The ferrofluid dilemma: fact or fiction?

Jayrosc

Jayrosc

Super Member
I've read lots about ferrofluid drying up and screwing up otherwise good tweeters, but is this something similar to the recap dillema? Some folks swear by recapping, others say never, and I gotta admit I've had a few pair of speakers with 1970's caps in them that run great. But ferrofluid? How does one tell if the fluid is shot? The possibility of bad fluid has scared me off buying many a pair of vintage speakers that otherwise appear to be in great condition.
 
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The best analogy for ferrofluid is motor oil in your car. It ages--gets gummy and can make a tweeter sound "dull". Primary factors are age, storage conditions and whether the speakers have been regularly driven hard (heat)--basically the same factors that impact caps (and motor oil in your car). If a speaker sounds "dull", it is always worth a shot to clean out the old ferrofluid and replace it with fresh--a pretty basic and cheap first option if you know how to disassemble a driver.
 
Just redid a pair of AR18b speakers. needed refoam. afterwards the tweeters are way too bright, the interweb's consensus is that the fluid dried up, and there's less damping involved. YMMV but i've not yet come across a tweeter that sounds duller without the fluid. Unlike a car without oil, you can run your tweeter without FF and not destroy anything. Worn shocks might be a better analogy, car still runs fine but the ride is harsh.

Feel free to follow the rabbit hole into ferrofluid, it's pretty interesting. In the end, i chose to wire a couple 3ohm resistors in line with the tweeter. Using 2 gets me ~1.5ohm and the "balance" has been restored to the speaker. Seems like adding the fluid is pretty straightforward, if you choose that route. Personally i'd do one of the pair and a/b it for posterity.

As far as old speaker caps, some are just fine yes, but until you replace a bad one you won't know what you've been missing.
 
What would be good is a database with tweeters that use ferrofluid -
Here's several that I've come across that has effected output of the tweeter (buyer beware)
B&W cdm-1( se,etc)
Mcintosh ht-1 (and variants - ones with three tweeters)
Kef ( from forums)
Sonus Faber grand piano, concerto
Older meridian speakers

Ymmv see above for factors that cause earlier decay
 
loudnoises said:
Just redid a pair of AR18b speakers. needed refoam. afterwards the tweeters are way too bright, the interweb's consensus is that the fluid dried up, and there's less damping involved. YMMV but i've not yet come across a tweeter that sounds duller without the fluid. Unlike a car without oil, you can run your tweeter without FF and not destroy anything. Worn shocks might be a better analogy, car still runs fine but the ride is harsh.
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This makes total sense to me--if the fluid just "dries up" and goes away, you are dealing with a straight-up air gap with no damping and would likely sound "bright" or "harsh". The handful that I have rebuilt, the FF had turned to "grease" and made them "dull". I guess it depends on the specific formulation of FF used. I do know people that have cleaned out the old FF and just not replaced it because they felt that it "opened up" the high end--but to each his own.
 
Here's a thought: ferrofluid comes in different viscosities. How would one know that the replacement approximated the original?
 
winters860 said:
Here's a thought: ferrofluid comes in different viscosities. How would one know that the replacement approximated the original?
Click to expand...

A very valid question, and my answer is that I have no f#$%&ing clue--and I doubt that this information is readily available from the manufacturer. I have two little bottles, and they have very informative labels--Ferrofluid--avoid contact with eyes, do not freeze, and shake vigorously before applying. I "assume" (and we all know what that means) that it is silicone based fluid, and has a viscosity similar to 20W-50W motor oil at room temp--so much for the technical data.

Ferrofluid obviously has a damping effect, but the primary marketing BS was cooling/heat dissipation for higher power handling of tweeters. Again--I have no clue as to what is "real" or not, but IME, the "gunked up" and "gummy" ones sounded "dull" and improved with cleaning and fresh fluid.
 
thymanst said:
What would be good is a database with tweeters that use ferrofluid -
Here's several that I've come across that has effected output of the tweeter (buyer beware)
B&W cdm-1( se,etc)
Mcintosh ht-1 (and variants - ones with three tweeters)
Kef ( from forums)
Sonus Faber grand piano, concerto
Older meridian speakers

Ymmv see above for factors that cause earlier decay
Click to expand...
I think it shows up in lots of old speakers. Genesis used it. PSB used to and probably still does. Allison Four Tweeters have it, and It looks as if its in the tweeters of a pair of Advent Maestros I have here. For me, it seems impossible to do the surgery required on any of these drivers in order to change the fluid. A shame, since it makes me walk past several speakers that I would otherwise grab.
 
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Jayrosc said:
For me, it seems impossible to do the surgery required on any of these drivers in order to change the fluid.
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All of the ones that I have done have been some sort of dome or compression driver (horn), so "the surgery" is fairly easy--typically, the magnet structure is screwed/bolted to mounting plate that houses the dome/diaphragm--separate the two carefully, do the cleaning with some IPA or denatured ethanol, let it dry and fill the magnet/voice coil gap with fresh fluid and reassemble. Just be careful with your alignment of the voice coil and magnet gap when putting it back together to avoid damaging the voice coil.
 
My experience:

ADS L-1290 and DCM TF1000. Both I replaced FF on one side and compared. The difference was huge. It went from...'meh, lets try other speakers' to 'yay, I really like these'.

I could not wait to do the other side. Happy camper now.

Think of it like this: the crossover recapping will address the bass and maybe mids, and the ferrofluid brings the top end back to specs, really opens it up.

I have no specs on the viscosity of the original fluids, but what I put in was less viscous than whatever was left after several decades of use. So I consider it a step in the right direction. Also, don't put too much fluid in, it will dampen the tweeters and reduce output.

Cheapest upgrade ever.
 
So, like ... if the oil evaporates, leaving the magnetic residue, what are the chances that just topping off the drivers with fresh mineral oil would "reconstitute" the fluid over time? I'd think that even if there is a performance hit when compared to stock, it'd be better than going dry.
 
image.jpeg After reading way too many posts on this subject, I suspect that some are suffering from Ferro-Phobia.
There is no magic here. The correct stuff is readily available,costs beer money and is not a difficult repair.
The amount of fluid for a one inch voice coil is a very few tear drops. The seller on that big auction site has pre-measured,squeeze packs. I've used it numerous times and yes, the results are dramatic.
Watch the YouTube video. You can do it!
 
I have just recently purchased 3 pairs of Energy 22's for my work shop system. After doing some research about them on the net it seems that the tweeters in these speakers are prone to failing due to gummed up ferro fluid. I took one tweeter apart to have a look and I did not think it looked too bad as the gap was fairly full and when I touched the ferro fluid with a piece of paper it seemed quite thin. I still went ahead and ordered 9ml from parts express and that should be enough to do my three pair and my brother in law's pair as well. I will post back here after I get a pair done and report on any performance changes. I will be in a good position to judge any differences because of my multiple pairs.
 
I took a good look at the tweeters in question today, one of them has some very obvious staining around the leads leading to the coil, looks like something wicked out for sure. one more point on that side.

At the very least the tinkerer in me is intrigued.
 
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