SpeakerTalk

speakerguru · Posted: Tue May 12, 2015 10:32 am Post subject: Ferrofluid in KEF tweeters

Extracted and edited from old posts and put here as a sticky

some info here http://ferrofluid.ferrotec.com/products/ferrofluid/audio/

KEF used to use the now obsolete APG512 which you won't find on this site. From memory it was a 75cp fluid. i.e. the fluid was used primarily to increase conduction of heat to the metalwork, not to provide damping. The base fluid is a synthetic oil and I guess everything dries/evaporates eventually.
In the APG L series, APG L17 would be the closest to the original low viscosity APG512. APG311 looks closer still and has a higher temperature rating.
APG S15N looks to be close to the original in viscosity. If Ferrotec are cautiously recommending it, then it is probably the most suitable for T33 use. The exposed part of the T33 vc is high temperature cured epoxy, aluminium and CA (superglue) adhesive. Not much risk of a bad reaction with an oil based fluid, I think, but no guarantees.

speakerguru · Posted: Tue May 19, 2015 10:13 pm Post subject:

APG S15N was available from KAST Services

http://www.kastservices.co.uk/tannoy-spares

but no longer Sad

dublin78 · Posted: Thu Mar 16, 2017 12:02 pm Post subject:

Hi
Sorry, I have looked around, but I cannot find any instructions as to how much ferro fluid to use in each tweeter (SP1191).
Any ideas?
Thanks

speakerguru · Posted: Fri Mar 17, 2017 1:13 pm Post subject:

Sorry I don't remember exactly. It would be around 100ul (0.1ml). It was applied by means of a graduated glass tube syringe. The magnetic field pulls the fluid out of the tube as soon as you approach the magnet gap.

flumoxed · Junior Contributor 10+ Joined: 30 Mar 2015 Posts: 18

Good HIFI VOF, NL sells ferrofluid formulated specially for speaker drivers. Price is about $20 for 1 CC (enough for 20 tweeters) compared to $6 for generic ferrofluid from Parts Express.

oldandintheway · Junior Contributor 10+ Joined: 16 Mar 2018 Posts: 18

So, is the gist of this that the generic ferrofluid from parts express would be no good for NT25?

speakerguru · Posted: Mon Apr 30, 2018 10:10 am Post subject:

Impossible to say as they don't list the viscosity.