[Martin] seems to have a knack for locating lightly damaged second-hand audio gear. Over the years he’s collected various types of gear and made various repairs. His most recent project involved fixing two broken tweeter speakers.
He first he needed to test the tweeters. He had to remove them from the speaker cabinet in order to gain easier access to them. The multimeter showed them as an open-circuit, indicating that they had likely been burned. This is an issue he’s seen in the past with this brand of speaker. When too much power is pumped through the speaker, the tiny magnet wire inside over heats and burns out similar to a fuse.
The voice coil itself was bathing in an oily fluid. The idea is to help keep the coil cool so it doesn’t burn out. With that in mind, the thin wire would have likely burned somewhere outside of the cooling fluid. It turned out that it had become damaged just barely outside of the coil. [Martin] used a sharp blade to sever the connection to the coil. He then made a simple repair by soldering the magnet wire back in place using a very thin iron. We’ve seen similar work before with headphone cables.
He repeated this process on the second tweeter and put everything back together. It worked good as new. This may have ultimately been a very simple fix, but considering the amount of money [Martin] saved on these speakers, it was well worth the minimal effort.
I’ve done the same thing, but I carefully peeled one turn of wire off the coil to get enough to reach to the terminal. But it was on a small headphone speaker. Just to see if I could, and it worked.
Please which kind of cable can you use to replace the built coil?
Please which kind of cable can you use to replace the burnt coil?
Broken tweeters? It’s all about the bass these days anyway.
no treble?
Treble is just the buildup to the drop….
One day you will grow up and listen to real music, I.E. metal or classical and you will need those tweeters.
I hear you on the classical, but most metal these days is so horribly compressed that having good tweeters won’t matter. The highs are so muddled and bland it may as well be mall music.
Do you seriously thing murdock and TERRA Operative were being serious?!
Sidenote: I find it hilarious that you hold up *metal* of all things as the example of real music to stand alongside classical. Everyone knows Burzum and Darkthrone are timeless examples of nuanced and balanced sound!
Don’t get me wrong, I love metal, and would absolutely include it in any list of music that will be mentioned in music history textbooks decades from today. It’s just that mentioning those two and only those two amused me.
@Blue Footed Booby
Or did I just miss an additional level of irony and get hoisted by my own petard?
I swear the internet kills brain cells.
You can’t kill the metal!
Made my day :D
I’ve toyed a bit with dissecting and repairing failed speakers. When there’s a break at the wire leading to the coil like [Martin] found, I’ve yet to see one that shows any evidence of overheating, like the discolored insulation that would inevitably result from melted copper. Instead I always see the wire was positioned in a way that favored flexure at a single point rather than spread out more evenly, leading to metal fatigue at that point and eventual failure. The wire end looks snapped, or if litz frayed, but not melted. The repair must be performed in a way that alleviates the situation or it will fail again, usually much faster. Move the voice coil and verify where the wire flexes. If it’s a single point, reshape the wire to act more like a spring and distribute stress. You can add some extra length and slack if necessary, using thin and flexible wire, or even a little light reinforcement like a dab of silicone or rubber cement as a stress relief.
Burn-out seems much more likely in the inner layers of the coil, where cooling is difficult even with supplemental oil or ferrofluid. It’s possible [Martin]’s tweeter was an exception, but the picture showing the failure is too small to gain any clues.
Hi Chris,
In my case both tweeters were burned as large portions of their wires were black from the connector to the coil with in both cases a rupture close to the coil.On one of these tweeters the wire burned in a place that was not in the coil yet but already glued to the tweeter dome and I had to scrape the glue off to fix it. For the other one, the problem came from a place where the wire was loose (yet very close to the coil) and the failure might therefore have been caused by both overheating and metal fatigue. I also gave wires a little more room to move (oscillate).
Thanks for the advice, I think I will add a little epoxy on my repairs to make them more durable.
Interesting. I guess the glue could have acted as a thermal insulator as well. Tricky spot to find a break, kudos for finding and repairing it. For the one depicted in your article, was the burn-out where the wire is squeezed between the black foam and the beige part? What is that beige part anyway, plastic or elastomer?
The beige part is made of a softer plastic (elastomer?) used to secure both wires I suppose. The burn-out on my tweeters was actually much closer to the coil. For one tweeter, it burned at the base of the coil (exactly where the coil begins) and the other one was a millimetre or so away from the coil. Note that the wire was glued (epoxy?) all the way from the coil to where the black foam starts and this part is not bathed in ferrofluid.
On the left, you can see a piece of tape securing both wires on the plastic. When I removed it to check both wires I noticed burn traces on the tape as well (but the wire was still conducting there).
Ah, those days when I was 15-yrs old… I couldn’t afford decent audio equipment, so I collected various donor stuff that has burned beyond service was willing to repair or it was just not affordable to do so.
I’ve once rebuilt a set of bass speakers that had burnt flex membrane and it’s entire coil base…. I still use it today with one of the amps that was on fire due to burned traces in the power section. I wouldn’t trade them for anything.
Oily fluid is ferrofluid. Originally developed as an assembly aid to keep the coils centered in the magnet gap, it turned out to also provide damping and cooling – properties completely unintended by the people who developed the material.
What I’d like to see someone try with a dual voice coil speaker is active distortion canceling. Apply a 180 out of phase pulse to one coil at the extremes of speaker motion. With current technology, the audio signal could be processed in realtime and the control signal ramped up and down for very fine control to prevent overshoot and the distortion and possible speaker damage.
Experiment to see if the frequency response can be extended, up and/or down, beyond manufacturer specifications. A successful design could be built right into the speakers, which would then need power and audio connections.
Making a universal module for any dual voice coil speaker would require it to be adjustable, with some way to tell when peak performance from adjusting is achieved. Built into the speaker or matched with a specific model of speaker would be the way such a gizmo would be commercialized.
I’m sure I’ve seen some old designs similar to what you describe. Strictly in the audiophile domain and quite expensive. It could be done inexpensively using current tech, but given that audiophiles with deep pockets might still be the target market, it’s likely it would still be priced high. And some distortion would still come from the inertial lag of the semi-rigid speaker cone, although I bet with all the neat magnetic and capacitive proxy sensors around today, one could find a way to cancel some of that too.
Ferrofluid was *not* designed to keep speaker coils/formers aligned, that was a use discovered well after its invention.
uhhh….ok….a camp radio would be nice….solar input 15 volt 3.2 amp solar panel…got a voltage regulator 12/24 volt plus a 7amp hour battery, and an invertor from 12 to 120 volts AC….
what does that have to do with anything???
This is somewhat counter intuitive to non-electronic types, but tweeters usually burn out from being driven by UNDER powered amplifiers. If you power a speaker from an under powered amp, and some dweeb maxes out the bass and turns it up really loud, the amplifier will clip the signal. Clipping is that harsh sound you hear when the amp’s output hit’s it’s maximum voltage and flatlines for a while till the input level gets low enough to dip below max. Clipping can turn a sine wave into a square wave if you’re watching the amps output on a scope. What happens is clipping generates a LOT of high frequency harmonics (and resulting wattage) that goes right through the high pass crossover in the speaker and into the tweeter. For a tweeter used to getting 1/10th of the total speaker power to handle more like 1/2 due to clipping usually means tweeter burnout.
Note that you are still overpowering the speaker. The answer is not a bigger amplifier. The answer is either 1. a clip limiter on the amplifier in question. 2. Bi or Tri amping the system such that the clipped signal are isolated to the respective speaker or 3. Don’t let dweeb’s control the volume knob on your stereo and run the system within the system’s limits.
Overpowering the speaker? I wouldn’t say that. Say your speakers are rated for 100w, but you hook them to a 40w amp thinking you’re doing a good thing, then you crank the amp into clipping on some heavy bass rap for a few hours – you’ll likely blow the tweeters. That doesn’t even have to be uncomfortably loud if a lot of bass is involved. Heavy bass requires a lot of wattage from the amp. It’s pretty rare to spend $200-500 on an AV receiver/amp that limits clipping (or even has a clipping indicator), and rarer for an average shopper to even know what bi/tri amping is (neglecting subwoofer – satellite home theater crap). The folks at Polk wrote a blog about how according to their repair dept, clipping was the #1 cause of tweeter burn out. Their advice? Listen for the clipping, and turn it down if you hear it.
The speaker (the assembly consisting of the enclosure, the drivers, and the crossovers) itself isn’t getting overpowered, but the individual driver (the tweeter) most certainly is, by virtue of getting (per your example) 500% more power than normal. That is, most certainly, an overpower situation.
A semantic issue, where both sides are correct.
Regarding speaker repairs, take a look at the dizzying array of domes, cones, voice coils, spiders, leads, terminals, baskets, surrounds etc. that are available on eBay for fixing dead speaker drivers. In pro audio this is how it’s done; when a part fails you replace the part rather than tossing out the whole assembly.
Just about anything that’s been put together can be taken apart, and often it can be fixed. I used to make a reasonable living repairing vintage audio gear and reselling it overseas. This sometimes meant mending a tweeter lead that had corroded through from being in contact with an acidic paper insulator. Or unwinding one turn from a transformer to splice a winding that was cut by mechanical damage. Or gutting an old ‘can’ type chassis mount capacitor that was shorted and stuffing it with modern capacitors for original appearance.