Hello there,
I am interested in peoples opinions regarding Ferrofluid.
Once hailed as quite a breakthrough > Is this still the case?
Have any 'lifespan' issues been found?
I'm actually quite out of touch regarding how many drivers still use it.
CHEERS 🙂
I am interested in peoples opinions regarding Ferrofluid.
Once hailed as quite a breakthrough > Is this still the case?
Have any 'lifespan' issues been found?
I'm actually quite out of touch regarding how many drivers still use it.
CHEERS 🙂
It is messy and sometimes leaks out of the gap - apparently not uncommon in dome tweeters.
I’ve seen a few posts on different forums where folks have had to take apart their tweeters, clean out the old, thick ferrofluid, and refill.
Given the huge numbers of tweeters with it vs the very few complaints I have seen about them drying up, I feel it’s pretty uncommon.
Given the huge numbers of tweeters with it vs the very few complaints I have seen about them drying up, I feel it’s pretty uncommon.
The newer FF formulations are much better and won't degrade as quickly as the older stuff. The difference is in the carrier oil, which is synthetic nowadays and usually ester based, which is very stable. The viscosity matters as well.
While most higher end tweeters don't use FF, its not as detrimental to sound as some think it used to be. I've tried some AB tests with Seas and Morel tweeters with and without FF. It tends to make the tweeter more forgiving with lower order xover with increased damping at Fs and barely reduces low level detail up top, but does reduce efficiency by about a dB or so. I still prefer none if possible, but there are some tweeters that sound great with it, such as the Morels. I wouldn't use it on most metal domes, as these will suffer at the extreme top end frequencies. On soft domes its not so detrimental, as these usually don't extend that far up top.
While most higher end tweeters don't use FF, its not as detrimental to sound as some think it used to be. I've tried some AB tests with Seas and Morel tweeters with and without FF. It tends to make the tweeter more forgiving with lower order xover with increased damping at Fs and barely reduces low level detail up top, but does reduce efficiency by about a dB or so. I still prefer none if possible, but there are some tweeters that sound great with it, such as the Morels. I wouldn't use it on most metal domes, as these will suffer at the extreme top end frequencies. On soft domes its not so detrimental, as these usually don't extend that far up top.
I used the non-FF Tymphany NE25VRS-04 in a couple of my recent builds, and love the lively high end. However, they have a rising FR from ~ 6Khz, and it may be that suits my ageing ears better
FF evaporates over time/temperature
Some voice coils like Dynaudio will soak significant amounts of "black blood"
Typically your tweeter coil is better cooled by a factor of three! (but protects not against very short power impulses)
The so-called colloid stability of some FF types is not good!
No tweeter has perfect centered coils , and cool/hot cycles can lead to non-round coils after cooling to normal room temperature , so injecting FF could lead to uneven distribution of FF along the air gap!
Very problematic is the wandering of FF out of the air gap due to capillaric forces , older Dynaudio tweeters were susceptible to that effect ...
If the coil and the carrier slit is well sealed and chemically neutral against FF it is possible to inject the correct amount of FF only to the inside of the coil carrier , thus minimizing the friction losses involved!
Slightly overdosing FF helps with losing FF over time ....
Also of course the carrier must be vented and the pole piece to allow for even air pressure in any cavities in the driver, but much more important so for the the inner ring space below the air gap! When transportation in excess height above sea level , the driver is effectively in a vacuum "chamber" , the air will not stay in a full closed gap by the FF !! Have not tested by myself but should be logic ...
Any fast/large pressure differences & coil excursions can lead to "splaying" of the FF !!
be careful when using FF it is not that easy!
It would be a good idea to write some information on the driver stating type of FF and amount of filling plus any other specification need for a repairment in the future!
Btw - shame on all those manufacturers to not include a schematic of the passive filter networks of their speaker boxes!
You know filter networks are no witchcraft devices anymore 😀
Welcome to the future!
Some voice coils like Dynaudio will soak significant amounts of "black blood"
Typically your tweeter coil is better cooled by a factor of three! (but protects not against very short power impulses)
The so-called colloid stability of some FF types is not good!
No tweeter has perfect centered coils , and cool/hot cycles can lead to non-round coils after cooling to normal room temperature , so injecting FF could lead to uneven distribution of FF along the air gap!
Very problematic is the wandering of FF out of the air gap due to capillaric forces , older Dynaudio tweeters were susceptible to that effect ...
If the coil and the carrier slit is well sealed and chemically neutral against FF it is possible to inject the correct amount of FF only to the inside of the coil carrier , thus minimizing the friction losses involved!
Slightly overdosing FF helps with losing FF over time ....
Also of course the carrier must be vented and the pole piece to allow for even air pressure in any cavities in the driver, but much more important so for the the inner ring space below the air gap! When transportation in excess height above sea level , the driver is effectively in a vacuum "chamber" , the air will not stay in a full closed gap by the FF !! Have not tested by myself but should be logic ...
Any fast/large pressure differences & coil excursions can lead to "splaying" of the FF !!
be careful when using FF it is not that easy!
It would be a good idea to write some information on the driver stating type of FF and amount of filling plus any other specification need for a repairment in the future!
Btw - shame on all those manufacturers to not include a schematic of the passive filter networks of their speaker boxes!
You know filter networks are no witchcraft devices anymore 😀
Welcome to the future!
That information is called intellectual property. Its hard to make a profit if you give away your property for free...
My own experience was switching from non FF peerless tweeters to Morel FF teeeters. The reduced sensitivity gave a more mellow and balanced presentation and also means I have not managed to melt the voice coils since 🙂.
I’m now using non FF tweeters with better (active) crossovers, so I think my days of melting tweeters are hopefully over!
I’m now using non FF tweeters with better (active) crossovers, so I think my days of melting tweeters are hopefully over!
IMO it's better to spec drivers that are capable of higher output without FF. It's a band-aid, and while it's definitely useful and space/power handling is always at a premium in speaker designs, I'd rather up-spec. I've pulled FF out of a number of drivers over the years, some really bad cases where the voicecoil was gummed in place. I'm sure modern formulations are dramatically superior and may be okay for the practical lifespan of a driver. As a fan of vintage drivers however, age WITHOUT ff is not inherently an issue as some assemblies stay on-spec and don't get brittle (handling/environment naturally contribute), while even modern ff would likely impose an upper limit to lifespan. I have a number of vintage drivers here that are impeccable. The JBL 123A/2213 as used in the L100 and 4311 can be perfectly on-spec over 50 years later, I have 2 pairs in my system today as the bass section of my surrounds, 100% on spec and sound great.
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I have this CD in 3 incarnations (German/UK/USA) each of them sound a little different! Of course the oldest "original" EMI/UK sounds BEST !!! (less dull) And clearly quite identical to the original LP that came out during that time ... I still remember the moment where a friend of mine and me are listening to the part where a bus halting with squeaky brake noises - we jumped up from our seats in fear as we were bus passengers standing too close to the street border with the bus coming up dangerously near us , so realistic was the "Q - Sound" on this fine recorded LP .... speakers were the smaller ESS with a bit of pyramidal shape and the big AMT (saran foil) radiates as a dipole .
There are parts of the music being brutally loud but fits the music very well!
Rogers overdriven voice is a jigsaw sometimes trying to cut off your ears 😀
Should be in every record collection , a must have :
Btw - the artwork is excellent 🙂
There are parts of the music being brutally loud but fits the music very well!
Rogers overdriven voice is a jigsaw sometimes trying to cut off your ears 😀
Should be in every record collection , a must have :
Btw - the artwork is excellent 🙂
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if someone has issues melting tweeters, they're driving them too hard crossed too low. A decent metal dome will comfortably play harmoniously in a 105 dB + 2 way system crossed above 2.5k 3rd order. I've tested this myself and its beneficial to have FF in the HF driver for the sake of improving power handling by at least 3 dB more output. Synthetic based FF has a vert high flash point. Its easily good for 120 deg C long term. If theres an issue with FF splashing, the VC former isn't vented enough to equalize pressure differences between the dome and VC gap. That really only happens with excessively low, shallow xover slopes. I retrofit some compression drivers with FF and never had issues with migration or splash. It makes little to no difference in treble quality and really bumps power handling, so much so I havent had any warranty come backs in my builds, even when stupid sound guys crank up amp preset gain to get around locked dsp limiting.
Yes, those were the reasons! Generally happened at parties or kids disco events. I should have hired some PA speakers!
Well I want to add a few points here being of significance too ... first , tweeter input rules!
A lot of modern recordings have constant spectrum content (white noise) up to 20kHz , while older recordings are having more decreasing spectrum like pink noise falling above 2kHz or so ....
The other issue is , in the more recent past , tweeters usually have short length/height underhung voice coils (deep gap/short coil) . 0.8mm to 1.2mm is the typical range .
Now have a look the old Dynaudio or Scan Speak data sheets (pure aluminium wires) , they have overhung coils at least doubling the coil height! Then take into account the coil impedance , again a doubling of the resistance! Funny right? How could it be that old stuff is way better than newly "overengineered" tech obscurities?
Can it be they design their stuff in a way that it will be accidently killed by the (over)enthusiastic customer easily? So they can sell more and more and more of their shiny stuff?
And let's not forget compression of the music signal , putting probably a much higher current load on the voice coil .
Once I put a simple test on a naked woofer coil (not in the air gap) 50mm dia. and 20mm winding height , I set the output for 32watt to 6 Ohm coil resistance and tested using three different signals : Marla Glen/Cost of living (bass-heavy track) , pink noise and pure sine wave 40Hz . After the song was over (4 min.) I touched the coil with my fingers - temperature was hot but burned not my skin at the fingers , pink noise was way hotter could not touch the coil longer than a few seconds , and pure sine applied was impossible to touch!
So the more you think and the deeper you dig , things could change your view entirely!
keep on digging in the dirt for the bonanza 🙂
ps .. another gem from the past excellent remix by Steve Wilson and a well-balanced sound , 2 drum kits playing(!) , if you like spacerock here are the originators themself :
A lot of modern recordings have constant spectrum content (white noise) up to 20kHz , while older recordings are having more decreasing spectrum like pink noise falling above 2kHz or so ....
The other issue is , in the more recent past , tweeters usually have short length/height underhung voice coils (deep gap/short coil) . 0.8mm to 1.2mm is the typical range .
Now have a look the old Dynaudio or Scan Speak data sheets (pure aluminium wires) , they have overhung coils at least doubling the coil height! Then take into account the coil impedance , again a doubling of the resistance! Funny right? How could it be that old stuff is way better than newly "overengineered" tech obscurities?
Can it be they design their stuff in a way that it will be accidently killed by the (over)enthusiastic customer easily? So they can sell more and more and more of their shiny stuff?
And let's not forget compression of the music signal , putting probably a much higher current load on the voice coil .
Once I put a simple test on a naked woofer coil (not in the air gap) 50mm dia. and 20mm winding height , I set the output for 32watt to 6 Ohm coil resistance and tested using three different signals : Marla Glen/Cost of living (bass-heavy track) , pink noise and pure sine wave 40Hz . After the song was over (4 min.) I touched the coil with my fingers - temperature was hot but burned not my skin at the fingers , pink noise was way hotter could not touch the coil longer than a few seconds , and pure sine applied was impossible to touch!
So the more you think and the deeper you dig , things could change your view entirely!
keep on digging in the dirt for the bonanza 🙂
ps .. another gem from the past excellent remix by Steve Wilson and a well-balanced sound , 2 drum kits playing(!) , if you like spacerock here are the originators themself :
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At 120 deg C the evaporation rate is high!
Compression drivers do not move much their suspension is ultra-stiff compared with Hifi-tweeters! (that's why I don't like them beneath other negative properties)
Coil overhang is typically very low so the coil is always in close proximity of iron nearby to keep the coil cool ....
regards - Cool McCool 🙂
My experiences are mixed: Morel Tweeters MDT33 from the 90’s were poor, both different and too less FF. Wiped it out.
The Accuton C44 midranges from 1992 were in good condition as I restored them last year. One needed a little „massage“ but then it messured as nice as new and both units with the same fr.
Now I have some SS D2608/913000, both measuring as they will have enough stuff inside.
Usually I prefer Tweeters w/o FF since I don‘t listen extremely loud and I never destroyer a Tweeter.
Regards J-C
The Accuton C44 midranges from 1992 were in good condition as I restored them last year. One needed a little „massage“ but then it messured as nice as new and both units with the same fr.
Now I have some SS D2608/913000, both measuring as they will have enough stuff inside.
Usually I prefer Tweeters w/o FF since I don‘t listen extremely loud and I never destroyer a Tweeter.
Regards J-C
It is even more difficult than you might think!
One question : Assuming full FF injection (minus the VC space) - how do you make sure the FF has the correct amount (both sides of the VC) in the geometric space of the air gap? Insertion by hand is anything but exact right?
None of you is cool & deadly as James Bond/007 would be on such a critical job 😀
About time for a DIY contest looking for Mr. Calm Hand? .... price is a brand new Jaguar 🙂
And , btw - what I REALLY HATE is when the air gap has no ventilation somewhere for the inner ringspace of the magnetic structure , like the old Usher T9950 had! (aka Dayton RS28F-4)
The only transducer that I remember of is the Jordan fullrange transducer that has the FF injected only on the smooth inner side of the VCoil!
Transducer design is an adventure of it's own 🙂
ps .. no coil is perfectly round (better than 90%) and at the true center position (again 90%) , often even skewed (Focal and Scan Speak - their workers must be drunk all day ..)
One question : Assuming full FF injection (minus the VC space) - how do you make sure the FF has the correct amount (both sides of the VC) in the geometric space of the air gap? Insertion by hand is anything but exact right?
None of you is cool & deadly as James Bond/007 would be on such a critical job 😀
About time for a DIY contest looking for Mr. Calm Hand? .... price is a brand new Jaguar 🙂
And , btw - what I REALLY HATE is when the air gap has no ventilation somewhere for the inner ringspace of the magnetic structure , like the old Usher T9950 had! (aka Dayton RS28F-4)
The only transducer that I remember of is the Jordan fullrange transducer that has the FF injected only on the smooth inner side of the VCoil!
Transducer design is an adventure of it's own 🙂
ps .. no coil is perfectly round (better than 90%) and at the true center position (again 90%) , often even skewed (Focal and Scan Speak - their workers must be drunk all day ..)