Crossover for KEF 103 Ref (Mid 70,s Model)

[Richard]

Hi Col, Phil,

Yes size can be deceptive too, here's a pic of those Alcaps from top down, all 50V,

7uF
25uF
40uF
80uF
4.7uF
4.7uF

the smallest value are in the biggest cans! I think they must be different construction, made better for tweeter parts of the xover rather than bass shunt perhaps.

A bit like film and foil caps are physically larger than metallised film caps of the same value,

[bencat]

Originally Posted by Richard

The caps will be electrolytic I think. Old Kefs used black ones with red resin ends labelled Elcap as Phil says but they were electrolytic afaik and could go high.

Later caps may be blue, labelled Alcap, but again both are electrolytics afaik.

I've some of the blue ones swapped out from a xover years ago and still measuring fine.

Of course you might want to change them and the wiring etc whatever they are but I'd be careful not to lose the Kef sound if that is the attraction of them.

Bear in mind any replacement inductors will likely have a different DCR so you will be changing the xover. Unless you play them at massive levels they are unlikely to saturate so I'd leave them and focus on the caps.

I am in two minds over this as there are two issues . One as mentioned is that if I like the KEF sound then changing things may just make things different but not better .

The other idea or option I am considering is to construct two complete new crossovers using Clarity Caps , decent resistors and full set of Inductors if possible the same as those in the original . Then mount them in a box and just disconnect the original and wire directly to the speaker connectors and use the outboard crossovers. I can then do any changes to resistor values (to compenstate for the different caps ) and any other things easily but if I decide either to sell the speakers or do not like what the new crossover does I can reconnect the old ones inside the speaker and back to original state .

What do you think ?

[Phil Y]

Hi bencat,
My opinion is that you need to be honest with yourself and decide if you like the speakers enough to be keeping them for a while. If yes, then it is worth having a tinker, if not then really there is no point in wasting your time and money on them. If you are truly undecided, I would just replace the internal wiring and solder it all. IMHO this will give them a lot more dynamics and detail but without changing their basic character in the way that a wholesale change of caps might.
Another thought, have you done this sort of modding before ? If not, you could just take the attitude that you will use them as a guinea pig to find what effect changing parts has, as a learning process. Then put them back to standard and sell them.

I agree with Richard that changing the inductors would be a waste of time.

As has been said many times on here, whatever changes you do, do them one at a time and give a decent gap between each change to let components 'burn in' and your ears adjust to, and properly assess, the new sound.

Well, reading that back, I have contradicted myself and not really answered your question.

My work here is done.

Phil.

[Richard]

Yes I agree with Phil, your proposal looks ideal but

1) would in practice be a huge amount of work ensuring that your new xovers were electrically similar to Kef's and

2) you still wouldn't have heard the Kefs as intended unless you check and replace any out of spec components in the original xovers.

Hence I'd jump to 2) first; don't worry about the inductors, check the resistor and change any duff caps. That gets you to the stage of having a listen to the standard version. The next step might be to change the electrolytic tweeter series caps for polypropylene and see if you liked the effect before going further with the other caps.