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Bi amping Kef 107s

 
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vistisen
Intermediate Contributor 50+


Joined: 01 Sep 2006
Posts: 57
Location: Denmark

PostPosted: Wed Sep 06, 2006 8:07 pm    Post subject: Bi amping Kef 107s Reply with quote

I have just purchased a pair of Kef 107's, the original model without bi wiring. These speaker are to replace my beloved Kef 104/2 which are the bi-wire versions. These speakers have given me excellent service for the last few years, I have bi-amped them using a pair of ARCAM amps. By putting the a Kef KUBE 200 inbetween the pre amp and the power amp running the bass units, I have been able to enjoy the bass extension the KUBE gives without the slight vailing of the tweeters and midrange.

What I want to know is, is there a good reason I can not do the same with the KEF107s, There is a XLR jack between the bass and head units. Can I not fit an XLR jack to the cable from one power amp (bipassing the KUBE) and run the bass units of the normal speaker binding posts via the KUBE on the other power amp. As I understand it there is a crossover in the head unit as well as in the bass unit
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Sep 06, 2006 8:28 pm    Post subject: Reply with quote

Quote:
is there a good reason I can not do the same with the KEF107s


The crossover PCB is behind the input terminals.

The head contains a circuit to light up the LED in the listening window.
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Parts
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Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Thu Sep 07, 2006 8:03 pm    Post subject: Reply with quote

The crossover is in the upper panel of the 107, with a further crossover in the head single wired to the main body with an XLR connection.

There is no led light ala 105.4 within the 107.

I had an early pair of Kef 107 crossovers which someone had cut up to facilitate tri-wiring, and have heard the main crossover needs modded for bi-wire ?

You may also be aware that the 107 KUBE has adjustments made for the treble and midrange, and if you do not use the KUBE the midrange and treble performance is affected, and the bass rolls of earlier.
So if biwiring it is advisable to have the KUBE running to the mid treble section as well as the bass section.

I think treble output can be comprimised if the tweeters are original, as the ferrofluid may dry up ? someone may confirm this ?
My own experience was that replacing tweeters when Kef had replacements was worthwhile, as my old ones sounded quite dull at one
point.

I should also point out that I do not think Bi-wiring the 107 had any great benifit, it was always better with a single high quality amp and single run of high quality cable.
Better to have one good amp than two half as good, and the same goes for cable. ( I think)
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vistisen
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Joined: 01 Sep 2006
Posts: 57
Location: Denmark

PostPosted: Fri Sep 08, 2006 6:51 pm    Post subject: Reply with quote

Thanks Parts.

Your post was most informative, and backs up my first impressions. I can see you have also answered my other post about missing upperbass. As this was experienced using my KUBE 200 in just between the pre amp and the bass amp. It would seem to back up what you say about the KUBE extending up into the midrange driver as well. I have decided to drop bi amping and get better cables instead. One day it will be monoblocks Laughing
I am considering sending the head units to Wilmslow audio to get better tweeters. I have talked to them on the phone and seem to know what they are talking about. They say that it would be a good idea to upgrade the crossovers at the same time. But as I live in Denmark, I would either have to remove them myself as the post to England for 100 KG of speaker is extreme. Exclamation

Do you know whether it would be best to use the KUBE that came with the 107's or a KUBE200? I have both, so I know that I could experiment. But to be honest I'm afraid that I will make myself hear differences. So I would like to hear other peoples advice.
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Parts
Senior Contributor 100+


Joined: 13 Jan 2006
Posts: 174
Location: Edinburgh

PostPosted: Fri Sep 08, 2006 8:03 pm    Post subject: Reply with quote

Hi Vistisen,

I would stick with the original 107 Kube, although I have been told it can be left out, it does adjust the treble/mid/bass balance and is supposed to contain or be part of the 107 crossover design. I have a preference in some instances for it in circuit, but I also prefer a fully balanced system.
I also think the Kube is detrimental to treble clarity and transparency.

I believe in the original Hi Fi News review they mentioned that without the Kube bass starts to roll off at 50hz ?

I am quite interested in any differences you have in your bass drivers and gasket/seals, as the frames on the original bass drivers was rather poor and the distance apart with the force canceling rod and decoupling was quite important, the old foam gasket compressed over the years, and if there was any overtightening of the drivers into the cabs the frame could deform slightly.

Have your bass drivers been replaced with quite different models and were the gaskets also replaced ? and where did you obtain the parts ? (would be great if the newer bass drivers had better power handling)

And do you know what driver Wilmslow Audio use to replace the T33 ? Did they give any sort of quote and details of the work they carry out on the heads ?

I myself used 107's , but have a blown bass driver, and would like to replace all four, and fit new seals and fittings.
I also feel the T33 lets the performance down a bit, I would love to find a better treble unit I could just drop into the heads as a replacement.
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vistisen
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Joined: 01 Sep 2006
Posts: 57
Location: Denmark

PostPosted: Sun Sep 10, 2006 9:18 am    Post subject: Reply with quote

Parts:

I do not know much about how the drivers were replaced as this was done by the previous owner. But I was told that the new drivers have a rubber mount rather that a foam mount. He did say that it took a whole day to do it! When I pluck up my courage, I'll take the top off one of the boxes and take a couple of photos that I can publish here.
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