Repairing Bose Active Noise Cancelling Headphones

[Mansour] was disappointed to find out that his Bose QC15 headphones had a dead right channel. These headphones have active noise cancelling, which uses a microphone to capture ambient noise and digital signal processing to insert an out of phase signal. Since they’re quite expensive, [Mansour] was determined to resurrect them.

First, he determined that the right speaker had died, so he found a replacement on eBay. These were designed for a different set of headphones, but matched the impedance of the original Bose part. After replacing the driver, it seemed that the repair was a failure. The sound cancelling wasn’t working, and a the playback was high-pitched. As a last attempt, he potted the speaker with glue, to match the original construction. Much to his surprise, this worked.

The problem was that the new driver didn’t have sufficient sound isolation from the microphone, which is meant to pick up passive noise. This feedback likely caused issues with the noise cancelling DSP. A little glue meant a $20 fix for a $400 pair of headphones.

30 thoughts on “Repairing Bose Active Noise Cancelling Headphones

  1. not to nitpick, but I kind of doubt those use a DSP. Probably just an inverting amp. All those caps and inductors suggest analog signal processing to me. I could be wrong…

    1. I could be just as wrong, but those capacitors and inductors could be parts of two (or more) switchmode power supplies, to create a symmetrical power supply from an asymmetrical supply like a battery, and possibly a separate supply for the digital circuit.

      I’d think it would be fairly difficult to suppress the local feedback from the speaker back to the microphone, and to provide just the right amount of power and phase shift to cancel external noise, over a large frequency spectrum, with just analog processing. Even with a decent DSP, it doesn’t exactly seem trivial to me.

      1. Well, presumably that’s why they cost so much. I have a pair of QC3s and after 5 years of fair use the fine plastic parts just crumbled and the pads skinned horribly, Still usable, though. Have had some problems with feedback and my phone not recognizing them probably because they present a higher-impedance load than passive headphones. So I’m thinking about modding them so I can bypass the fancy active electronics when needed.

        1. You could build an adapter cable with a 3.5mm jack and socket connected straight through, with 33 ohm resistors between the signals and ground. That should provide the load your phone wants to see.

        2. You can sew the earpiece covers on some models… QC2 perhaps? Not sure what model I have. Anyway, a few pictures of the process: http://people.renci.org/~escott/bose_headphone_repair/index.html . I’ve had to sew pretty much every inch of mine back together. And of course, the usual failure mode is that the plastic fails where the headband comes into the top of the cans. All in all, a pretty junky product for the (outrageous) price. Sure, they were a gift, but…

          1. I just replaced my worn out earpiece covers for about $10 (ebay) and 5 minutes (following a Youtube instruction).

            Intermittent cutting out of the right side of my QC15s brought me here, I have to tap it to get it to work.

        1. I actually disassembled the headphones again and there aren’t any significant chips on the other side. See the post for the new photo of the back side.

  2. could you not just use the inverse of the input?? a hight speed not gate ?? why shift phase ?? I have little electrical engineering experience so I’m probably overlooking some obvious reason that would fail.

    1. The ‘not gate’ you refer to is digital, but you’re dealing with analog signals. Also, you want to cancel out the ambient noise, i.e. what’s picked up by the microphone somewhere in the headphone shell. With that microphone signal the signal processor performs some trickery so that the result is a signal that is roughly the inverse of the amount of ambient noise that would pass through the headphones to reach your ears.

  3. Nice, its amazing how much useful stuff gets needlessky trashed these days because it needs a 2 dollar part.
    I acquired some nice wireless headphones a while back because it had the “special” AAA batteries with conductive collar a third of the way along whose absence prevented the headphones from charging. Fixed:-)

  4. As something between trashing it and fixing it, Bose will give you a new pair of QC15 headphones for $100 plus return of the old ones, at any time.

  5. You know, if you are going to sell headphones for 400 bucks, you’d better make replacement parts available I say. It’s basic stuff.

  6. Hack-a-Day-ers,

    I’m an engineer for a company that provides In-Flight Entertainment systems to commercial airlines. The full-up system – servers, video displays, handset controllers, audio jacks, everything but the headphones because those are throwaway. Part of our system is an active noise-cancelling module. It works at least as well with $3 Chinese headsets as the Bose headphones on their own. It is all analog. No need to add DSPs other than to make it appear that the headphones are “worth” the $400 price tag.

    1. I guess designing specifically for airplane noise can boost the performance of the system, but I find it hard to belive that a $3 headset can be very much effective in active noise cancelling. Would you be able to share any details about this In-Flight systems… like what is the perceived noise attenuatinon for each frequency range, where is the power supply located, MICs, etc.

  7. Hi there, I wonder if anyone can help me. I am repairing a pair of this headphone where the negative terminal in the battery compartment was broken off so I wanted to know if someone knows where the wire from negative terminal enters the main earpiece unit. I would be grateful for any description or a close-up picture showing the wire going in from negative battery terminal.
    Kind regards
    Annie

    1. In the photo on this page, look at the series of colored wires that are soldered on the right side of the board. The solder blob on the top right of number “2″ is the battery’s negative.

  8. Hi there,

    I was recently travelling and noticed, what appeared to be, my battery had exploded within my headphones. I tried to clean it out first with a q-tip and then a q-tip with some rubbing alcohol on it, but when I insert the AAA battery – my headphones no longer work :(

    Does anyone know what I can do to troubleshoot this or maybe even replace that whole unit? Or will I have to replace my headphones… :(

  9. I figured out what the problem was for my QC-15 Headphones not powering up. Its definitly a design defect with this model. The problem is that the wire that runs from the battery compartment to the negative post on the door/hinge has a fatigue failure problem. Through many repetitions of opening and closing the door to change the battery you inadvertently cause the wire to snap, very similar to how a paper clip breaks when you bend it back and forth a bunch of times. The wire is pretty hard to see too because they have it pretty well hidden on the little hinged cover and it dissappears into the headphones maybe 3/4″ down from the edge of the hinge. You really have to look to see it.

    What really gets my goat here is that it seems that quite a few people are experiencing an issue where the unit just fails to power up all of a sudden and end up sending the unit back to Bose for close to $100 for a “replacement”. That is just plain old robbery for an almost built in failure point on a pretty expensive pair of headphones. When they get your headphones in they replace one tiny wire and then ship them to the next customer for another hundred dollars. Its insane.

    The only reason I found it was that it happened right after i changed the battery which got me thinking about what could have possibly happened just from changing the battery. SO check the negative post wire to see if its broken. Also its worth mentioning that the wire could be intact and still broken internally. Mine was just snapped right in half though.

    1. Hi Ryan,

      Can you post pics of the design defect? I am really upset with Bose, got of their customer support. The usual right QC15 side of the headphones has gone blank. If I tap, I hear a crackling sound with music for like a nano second and it dies on me.

      I have no choice but to get this repaired. I have no experience in soldering and glueing like mentioned above and frankly it is all daunting. But, if what you say is true, perhaps I can be inspired to push myself in learning and fixing the fatigued wire from the negative terminally the battery to the soldering blob.

      Has anyone had any issues with the qc25. They have done away with the battery.

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