Ferrofluid

I have done it many times.... If your listening habits would never strain the tweeter, I would normally remove the fluid rather than replace it. Can sound slightly better, never found it to sound worse.

I have changed the ferrofluid in my tweeters.  The ease or difficulty in doing so depends entirely on how hard or easy it is to dissemble the tweeters.  It turns out in my case it was easy to dissemble to tweeter to be able to get to the channel where you wipe out what's left of the old ferrofluid and add the new.

Personally, with nicer speakers like yours I would just send the tweeters to Millersound and have him do the work.  I'm sure it would be quick turnaround (guessing days) and very reasonable and Bill is great to deal with.

Millersound Speaker Refoaming, Speaker Reconing and Repair Services

Regarding "ferrofluid", from the net:

"Ferrofluid cools down the speaker coils which are susceptible to extreme heat. Ferrofluid transfers and dissipates the thermal energy produced by the strong vibration of the moving driver. As magnets increase in temperature, they lose some of their power."

Unfortunately replacing ferrofluid in tweeters that used them is something you must do ever decade or two.

Thank goodness we have more or less moved away from that.  You might also look at DIYaudio for help.

@timlub @jetter @erik_squires   Thank u all who posted. And thank u jetter for mentioning Bill from Miller sound. I will definitely be calling him about this. I have a couple questions. By cleaning out the old ferro fluid and putting in new what will I really hear if anything. And what if I do not do this. Would it cause any harm to the tweeters since my speakers were built in the 90s ? Also I will be upgrading all my 8 crossovers (4) in ea speaker very soon also. Like it did mention in post I already think they sound phenomenal. But since they are from the 90s and I do plan on not selling I think it’s a good idea for an upgrade on all I can do for them. 

Ok.  So I just got off the phone with Bill from Miller sound. Very nice guy BTW. He said that he definitely does that it is very responsible $105 ea tweeter. But he said to be extremely careful shipping them if I can’t make the 2.5 hr drive to PA from NJ where I am. But —— he said IF I still hear good and loud treble with my tweeters they are definitely still good with the ferro fluid and he advised me not to touch them. BTW last night before I even heard about this Ferro fluid thing I was up in my music room for about 5 hrs enjoying my system and I decided to take all 6 speaker covers off and listen for the rest of the time with them off. And as I was listening to the Cars - Dangerous Type , btw I love the drums thundering and exploding on that song with my speakers. So i definitely heard the great loud detailed treble on both tweeters. So I will definitely take Bills advice and until I hear anything different ( negative) with them I’ll leave them be. Bill also mentioned a place closer to me in NYC that he recommended that does great work on speakers too. It’s called Technetron. That way I could bring them in instead of taking a chance and shipping them and having them get damaged in the mail which I very much appreciated him telling me that also. 

There is no set rule regarding how long ferrofluid lasts.  I have read 10-15 years is typical.

Chances are your ferrofluid is still basically still ok and you will hear little or no difference after having it changed, but who knows.  My speakers were also built in the 90's, and I think it is wise to change the ferrofluid to ensure no damage.

About the crossovers, I will leave it to the experts here to recommend whether or not to update them if they still sound great.  The question is if crossovers with high quality parts like your (and my) speakers last longer than those with more generic parts?  A quality repair guy once told me he thought they do.

Better yet, see if you can talk with B & W about the advisability of updating the crossovers or not. 

@jetter Right now I will hold off and put the ferro fluid on the back burner. I’m just very glad to know more about it and more importantly where to go to have them serviced. About the crossovers. I found a guy on EBay who makes crossovers from original speaker schematics using all much higher quality caps and resistors than originals including better wiring etc.  Says as follows. This auction is for B&W brand 800 Matrix. This auction is for a pair of new crossovers. They are built to the original schematics with the improved parts quality and some small tweaks to take the speakers to another level of sonic purity.  Service provided   Full crossover upgrade. Replace capacitors in tweeters with premium film capacitors. Replace midrange capacitors with poly film capacitors. Replace tweeter/ midrange resistors with film type resistors. Replace all capacitors in woofer section + film bypass. Replace woofer inductors with 14/15 awg steel low distortion core inductors. Replace midrange inductors with air core low distortion type. Replace all resistors with higher power type.  In return you will get more powerful better extended low frequency , more dynamic clearer midrange. And smoother higher resolution highs. The speakers will come to life with more detail and dimensions.  20+ years of experience in high fidelity crossover design. He has a lot of great reviews with his crossovers. I was emailing him last night and seems very knowledgeable and gets back to you right away. He also offers a 3 year warranty. And said his crossovers will be good for at least 30 yrs. His username is Crossoverchef-com   Check him out. 

@tattooedtrackman  I will defer to those with more experience.  But if it was me and I did not notice anything that sounds wrong, as in your case, I wouldn't even think one thought of messing with my crossovers.

I would just sit back and enjoy your beautiful system.

Ferrofluids main purpose is to dissipate heat. When the coil heats up, it naturally cools within the fluid. I do not drive my speakers crazy hard an have compared sound with and without fluid several times. I always heard a tad more information without fluid, so I normally remove it. I have also measured many tweeters with and without ferrofluid, resonance also goes down a bit when it is removed and don't take this as a recommendation to remove it. I've been building, repairing and modifying speakers for more than 40 years, I would do this to my own, but to someone without personal skills, I would recommend to leave alone until it needs to be done. Ferrofluid  will thicken as it ages, so overtime, it will hinder driver movement and heat transfer 

if the tweeters sound good it's probably OK.  The risks to not replacing the ferrofluid on time is audible but also the risk to the voice coil.  The gunk may add physical friction and therefore heat the voice coil.

@timlub Thats exactly what Bill said at Millersound about it thickening as it ages and will harden overtime. Do u also build crossovers. ? If u do and or know about crossovers I would love your professional opinion on the crossovers from a maker on eBay as I mentioned a few posts up. You can look them up on EBay if u have it. Just search for B&W 800 Matrix crossovers. Thank you and I appreciate it. 

@tattooedtrackman     Yes,  I do design, build, mod and repair crossovers.  I know what I'm doing and want you to please take to heart what I tell you  here. Your speakers crossovers are well thought, complicated expensive. When I build,  Each woofer, tweeter mid, midbass and each crossover part is hand measured and matched for accuracy. If you want someone to replace caps and resistors, fine, upgraded parts will be audible, but understand, 1 person may say Wow, what a shocking improvement and another may say, well, I can tell its done, but it wasn't much different.  You can spend a ton and not hear alot of difference. With that said, when you replace inductor coils,  you are changing the line impedance sometimes over an ohm on a single part.  If you take off a 3mh ferite core, it may have a resistance of .8 ohms, when you change to a 3mh air core, it could be more than double that.  So you think you have a crossover frequency of say 3000hz, but because you changed the line impedance to that part, you may now be at 2800 or 3200.  On top of that, when I build, I build to have phase and time alignment, when you change parts without a proper plan, you throw that right out the window.  If you want to replace resistors and a few caps, I'm happy to pull schematics and tell you which to change and good idea of what to buy, but unless you are very highly qualified at speaker design, do not change the inductors.  It is alot of work to get this right and it is easy to blow by someone that can solder, but really doesn't know what they are doing,  So EBAY, for me, especially on such a nice speaker, That is a big NO WAY.  

@timlub   Tim. Thank you for your detailed reply. I really appreciate it. I want to say first if all that I would not even think of doing this if I didn’t have someone to install and solder the crossovers in for me. When I first bought my ARC REF 750s and was playing them the first few hours I had a tube arc and it took out a resistor. I called up my ARC dealer here in NJ and he hooked me up with an awesome Technician. I ordered what I need from ARC and when the parts arrived he came to my home and installed and soldered everything and also checked both amps out and gave them a clean bill of health. And said that they are in excellent condition. So when I told him and showed him and had him read about those ( supposedly) upgraded (better sounding 🤷‍♂️) crossovers on EBay he said that they sounded good. And that he would have no problem replacing and soldering them in at my home.Now mind you and I know he does not build crossovers or maybe he does not know much about building crossovers other than how to install and solder them. So he is just probably also going by what he read about them from what I sent him. Ok. Now I have some questions and opinions from u Tim. Knowing that my speakers are from the 90s and since I had them now about 8 yrs now and really never had a problem with them. Would u think I would need to change or replace the caps and all that is involved in the cross overs ? Wouldn’t that be like an amp dating back to the 90s ? Changing upgrading the caps and resistors etc ? Also what I did want to mention is the only issue I do have with my speakers is the highs coming from the tweeters being too bright along with the voice. Now it’s not all the recordings but many. My question is if I do change and upgrade the crossovers can something be done about that with the crossovers from the tweeters ? Now let me also say that I only listen to digital. I also have a ARC Ref 6 that I bought brand new a few years ago and only put on 600 hrs. I did just have gotten it upgraded from ARC to the Ref 6 SE. and have it now for about 2 months. All my tubes in my amps and pre amp have about 700 hrs on them so I know it’s not from the tubes. But it’s really that brightens and some recordings are too bright IMO. Other than that the speakers sound phenomenal. Especially the powerful bass. And I really thought u was going to loose ALOT of that when I replaced my Krell FPB 600 which are known for thunderous bass with B&W s. But it’s definitely not the case. I did loose some but definitely made it up for all the other quality’s with the ARC 750s. Now I also wanted to ask you IF I did want to upgrade all my 8 crossovers can u possibly make them for me with your expertise and knowledge? 

@timlub Also forgot to tell u I also have and am using 2 Krell B&W BAFs. ( Bass alignment filters for my 800 Matrix.u can also see my system and all the components and cables etc etc from my profile. 

So, I hear you, but again. I would not rebuild those crossovers. A few parts replacements yes, but you would need to measure every inductor for its resistance then figure into the crossover, when the resistance changes on this tweeter, mid etc, how many other parts have to change value to keep the crossover at the same frequency.  When you change coils,  It appears to the other parts in the crossover that you have actually changed the impedance of the driver itself.  So, your speaker goes a little out of whack when you change the parts, a little more on the mid parts and even more on the woofer.  It can change a speaker to being withing 2 % matched parts to being off 20% in matched parts.  I'm being a bit tough with that description, but the point is, the more inductors there are in a design, then the more you change, the more you risk of destroying the original design. 

So, unless you just don't like the original design, I would only do key parts changes. I have not looked at a schematic, I don't know the slopes chosen or the topology of the crossover, butterworth, likwitz etc.  Now parts choice is a can of worms that very few would agree upon in this forum.  Capacitors,   There are more types than this, but in speakers, normally, you have Electrolytic, then step up to mylar/polyester, then poly carb then polypropylene, then polystyrene and lastly teflon. If I recall correctly, B&W used a lot of Solen parts.  I find the Solen parts to be very decent sounding,  they don't get harsh, they may be a little dry, but they don't do anything particularly wrong.  These boutique caps can get very expensive and yes, I can hear a difference between these parts, but for most people, I believe that they would find a nice improvement changing parts, but not night and day. So for my taste, I would take start with the series caps and all resistors.  This should make a nice change, not cost you a second mortgage and no matter who bought your speakers, the main character of your speakers remains intact and you have simply made a true upgrade by anyone's opinion.  The wrong mod can hurt their value.... I hope this makes since,  Tim

Just take it to the local mechanic 

@timlub   Hey Tim. I definitely hear what you are saying and totally makes 💯 sense. I really would like to get the most performance out of those speakers and I know totally agree what u are saying about only replacing the necessary parts and caps. Maybe some better wiring too ? I would really love for you to do the work on these crossovers for me if u would like to take on the job. I appreciate your time  everything you said to explain all of this for me. And I’m sure I’m making the right decision now not buying those crossovers from eBay. And he also sent me a pic of the new crossovers and they look totally different with a lot less parts and caps. And it looks like they are mounted on a piece of plywood and not a circuit board. If they are. I forget when I installed them when I got my speakers. 

My only FF experience was when I rebuilt my Boston a400’s. It took me maybe 10 min per tweeter . One had tarry looking FF, the other looked fine - go figure.

I replaced both anyhow. I used a meter ( $20 off Amazon ) to check capacitance of the caps and a few were off so I replaced all with film caps.

You should get meter and check them before replacing . I have a 40 year old set of ads 1230’s and and 42 year set of GNP Valkeryies and both had all caps in spec so why replace them? I’ll read posts of ADS owners sending their crossovers to Richard So to be recapped but why bother if they are fine?

Btw, a good track to show off how good your speakers are is the song by the cars called “Drive”. If they are revealing, after the second stanza , you’ll hear bongos playing a counter melody in the back ground of the “duh duhs”.

@katman   Thank u for your reply. I will certainly think about that and possibly I can have my service tech come by and check out the crossovers. I have said that about the Cars song She’s Dangerous. The drums in that song sound phenomenal on my speakers. 

I can do the work, if you think that you can pull them and ship,hit me on private message

No need for a tech, just order a capacitance meter off Amazon $20, put either lead on either side of each cap and see if the number on the meter is with 10% of the number on the cap.

It’s really that simple and you can do both crossovers in 15 min, no chance of damaging anything .

In the time it takes to call someone up and explain what you want you can have one done. But hey, it’s your call.

@katman   You might want to look up his speakers, there are 14 caps in each speaker, not to mention relays, half wave rectifiers and Zeners. The crossover is on multiple circuit boards to handle independent functions, they are not surface soldered and tacked down. I'm not saying that this is a nightmare to do, but you better know what you are tackling.  

So, all you need is a $20 meter?  I have 3 LCR's (meters) and a computer that measures capacitance.  I'm lucky to have some reference parts that I have exact measurements for. I don't disagree that on many crossovers, its a fairly simple chore to change caps, but his speakers are complicated and would not want to see them messed up.  Cheap meters can be off quite a bit in their tolerance.  Just don't believe that in this case that you gave the best advice.  

There’s nothing inaccurate about a cheap meter, they are all good. I see no relays in that crossover ( or any other crossover ) and diodes generally don’t go bad.

a meter would confirm to op that all caps are good and I bet they are as they used quality components.

I wouldn’t change a thing about the crossovers and I think that is good advice.

Personally, I would not spend a nickel on those crossovers , I’d triamp them but then I have an active crossover sitting in a drawer and the amps to run it, I would not recommend this route to OP.

No difference in meter accuracy? You would triamp passive crossovers?

doing nothing is not bad advice, these are nice speakers. 

Also, a trusted ferrofluid might cost $30 to $35.  If you feel that yours is drying up and you don't want just remove ferrofluid, this is still a good option. 

@timlub Tim. I left u a PM on here. Mike. 

Hi Mike, we'll, I've tried to get ahold of you. Audiogon blocks personal information sharing, I believe that it is to stop sales and transactions outside of Audiogon. I realize that I was just helping you with an issue and you certainly had no ill intent. Overall, it would  be nice if Audiogon created a form or something to share personal info when no one is trying to profit.

I don’t want to spin this into a Triamp thread but when I say triamp, I said use an active crossover , not passive .

You can call me a hypocrite as I have my energy 2.8’s passively triamped but I plead innocence as :

1) the manual says don’t use an active crossover with them.

2) I have three NAD 208 amps, might as well use them, right?

Hi @katman well, I do agree that in a perfect world, active crossovers are always better than passive crossovers. There are a few scenarios where they are not, I’ll give you one quick example.

When designing a speaker, I always use the crossover slopes that will achieve the best alignment more the given drivers that I am using.

I have taken drivers and used Linkwitz 12 or 24 and just could not get rid of a hump or a dip or maybe achieve a good phase response, Switch to Butterworth 6/12/18, same, switch to Bessel or Chebechev... yada yada. It can take alot of work to get the best out of a crossover design. I have yet to see a electronic that give the flexibility to change apc/cpc slope types and rolloff.

I believe that there are several threads here that tackle the subject. If you don't find them, you could easily start that thread. 

Again, if all the stars fall into alignment, electronic crossovers are definitely better. I hope this helps. Tim

No, won’t start another thread. My thought was , if you have a quality, well designed speaker , going to active bi/tri amping is more likely to improve things that 

than trying to “improve “ the crossover which isn’t likely to improve anything . Most likely, in this situation , best thing to do is nothing .

One way to make those speakers sound better is to temporarily hook up an old avr with room correction , turn off all tone controls and try to get freq response flat ( +\- ) by changing speaker location, angle and adding /removing room conditions .

Then, get rid of that avr.

tattooedtrackman

Thanks for a great post-question here

I also have the Matrix 800s speakers and love the sound. I looked into replacing the ferrofluid some time ago. Contacted B@W North America they would not do the work here in the states. They wanted me to ship them back to England i passed.I remembering that they told me that there is only one type of ferrofluid to use in the Matrix 800 speakers and any other would cause damage to the tweeter. What the specific brand or type is i do not remember.  tattooedtrackman Please keep us posted with your journey.

timlub thanks for all your great info. Where are you located? 

I'm  in the St. Louis area

@68pete I definitely will keep all updated. Looking forward to hearing some really nice improvements in about a month. 

Please Keep us updated on your finding.

Another Matrix 800 owner here

@tattooedtrackman sent me a woofer, a mid, both tweeters and his crossovers from his B&W 800 Matrix. He had a crack in his woofer, a nice dent in his mid and complained of harshness in his tweeter.

I repaired the woofer and removed the dustcap for the mid and took out the crimp. Then measured the tweeters. One measured as though it had dried ferrofluid, the second measured as though it was just drying up. I went to remove the ferrofluid and noticed that on 1 tweeter the voice coil gap was a bit off. I removed the ferrofluid. It was overfilled and drying up. I rotated the voice coils and put them back together. FS was cut in half with the old fluid removed, but one was still off a bit, but they still measured a bit better than when I got them overall. I then upgraded Every Cap in the crossover, redesigned the tweeter section to close a sizeable hole between the mid and tweeter and sent them back. Mike’s initial impression was that everything was better, but it wasn’t long before he was feeling that there was a harshness out of one side that wasn’t on the other. He pulled the tweeters and crossovers and sent them back to me. I disassembled the tweeters, the voice coil magnet gap just wasn’t right on one of them. I took a spacer and moved around the gap trying to get in back in round. I soon felt comfortable that there was a clear improvement. I went ahead and measured out just enough ferrofluid to say that it was enough and replaced the coils. this time continually rotating and remeasuring until I got a very close match between tweeters. I then changed added a bit more resistance and changed the inductor coil on the tweeter crossover.. Even though the same 18db per octave slopes were used, the design was a fair bit different than the original. B & W used 18db bessel slopes. The mids were rolling acoustically at 24db per octave, with the hole between mid and tweets, crossover point was 10db down. I lowered the crossover point by 200 hz and I changed the slope on the tweeter from bessel to butterworth. The butterworth slope along with the slightly lower crossover point gave us a linkwitz alignment at 2200 hz. So, the hole was gone, what was a hole is a smooth transition response. Mike has only had these back for a few days, but that is what was done. I really believe all problems were taken care of.