KEF Reference 104/2

[sub]

Hi all, transferred here from the old NZ forum.  Have recently purchased a second hand pair of these iconic speakers, and in process of refurbishment - even though they sounded pretty awesome as is.  Am replacing capacitors, replacement sets supplied by Falcon Acoustics,  on the xovers, and donuts on the bass drivers.  Following the advice of only making one improvement at a time, will wait to hear how things sound before deciding to replace the T33 tweeters.  If they need replacing will go with Morel MDT29-4s.

 

While searching for information online, and when disassembling the speakers, I have come across a couple of mysteries that perhaps knowledgeable folk here may be able to help with.  Have searched prior posts here without result.

 

1.  How old are my speakers?  In production 1984-1996, and biwire terminals introduced 1990.  My spkrs have only single wire terminals, so I assumed 1990 or prior.  However, my spkrs have metal gold coloured terminals.  Photos on line show older models had plastic terminals.  I read somewhere that gold coloured metal terminals introduced “late in the series”, but no dates given.

Have also read a review where the guy said he owned two pairs of these speakers, one set circa 1985, and the other made in 1993, and gave the serial number which is only a few digits away from mine - 28583 A&B.  I read KEF data lost when company changed hands, so KEF cannot compare serial numbers to date of manufacture.  So, were single wire versions still made post 1990, and were the Raymond Cook Signature versions the only ones biwire capable?

 

2..  When disassembling, all speaker surrounds found to be of rubber and in sound condition.  Speaker A had perished foam donuts on both woofers, whereas speaker B had intact “rubber” donuts on both.  I have never seen rubber being used for donuts, and online searches finds no reference to them, all replacement donuts on the market are made of foam.  Were rubber donuts ever on the market?  It seems strange that someone would have gone to the bother of replacing donuts on one speaker and not the other.  So, did KEF ever use rubber donuts when assembling these speakers?  If so it seems impossible to believe they would have provided a matched pair, one with foam and the other rubber donuts!

 

 

[Al.M]

You shouldn’t replace the tweeters with different ones unless the crossover circuit is adjusted properly to compensate for the different specs as the sound is likely to change. If the original tweeters are still working then no need to do anything. If no good try to get someone to repair or source seconds on the net.

 

Biwire, metal or plastic cable posts, doesn’t matter, as the inner core metal connection will be the same, just a cosmetic issue otherwise.

 

Woofer roll surround replacements by the previous owners is simply a mistake. Try to source the proper original type replacements as different ones may change the bass response and the sound.

 

Perhaps try to not go overboard and spend on such refurbishments in case you upgrade and onsell in future to keep in budget and cost recovery, if it matters to you.

[sub]

Yes, have read that advice before, and I believe it could be very relevant.

However, the Morel MDT29-4 was designed as a replacement for the T33, and from many, many posts and YouTube DIY vids i have seen, they work very well with the SP2050 crossover.  As I said, will only replace the tweeters if the new caps don’t improve things - presently  just a tad of edge in high tenor and soprano voices.  General consensus is  that after circa  39 years the cooling ferro fluid can harden and replacement is recommended.  The T33 is no longer made. 

 

My point about the metal connectors, was to provide  a clue as to manufacture date.

 

The donut replacements on spkr B could very well be a mistake, they look professionally installed,  but, out of interest,  I am really looking for info as to when and by who rubber donuts were made.  Finding these installed has created a bit of a mystery which I would like to find an answer to.

 

It is my intention to replace donuts on all 4 woofers with the same material.

 

Once repaired I will be keeping these spkrs (barring winning lotto!) for the rest of my life.

Edited May 4, 2019 by sub

[EV Cali]

Hi sub

Mine are the single terminals and serial number is 010562.

I have done most things to mine , doughnuts to all four woofers, voice coil and everything else to one one woofer, repair and respray water damaged cabinets and now the tweeters.

I have not yet done a recap of the cross over . Mainly because I am not confident that my knowledge and soldering  is up to it and they just sound so good I find it hard to justify.

But perhaps I would think differently after they were done.

I would not say the replacement tweeters made a great difference but it was an easy swap with recommended replacements.

I have fitted a skirting around the bottom to cover some of the water damage. Now it done I quite like the balanced look it gives the speakers.

 

 

One of mine. 

[Peter_F]

7 hours ago, sub said:

2..  When disassembling, all speaker surrounds found to be of rubber and in sound condition.  Speaker A had perished foam donuts on both woofers, whereas speaker B had intact “rubber” donuts on both.  I have never seen rubber being used for donuts, and online searches finds no reference to them, all replacement donuts on the market are made of foam.  Were rubber donuts ever on the market?  It seems strange that someone would have gone to the bother of replacing donuts on one speaker and not the other.  So, did KEF ever use rubber donuts when assembling these speakers?  If so it seems impossible to believe they would have provided a matched pair, one with foam and the other rubber donuts!

Should definitely be foam surrounds and donuts, not rubber.  Some people use rubber surrounds as it lasts longer than foam, however they perform better with foam, as they were designed to do.  

[Al.M]

If it’s hardened tweeter ferrofluid it should be possible to clean out and fill with fresh fluid. Cheaper than new tweeters.

 

see YouTube instruction videos.

[sub]

Yes, I’ve heard that foam surrounds may sound better/different (as opposed to donuts) which apparently always were made of foam) but production models of this spkr were produced by Kef using rubber on the woofer surrounds.  The mid surrounds were always made of rubber.

 

[sub]

4 minutes ago, Al.M said:

If it’s hardened tweeter ferrofluid it should be possible to clean out and fill with fresh fluid. Cheaper than new tweeters.

 

see YouTube instruction videos.

I’ve read that too, but also read it doesn’t always work.

Besides, that’s not why I created this post!  Just want my two questions answered, if possible.  Not here for an argument!

[Peter_F]

28 minutes ago, sub said:

Yes, I’ve heard that foam surrounds may sound better/different (as opposed to donuts) which apparently always were made of foam) but production models of this spkr were produced by Kef using rubber on the woofer surrounds.  The mid surrounds were always made of rubber.

 

All the sets I've owned were foam surrounds from factory on the LF drivers.    

[Rockman]

9 hours ago, Peter_F said:

All the sets I've owned were foam surrounds from factory on the LF drivers.    

I purchased my 104/2s  "brand new" in the 80s & they have rubber surrounds on the 8" woofers with foam donuts, ser nos. are in the 68xx.  I also know of a least 2 other sets with rubber woofer surrounds from new.

 

However, I have never seen or heard of rubber donuts & would be suspicious that they were not original.

 

I don't believe the Morel tweeter was designed to replace the Kef unit but has been found (with some modifications) to be a satisfactory replacement as have some Vifa & Audax  4 ohm models.  All of the suggested replacements require some level of modification to fit except a model offered on eBay from the US.  The tweeter branded 'Midwest Speakers', & made in China is said to be made to replace the T33 & is a drop in fit.  Price seems to be reasonable at US$45.

 

I wouldn't be in a hurry to replace the caps on the xovers as it will be quite expensive if u can't do it yourself, there is a lot.  Have a look at them & if there are no leaks or bulging/swollen examples I would leave well enough alone.  Capacitors on speaker xovers  have quite a long life because they are not subjected to heat stress as they would be in an active circuit.  Heat is an electrolytic capacitors greatest enemy.  Any recap should include an effort to substitute with film caps where possible & this would be possible with about half the number, say 8 or 9.

The 104/2s when operating correctly are an awesome speaker that seem to fly under the radar.  They were part of the KEF Reference series made on a separate assembly line by Kef's best & most experienced tech's using computer matched components.  They are considerably more accurate & natural than most of the more fancied older speakers like Gales & NS1000M, that change hands for double the money.  Just check out the relevant response graphs to see the Kef's  superiority.   Err.... perhaps it's not such a good idea for Gale fans to look at that speakers measured response.

[sub]

Thanks Rockman, very informative.

i already have the replacement capacitors - bought from Falcon Acoustics UK, and a skilled friend will be doing the de-soldering and soldering job for me tomorrow.  No charge!

You are probably right about the Morel tweeters, but I did read that claim on someone’s website.   However, will wait and see how they sound after new caps and new donuts installed before deciding about tweeters.

 

 Re the rubber donuts, I recently learnt that KEF introduced them late in the production run and rubber replacement sets were also available for a while.   

 

Re date of manufacture, the answer was staring me in the face!  All four B200 woofers have date made on them - 22 May 1990.

[Peter_F]

2 hours ago, Rockman said:

I purchased my 104/2s  "brand new" in the 80s & they have rubber surrounds on the 8" woofers with foam donuts, ser nos. are in the 68xx.  I also know of a least 2 other sets with rubber woofer surrounds from new.

 Actually I stand corrected and you're right, the surrounds in the LF drivers are rubber and only the donut surrounds are foam.  This getting old (oldtimers) and my memory of late is really p*ssing me off.  

[Rockman]

25 minutes ago, Peter_F said:

  This getting old (oldtimers) and my memory of late is really p*ssing me off.  

Actually I know the frustration well as I have now exceeded the allotted three score & ten Summers. 

[Rockman]

sub....that explains the rubber donuts on one of your pair but, which is original? I suspect the foam type is so what will u do since the rubber is no longer available?  I think I'd replace the foam & compare them side by side in mo no before replacing the rubber with foam also.

The xover issue is not to be taken lightly if the original performance is to be maintained.  It is firstly a very complex xover which is then very tightly spec'd & matched between pairs.  Although the caps are nominally 10% tolerance KEF ordered them to a much tighter spec from their supplier & then further sorted them with, I understand, a very high rejection rate.  I believe they required  +or - 0.5% tolerance components for the Reference Series.  Falcon, I understand, match the caps to +/- 2-3% side to side but not necessarily to the base spec.   If it were me I'd be measuring the originals side to side & if they are the same I'd assume they haven't drifted & unless  able to match with new caps of that exact value I wouldn't replace.

With regard to the biwire terminals, I have seen examples with lower ser.nos. than mine that have 4 binding posts.  My ser.no is 68xx, purchased new in 1985 so they were available that way long before 1990.

[sub]

Interesting Rockman!  The biwire info I read was on the KEF USA historical website, which stated biwire was introduced in 1990,  your photo proves that wrong!  

Also seems that you have to have reached 3 score and 10 + to appreciate and have knowledge of these speakers.  I’m in that bracket as well.

Re capacitors, I am encouraged to replace them with the caps from Falcon (they cost me $160NZ so I don’t want them to go to waste) by the discovery that some non standard work has previously been done on the xovers.

On spkr A xover, caps at C13&14 in the HF circuit, have had a polyswitch connected to them in parallel. 

On spkr B the same caps at 13&14 have been replaced with no name ring ins. 

Before purchasing from Falcon, I did a lot of searching for info on line, and Falcon was highly recommended by many.  They claim to use caps made by Alcap to the same specs as Kef (who no longer have genuine Kef  parts for these speakers) and then Individually tested to ensure within 2% tolerance.

i only have a multimeter whereas I am told  a properly calibrated deviation bridge is necessary for checking caps accurately.

Having the caps replaced tomorrow. At least there will be no charge, but taking some home preserves down to give to the guy!

Edited May 5, 2019 by sub

[Peter_F]

This a lovely set I completely restored a few years ago and finished them in laminate, which significantly improved the sound (and looks).  The crossovers in these are a superb, high quality build, with all the caps still in spec and no leakages.  I found the midrange a little grainy for me and had the midrange caps upgraded.  Overall these are wonderful speakers and hard to beat for the money.  

 

Edited May 5, 2019 by Peter_F

[sub]

PeterF, they look gorgeous, and must sound awesome as well!  Well done.  As per my photos in my previous post, mine are in excellent original physical condition, so will be staying as is.  Interesting that the lamination finish changes the sound.

 

Rockman, I didn’t respond to your suggestions re replacing donuts.

My nearest reliable technician is a 4.5 hour drive each way from where I live, and while I did contemplate just replacing the rotted donuts, then comparing side by side before deciding to replace the rubber donuts, that isn’t going to be practical.  Doing it myself is not an option thanks to worsening essential tremor!

 

i will be going to Axent Audio in Auckland, loudspeaker specialists who have been in business for over 30 years, and know the Kefs well.  Who knows, they may well still have rubber donuts in stock!  Love visiting there, a large sprawling display room with side demo rooms.  They sell an enormous amount of second hand gear along with selected new brands.

[sub]

Axent Audio, Auckland, Have replaced the donuts - now have foam donuts on all four woofers.  Prior to that, a friend installed the replacement capacitors on the crossover boards.

I disassembled the speakers myself to save labour costs (and the effort of    transporting two 35kg  spkrs).  Put everything back together two days ago and have had about three hours of music through them.

i know it will take several hours for the new capacitors to settle down, but  I am very impressed so far.  It seems I may not have to replace the tweeters after all, as the edginess previously experienced is gone.  The problem must have been in the xovers.  They sound superb.  Axent Audio did a perfect job.  There is a previous post on this site where Axent are recommended, and the author praised the expertise of someone named Barry who was the expert tech at Axent.  Sadly Barry died last year, but it seems his apprentice is carrying on the good work. 

[Rockman]

Pleased to hear u have sorted all the issues & have the speakers back together & working well.  I'll be surprised if they don't keep u satisfied for many years to come they really are excellent speakers.

Mine need the donuts replaced too & I bought the replacement foam type a couple of years ago just need motivate myself to get started.   Hasn't been a pressing need as they haven't  been used since I acquired a pair of Quad 988s a while back & which continue to amaze me. 

Incidentally, I spent a decade or so in Christchurch, late 60s & thru the 70s.   Had a pretty good system there with Quad amps,  B&W speakers,  Thorens & Dual t/tables.   Very fond memories of that period, of the country & the people.   

[Cameron Miller]

Not sure if still relevant but i have a pair of tweeters left over for these from when i did mine

they are not the kef but scanspeak (i think would have to check) direct replacement on the advice from one of the engineers who built the kefs. i ran them for a while and found some kef ones so replaced them but much preferred the scanspeak and never got around to installing them again and have sold my 104/2 so they are surplus now

[Straw]

On 01/07/2019 at 2:50 PM, cambam007 said:

Not sure if still relevant but i have a pair of tweeters left over for these from when i did mine

they are not the kef but scanspeak (i think would have to check) direct replacement on the advice from one of the engineers who built the kefs. i ran them for a while and found some kef ones so replaced them but much preferred the scanspeak and never got around to installing them again and have sold my 104/2 so they are surplus now

If you still have those tweeters I would be interested. I know a long shot after well over a year. I have just bought a pair but the tweeters are pushed in and definitely not original.