Ferrofluid in the tweeter

Hello,
is the ferrofluid in the tweeter a problem in the long run?
I see that Harbeth and PMC, among others, use ferrofluid.

PMC give a 20 year guarantee?

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It shouldn’t be an issue for the lifetime of the tweeter. It’s really there for power heat dissipation, though critically it does rob a bit of performance… but really if you need relatively high power from a small voice coil cost effectively the subtle ferrofluid compromise is where it’s at.

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This has always intrigued me. Where is this ferrofluid ?
Most tweeters spend most of the time being vertical upright, logically this ferrofluid should drip out.
Much as I would imagine the bearing oil of a turntable if mounted along the wall.
Perhaps some snake oil vendors are missing out of supplying ferrofluid spray we could all use.

Ferrofluid can dry out and harden over time, but can be replaced, apparently. The tweeters in my ATCs don’t use ferrofluid, but its inclusion wouldn’t stop me buying speakers if I liked the sound of them.

Roger

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Does it make the upper frequencies sound more fluid ?

I thought most ferrofluids went into the metal designed milk bottle tops. :innocent:

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ATC have that sticky midrange dome. That could be a nightmare if there was a swarm of bar flys in the area.

Or perhaps fluidity with sounding occasionally ferocious?

It’s a magnetic ‘ferrofluid’ and is inside the magnet assembly in between the pole piece and voice coil gap.

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It’s basically tiny (nanoscale) magnets suspended in liquid, so is attracted to the magnets in the driver and doesn’t drip out.

There’s a rather fun and slightly mind-bending video showing how ferrofluid reacts to powerful magnets and to a superconductor. A quick search should find it.

Roger