View Full Version : ferrofluid cooled tweeters....


dowey
10-14-2011, 11:18 PM
how long is the average life span on these? how can you tell if they are bad or dried up? thanks...

SaSi
10-15-2011, 03:27 AM
The estimates vary. I've read that 20 years is too much but I've heard ferrofluid cooled tweeters that perform fine (to my ears) beyond that life span.

KenP
10-15-2011, 08:42 AM
Perhaps a dumb question but what keeps it in place, you'd think it would all collect on one side and run down into the spider.

kb9qkc
10-15-2011, 10:49 AM
my epicure 3.0 tweeters are ferrofluid cooled and are still working as they were day one. ive refoamd the mids and they are ferrofluid cooled as well and they are still working great. if you refoam the tweeter or mid and its not dried up its a good sign. the speaker are probably close to 30 years old

Putterman
10-15-2011, 11:02 AM
My understanding is the tweeters have ferrofluid primarily to increase power handling and secondarily to damp tweeter resonances. This would seem to indicate that they would be more easily overdriven and possibly peaky if the ferrofluid is gone.

Copa1934
10-15-2011, 03:06 PM
how long is the average life span on these? how can you tell if they are bad or dried up? thanks...
Mach One (40-4029) speakers have been in use for over 30 years and of the ones taken apart (mostly per the VL Mach One thread) none have mentioned anything "wrong" with the fluid. As stated it's mostly to dissipate heat faster. When you consider how many people brag about hard partying with their Mach One's obviously it must be working.

SaSi
10-15-2011, 03:07 PM
Perhaps a dumb question but what keeps it in place, you'd think it would all collect on one side and run down into the spider.

The magnet is keeping the fluid there, is the short answer.

Ferrofluid comprises of tiny ferric dust immersed into neutral liquied of rather decreased surface tension (not easy to evaporate).

Fills the tiny voice coil gap and the magnetic field keeps it there. It does cool things down (has higher heat dissipation than air) and it does also dampen resonances (decreases the mechanical Q of the system).

The ferric dust can't really leave the gap. The liquid carrier itself can evaporate and the time it takes depends on storage conditions as well as usage (repeated use at high power levels makes the liquid evaporate faster).

I've read somewhere (can't remember where) that depending on the size of the particles, they can remain in "liquified" form even if part of the liquid evaporates. However the mechanical properties would shift.

Nikko75
10-15-2011, 03:51 PM
Ferrofluid, it depends and how hard and hot the tweeters were driven will affect it too. You'll eventually be able to tell something isn't right in the sound, the response in the crossover region mellows (dips) for starters.
The Energy 22 tweeters were known for failure after the ferrofluid finally dried up. There are a few people around who have the parts and know-how to repair them but the famous Hiquphon tweeters even without ferrofluid will outperform these by a far margin, not to mention just about anything else. A bonus is that they also cost less.

dowey
10-15-2011, 07:43 PM
funny you should mention the energy 22, i just got a pair of energy c2s and no matter what i do something doesnt sound right, i tried to force myself to listen for a week and only made it a couple of days, both tweeters seem to play at the same volume but somethings missing...

Copa1934
02-09-2012, 03:04 PM
how long is the average life span on these? how can you tell if they are bad or dried up? thanks...
Revisiting. After taking apart a Mach One midrange (myself) I've found a couple interesting things. One the fluid in mine (non working unit) is almost black in color and thick like molasses. I've seen some images of ferrofluid and it didn't look black and I don't recall it being described as being as thick as molasses.

My point? While I'm sure ferrofluid does it's job commendably, I now believe it's useful life is proportional to age and certainly use, or more to the point abuse. To say that a speaker doesn't diminish in sound production is questionable to me since this syrupy mess in my midrange had to have at least some impact on the performance of the driver. I can't imagine such small windings having sufficient power to completely overcome the resistance of the fluid.

It would be interesting to see measured performance of drivers with old fluid and then after refreshing the fluid. I would be surprised if the performance didn't improve.

I see this stuff on ebay now, but the prevailing issue is "how much"? Assuming the old stuff has evaporated to some degree how would one know. Cleaning out this stuff is a pain.

Last, I didn't notice and burnt wires on the VC, in fact the VC looked very good, even under higher power magnifying glasses. There is an open, I just can't figure out where.

bktheking
02-09-2012, 06:27 PM
My energy 22 tweeter fluid was the same, thick and black and not dried up.

JimPA
02-09-2012, 08:44 PM
The Dynaudio D-28H [Sen Lab] tweeters in one set of speakers from 1980 still work with ferrofluid..

Copa1934
02-10-2012, 01:21 AM
The Dynaudio D-28H [Sen Lab] tweeters in one set of speakers from 1980 still work with ferrofluid..
I think people are missing the point. Is it at all possible that ferrofluid can deteriorate and may actually be impairing performance. I worked in the automotive industry for years and it never stopped amazing me how many people don't "hear" a problem with their vehicle simply because the problem was slight and gradual.

I'm curious as to whether or not there is evidence supporting the possibility that this fluid does break down, either from age or from sufficient use/misuse/abuse, etc?

I don't doubt your speakers work, my 30+ year old Mach One's still do too (having the magic fluid in both mids and tweets). However, that doesn't mean it is safe to continue operating them with that same old fluid.

JimPA
02-10-2012, 11:24 AM
I would hate to try and disassemble the tweeters since thay are no longer available. I agree with the how the ferrofluid might break down. Changing the fluid is not as simple as changing the oil in a vehicle. I did have a pair of the tweeters in another set of speakers that were in my truck that appeared to dry out. Being exposed to the elements in auto sound use is harsh. All of my indoor speakers I keep out of direct sunlight which should be of some help.

Kahoona
02-14-2012, 11:54 AM
Hi
I have a flat tweeter from an SB-M5
http://www.audiokarma.org/forums/showthread.php?t=413317&highlight=Ferrofluid
That I am thinking of trying to repair. I can tell you that the Ferrofluid that was in the gap was thicker than molasses and actually pulled a couple of winds of wire off of the coil when I removed it. I remived as much as possible while using only a Q-tip lightly dampened with mild soapy water.If I can find the break in the coil I may try to repair it but the big question is will the Ferrofluid short out the repair to the gap walls rendering it useless? Do I seal the solder joint and how?? This tweeter is unavailable and rare and I would love to do the repair and have working again. Can anyone direct me to any info on working with Ferrofluid or offer any advice? I could then be able to tell you how the repaired tweeter with new FF compares to the other original one.

Copa1934
02-14-2012, 03:14 PM
Hi
I have a flat tweeter from an SB-M5
http://www.audiokarma.org/forums/showthread.php?t=413317&highlight=Ferrofluid
That I am thinking of trying to repair. I can tell you that the Ferrofluid that was in the gap was thicker than molasses and actually pulled a couple of winds of wire off of the coil when I removed it. I remived as much as possible while using only a Q-tip lightly dampened with mild soapy water.If I can find the break in the coil I may try to repair it but the big question is will the Ferrofluid short out the repair to the gap walls rendering it useless? Do I seal the solder joint and how?? This tweeter is unavailable and rare and I would love to do the repair and have working again. Can anyone direct me to any info on working with Ferrofluid or offer any advice? I could then be able to tell you how the repaired tweeter with new FF compares to the other original one.
I recall checking out your post. VC on yours looks burnt, judging by the images anyway. There are a few sellers on eBay with the stuff. It's not cheap, but not terribly expensive either. Quantity certainly is a question since VC diameter is only one factor. There's depth and how much vacant space inside the "chamber" since it's not just a gap you'll be filling. I'm thinking, out loud of course, that since it's magnetic in nature and it doesn't pour out of the gap, the only issue would be overfilling? I guess you could fill the "chamber" (rubbing alcohol?) till full, then pour that into some kind of measuring cup, preferably small with many graduations. Any amount less than that should be effective enough.

Does anyone know if there needs to be an air pocket for compression (when the cone/dome, travels inward)? If so, then certainly less than measured. Maybe we'll work out the science here?

Kahoona
02-14-2012, 03:48 PM
I recall checking out your post. VC on yours looks burnt, judging by the images anyway. There are a few sellers on eBay with the stuff. It's not cheap, but not terribly expensive either.


Hi
Thanks for the reply. Yes it is burnt on one side . Does this mean that it is not reparable, particularly since it would be submerged in conductive liquid after repair?
Are you talking about replacing the coil and it's Mylar tube section only and keeping the original holder and flat honeycomb diaphragm?Wow. That would be an adventure for sure!
The Ferrofluid comes in single use packets according to coil diameter. I checked that out. You empty one packet into one gap. The fluid in these did not come close to filling the entire gap, just the lower area where the coil was.so that would not be a problem and the other one should be done.

Bellair
02-14-2012, 04:15 PM
Ferrofluid was a major advancement 40 years ago....nowadays I look for tweeters without it because it tends to over dampen and lacks "life" The Vifa ring tweeters are a good example of no ferrofluid.

Kahoona
02-14-2012, 04:42 PM
Whew! Tried to solder coil wire but just too small for my big hands and short patience. Looks like we may have an Orphan Speaker and some parts for Barter town!
"I got better things to do with my time
I don't care anymore,no no,no no"
Phil Collins

JimPA
02-14-2012, 10:01 PM
Who was the first to use ferrofluid in tweeters?

ken kantor
02-15-2012, 10:59 AM
how long is the average life span on these? how can you tell if they are bad or dried up? thanks...

There are hundreds of types of magnetic fluid, each of which has a different life span under different conditions. Also, not all driver designers know, or have the freedom to apply, best practices. Properly selected and used, a fluid-filled tweeter can last 40 years with very little degradation. On the other hand, many people find their tweeters shot after less than 10 years. (When mag fluids were first introduced, some over-enthusiastic manufacturers erroneously used water-based formulations and/or paper formers, which lasted weeks or less.)

The easiest way to check the condition of the fluid is to run an impedance curve and look at how much bump there is around resonance. Ideally, this should be compared to both a working reference and a non-filled unit. Still, simply looking at the curve can usually tell you a fair amount.

-k

automojo
02-16-2012, 01:01 AM
The fluid was also used for damping, so when it dries up the driver will obviously change.
There is some school of thought that the fluid inhibits the sound in a negative way.
Personally I always thought the ferro fluid as a compromise, the driver/ compliminting drivers and crossover should be designed with a power rating in mind that shouldn't require cooling fliud.
Probably why I prefer the Great Heil, stick a fuse on it, drive with a nice amp that doesn't clip right away and your good to go. Plus they easily outpreform any domes or cones I have heard in the last 40 years or so.

JimPA
02-16-2012, 01:15 AM
I think most forum users assume ferrofluid is used to prevent voice coils from over heating. It also dampens resonance. I think this became a secondary and complimentary affect to protect the tweeter at lower crossover frequencies.

Does having lubricated voice coils on the tweeter slow transient response.

It has been stated it does.

Having the lowest tweeter inductance should increase transient response compared to tweeters with higher inductance values.

What effect does having tweeters with ferrofluid have in auto sound during freezing temperatures. Do you have to let the tweeters warm up. And what would be the correct method in doing this?

I have learned never to assume anything.

Pete B
02-17-2012, 11:47 PM
http://www.audiokarma.org/forums/showpost.php?p=5272775&postcount=31

http://www.linkwitzlab.com/images/graphics/sb186-48.gif

http://www.linkwitzlab.com/images/graphics/sb186-50.gif

koseltri
02-18-2012, 12:18 AM
I bought some T/E 360's and when I went to refoam the mids the ferrofluid had dried and turned so stiff the cones wouldn't move, they felt like frozen Polk drivers. I had to wash out the residue with acetone.

kb9qkc
02-18-2012, 07:55 AM
again ferrofluid isnt only used in tweeters. my epicure 3.0 not only have ferrofluid in the tweeters but the midrange have ferrofluid in them as well. the woofer did not have any as i could see.

cableguy2
02-18-2012, 11:09 AM
I want to ask the question someone else did, who was the first to use ferrofluid in their tweeters? I was thinking maybe Genesis, but am curious as to who did it.