttps://uploads.tapatalk-cdn.com/20180130/19c2a026d5317618854a10364f4c64a5.jpghttps://uploads.tapatalk-cdn.com/20180130/8530811440789325f2ba41f92d5f2f22.jpg

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walpurgis

30-01-2018, 11:27

Yes. Looks like somebody has had a tinker with them.

The furry component I believe is a wirewound resistor and will probably measure OK despite the looks, although you can change it without harm.

The bass drivers should carry the SP1063 label. Judging by the brushed on Plastiflex cone doping, those look rather like the SP1014 from the Chorale. I could be wrong, but I believe the SP1063 had a sprayed on thinner coat. I don't think there's much between them in characteristics though.

The tweeters look a bit tired, but may sound OK.

Edward

30-01-2018, 11:44

No the main drivers are SP1063 with a date of 110276 whereas the wonky T27 tweeter has a date in 1974 so clearly have been changed.

Any initial ideas as to what I can start on to cure the distortion please?

walpurgis

30-01-2018, 11:47

Change the caps first and see how they sound then.

Edward

30-01-2018, 12:29

Change the caps first and see how they sound then.

Many thanks for all your help Geoff. Really appreciated.

I'll need to summon up the courage to desolder things and go from there. Any recommendation on caps to use?

WESTLOWER

30-01-2018, 12:46

I'll need to summon up the courage to desolder things
Edward, don't hold the hot end! :lol:

Edward

30-01-2018, 14:56

Edward, don't hold the hot end! [emoji38]Well I'll try not but I'm pretty clumsy so will stock up with lots of plasters. [emoji3]

Or next time you are around you can guide me.

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walpurgis

30-01-2018, 15:22

Any recommendation on caps to use?

I used alcaps from this seller: https://www.ebay.co.uk/itm/Bipolar-Capacitor-Alcap-50v-1uf-to-470uf-Sold-In-Pairs-Speaker-Xover-Caps-HiFi/263417301111?hash=item3d54e50877:m:mxgNKPtsdBbyjrf SbH0-1Tg

I think they're 50 volt rated or above, more than adequate. You'll find some are larger than the originals. Not a problem. Don't cut the wires too short.

The seller, Cricklewood Electronics will probably not stock the 0.56uF value. I can let you have a couple if you need them.

karma67

30-01-2018, 16:58

falcon acoustics are also a good choice for alpcaps edward,probably more choice with them too.

Edward

30-01-2018, 17:46

I used alcaps from this seller: https://www.ebay.co.uk/itm/Bipolar-Capacitor-Alcap-50v-1uf-to-470uf-Sold-In-Pairs-Speaker-Xover-Caps-HiFi/263417301111?hash=item3d54e50877:m:mxgNKPtsdBbyjrf SbH0-1Tg

I think they're 50 volt rated or above, more than adequate. You'll find some are larger than the originals. Not a problem. Don't cut the wires too short.

The seller, Cricklewood Electronics will probably not stock the 0.56uF value. I can let you have a couple if you need them.

Thanks Geoff. I'm gonna try desolder everything tomorrow, measure all the caps, make a list and see how I go. Cricklewood is not far from me so may just pop down there. Let's see if I need 0.56uF and if so will contact you for a price etc. Thanks.

falcon acoustics are also a good choice for alpcaps edward,probably more choice with them too.

Yes I did notice that they have cap sets for a range of crossovers but not for the Kef one I have. Once I get all the caps off I'll see how I go with either Cricklewood or Falcon.

I suspect I'm overthinking all of this, it is probably all very easy replacing the caps.

walpurgis

30-01-2018, 18:03

I'd not desolder until you have new parts to fit. It'll save having to keep referring to photos or diagrams to recall where bits went. Don't bother measuring the caps, even if they measure OK, their life expectancy is limited and replacing all is the best route. They are after all, forty years old.

You won't need a price for the 0.56uF. They're free.

I'm pretty certain Falcon will be dearer than Cricklewood Electronics.

Yes. Changing caps is dead easy on these. Disconnect the crossover and take it right out, it's much easier that way. To disconnect the tweeter wires, just pull back the small piece of sleeving to expose the soldered joint. You may need some heat shrink sleeving to replace these.

karma67

30-01-2018, 18:32

falcon offer a better tolerance on the cap value geoff,thats why they may be slightly more expensive.

walpurgis

30-01-2018, 19:04

Maybe, but the tolerance is not too critical.

Edward

30-01-2018, 19:06

Thanks Geoff. Good points. I'll remove the xovers make a list and only when I get the new caps (and resistors?) replace them on a one to one basis. Thanks for the free offer. [emoji106]

I was wondering about the tolerances mentioned. Some cheaper caps have a stated tolerance of 20% I wonder if that will make a noticeable audio difference on such old speakers.

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karma67

30-01-2018, 19:11

it is in my book,if your going to change the caps that work you might as well get them as close to the original designed value as possible no? otherwise why change them?
but then im fussy about things like that lol

walpurgis

30-01-2018, 19:11

The Alcaps are 10% tolerance. Perfectly adequate. If the resistors measure OK, I'd not worry too much about them.

karma67

30-01-2018, 19:13

yeah but they do 5% as well :ner:

Edward

30-01-2018, 19:27

I'll do a price comparison and see what the differences are. If not too much I'll go for the higher spec ones - at the very least when/if I sell the speakers I can say 'audiophile' caps have been used. :eyebrows:

But anyway this is only a fun learning project - I really don't need more speakers. My wife was amused when I told her I had got yet another set of speakers - this would be my 6th set. But she could not argue against £12.50.

Why do resistors put a furry coat on? Did they get cold or something? :dummy:

walpurgis

30-01-2018, 19:33

Why do resistors put a furry coat on? Did they get cold or something? :dummy:

When the resistors get hot, the lacquer breaks down exposing the ceramic coating, which is porous and absorbs atmospheric moisture which evaporates when the resistor gets hot again loosening the surface, giving that fluffy look. It has no effect on the resistor's value.

walpurgis

30-01-2018, 19:36

But anyway this is only a fun learning project - I really don't need more speakers. My wife was amused when I told her I had got yet another set of speakers - this would be my 6th set. But she could not argue against £12.50

If you get these working nicely, you'll probably like them as much as your Tannoys. I use mine alongside the Cheviots and both sound excellent.

Edward

30-01-2018, 19:43

If you get these working nicely, you'll probably like them as much as your Tannoys. I use mine alongside the Cheviots and both sound excellent.

I'll be very pleasantly surprised if the Kefs get anywhere near the sq of the Tannoys.

Speaking of which I will be away late March for a while so I plan on having Paul at RFC do a recap and other work on them then. He says his fettling will further improve the Eatons.

Edward

31-01-2018, 20:36

So I pulled out one of the crossovers, made a list and went along to Cricklewood Electronics to get the caps.

A bit of confusion on values etc but I think I got correct ones but would most appreciate a double check.

First value is what is on the xover and second value is what I bought. I took the xover with me and the guy at the shop was most helpful.

2 x 30 mfd (50v) - 2 x 30 uF (100v)

4 x 10 mfd (50v) - 4 x 10uF (100vnp)

4 x 5 mfd (50v) - 4 x 4.7uF (100 vnp) 4.7mfd was the closest they had.

2 x 3.3 mfd (50v) - 2 x 3.3uF (50 vnp)

2 x 0.69 mfd (50v) 2 x MA684k 630v (am confused about this).

Also, from schematic I got from the interweb, tried to ascertain what resister is used. So purchased 2 of 4r7 5% 58ev. But will likely not replace them.

Here is the schematic I found, some values are different to what was on the xover so whoever put the schematic together may have got things incorrect.

http://imapnet.com/aos/sp1052%20schematic.jpg

walpurgis

31-01-2018, 21:44

All looks OK apart from this:

2 x 0.69 mfd (50v) 2 x MA684k 630v (am confused about this).

I'm not sure what you've been given there.

The value is 0.6uF. I used 0.56uF which is close enough. I have plenty of spares.

That schematic is wrong by the way.

Edward

31-01-2018, 22:04

All looks OK apart from this:

I'm not sure what you've been given there.

The value is 0.6uF. I used 0.56uF which is close enough. I have plenty of spares.

That schematic is wrong by the way.

Ah thanks Geoff. Is the new resistor ok or should I leave well alone?

PM incoming btw.

cheers
Edward

walpurgis

31-01-2018, 22:09

Edward

31-01-2018, 22:31

Chances are the resistors are fine, although changing them for the 4.7 ohm ones won't hurt if you want to.

In every photo I've seen online of the Corelli crossover, those resistors are furry. Mine aren't though. :)

Can one measure the resistance value whilst still in circuit?

On some of the caps I got they will have to stand quite proud due to size issues.

struth

31-01-2018, 22:33

not really. you will get spurious readings

walpurgis

31-01-2018, 22:45

On some of the caps I got they will have to stand quite proud due to size issues.

I did mention the size difference. If you think the caps may vibrate against each other, use a little blob of silicone sealant between them. You won't need much. A small tube will be enough. I use clear, but any colour will do obviously.

Like this: http://www.ebay.co.uk/itm/SILICONE-TUBE-SEALANT-WATERPROOF-CLEAR-KITCHEN-BATHROOM-BATH-SHOWER-70G/322778122642?epid=1608006720&hash=item4b27134992:g:sZAAAOSw~oFZx873

Some bargain shops or pound shops stock it too.

Edward

31-01-2018, 22:51

Oh I have plenty of sealant! The good lady keeps hassling me to remedy something - but you know how it is - always something more important to do. :)

spendorman

01-02-2018, 03:07

Macca

01-02-2018, 08:59

No the main drivers are SP1063 with a date of 110276 whereas the wonky T27 tweeter has a date in 1974 so clearly have been changed.

Maybe not, KEF probably had thousands of drivers sat in stock back then, sometimes for years before they were built into a speaker.

Edward

01-02-2018, 18:43

All looks OK apart from this:

x 0.69 mfd (50v) 2 x MA684k 630v

I'm not sure what you've been given there.

The value is 0.6uF. I used 0.56uF which is close enough. I have plenty of spares.

That schematic is wrong by the way.

been researching why I was given a capacitor with seemingly strange markings. But all is clear when I look at this reference (http://kaizerpowerelectronics.dk/theory/capacitor-code-table/).

So basically 684k means 0.68uF with 10% tolerance. (68*10,000 / million = 0.68uF with 10% tolerance).

walpurgis

01-02-2018, 18:51

Oh well. You have a couple of 0.56uF on the way, which are quite small, so may be easier to mount.

Edward

01-02-2018, 19:02

Indeed - the ones I purchased are significantly larger than originals. No doubt due to the high 630v rating when 50v was all it needed.

Once I have yours (many thanks btw) I will sit down and work out best way forward on the caps - and resistor.

I'm assuming the inductors will not have perished - all my reading indicates that these typically are the last to perish.

walpurgis

01-02-2018, 19:17

The inductors should be OK unless somebody has put ludicrous power through them, but the drivers would blow first anyway. I've never found a dud inductor in old speakers, not even sixty year old ones. It can happen though.

Lawrence001

01-02-2018, 21:16

Edward

01-02-2018, 21:53

Some of the Kefs I've recapped use low loss caps on the treble, do any of your caps have LL on them or similar? Some people recommend changing these to polyprops but opinion is divided as the lower ESR could increase output. Ie smoother but too bright, or swings and roundabouts.

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Nope nothing like that. Just bog standard caps so far as I can see.

Cricklewood essentially had only two types Alcap and Ansar. The Ansar caps were £5 each and upwards and given that this project is only for fun and learning I went with the cheaper Alcaps. Still the caps cost me slightly more than twice what the speakers costs me. Hopefully things will work out in which case I will do a light sanding and then Danish oil.

I'm away tomorrow so realistically it will be earliest Monday when I do the work.

Lawrence001

01-02-2018, 22:24

They will definitely benefit from a recap the only question is by how much. Usually it's night and day and you realise that when people describe vintage speakers as warm and cuddly they are really describing the effect of the dried out caps.

PS I've installed music monkey, deleted AVG which was driving me nuts, switched off all the autostart bloatware that's built up on my laptop and I'm ripping to flac in about 4-5 mins now [emoji846]

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Edward

01-02-2018, 22:33

Lawrence001

02-02-2018, 11:23

Yeah never heard of it either but someone recommended it for the olive, it works nicely and now I can get the album art on the olive too. It seems to need embedding in the track metadata rather than just saving an image in the album folder which the olive won't pick up.

The key thing is it allows you select degree of compression for flac which I couldn't find on EAC amongst all the complex settings about your drive etc. Setting to lowest compression rate (fastest) has speeded up the rip by a factor 4-5 times.

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karma67

02-02-2018, 19:03

They will definitely benefit from a recap the only question is by how much. Usually it's night and day and you realise that when people describe vintage speakers as warm and cuddly they are really describing the effect of the dried out caps.

a different experience to me,ive fully re capped and rewired 3 pairs of ditton 44's and a pair of ditton 66's and none of them were night and day different from before.

Lawrence001

02-02-2018, 21:23

Were they Alcaps? It's always benefitted the 60s/early 70s Kefs I've done.

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Edward

02-02-2018, 21:36

Mostly. Couple of Jenson and a pair marked 'MA'.

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karma67

02-02-2018, 22:17

Were they Alcaps? It's always benefitted the 60s/early 70s Kefs I've done.

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yes,i always change like for like,dont get me wrong there was a difference,just not night and day.
i didnt want edward getting high expectations thats all.

Edward

02-02-2018, 22:30

Oh sorry I just realised Lawrence you were replying to Jamie and not asking me. Blame tapatalk for my confusion.:)

Jamie, main reason for replacing caps is to cure an issue evident on one tweeter. Geoff reckons it is due to LF getting through to the tweeter. No cap looks blown so I'm just gonna replace all. If SQ improves then great but what I did hear despite the issue was very good. My current reference point for comparison are Tannoy Eatons.

Hopefully I will do the recaps soon but some urgent work has got in the way.

walpurgis

02-02-2018, 23:39

These speakers are worth a bit of time, money and effort. You should find once sorted, that they sound a bit special. I spent a few quid getting mine up to scratch and my mate spent even more on his, which he wanted after hearing mine. Both of us find that on the end of a good system the results are very nice indeed (oh, and both of us are Tannoy users too). They are also an appreciating asset, values have doubled in the last couple of years. I've seen asking prices approaching £200.

alphaGT

03-02-2018, 09:19

Can one measure the resistance value whilst still in circuit?

On some of the caps I got they will have to stand quite proud due to size issues.

I was taught to pull just one leg, then measure.

Russell

walpurgis

03-02-2018, 09:21

I was taught to pull just one leg, then measure.

Russell

Yes.

walpurgis

03-02-2018, 19:06

Crossover recap photos before and after, taken by my mate when he did his.

http://i66.tinypic.com/vg7rjc.jpg

http://i63.tinypic.com/2rhojmh.jpg

karma67

03-02-2018, 19:41

interesting that edwards says there are no low loss caps on his,yet your friends crossover shows 2 used

walpurgis

03-02-2018, 20:33

Falcon Acoustics quote the replacement blue Alcaps as being low loss types.

karma67

03-02-2018, 20:52

yes but i mean on the original elcap crossovers.

walpurgis

03-02-2018, 21:10

yes but i mean on the original elcap crossovers.

Yes, I know what you were saying mate. :)

Lawrence001

03-02-2018, 23:32

I wonder if the 2 that are joined by cable ties in Edward's are LL types, you can't see the spec in the photos?

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Lawrence001

03-02-2018, 23:35

Mind you the 3.3uf in Edward's isn't a LL but it is in the other. I wonder if Kef introduced the low loss types as an improvement later on.

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walpurgis

03-02-2018, 23:39

I know some are finnicky, but really, there's a fair latitude on capacitor performance and tolerance in speakers.

Edward

04-02-2018, 18:52

So I replaced all the caps on one of the xovers The desoldering and soldering was reasonably easy to do.

Wired it all up again and plugged it on and big breath.

Drumroll ...

Nothing! :doh: zero sound from the one channel.

I've obviously done something wrong - probably something simple.

Xovers before ...

http://imapnet.com/aos/kef/original_small.jpg

After (of course I clipped all the legs)

http://imapnet.com/aos/kef/new_small.jpg

walpurgis

04-02-2018, 18:55

Check all connections and joints. Make sure nothing is touching and shorting.

Edward

04-02-2018, 19:00

Check all connections and joints. Make sure nothing is touching and shorting.

I'm hoping it is something as simple as the solder joint with the inputs. But run out of time for a few days .... :unfair:

karma67

04-02-2018, 19:35

lets see a pic from the other side with the solder joints,it may help identify a problem

Edward

04-02-2018, 20:01

lets see a pic from the other side with the solder joints,it may help identify a problem

Here are before and after views of the rear. I did not take a pic after I snipped all the legs etc.

http://imapnet.com/aos/kef/rear_before.jpg

http://imapnet.com/aos/kef/rear_after.jpg

Lawrence001

04-02-2018, 20:12

Did you snip the wires off the back before replacing, they look like they are crossing the pcb traces?

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walpurgis

04-02-2018, 20:31

I see a couple of soldered joints that look as if they may not have 'flowed' properly. Might be worth looking at.

Edward

04-02-2018, 20:33

I removed the old caps with a desoldering pump and then cleaned up with some braid. I then inserted new caps, bend wires, solder and then clip wires.

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Edward

04-02-2018, 20:34

I see a couple of soldered joints that look as if they may not have 'flowed' properly. Might be worth looking at.Will certainly look again and reflow suspect joints. But would that account for zero sound from both drivers?

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Edward

04-02-2018, 20:39

Is there any way I can test the xovers using a multimeter?

I did read the tweeter using a mm. I think the tweeter needs replacing as it read ca. 27 ohms. [emoji848]

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walpurgis

04-02-2018, 20:40

But would that account for zero sound from both drivers?

Possibly if you have a short somewhere (which may not be good for the amp, so take care).

Macca

04-02-2018, 20:40

It could do. Seems to me that if you haven't got a complete circuit then current won't flow.

Edward

06-02-2018, 18:11

It works! :champagne: :carrot: :yay:

Really simple error on my part. Turns out that the positive lead to the internal binding post had a weak connection (found with continuity testing). Resited and resoldered and all is good.

Been playing for 30 mins or so and sounds absolutely awesome. Using my goto album (https://www.discogs.com/Dallas-Wind-Symphony-Howard-Dunn-Fiesta/release/4846911) (DR =21) and speakers just breeze through it. Lesser speakers wimp out on the more difficult areas.

Next steps: redo the other xover, clean the main drivers (any hints?) and then focus on the woodwork. May well use one of the solutions in this thread (http://theartofsound.net/forum/showthread.php?56617-refinishing-walnut-veneer-speakers).

walpurgis

06-02-2018, 18:16

sounds absolutely awesome.

Told ya! :)

Wait till you get the pair finished. You'll be delighted with them.

Edward

09-02-2018, 18:25

Managed to grab a couple of hours to recap the other crossover.

Wow, really good sound, especially considering the Kefs being a small(ish) 2 driver closed box design. Very articulate, clean, natural, coherent from top to bottom. Really singing and confident. Whilst bass does not (obviously) go low it is tight and well defined. Mid and top I would describe as delicious. Very musical.

Not as much 'scale' as the Eatons or Kudos - but close.

Not bad for ~£40 so far. :eyebrows:

Next up - clean main drivers and then woodwork.