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Thread: Kef Corelli SP1051 - possible fix and servicing.

  1. #1
    Join Date: Mar 2017

    Location: London N2

    Posts: 678
    I'm Edward.

    Default Kef Corelli SP1051 - possible fix and servicing.

    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. 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) 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. I've already found a schematic for the xover - I guess I will have to first learn to understand what a schematic is.
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  2. #2
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 34,455
    I'm Geoff.

    Default

    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.

  3. #3
    Join Date: Mar 2017

    Location: London N2

    Posts: 678
    I'm Edward.

    Default

    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.



    Sent via Tapatalk
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  4. #4
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 34,455
    I'm Geoff.

    Default

    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.

  5. #5
    Join Date: Mar 2017

    Location: London N2

    Posts: 678
    I'm Edward.

    Default

    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?
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  6. #6
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 34,455
    I'm Geoff.

    Default

    Change the caps first and see how they sound then.

  7. #7
    Join Date: Mar 2017

    Location: London N2

    Posts: 678
    I'm Edward.

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    Quote Originally Posted by walpurgis View Post
    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?
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  8. #8
    Join Date: Mar 2016

    Location: Barnet, london UK

    Posts: 745
    I'm Adam.

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    Quote Originally Posted by Edwardlon View Post
    I'll need to summon up the courage to desolder things
    Edward, don't hold the hot end!
    "lack of passion is fatal"
    Garrard 401 / SME 3012 J7 Rewired / audio-technica ATP-12T - phonomac modified / Ortofon Vintage SPU GE /Shure M3D /DV XX2Mk2 / The Cartridge Man Music Master with isolator / Vintage GE VRII Mono / WAD 300b Power modded, TJ Mesh Plate Valves / David Coe AD Audio 'Satchmo' Pre & Phono / Hashimoto HM-7 SUT / Tannoy 12" MGs in RFC Custom Rutland Cabinets with RFC Custom Crossovers / Speaker Cables: Duelund DCA16GA Tinned Copper / Rpi3 & Digi + pro / SW1X Audio Design USB-SPdif / SW1X Audio Design DAC 1 Signature / Interconnects: Duelund DCA20GA home brew /SW1X Audio SPDIF AERO 6 / AD Audio Silver USB / Synology NAS Drive / Roon / Tidal HiFi / Mains Power Conditioner

  9. #9
    Join Date: Mar 2017

    Location: London N2

    Posts: 678
    I'm Edward.

    Default

    Quote Originally Posted by WESTLOWER View Post
    Edward, don't hold the hot end!
    Well I'll try not but I'm pretty clumsy so will stock up with lots of plasters.

    Or next time you are around you can guide me.

    Sent via Tapatalk
    Source: Win10 server, Win10 Mini-ITX Renderer running JRiver & Tidal/Roon
    DAC / Preamp: Perreaux DP32, Secondary DAC:
    Chevron Paradox
    Amp: Radford Revival STA25, TubeHunter Class D IRS2092
    Speakers:, Tannoy Eatons, Kudos Cardea C2, BatPure Supertweeters (and others)
    Power Conditioner: ISOtek Qube 1k
    Currently resting: Radford Revival Prototype preamp, Paul Baldwin 405C amp, PMC LB1 Signature

  10. #10
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 34,455
    I'm Geoff.

    Default

    Quote Originally Posted by Edwardlon View Post
    Any recommendation on caps to use?
    I used alcaps from this seller: https://www.ebay.co.uk/itm/Bipolar-C...BbyjrfSbH0-1Tg

    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.

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