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KEF B139 SP1044 fs 43Hz?
KEF B139 SP1044 fs 43Hz?
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Old 1st October 2013, 09:26 AM   #1
markus76 is offline markus76  Germany
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Default KEF B139 SP1044 fs 43Hz?

Hi guys,

Just measured two KEF B139 SP1044 I had found in the basement:

KEF B139 SP1044 fs 43Hz?-kef-b139-sp1044-png

Looks like fs is 43Hz. That's pretty far from the specified 25Hz. Is it time to let them go?
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Old 1st October 2013, 12:32 PM   #2
Smiley 09 is offline Smiley 09  Europe
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Quote:
Originally Posted by markus76 View Post
Hi guys,

Just measured two KEF B139 SP1044 I had found in the basement: Looks like fs is 43Hz. That's pretty far from the specified 25Hz. Is it time to let them go?
Hello markus76,

A friend of mine have LINN ISOBARIC PMS speakers and he noticed after a long time of no use his main speakers due to some higher reasons (he move to a new finished house) - the speakers were playing a very thin sound overall and the worst of it, the bass was without any kind of extension - thin and boring.
He think to sell all the old stuff and go for something new. He invite me to come to his new place and while we listening the music (Linn LP12 as a source) I was really disappointing of his systems weak sound.
Than I remember my old friends words that rubber in a phono cartridge which keep the cantilever in its place become to loose its elastic properties. So I use the very thin wooden toothpick slightly round its nib put some thin film of a glycerine's oil on it and do some light, very precise rubber massage all around cantilever - The repeat listening test was a shock for bot of us Sound was become very enjoyable & listeneable.
From this experience learned I suggest him to use a Glycerin oil (a solution for external treatment of a car tires) to apply it on all speakers rubber surrounds (outer & inner) and at the theirs spiders too. He did it and then run all mid ranges and woofers for a a week with running a slow sweep from 10Hz to 250Hz 5 mm PP in a basement - (PC generated and ser + parallel connected driven with one NAP135) (Speakers were removed from encl. and were run in a free air). After the speakers were treated this way he put all of the speakers back to the encl. After the first play of some music he was so unbelievable surprised of the nice & pleasant sound that he come to pick me up after my job and insist I have to hear the beauty of the sound he have now.
Yes we spend all the afternoon and almost all night absorbing LP after LP and we were really enjoy that happening . . .

He is happy now and he will keep the old fashioned audio gear at his new home until last.

Now I wonder to suggest to You to try the same with Yours KEFs and I'm sure You won't be disappointed
They will return You the joy they were designed to.

With my best regards,
Andreas
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Old 1st October 2013, 12:55 PM   #3
markus76 is offline markus76  Germany
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^
Thanks Andreas, I'll try that.
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Old 1st October 2013, 02:20 PM   #4
markus76 is offline markus76  Germany
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After applying glycerine to the upper part of one of the rubber surrounds, fs dropped already by 3Hz. Only 15Hz to go

KEF B139 SP1044 fs 43Hz?-glycerine-top-png
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Old 1st October 2013, 06:20 PM   #5
Smiley 09 is offline Smiley 09  Europe
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Quote:
Originally Posted by markus76 View Post
After applying glycerine to the upper part of one of the rubber surrounds, fs dropped already by 3Hz. Only 15Hz to go
Dear Markus,

Please do as follow:

Put very small amount of the Gl. solution on Yours 1.st an 2.nd finger then go with both of them over ext. Alu spkr frame one finger at the outer top half of rubber surround and the 2.nd. finger to inner lover half part of the surround now touch with both fingers the rubber surround and lightly tightly circle fingers together to apply the ''Massage'' to the both sides of the rubber surround at once - With left hand secure the membrane to not move excessively - and please be careful to not apply the solution to the Styrofoam couse it might evaporate latter .... Go this way all around to come to the start position. This is necessary to assure the solution to go as deeply as possible in to the rubber surround after this is done please use some 6mm wide paint brush and apply very, very thin coating of the same solution to the spider - only to the waves all around on it. After this is finished take some amp and a notebook comp. to the basement and apply previously mentioned sweep to the drivers and adj volume on PC mixer sound card to make some 5mm PP membranes movements for some days and You'll be surprised after this =>

With my best regards,
Andreas
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Old 1st October 2013, 06:46 PM   #6
Boden is offline Boden  Netherlands
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Hi Markus,

This what I wrote in a B 139 thread some years ago. Your experience seems to match mine.

Welcome to the wonderful world of KEF in de late seventies/early eighties. QC either absent or on sick leave.

I owned a number of B 139 's with Fs around 36 and 40 Hz (!) and rubbing VC's at any level over 2-3 Volts driving voltage. Cones were not flatly glued in place..

They worked reasonably well in my Chris Rogers' Practical Hifi ' PRO 9 TL, but in terms of build quality, power handling plus specs they were definitely not something to write home about.

Hope you have more luck with your samples.



Regards,

Eelco
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Old 1st October 2013, 07:19 PM   #7
markus76 is offline markus76  Germany
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Applied glycerine to the other side of the rubber surround too. Now we're at 34Hz after 5h (yellow curve):

KEF B139 SP1044 fs 43Hz?-glycerine-top-bottom-png
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Old 1st October 2013, 10:15 PM   #8
badman is offline badman  United States
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Now you're getting somewhere!

You can also run some tones through 'em to loosen them up.
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Old 1st October 2013, 10:16 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Boden View Post
QC either absent or on sick leave.
Eelco
Hi,

The KEF Constructor series of drivers were simply the rejects.

rgds, sreten.
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Old 2nd October 2013, 08:56 AM   #10
markus76 is offline markus76  Germany
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Just cleaned the rubber surround of the other driver with a damp cloth. Just water, no glycerine. The effect on fs is nearly the same. So I guess it's not the glycerine causing the lower fs.
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