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Long standing problem with Ref model 105 (1977)

 
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BobL
Intermediate Contributor 25+


Joined: 27 Jan 2004
Posts: 38
Location: West Midlands, UK

PostPosted: Wed Jul 28, 2004 9:30 am    Post subject: Long standing problem with Ref model 105 (1977) Reply with quote

Don't get me wrong, I love my R105s they still stun me nearly 30 years on.

The problem though is that some vocalists can provoke a severe breakup in the mid/hf drivers that happens at too low a volume to be just overload.

Both speakers do this and have from day 1. Years ago, Kef sent me a diagram of an active xover for the mk2 R105. I built it and found that I could go far louder and never got a trace of this breakup. So, as I thought it was not the drive units. I never got the xover to sound right though.

For years I thought that either certain frequencies or patterns caused the passive xover to create an electrical load that no amp could sustain. I still think the problem is with the xover.

What could it be?

Inductors saturating?

Inductors affecting each other magnetically?

Any thoughts anyone?

Capacitors have all been replaced recently (well worth doing) made them sound as new but did not fix the problem.

Cheers,

Bob.
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terry
Senior Contributor 200+


Joined: 22 Apr 2003
Posts: 262
Location: UK

PostPosted: Mon Aug 02, 2004 9:40 am    Post subject: Re: Long standing problem with Ref model 105 (1977) Reply with quote

BobL wrote:
Don't get me wrong, I love my R105s they still stun me nearly 30 years on.

The problem though is that some vocalists can provoke a severe breakup in the mid/hf drivers that happens at too low a volume to be just overload.

Both speakers do this and have from day 1. Years ago, Kef sent me a diagram of an active xover for the mk2 R105. I built it and found that I could go far louder and never got a trace of this breakup. So, as I thought it was not the drive units. I never got the xover to sound right though.

For years I thought that either certain frequencies or patterns caused the passive xover to create an electrical load that no amp could sustain. I still think the problem is with the xover.

What could it be?

Inductors saturating?

Inductors affecting each other magnetically?

Any thoughts anyone?

Capacitors have all been replaced recently (well worth doing) made them sound as new but did not fix the problem.

Cheers,

Bob.


Certainly seems puzzling. Could it be something quite different. Have you always used the same amp? What about connections or cabling and poor connections? Did you use the same amps when you went active?

I suspect that some of our contributors to the site from your geographical area could be interested in helping to diagnose the problem. Have you emailed any of them? What about Colin Royle?

Terry
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BobL
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Joined: 27 Jan 2004
Posts: 38
Location: West Midlands, UK

PostPosted: Mon Aug 02, 2004 3:04 pm    Post subject: Reply with quote

Over the years I've used several power amplifiers including, Linsley hood 75watt, Quad 405, Sage Audio and recently Arcam P7. The P7 using 4 channels driving the head unit and the base driver from different amps.

Speaker cables, again I've tried 6 or 7 different ones over the years.

I don't think this is a fault, I think it is a design issue but I do'nt really know what is less than excellent about the design.

Cheers,

Bob.
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qguy
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Joined: 08 May 2003
Posts: 85

PostPosted: Tue Aug 03, 2004 4:17 am    Post subject: Reply with quote

I have a similar problem with my 105/2... I disconnected the STOP circuitry and viola the problems gone...not sure if the original 105 has a similar circuitry...
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proffski
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Joined: 22 Aug 2003
Posts: 1297
Location: Tewkesbury UK

PostPosted: Sun Sep 05, 2004 6:25 pm    Post subject: Reply with quote

This is a new one on me, any problems may just be extraplated by a close look at the speakers impedance/frequency plot sweep. How does it sound with white noise, is there a discernible peak or trough?
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RSD123
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Joined: 29 Sep 2005
Posts: 8
Location: Guelph, Ontario Canada

PostPosted: Thu Sep 29, 2005 4:28 am    Post subject: Reply with quote

I have an all original pair of 105.2's and have never experienced distortion or breakup on them at ANY volume level
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adam_audio
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Joined: 07 Jul 2005
Posts: 53
Location: Land Of The Lost

PostPosted: Mon Oct 03, 2005 9:09 am    Post subject: Reply with quote

RSD123 wrote:
I have an all original pair of 105.2's and have never experienced distortion or breakup on them at ANY volume level



Neither have I, but then again my protection circuitry is removed as well.
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Mon Oct 03, 2005 11:48 am    Post subject: Reply with quote

If you want pseudo studio ear shattering levels from a Ref. 105 you give each speaker a "standard" recording studio amplifier.

An Amcron DC-300A, let the bass units have 75 Watts into 15 Ohm and back off the gain to the other channel so you're getting about 45 Watts into 15 Ohm.

I've heard this kind of set-up when Yes were recording and I had to leave because my ears hurt Crying or Very sad , but returned to listen to the playback session Cool .

Their "standard" one-take setting were, everything turned up full, just below blowing up/ frying a driver level.

That's why all early Yes recordings on vinyl are a little bass shy.

I'm afraid that a poncy five channel amplifier that is specified at 85 Watts into 4 Ohms will never be up to the job no matter how much current it purportedly produces.

The Ref. 105-2 is not really suitable for this type of experimentation, as the bass units and crossover topography are different; in addition protection circuits have replaced fuses.

If you have to disable the S-STOP circuits to get the performance levels you require from a KEF design, you should really look elsewhere, either upgrade to a KM1 or change to JBL, Klipch, Altec Lansing, ATC, etc.
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BobL
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Joined: 27 Jan 2004
Posts: 38
Location: West Midlands, UK

PostPosted: Sat Dec 31, 2005 11:14 pm    Post subject: Reply with quote

ColinR wrote:
If you want pseudo studio ear shattering levels from a Ref. 105 you give each speaker a "standard" recording studio amplifier.

I'm afraid that a poncy five channel amplifier that is specified at 85 Watts into 4 Ohms will never be up to the job no matter how much current it purportedly produces.

The Ref. 105-2 is not really suitable for this type of experimentation, as the bass units and crossover topography are different; in addition protection circuits have replaced fuses.



Your post is unclear in that I'm unsure to who's comments you are replying.

I suspect the "poncy 5 channel" bit was aimed at me. I can only suggest you actually check your facts before posting such an inacurate and insultung comment.

But just for the record - the P7 is a 7 channel amp and rated at well over 150W RMS into 8Ohms all 7 channels driven. Where you got this 85w into 4ohms nonesense I have no idea but I am certain that it is a damn site better than a feeble 75W into 15 ohms that you claim for your Amcron.

I am also well aware of the differences in r105 and r105-2 and with the exception of Darlek shape, just about everything is different.

Oh and I don't require ear shattering levels either.

And finally the "Yes" recordings are IMHO just about the worst recordings (post 1960) I have ever heard in my life.
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Sun Jan 01, 2006 4:16 pm    Post subject: Reply with quote

Quote:
Your post is unclear in that I'm unsure to who's comments you are replying.


Everybody, as the original post's replys have included the Ref 105-2.

For a on-to-one dialogue I'd use some form of email.

KEF Ref 105 do need some "serious iron" with a high damping factor to drive them and not some AV kit whose specifications are subject to marketing hype, hence a
Quote:
85 Watts into 4 Ohms
was cited.

No suggestions or inferences were made about the suitability of your P7, whose specifications I do know, or comparisons drawn against equipment from altenative vendors of "serious iron" such as Audionote, Macrotech or Krell, which may (or may not) have better synergy with the 105's.

So I find your comments
Quote:
I suspect the "poncy 5 channel" bit was aimed at me. I can only suggest you actually check your facts before posting such an inacurate and insultung comment.
somewhat misplaced.
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Fri Jan 13, 2006 10:07 pm    Post subject: Reply with quote

I would have to agree with Kef needing a decent amp, Its not all about watts though, you need a bit of current there too.

As for "taking the protection cuircuts out, should look elswhere" comment, why ?
Speaker protection was used by a lot of manufacturers back then, Gale, Nightingale etc, some people wanted it back then and it was a sellable feature which manufacturers found to be worth the deteriation in quality.
This was probably due to the ease these speakers could be damaged due to irresposible listeners with underpowered amps which usually fried the tweeters.
I am not even sure the manufacturers were bothered about quality back then as a lot of speakers were more a statement of good engineering and working practice, look at the floor coupling and wiring back then, it was not deemed a factor in sound quality.

Fitting better floor coupling and rewiring old Kefs can really show what they are capable of, sadly though you have to remember that the drive units and crossover components of this era deteriorate with age thus compromising sound.

And 15 year old ATCs sound just as bad as 15 year old KEFs or QUADS, they are tyred speakers which will not sound as they did when new, even when refurbished. All you have is your personal taste to choose from.

I also agree with the S-stop protection problems , this was a common problem as was the protection hampering the use of big muscle amps. The long white ceramic parts ? (202-6 10% etc) in the crossovers also used to wear a bit , getting loose where the wire leads out leading to audible distortion , it was benificial to dampen these underneath.
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