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View Full Version : Tweeter decreased frequency . Csuses?


philv
09-12-2019, 09:47
Hi,

I have a 30 year old tweeter that has an obviously reduced frequency range.

Listening to one tweeter and then the other, one does not play as high when i use test tones.

They are kef t33 ferrofluid filled.

Is it possible one is gunned up more than the other with congealed old ferrofluid?

Other than crossover or amp which i will test by swapping tweeters, etc, what could cause a decreased frequency response?

Also, what physically breaks when a tweet fails?
Is it the voice coil breaking?

Thanks.
walpurgis
09-12-2019, 09:55
Dried ferrofluid is likely, but shorted coil windings are also possible. Check the coil resistance with a meter.

Failing crossover caps could also be the cause.
YNWaN
09-12-2019, 09:56
If electrolytic capacitors are used in the crossover (which they would have been thirty years ago) then they can increase in resistance as they get older. Also, if there is ferrofluid in the voice coil gap it could have dried up.

——
Edit, Yes, it’s the voicecoil breaking if anything, there isn’t much else to break.
philv
09-12-2019, 19:50
So, swapped tweeters over and the problem follows the tweeter.
So problem is with the tweeter.

I have cleaned the gap and the coil on the bad tweeter.

My hearing is pretty crap.

The good tweeter i can hear the 7 khz test tone.
The bad tweeter i can only hear the 4 khz test tone.

Here are some images,
Any obvious problems?

Thanks

https://i.imgur.com/OCnlKPm.jpg
https://i.imgur.com/I3h3sve.jpg
https://i.imgur.com/AX8J5Gq.jpg
https://i.imgur.com/OCnlKPm.jpg
Pharos
09-12-2019, 23:08
You should consider that the surround may have changed its compliance.
YNWaN
09-12-2019, 23:37
Yes, was just what I was thinking.
philv
09-12-2019, 23:50
What do you mean by surround?
The diathram?

You should consider that the surround may have changed its compliance.
YNWaN
10-12-2019, 08:42
No, the bit around the edge of the diaphragm that connects it to the rest of the component.
philv
10-12-2019, 08:54
No, the bit around the edge of the diaphragm that connects it to the rest of the component.

Ah...i see.
So, nothing can be done then i guess.

Not to worry, i knew it was buggered before purchase.

Thanks.
YNWaN
10-12-2019, 10:09
No, if exposure to sunlight, smoke etc. has caused the suspension to harden then its stuffed.