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KEF 105 question
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jls17
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PostPosted: Wed Mar 20, 2013 9:25 pm    Post subject: KEF 105 question Reply with quote

I'm new to all this but have just got hold of a pair of vintage KEF 105's which I haven't been able to listen to yet. I'm still looking for an amplifier which will do them justice. I had been thinking of a Quad 405/44 combination but have got the impression that they would benefit from having more current than the 405 can deliver. I'm now thinking along the lines of a Quad 606 Mk2 if I can find one but am feeling a bit confused after lots of conflicting information, some of it from people who may not know the characteristics of these speakers very well. I would really appreciate some advice from someone who knows and loves these speakers and I thought this forum looked like a good place to find such a person! Also a lot of people on here seem to have the expertise to carry out their own repairs/upgrades but I certainly won't be attempting that and was wondering if anyone has any advice on where to look if I do need to get the speakers checked over. Thanks
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Jay_Plesset
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PostPosted: Thu Mar 21, 2013 3:44 am    Post subject: More power is better Reply with quote

I was a dealer at the time the 105 was introduced, and remember bridging a pair of Carver amps for a test. Was wonderful! They never sounded "loud", just got big....
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Thierry
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PostPosted: Thu Mar 21, 2013 9:17 am    Post subject: Re: KEF 105 question Reply with quote

jls17 wrote:
I'm new to all this but have just got hold of a pair of vintage KEF 105's which I haven't been able to listen to yet. I'm still looking for an amplifier which will do them justice. I had been thinking of a Quad 405/44 combination but have got the impression that they would benefit from having more current than the 405 can deliver. I'm now thinking along the lines of a Quad 606 Mk2 if I can find one but am feeling a bit confused after lots of conflicting information, some of it from people who may not know the characteristics of these speakers very well. I would really appreciate some advice from someone who knows and loves these speakers and I thought this forum looked like a good place to find such a person! Also a lot of people on here seem to have the expertise to carry out their own repairs/upgrades but I certainly won't be attempting that and was wondering if anyone has any advice on where to look if I do need to get the speakers checked over. Thanks


Hi,

You have a got one of the best loudspeaker systems ever available on the market.

I have used mine with many amplifiers ranging from 40W/ch up to 250W/ch. A big reserve of power permits reproducing music peaks without stress as the 105s can take lots of watts before they distort.
One of the best combinations I have used for reasonable listening levels in a domestic environment is a Quad 44 / Quad 606 setup.
I have also used a Quad 405 and it was a perfect match too. In terms of maximum sound pressure the difference between a 405 and a 606 is non existent but the 606 has a bit more of authority in the bass.
Both amps are based on current dumping design, hence identical distortion figures and audio transparency.

Enjoy your new system and welcome to the mad house.

Thierry
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audiolabtower
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PostPosted: Thu Mar 21, 2013 11:17 am    Post subject: Reply with quote

I built a 405 when they first came out, the most noticeable upgrade is a more modern op-amp, but if you look at the Ludwig/Snook upgrades on the web you can get the performance nearer to more modern amps. It works ok with speakers that will not stress it, ie nothing less than 6 ohms without too much reactance. I would say a 606 would be better.

Personally I would prefer something like an Audiolab 8000P or similar giant killer, as more transparent than the Quad since the 105 can have stupendous imaging and an amp with "blacker" background and deeper depth brings real advantages.

If your 105s sound fine ok, if not Falcon sell a set of new caps for the crossover, the reversible electrolytics can drift after 35 years spoiling the balance that Kef worked so hard to achieve with closely matched and selected parts.... way beyond the effort most other speaker manufacturers made.

In good condition they are definitely one of the best speakers ever made.
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Innercity126
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PostPosted: Thu Mar 21, 2013 5:37 pm    Post subject: Reply with quote

Ditto on Thierry and Audiolabtower's comments.

I'm not sure what your conflicting information is in regards to, but I can assure you that any of the Quad's mentioned above would be excellent performers with the 105's.

I am currently using a pair of 200 WPC Emotiva mono-blocks on my 105's and they sound stunning. However, I have also driven the 105's with a 50 WPC Jolida tube integrated amp, and they sounded equally as nice, with perhaps a slight softening of the bass.

Do you suspect that there might be an issue with them? If not, then you should simply hook them up with whatever you have and give them a listen. That way you (and us) will be better advised by any concerns you may have afterwards.

In the meantime, you are in for a real treat. I consider the 105's to be among the best sounding loudspeakers I have ever owned. And this is coming from a dyed-in-the-wool Infinity Kappa 9 user of many years.

Since owning, and recently rebuilding, my 105's, I have grown to respect and appreciate just what these understated (looking) transducers can do. They have quickly become my loudspeaker of choice when it comes to detail and transparency, yet they are capable of displaying the subtlest of nuances that give music real emotion. They are indeed a very special loudspeaker.

Let us know how you get on...

William
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jls17
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PostPosted: Thu Mar 21, 2013 7:12 pm    Post subject: Reply with quote

Thanks for the replies. One of the criteria I forgot (didn't dare!) to mention was that I'm keen to have tone controls which seem to be absent on most modern amps. I know most audiophiles are horrified by the idea of tone controls or any attempts to "colour" the sound but I listen to a lot of quite variably recorded old reggae 45's from 60's /70's Jamaican studios and they can sometimes benefit from a bit of tweaking...The Quad 44 would fit the bill from this point of view and it sounds as though the 606 would be the better power amp to partner it if it has ,as you say Thierry,more authority in the bass. I don't know how the Audiolab would compare and whether it could be partnered by a pre that has tone controls? I was drawn for a while to the idea of tube amps for their allegedly "warm" and natural sound but thought that power might be an issue there for the 105's unless I shell out some serious cash....The conflicting information I was referring to was that some people have said that the 105's want a decent amount of current to control the bass drivers and that this affects the sound even at lower volumes and one or two people have said that's rubbish and that the speakers would only ever be using a fraction of the power that most amps can deliver unless I'm planning to get myself arrested for disturbing the neighbours! I'm afraid when it comes to ohms and impedances I'm completely lost so have to rely on those more clued up than myself and I'd feel more confident taking advice from you guys who know these particular speakers than from anyone else.I'm looking forward to getting to hear my 105's . I've no particular reason to expect there's anything wrong with them other than that they are almost as old as I am and some of my components could do with replacing!! I've been in touch with Falcon who were very nice and may be able to help me out when(if) they're less busy.I'll certainly see what they sound like first but if there's nothing glaringly wrong I'm not sure I would be able to tell if they are performing at their best or whether they would benefit from the crossovers etc. being checked out.
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audiolabtower
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PostPosted: Thu Mar 21, 2013 9:16 pm    Post subject: Reply with quote

The 105 is an easy load compared to most of today's speakers with a minimum of 6 ohms, not very reactive. Therefore they do not need a lot of current, voltage drive is more important, but a better amp will grip that big 12 in unit in the bass.

For what it is worth on my torture tracks at very high (detached house) volumes I rarely light the 60W peak led. Quality of the amp, and damping factor gripping the bass is probably more important than watts, but a powerful amp can give that "rolls royce" "no hint of strain" feeling.

If they sound right it is instantly recognisable. from bass to high treble everything is even, no frequency range dim or forward. Cellos as immediate as violins, singers etched in the middle of the speakers as if in the room, beautiful smooth treble even when loud.

Many years ago I bypassed the fuses on mine, if still using them clean all contacts with metal polish and make sure they sit tight.
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rx7rotary
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PostPosted: Thu Mar 21, 2013 10:55 pm    Post subject: Reply with quote

audiolabtower wrote:
The 105 is an easy load compared to most of today's speakers with a minimum of 6 ohms, not very reactive. Therefore they do not need a lot of current, voltage drive is more important, but a better amp will grip that big 12 in unit in the bass.

For what it is worth on my torture tracks at very high (detached house) volumes I rarely light the 60W peak led. Quality of the amp, and damping factor gripping the bass is probably more important than watts, but a powerful amp can give that "rolls royce" "no hint of strain" feeling.

If they sound right it is instantly recognisable. from bass to high treble everything is even, no frequency range dim or forward. Cellos as immediate as violins, singers etched in the middle of the speakers as if in the room, beautiful smooth treble even when loud.

Many years ago I bypassed the fuses on mine, if still using them clean all contacts with metal polish and make sure they sit tight.


Sorry to bump the thread like this. But my question is related. In regards to bypassing the fuses, what are the advantages? Any noticable difference etc?

m
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audiolabtower
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PostPosted: Thu Mar 21, 2013 11:51 pm    Post subject: Reply with quote

I haven't had the fuses for 30 years probably so cannot remember. However I remember magazine letters from owners describing worthwhile and very noticeable differences bypassing or cleaning after they had become oxidised. Stands to reason since would have the same effect as a high resistance and possibly rectifying speaker connection or cable?

Besides fuses were generally replaced by polyswitches industry wide, the 105 drivers are pretty robust, and after all Kef replaced them with a more expensive S-Stop circuit in later revisions.
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rx7rotary
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PostPosted: Fri Mar 22, 2013 1:55 am    Post subject: Reply with quote

audiolabtower wrote:
I haven't had the fuses for 30 years probably so cannot remember. However I remember magazine letters from owners describing worthwhile and very noticeable differences bypassing or cleaning after they had become oxidised. Stands to reason since would have the same effect as a high resistance and possibly rectifying speaker connection or cable?

Besides fuses were generally replaced by polyswitches industry wide, the 105 drivers are pretty robust, and after all Kef replaced them with a more expensive S-Stop circuit in later revisions.


So bypassing with some solid piece of wire would be the way to go I assume?
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audiolabtower
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PostPosted: Fri Mar 22, 2013 2:40 pm    Post subject: Reply with quote

Yes, if possible soldered. Besides as SpeakerGuru has explained in another thread the original fuses were very specifically selected for the thermal characteristics of the coils they were supposed to protect. If they are old or blown you cannot anyway replace them with accurate equivalents so would probably over-rate which kind of defeats the purpose of having them.
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iso
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PostPosted: Sun Mar 24, 2013 1:10 pm    Post subject: fuse Reply with quote

audiolabtower wrote:

Many years ago I bypassed the fuses on mine, if still using them clean all contacts with metal polish and make sure they sit tight.


I am currently restoring Harman Kardon Citation 12 power amp. It does have protection against short circuit and overheating. But actually nothing to protect speakers when output stage fails and considerable DC exists on the output.

I have considerd fuse to be the easiest solution, but I have found fuseholders to be quite unreliable very often. Therefore I have tought that soldering fuse in the circuit might be one solution to be considered. Failures that cause damage to the speakers are not too common. It might be possible that you do have to solder the fuse only once. If such failure exists, the fuse will protect speakers.

Amplifier otput is best place for DC protection. But same idea can be used when protecting tweeters or mids for overload.

Best Regards

Kimmo
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audiolabtower
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PostPosted: Sun Mar 24, 2013 2:38 pm    Post subject: Reply with quote

Or you could add something like the triac circuit Peter Walker added to the speaker outputs of the Quad 405, only 5 components and no power required?

I remember him telling me once (if my memory is correct!) the amp was protected for bias diodes going short, but they found some that failed open circuit. The purpose of the added speaker circuit was to short the output and blow the supply fuses much quicker than they would otherwise blow, thus removing power instantly and protecting the speaker 100%.
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iso
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PostPosted: Sun Mar 24, 2013 7:25 pm    Post subject: Quad protection Reply with quote

Quads approach for protection is pretty good. Especially on later units like 240, where active power supply groundding needs only one power rail fuse. Only drawback is that you have place short circuit protection limit somewhere. If this figure is exeeded even for short time, output stage will clip.

I am now experiencing same kind of behaviour with Citation 12. This unit has been made in 1971. One pair of TO3 output devices will most likely handle less than 10A and similar short circuit protection is used... without triac. LF is smooth and pretty accurate, but when massive LF transients exists, it lacks authority and most likely clips due protection or non leaked but aged main reservoirs.

Problem with this vintage gear is that too many improvements will ruin their character. HK used only mains fuses for the transformers, so this better protection will need at least 4 additional fuses and accosiated circuity for this improved protection.

Best Regards

Kimmo
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proffski
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PostPosted: Mon Mar 25, 2013 4:28 pm    Post subject: Re: Quad protection Reply with quote

I'm lost guys, anybody seen the KEF 105 forum?
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