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My new replacement drivers.

 
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Wed Nov 01, 2006 8:42 pm    Post subject: My new replacement drivers. Reply with quote

Hi all,

I thought I would share my good news.

Well today, after calling and and waiting and having setbacks since Feb 10th earlier this year with Kef Audio, my four replacement Kef R1215X bass drivers arrived.

I had initially been led to believe I would get them for the price quoted in Feb, but this didn't happen. I got billed 305 for the four of them, roughly 100 more than expected.

There was an initial problem with the first replacements last year not being to spec, I believe it was regarding the conical depression on the magnet assembly ? Well these are just supplied with longer bolts to rectify this.
I guess the actual driver specification will be exactly the same. They look identical But I do not know where these spares are manufactured.

It was quite good timing, I had been about to take a chance and buy four replacement drivers from the states, which were old and second hand from a pair of tatty cabinets, but decided against this.
Then I was going to place a bid of 1200 on a walnut pair of early models with boxes on ebay, but the seller "geoffatacoustica" with a feedback of 98, expected payment by credit card over the phone the day after the listing ended, but I would have needed a week to transfer money, his loss as they only fetched 870.

Well I now have "new" midrange units (purchased in Feb), these 1057 replacements were manufactured by Harbeth to original spec.
And I now have four "new" R1215X bass drivers, from which manufacturer I know not, but am confident there are up to spec.

I replaced the crossovers with NOS in the mid/late 90's around 97/98 I think ? so these are hopefully still in good order.

I expect these replacements are better than buying a decent pair of Kef 107 second hand with an unspecified driver lifespan, at least with all new drivers I will have around another 15yrs of enjoyement from my own pair.

All I need now is,
Bass driver/force cancelling rod fitting instructions to ensure I know for sure how much decoupling is needed from the cabinet etc (as the bass drivers should not be fixed rigidly to the cabs) for peice of mind.
A new pair of treble units either actual new T33 replacements or retro-fitting some better unit, ribbon or otherwise.
And the most important item I am after, a professional K-UBE , full size with XLR in and out.

I am thinking of giving the main cabs a gentle wire wool and wax workout, and polishing the head assemblies, and maybe fitting WBT terminals to the heads and bodies before using these 107's again.

Very Happy

Steve
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centaurus
Senior Contributor 100+


Joined: 21 Apr 2006
Posts: 125
Location: Okland, CA

PostPosted: Thu Nov 02, 2006 6:46 pm    Post subject: Reply with quote

wow, you are spending some serious cash on your 107's!

what was wrong with the original drivers?

Robby
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Thu Nov 02, 2006 8:31 pm    Post subject: Reply with quote

Hi Robby,

One of the speakers has some distortion in the bass, I think one of the drivers has been damaged (due to a liitle too much low frequency and power).

The mids are fine, I just wanted to refurbish the speakers with new drivers throughout, as they are around 15 years old or so.

As for the treble units, these suffer with age, though I have a couple of old stock tweeters "new" or re-built as new drivers would be better, the treble was one of the weak points of the 107 so upgrading these to ribbons or similar may be a good step.

I am quite fond of the Kef R107's sound and performance wise, but spare drivers are rare, and not many Kef R107 sound at all as they should due to age and lack of service etc, main problems are dried up ferrofluid , and weak surrounds and colapsed gaskets on the bass drivers. So best to ensure they are performing to specification and have spare drivers for continued use I think.

Most speaker drivers suffer and tire with age, some companies like ATC I believe will sudgest replacing certain drivers after certain amounts of time and use, this I myself think is good practice.
The foam on Kef coupled cavity drivers can rot, it has a life expectancy of around 15yrs in average conditions, so even though the bass drivers may look mint and have superb condition surrounds, the surrounds may not be as compliant or offer the same support as when new.

There isnt much on the web about servicing or repairing Kef R107, not to mention any sort of mods or upgrades, this is a shame as the Kef R107 is to me one of the best speakers they designed, and still quite capable of holding its head up with a lot of todays speakers.

Regards,
Steve.
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centaurus
Senior Contributor 100+


Joined: 21 Apr 2006
Posts: 125
Location: Okland, CA

PostPosted: Thu Nov 02, 2006 8:45 pm    Post subject: Reply with quote

interesting, i would think that drivers, as long as not abused should last forever (sans surrounds of course). only the tweeter used ferro-fluid, right? not the mids and woofers?

how does the foam "doughnut" harm sound quality if it disintegrates? it looks more like a gasket to keep crap from falling into the voice coil. nothing more.

the B110 is a very special driver. i don't think i'd want something else in their just because the B110 is "old." if that were the case, there would be no market at all for vintage speakers.

i'm with you on the tweeter though. the ferro-fluid does seem to screw up the tweeter. and from my understanding, the T33 was never that great to begin with,

see ya,
Robby
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Thu Nov 02, 2006 10:19 pm    Post subject: Reply with quote

Hi Robby,

The bass drivers in the 107 have foam surrounds and centre pieces, and if the centre turns to powder then it will get into the voice coil.
The bass drivers in the 107 get quite a lot of abuse what with heavy cone excursion and EQ from the Kube etc, not to mention atmospheric conditions/humiditycentral heating etc, paper cones, spiders foam surrounds and voice coils dont last forever and all the above can affect their measurement and performance over the years.

With age most driver adhesives suffer, even a driver hitting an end stop can go on for a bit before the damage caused by the driver bottoming out makes itself known, the heat generated at the voice coil can over the years weaken the coil itself I believe ?

There is a good market for used vintage speakers, but mainly because ebayers have not got a clue and many prices are put up by online reviewers, many have the opinion that any old un is a good un, but most do not realise there were specifications and measurements which change in abused and well used old speakers, so just because one sees a mint pair of LS3/5a go for 1000 they think their models are worth the same, up to the point where some bidders lose sense of any value and an old pair of LS3/5a go for $3500 canadian dollars.
The adhesives and materials in crossovers, drivers and cabinets and dampening do not hold their original properties indefinately. I have foam from old MK1 Kef 105's which seem damp and smelly, and slightly fragile, a pair of 105.4 bass cabs which have a couple of loose joints, B110 1057 8ohm mids with cracks in the rubber surround etc etc.
Most old Tannoys need serviced, and getting the proper matched drivers in old Rogers and Spendor is nigh impossible, with many a seller putting any old T27 or B110 or Celestion driver in there.

My own B110 replacement is an actual B110 replacement made by Harbeth to the same standard and specification as the speakers original driver, I would guess this will be as good as, if not better, than the original. So its not a case of putting something else in there. After 15 years of various types of abuse at the ends of all sorts of amplifiers and music, are the old 1057 mids going to be as accurate as new 1057 mids ?

One could take a pair of something like Linn Kans which have been on the end of a Krell amp and playing heavy metal at high volume for the last 15 years, and compair a pair of Linn kans which have been playing choral music with a 30w Naim amp for the last 15 years, Would they sound the same ?
An old speaker may not show any problems with a gentle amp with little current and output, but something may give at the end of something with huge power and current reserve and dynamic capability.

My own experience has shown that most old speakers do not sound as they did when new, I have compaired mint and tatty versions of a few speakers and sadly not all are looked after or have aged gracefully.
My Rogers Studio 1 speakers were mint boxed, well looked after and sound superb, I have heard a few well used old pairs which sound nowhere near as good.

One of the biggest differences is in bass and treble performance, and even the difference a new old stock driver can make over an old stock used driver can be quite distinct.

Regards,
Steve.
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