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Old 29th March 2007, 10:46 AM   #1
appel is offline appel  Denmark
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Default Crossover instead of Kube on KEF?

Hi.
A crossover instead of the Kube? Hmm.
I have a pair of KEF 107 - driven by the danish LA Audio mono tube amps. I am not quite happy with the Kube though, muds up the perspective and sound, so I mostly play without it. If you want superb clarity, pure 3d sound (but 'lack' of deep mid/bass) leave the Kube! A sofisticated bit of electronics, but it is filled with lots of ICs etc. A pitty as the 107s are very capable in the lower area.
I know very well the KEF 107 should not run without the Kube but in the long run I prefer the extreme fine sound and perspective from the pure 107s.

Has anyone tried to build or rebuild a crossover to replace the Kube? There has been a lot of discussions about these Kubes through the years. Maybe AndrewJ, former ingeneer of the Kubes, can answer whether it is adviceable or not. Lennart Andersen, former owner and guru from LA Audio, intend to build a pair of crossovers - or change the existing ones, but before that any info here would be appreciated.

By the way - look up Lennart Andersens new site: www.triodes.dk, with some exciting, new tube amps - named 'Audio Design by Lennart Andersen'. Still the champ...
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Old 30th August 2007, 01:55 PM   #2
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Default KEF 107s without Kube

I also run my 107s without Kube.
They are not needed in my system, nor can they be used.
I'm running balanced between pre/pro and amp, so.....no Kube.
Furthermore I and others have found that Kube is not needed in these days of subs. Prior to subs, yes, but not now.
I set my pre/pro to assign crossover at 100 Hz.
Sounds good.
HTH
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Old 30th August 2007, 10:09 PM   #3
forr is offline forr  France
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Hi,
I am looking for the Kube schematics.
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Old 30th August 2007, 10:18 PM   #4
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Default Schematics for Kube

You might try KEF-AMERICA:

KEF America
10 Timber Lane,
Marlboro, NJ 07746
Telephone: (732) 683 2356
Fax: (732) 683 2358
HTH
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Old 29th November 2007, 06:31 AM   #5
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Default Re: Crossover instead of Kube on KEF?

I just own a pair of KEF 107/2 NOS without KUBE ,and i replace with my B&W 801F, I only hear good sound stage thats all , totaly no bass at all , my system are Audible illusion m3 to Classe audio DR 10 to KEF 107 , Plaese help
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Old 29th November 2007, 12:17 PM   #6
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Default re: bass for KEFs

concerto_r wrote about missing bass.
One issue to address is the surrounds. While NOS you need to check the surrounds on the woofers. My 107s were bought used and needed new surrounds. While 207s are more current I still would check.

Though my system includes a subwoofer I sometimes don't use it. With my pre/pro crossover management set to 100 Hz I get really great bass, HTH
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Old 29th November 2007, 02:15 PM   #7
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Default Re: re: bass for KEFs

I just open up bottom cover with two big sponge , i only saw the bottom woofer , very new , look like there have two surround , outter & inner one , no problem at all , and i try to put up with my DENON A1se as pre with tone control ,( BASS + 12 ) sound look Ok , got bass , but with tube pre , only mid & hi with sound stage , huuuh heart pian , look like need advise from all of you , please help , which power amp are match with this speaker ? like Classe Audio go very well with B&W 801 , Audiolab are good with Celestion , even the 600si , what about KEF 107/2 ?
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Old 29th November 2007, 08:12 PM   #8
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Default Lack of bass on KEFs

Assuming the other surrounds are OK and they probably are, be sure (if this is a 207/2) that you are feeding everything. My 107s only have one set of connections. If yours have two sets make sure both are fed form amp. Another thing to check is whether the woofer feeds are connected to crossover.
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Old 26th February 2009, 02:23 AM   #9
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Has anyone tried to build or rebuild a crossover to replace the Kube? There has been a lot of discussions about these Kubes through the years. Maybe AndrewJ, former ingeneer of the Kubes, can answer whether it is adviceable or not.

This is my first post on diyaudio. I have been tinkering with hi-fi for years, but I confess, I am no expert. I am here to seek help from the more experienced and knowledgable on this forum.

I'm posting in this thread, as I am looking at any possible changes to the 107 crossover, to compensate for removing the Kube out of my system. You have to wonder if Kef missed a trick with these speakers by using op-amps ( NE5552 ) ala Kef Kube to perform EQ . I realise it's an important aspect of a loudspeakers interaction in the room, but the Kube in my view is a sonic disaster.
I went to the trouble of bypassing all except one I/V op-amp in my Sony SCD-1 ( please have a look at this site, this guy talks sense http://www.lampizator.eu/ ) only to have to plug into the Kef Kube with average op-amps and a "Made in China" cheap style AC supply to ensure the correct in-room response.

I am tracing through the crossover in the 107 to see if any compensations have been made. I half expected to see that the LF section would have some attenuation via L-pad resistors, but it does not look like this is the case. Perhaps the MF unit is attenuated less than it otherwise would be ( 96db sensitivity ) ? I've not got that far yet, I've only looked at the LF section so far.
I have attached the 107 Low Frequency Crossover circuit diagram.
To me, it's an odd looking circuit for a LF crossover ( to what I've seen before ). On first inspection it appears that 2 notch filters are being used, C4/L1/R2 for 60Hz ( mains ripple perhaps ), and C5/L2/R2 for 150Hz.
Any assisatance on this would be very much appreciated.
Also, Is R1/C3/R2 for impedance stabilisation ( Zobel ) ?
I hope this saves time for others, I asked Kef for a circuit diagram, but nothing so far. If anyone has a proper circuit diagram, that would be very welcome too. I will trace the MF/HF unit next, but does anyone have a schematic for this ?


Thanks
Attached Images
File Type: jpg 107-lf-top.jpg (96.3 KB, 591 views)
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Old 26th February 2009, 02:58 AM   #10
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Default Kube vs. Sub

This doesn't answer your question, but the subwoofer seems to do a lot for the spectrum. One wonders whether, if subs existed when 107s were first produced, the KUBE might not have been needed.

Of course I'm speaking to a HT environment. I still plan to try my KUBE(s) (two of them) in a 4-channel array without sub and compare.
Since my last post I lowered the crossover point in my pre/pro to 60 Hz.
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