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Post by Boomzilla on Nov 27, 2013 19:45:36 GMT -5
Many, many speakers from the 1990 & 2000 decades had metal-dome tweeters damped with "ferrofluid." The idea was that the viscous fluid, magnetically held in the tweeter voice coil gap, would dampen resonances and ringing in the (then new technology) metal-dome tweeters. Now, in 2013, many of those tweeters sound dull, or have quit working altogether. This happens because the liquid in the ferrofluid has evaporated, leaving a muck or solid in its place. The muck reduces amplitude of the tweeter (making the speaker sound "dull" or "muffled"). The solid prevents the tweeter from working at all. Most people throw away their speakers at this point and buy new ones. But with a bit of elbow grease, the tweeters can be restored to "like new" performance. This thread shows how. Most speakers have removable grilles, but the ones my friend gave me were fitted with "socks" that were secured at the top with a tied-string closure. To drop the socks, untie the string. Then, at the end of the string tips, tie a knot. Why? Because if you don't the strings will retreat into the top loops in the socks and you'll never get them out again (I speak from experience here...). Once the socks are gently pulled down, unscrew the tweeter faceplates from the cabinets. You may need to wiggle the tweeter edges with your fingernails to get them to come loose. The manufacturer of the speakers I was working on (Paradigm) inset the tweeter faceplates to be flush with the cabinet face. After removing the tweeter from the cabinet, stop and mark which wire goes to the + terminal of the tweeter. Paradigm made it easy for me: Blue wires were + or positive and green ones were - or negative. They also (thoughtfully) supplied a + and - molded into the back of the tweeter's faceplate, so I didn't have to mark that either. Had Paradigm failed to do these things, I'd have needed to use a marks-a-lot to mark one of the wires (wouldn't matter which) and then use an awl to scratch the matching terminal on the tweeter. Why not just mark the tweeter with the marks-a-lot? Because solvent will be needed to clean the tweeter, and when applied, it will wash away any marks-a-lot on the tweeter.  Once marked for polarity, I undid the three small screws that hold the faceplate onto the tweeter. The screws are TINY, but the pole magnet on the tweeter is STRONG. The domes are so delicate (think of them as "gold leaf" says Garbulky) that allowing any of the screws to be drawn onto the dome by the magnet will DENT the tweeter dome: After that first, I discovered that if I pointed the dome down, and then undid the screws, gravity would drop them to the table top without falling into the dome. To touch the dome is to dent it. Once the faceplate is off, lift the dome and voice coil out of the magnetic gap. The voice coil former, fortunately, is more robust than the dome itself. I used rubbing alcohol on a q-tip to wipe the magnetic fluid off the outside (wire side) and inside (coil former side) of the tweeter dome. Once the voice coil is clean, the real work begins. The magnetic gap where the coil resides must also be mucked out: There's just no easy way to do this. My method was as follows: Drip some rubbing alcohol into the gap. While holding a paper towel over the assembly, use a can of compressed air to blow the alcohol and muck out of the gap (this can be messy). Then drip some more alcohol into the gap and, using folded scraps of newspaper, keep dipping the muck out until your newspaper comes out clean. This takes about five to ten minutes per magnet. Once clean, add a SMALL amount of new ferrofluid (Parts-Express.com sells it). Then place the voice coil back into the gap (carefully - bend the coil former & you've got a throw-away). Now replace the front plate of the tweeter that holds the voice coil assembly in place. Remember NOT to let the retaining screws loose or you'll have a dented dome! Use your VOM to make sure that the coil still has continuity. The DC resistance should be somewhere between 4 & 6 ohms for most tweeters. Once done, re-connect the wires (making sure the polarity is the same as when removed). Screw the tweeter mounting plate back onto the cabinet and you've got some "like new" tweeters that again function as they were intended. Now shimmy the sock back up the tower, tie the ends to tension the sock, replace the top cap, and good for another 18 years! Boomzilla |
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Post by garbulky on Nov 28, 2013 0:49:43 GMT -5
Much respect B'zilla. I had a heart attack by the time you had to disengage the tweeter from the coil. Definitely not for me!
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Post by Darksky on Nov 28, 2013 1:47:33 GMT -5
Excellent instructional thread, Boom.
I don't want to go to off topic, but I am curious, for this type work, do you have an Opti-Visor?
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Post by Boomzilla on Nov 28, 2013 9:06:36 GMT -5
Hi Darsky =
Nope, I don't but I should probably get one. I currently use a jeweler's loupe, same as when I'm working on watches, but the visor would give some depth perception (lacking in the monocle) so I should visit Harbor Freight... Thanks for the idea - I also see that they make them with LED illumination! Cool!
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Post by Darksky on Nov 28, 2013 10:52:05 GMT -5
When you order one, get the opti loupe too. It allows you to get super close up with just a flick.
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Post by Boomzilla on Nov 28, 2013 11:02:56 GMT -5
Will do - Thanks again Darksky!
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Post by ocezam on Nov 30, 2013 10:38:45 GMT -5
In your other thread you said you just added some new fluid in an attempt to dilute the existing fluid to something close to normal, but were unsure if it worked. Now you did a complete disassembly and refill. Did it work this time? How different is/was the sound when you first brought them home? After the first attempt? And finally after the complete disassembly?
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Post by Boomzilla on Nov 30, 2013 12:17:29 GMT -5
Different speakers. The ones I added some new ferrofluid to were Paradigm Studio 20s v.3. They did perk up after the fresh infusion. Were they "like new?" I don't know - I've never heard new ones.
The second set I worked on were Paradigm Eclipse BP speakers (one front & one rear tweeter per speaker). When I was given the speakers, they had no treble at all. The tweeters were almost completely frozen by the muck. The previous owner didn't want to mess with them, so he got some new speakers and gave me his old. Since I had nothing in them, I had nothing to lose by experimenting. Rather than add any fluid at all, I completely disassembled & cleaned each tweeter and then added some new ferrofluid.
They now have treble again. Is it "like new?" I don't know - I've never heard new ones. From what I've read on the internet, Paradigm originally "voiced" the Eclipse speakers with the tweeters -3dB from the woofers. Perhaps they thought that in a normal room, the rear-firing tweeters would make up the difference? Again - I don't know. The Eclipses certainly are NOT "bright" now, but they do sound clean although not exceptionally extended. If I had a preamp with a tone control, I could crank up the treble a notch to compensate, but I don't have a preamp. Therefore, I plan to (eventually) vertically bi-amplify the Eclipses, using the rotary volume pots on the individual channels of the Crown PS-400 to bring the tweeters up to whatever level sounds good to me.
Don't get me wrong - The speakers sound very good now. They throw a HUGE soundstage in my room completely equivalent to what the Magnepan 1.6QRs can do, but without the slight treble peak that the Maggies have. I could totally live with the Eclipses as they are now (and until something better comes along, I plan to). I believe that what I'm hearing now is what Paradigm intended in this design. If I didn't have sound absorber panels in my room, the sound would probably be perfect. But with the deadening effect of the panels, the Eclipses sound just slightly dull in the upper treble. This is consistent with what I've read online in reviews of the Eclipses.
So to summarize, and to answer your question, ocezam, yes - the improvement was worth the effort. The "clean and replace" method does a MUCH better job of restoring the tweeters than does the "dilute with some more fluid" method. On the Paradigm Studio series speakers (considered by critics to be slightly on the bright side from the factory), the dilution method was sufficient. But with the Eclipses (slightly on the recessed side from the factory), the entire clean and replace cycle is needed to restore the treble IMHO.
Hope this helped - Boomzilla
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Post by brubacca on Dec 9, 2013 13:51:14 GMT -5
So I recently tried to put my Paradigm Studio 20 (V1) back into the mix. And they just didn't sound right. I also had someone ask to buy them so I decided that before I sell them I should check them out. Well turns out that the tweeters are putting out 10dB less than the woofers. I ran a HT Processor test tone to just the LF and HF and measure the output with my iPhone.
I called paradigm and I can get new Diaphragms for $30 each.
Is the diaphragm the dome and connection part, but not the magnet? I'm thinking that it is the triangular piece at the bottom of your second photo...
Anybody think that they are worth fixing?
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Post by Boomzilla on Dec 9, 2013 18:15:04 GMT -5
A new diaphragm probably won't help. Your current diaphragms are electrically intact (or they wouldn't be playing at all). What has happened is that the "ferrofluid" that Paradigm initially put in the voice-coil gap has thickened to the point where it is restricting the diaphragm motion. This is a physical problem, not an electrical one. To get the old OR new diaphragm to work, you'll need to do what I did in this thread. Pull off the existing diaphragms, clean the goop off of them, clean the goop out of the voice coil gap in the magnet (the hardest part), and then just put the clean diaphragms back in. I've tried it with and without new ferrofluid from parts_express.com - No difference that I can tell.
The main thing is the cleaning. Replacing diaphragms into goop-filled voice coil gaps won't fix the treble.
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Post by brubacca on Dec 9, 2013 20:45:20 GMT -5
Sounds like a good week after Christmas project. What's the worst I can do? Thanks!
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Post by Boomzilla on Dec 9, 2013 21:15:14 GMT -5
Sounds like a good week after Christmas project. What's the worst I can do? Thanks! Worst you can do is damage a dome or coil badly & have to buy a replacement. The magnet is too meaty to damage. Just make sure you get all the goop out of that magnet! |
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Post by dutchie on Mar 12, 2014 9:12:39 GMT -5
Very interesting Boomzilla. I do have the Paradigm Eclipse myself for 15 years now, and I love the idea from repairing or restoration the tweeters. What I do not understand is how much ferrofluid do I need to pour in the gap? Is there a measurement for each tweeter in order to let them sound equally? I have never done this in my life but I would like to give it a try. I live in North East Thailand and I have no credit card so I can't order it from abroad. Is there a way to make ferrofluid with the right components myself? I have found some information on the Internet, but I am afraid that I will mess up the tweeters. Please give me your valuable response.
Regards Dutchie
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Post by Boomzilla on Mar 12, 2014 10:21:56 GMT -5
Hi Dutchie - PM sent.
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KeithL
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Post by KeithL on Mar 12, 2014 10:40:48 GMT -5
I've never personally replaced the ferrofluid in a tweeter - but a few basic technical details come to mind.....
* Ferrofluid is really microscopic iron particles (or another ferromagnetic equivalent) "floating" in a viscous liquid. If it "dries out", the liquid will get thicker, or solidify, but the particles will remain. Therefore, if you add new ferrofluid, it will have both the new "proper" mix PLUS the original magnetic particles. This will definitely not be at all the same as the original OR the replacement fluid by themselves - so fully removing the old fluid seems to be essential (if you want "normal" performance).
* You can't overstress the importance of being *careful* when handling the dome and diaphragm. Domes, especially the aliminum ones, dent VERY easily. (Incidentally, if you do get a dent, a very slight dent won't necessarily affect performance much, and you can "pop out" a dent by VERY CAREFULLY touching the corner of a piece of sticky tape to the center of the dent, then pulling gently to "pop" it. On mylar or silk domes, this can often return the dome to perfect shape; on aluminum ones, it will usually leave a slightly rumpled surface that may well sound fine.) You've also got to make sure to line the diaphragm up properly when you replace it so the voice coil doesn't touch the magnet. (If you bend it out-of-round you will have to get it back to perfectly round.)
* With SOME drivers (especially older and more expensive ones) you can get replacement diaphragms from the manufacturer - and even from some third party vendors (Google "rebuild" plus the name of the speaker or driver). (Or ask Parts Express .)
* Likewise, some vendors (both manufacturers and third parties) offer specific replacement drivers for specific speakers. (It always pays to check. While rebuilding and reusing is always cool, if it turns out you can replace the whole tweeter for $10 or $20, then it probably makes sense to do so.) These may often be slightly different, and so may change the sound - for better or worse - so be careful on that score. if you have especially old speakers, you may find that a modern tweeter is an improvement. (I wouldn't go that way unless I was displeased with the sound to begin with.)
* You CAN add ferrofluid to a tweeter that didn't originally have any. Doing so MIGHT reduce resonances, which might make it sound smoother, will probably also reduce efficiency slightly, but may increase power handling capability quite a bit..... It will change the sound, so only try it if that is part of your goal. (Note, the ferrofluid also MIGHT destroy the driver if it reacts with the adhesive or other components, so this is definitely a "youse takes youse chances" sort of experiment - but the results could be very pleasing.
* SYMMETRY is very important. Try to put the SAME amount of ferrofluid in the left and right tweeters (otherwise, they may well sound different, which would be bad).
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Post by voyager7 on Nov 17, 2014 10:26:17 GMT -5
Hi Everyone! Just to add to this interesting thread, I bought 3 pairs of Scandyna/Blueroom MiniPod speakers in 2006. Recently I have noticed that the trebles produced were getting really muffled/dull. I knew the tweeters were not blown as I never played them very loud and treble was being produced albeit at a VERY low level, to the point of almost being inaudiable. This led me to conclude either a component on the crossover was blown (again, unlikely) or, after reading this ferrofluid thread, the fluid had dried up and made the voice coil gunked into the magnet motor. (Little movement of the voice coil=little sound I thought.) I started by removing the soft dome silk tweeter and trying to remove the magnet from the voice coil. This was quite difficult as the magnet was glued into the voice coil surround. However after some perseverence with a large flathead screwdriver and breaking a couple of bits of the plastic surround, I got the magnet off and found that the ferrofluid had gone thick and brown, so much so that the voice coil was being stuck inside the magnet motor gap. After cleaning the voice coil with some cotton buds and white spirit, I tried to clean the round voice coil gap by filling it with white spirit and cleaning with bits of thin cardboard and rinsing with more white spirit. I re-assembled the tweeter, but before doing so I filled the round voice coil gap with PTFE spray to allow the voice coil to move easily in the magnetic motor. On re-assembly, I originally pushed the magnet right back flush to the voice coil housing as it was originally,but when I listened to the tweeter, it still sounded really low level, so I used the screwdriver to ease the magnet about 3mm and boy what a difference it made! The trebles were back and at a proper level. I repeated this procedure with 4 of the 6 tweeters and managed to carelessly damage one of the voice coils with the screwdriver (if you are considering attempting this repair, be VERY careful easing the magnet off the voice coil!) however I bent the voice coil back into a perfect circle and it sounded fine in the end. Interestingly on the 5th tweeter repair (yes 5 of the 6 were bad!) I only eased the magnet 3mm back whilst it was still playing music connected to the amp and the effect was immediate so I did not disassemble the last tweeter fully, but glued it in place as I had done with the other 4. Now I have 6 fine sounding speakers again, saving myself almost £200 in new tweeters! I would be interested if any speaker experts here could explain why the last one just needed the magnet to be backed off the voice coil around 3mm for the trebles to come back and be audiable again? |
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Post by jime on Dec 12, 2014 11:55:30 GMT -5
Very interesting Boomzilla. I do have the Paradigm Eclipse myself for 15 years now, and I love the idea from repairing or restoration the tweeters. What I do not understand is how much ferrofluid do I need to pour in the gap? Is there a measurement for each tweeter in order to let them sound equally? I have never done this in my life but I would like to give it a try. I live in North East Thailand and I have no credit card so I can't order it from abroad. Is there a way to make ferrofluid with the right components myself? I have found some information on the Internet, but I am afraid that I will mess up the tweeters. Please give me your valuable response. Regards Dutchie I have the same question as Dutchie. How much ferrofluid and where/how to apply (once they are cleaned out). I am rebuilding tweeters from Paradigm studio reference 40s, and one driver is noticeably louder than the other. Perhaps you can share your answer with all of us? Regards, Jim |
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Post by jime on Dec 13, 2014 14:10:38 GMT -5
I have the same question as Dutchie. How much ferrofluid and where/how to apply (once they are cleaned out). I am rebuilding tweeters from Paradigm studio reference 40s, and one driver is noticeably louder than the other. Perhaps you can share your answer with all of us? Regards, Jim |
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Post by Boomzilla on Dec 13, 2014 15:01:05 GMT -5
I used about two or three drops per tweeter. You want to fill, but not overflow the voice coil gap. And you have to remember to leave room for the voice coil itself (which takes up most of the gap). I put my coil into the gap partially, lifted it & wiped excess fluid from the magnet's face, then repeated until the coil fit all the way into the gap without overflowing any fluid. Then I bolted it back together.
My first tweeter, I put way too much fluid in (and had to mop out some). On the second try, I got it right.
Hope this helps!
Cordially - Boomzilla
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jime
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Post by jime on Dec 14, 2014 13:44:14 GMT -5
I used about two or three drops per tweeter. You want to fill, but not overflow the voice coil gap. And you have to remember to leave room for the voice coil itself (which takes up most of the gap). I put my coil into the gap partially, lifted it & wiped excess fluid from the magnet's face, then repeated until the coil fit all the way into the gap without overflowing any fluid. Then I bolted it back together. My first tweeter, I put way too much fluid in (and had to mop out some). On the second try, I got it right. Hope this helps! Cordially - Boomzilla Perfect, thanks very much, Jim |
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