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Bi amping Kefkits with 2x Stereo 20

foxwelljsly

foxwelljsly

Me too, I ate one sour too.
Anyone here Bi-amped kefkits or similar with 2 Leak stereo 20's?

Is it worth it? If so what crossover configuration would be best? I have never used active amplification and am utterly clueless about this and ask as I have been offered a second stereo 20 at a knockdown price.

I assume that bridging, if it is possible (which I sincerely doubt), only offers more volume and no improvement in fidelity.

any advice very gratefully received

Simon
 
if your kefkits are two way you could go active.

bridging increases output impedance and although it increases power it reduces drive.
 
Why not use Martin Colloms’s method of putting one Stereo 20 on the left channel, and the other amp on the right channel? His method is to hook up the left channel of the LEFT hand amp to the tweeter, and the right channel of the LEFT hand amp to the mid/bass driver.

The same arrangement is used for the RIGHT hand amp. You thus are bi- amped using two amps. I assume that you can split the existing crossover accordingly if you have not already done so.

Eguth
 
They're B139/B110/T27 3 way kits. I was thinking of running the B110/T27 with a two way crossover off one amp and the B139's off the other amp. Or would I have to get a third amp, so I have one channel for each driver?

cheers
 
The beauty of Colloms upgrades, which I have to restrain myself to not describe in too glowing terms, will be lost if you use your two excellent Leak Stereo 20s in the way you propose. I would say, myself, although I assumed (wrongly) that it was a 2-way you were using, that you would be better off to use the two Leak amps for mid and tweeter, one amp per channel in Colloms configuration, and buy yourself an additional stereo amp for the B139.

I have a tri- amped system myself, and have used Collums upgrades for years with superb results, adding an active crossover (mono) for the mono subwoofer.

You have a pm!

Eguth
 
Interesting. So, stereo 20's to actively power the T27's and B110's and a solid state power or some such for the B139's in a subwoofer? I have thought something similar, but always assumed the Leak to not have enough oomph for a subwoofer.

I thought I might be able to use the existing two amps with the existing cabs (which have only just been built) with a few extra electrical compnent doo-dads and speaker cable. I might just get an extra stero 20 and straight tri-amp and see how it all sounds.
 
The Colloms upgrades do not use active crossovers. They use your existing crossovers. Depending on how far down the Colloms route you want to go you can just leave them in situ, splitting them and adding extra speaker terminals on the back of the cabinet, or (better) remove them, place them in separate boxes close to the amplifier output terminals or, (even better) add another amp, one stereo amp per channel. While you are at it you can upgrade the internal components of the crossover and/or optimise the cable type. I have gone the whole hog, and it is the finest improvement I have ever made, equivalent to spending a great deal of money: AND it is very inexpensive to do!

The Colloms improvements I was suggesting did not envisage that you get a subwoofer, but if you do, you could power it with an active xover.

In your case you could split the crossover, and use one channel of one LEAK to drive the T27 and B100, and the other channel to drive the B139; (same for the other speaker and your second LEAK). A subwoofer could be added later as an active self contained unit with its own adjustable crossover point etc..

Alternatively, you could drive the T27 with one channel, and the B100 with the other channel, and purchase, say, a powerful transistor amp (as I have done) and drive the B139 via an active crossover (same arrangement for second speaker).
 
Oh yes, I should have added that going ‘straight tri-amped’ will NOT give you the superb benefits to be had by following Collom’s route.
 
i would suggest that tri amped active operation should sound significantly superior to passive no matter how many amps are driving the crossovers.
 
Hi,
are the Colloms improvements documented anywhere.
cheers
dogrun.gif
 
The Kef crossovers for the B139/B110/T27 combinations are complex to iron out the uneveness of the drivers' responses. I'd split the crossover's and use a ss amp on the B139s.
I've split a Kef crossover for the CS1 LL3-alikes and they sound great.
 
For anyone wishing to get a bi or tri amped arrangement that I can vouch for [not only after my own Colloms upgrades but also another entirely different speaker I helped to modify (a B&W 1960s model, that was partially active originally)] I would suggest that you get a hold of Martin Colloms’ two articles and study these carefully.

These are:
1) BI WIRING, by M.Colloms, p.49-51 Hi Fi News, June 1986; and
2) POT POURRI, by M. Colloms, p.44 Hi Fi News, October 1986.

In my humble opinion these are the two best hi fi articles I have ever read, and following their advice and upgrade route I made possibly the most significant improvements to my system, and at very low cost, that I ever have made.

If you contact Hi Fi News they may be able to provide you with photocopies. Alternatively, your local public library should be able to obtain these for you.

There is no reason why you should not use only part of the passive crossovers as I have done and as Chrisallan suggests (with whose views I concur), and combinine passive crossovers with active crossovers so as to optimise the performance for each driver.

Eguth
 
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