Hey guys. So I have been texting someone from Germany I met online as he also has a pair of B&W 800 Matrix speakers. He mentioned that he treats his tweeters every so many years with Ferro fluid. It was kinda hard to actually text about it online with someone I just met from another county. I did google it and looked on utube for some videos and there are some. It’s seems it should be done about every 10 years or so. And u actually have to take the tweeter out of the cabinet disassemble / remove the voice coil clean out the old Ferro fluid and add new Ferro fluid. It’s seems to be some kind of a magnetic liquid used in speakers especially tweeters for better clearer sound, highs, voices etc. It really looks like a job for the experienced in rebuilding speakers. Has anyone heard of this or had it done ? I’d really love to know from folks who had experience with this. My speakers are from the 90s and even though they still sound phenomenal I’d really like to know more about this. I do plan on keeping my speakers for the long term. Thanks to all in advance. 

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@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.