Does ferrofluid always dry out?

[Dogen]

Hi all! I have a pair of Tannoy 615 speakers from the early 90s. I know this speaker uses ferrofluid tweeters, but after 30+ years I don’t hear any degradation in the treble. What would I hear if ferrofluid were dry? And is it possible it’s still in good shape? I could have it replaced, but how do I know it’s needed? Many thanks

 

[Wolf11Man]

All FF will dry out.
If you are lucky, the FF has dried in a way that it doesn't rub inside the magnet gap and voice coil . So you hear it as if it had no FF at all.
The FF increases heat transfer and is damping out the resonance curve. The problem may come from the (passive) crossover, it is designed for a certain impedance, which will change without FF. So the sound may not be as it once was.
If you have someone who can clean magnet gap and voice coil and replaces the FF without charging more than a new tweeter would cost, your speaker may sound different when renovated. Hopefull better.
If your are not used to handle objects within a few thousands of an inch tollerance, better don't try DIYS. This is nothing you will succcessfuly finish the first time you try.
You need some instruments too, generator, test amp, some software and a measuring microphone to document before/ after with a near field response curve, best a distortion measurement. This will tell you how the restoration has affected the tweeter. Otherwise it is no perfect job and the tweeter may sound worse than before.

PS also have all electrolitc capacitors of the x-over replaced. Do not "upgrade" or change foil capacitors, coils and resistors!

 

[Dogen]

This is not a job for me! Luckily I know an audio repair person who can likely do it. I’m not sure new tweeters are available for these, so I might want to give it a try. Plus, I’ve become attached to the marble hexagonal tops, perfect for cold beverages. Thoughtful reply - thanks.

 

[Roland68]

This is not a job for me! Luckily I know an audio repair person who can likely do it. I’m not sure new tweeters are available for these, so I might want to give it a try. Plus, I’ve become attached to the marble hexagonal tops, perfect for cold beverages. Thoughtful reply - thanks.

I would also like to add that some developers, speaker manufacturers, and modifiers intentionally remove the ferrofluid to alter, improve, or adjust the characteristics. The resulting lower power handling is either factored in or accepted as a trade-off.
Listen and take measurements first; refurbishing might not actually be an advantage.

 

[Tassin]

Here's a testimony by Archimago who replaced the ferrofluid in his tweeters, including measurements before and after. Informative read.

DIY: Tweeter Ferrofluid Change - with pre- and post- frequency & distortion changes. And on-line amiability among hobbyists.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[Dogen]

I would also like to add that some developers, speaker manufacturers, and modifiers intentionally remove the ferrofluid to alter, improve, or adjust the characteristics. The resulting lower power handling is either factored in or accepted as a trade-off.
Listen and take measurements first; refurbishing might not actually be an advantage.

I don’t hear any issues with either speaker, and the measurements from Audyssey don’t show any degradation (but that’s not very accurate, I think). Am I creating a problem? Any risk to running them as they are?