New Tweeter for kef concertos

[lilolee]

Spotted this somewhere. A guy wanted to get more sparkle out of his T27 adorned speakers. He was very happy.

The modification was adding a Coles 4001 and a 3-way crossover filter by Skytronics labeled ref. no 900.596

[Rob042]

I have heard of this mod - but didnt wished to add another driver into the mix.
ie thought it would be better to stay with three.

Rob

Rob,
These may be of interest to you: eBay.

[Rob042]

thanks for the link Matt.

Rob

[Martin213]

Hi Rob,
I have finally found the article by C.J.Rogers on the R50 transmission line if you are interested.It uses the B139 bass driver,crossing over at 375hz to the B110,then at 3khz to the T27,and at 10khz to a ITT-STC-4001G super tweeter.
I quote "Both the tweeters were again chosen for their flat response in their working range,and for their superior polar response."
Regards
Martin

[Rob042]

Martin
thats sounds very interesting - could you send me a copy?
thanks

rob

[Martin213]

Originally Posted by Rob042

Martin
thats sounds very interesting - could you send me a copy?
thanks

rob

Of course
PM me ur email addy please,will send it to you.

[Yellow]

Hi Rob,

Sorry to barge in on this thread after 6 weeks or so, but the problem may be quite simple to solve. How old are your T27's, and their respective crossovers?

The problem may easily lie with the electrolytic cap that partners practically any tweeter on the market. Even if you have a Polyprop cap in there, they have a shelf life of usually 6-8 years maximum before they dry-out and their properties alter drastically. I recommend you get a couple of new electrolytic caps to try out first and maybe a couple of feed resistors too (if the T27s need them?) and start there.

Next place to look is the ferrofluid in the coil gap. Be VERY careful here though. You need to see if there has been any congealing of the ferrofluid. I have experience of this stuff going solid when it comes into contact with various adhesives. Trapped in a tweeter's environment, even the vapours can cause the surface of the ferrofluid to start to harden over time, causing a massive loss in the ability for the tweeter/coil to move - hence a massive loss in output.

Check these out first before buying new drivers.

Regards,

Neil.

[Rob042]

Cheers Neil
the xovers are only a year old - but the speakers had been in a heated room unused for some 20 years -so the tweeter could be suffering from fluid loss.
will have a look.
thanks again
Rob

[Shane]

Are you sure the T27 had ferrofluid? It dates back to the mid 60s, whereas I remember ferrofluid being a radical new innovation at least ten years later. Definitely worth checking out before you start taking your tweeters to bits to find out if it's missing!