PSB M4U 2 headphone failure and fix

I had wanted a nice pair of noise cancelling headphones for some time. The undisputed champion of "noise cancelling" is Bose. At the time this was the QC15, more recently replaced by the QC25. I have tried many NC headphones, and can confirm that the noise cancelling system in these headphones is amazing. However, they are rubbish to actually listen to music on. So after trying out a bunch of headphones, I went with the PSB M4U 2s.

These headphones appealed to me for many reasons. The sound out of them was excellent. They offered not only noise cancelling, but also had a built in amplifier that could be turned on without NC. The cable was removable and could be attached to either side of the headphones. They functioned as a headset. They functioned and sounded great with no battery at all (passive). And lastly, they seamed very well built. No plastic snaps but screws all over, with metal and high quality polycarbonate.

If there was one downside it was the price. And really, the price was justified but I didn't want to spend $400 at the time. I managed to find them used for half that. I have enjoyed wearing these almost every day for over a year. But two weeks ago the left channel just stopped working.

Customer Service & Warranty

I contacted PSB about getting them fixed. I didn't expect warranty service because I purchased them used, but I was expecting to be able to pay to have them fixed. This proved to be false. Unlike PSBs other products, which are made right here in Ontario, Canada, their headphones are made in China. PSB informed me that they do not service out of warranty headphones. I called the two closest authorized PSB dealers, and was informed that they cannot service them because PSB does not supply parts and I should contact PSB directly. I contacted PSB again about getting parts, and they informed me that they do not provide parts. So it appears, that if you have a fault with your M4Us after the 2 year warranty has expired, you're on your own.

The Flaw

First off, these headphones were purchased used. It's very possible that this flaw was fixed in later units. I took apart the left side of my M4Us. As expected, the headphones are well built using hardware instead of glue and plastic snaps. This was until I get it all apart. On the inside it was apparent that PSB chose form over function. The cable used to connect the two halves of the headphones together was wholly inadequate. It was tiny, to facilitate hiding it within the head band.

I've created an image with two areas highlighted. You can see that the individual cables fray where they come out of the sheathing a 1. One of the cables for the speaker was being held by just one copper strand when I took things apart. You can see in the area marked with 2 that another wire had completely come disconnected. 2. also illustrates what I would call the main design or assembly flaw. The cable sheathing terminated right where the housing ends for the main body of the headphone earpiece. I've pulled it out to work on it, but this explains the fraying. The cables were rubbing up against the plastic here. 

Overall, there are 12 conductors coming in through that tiny cable. They are small and fragile. I had another 3 come off their solder joints just while trying to take the unit apart. 

The Fix

You will need the following items to fix these headphones:

1. #0 Philips screwdriver
2. #6 Torx Screwdriver
3. tweezers and/or small needle nose pliers
4. precision wire cutters
5. thin masking or electrical tape
6. precision tip temperature controlled soldering iron
7. flux
8. heat shrink tubing
9. heat source for shrinking the tubing

You might also need extra cable if things are really bad. I found replacement headphone cable on Deal Extreme which I have ordered but didn't need. 

1. Take apart the headphones by fist removing the ear padding on the side that has stopped working.
2. This will expose 4 Philips screws holding the speaker into place.
3. Be careful pulling the speaker housing away as there is very little slack in the cable.
4. Twist the speaking housing to get to the two Philips screws holding the main body together.
5. Place the speaker housing back into the cover for the main body to prevent accidentally dislodging any cables further.
6. Again, be careful pulling this second part away as there is little slack in the cable.
7. Use your pliers or tweezers to remove the tape holding down the wire. 
8. At this point you have enough clearance to start unscrewing the part of the headband that holds the speaker in place. This is where you need the Torx screwdriver. 
9. Take apart the two halves of the speaker holder, pay attention to the copper spring attached to the metal armature and remove the cable from the cable guide.
10. Now you have slack in the main cable which will allow you to pull it into the main part of the speaker housing so that you can work.
11. At this point I would take a photo of all the cables so that you have a reference of what goes where if something has gone wrong later.
12. Cut away any excess wire that has frayed from any split connections.
13. Add flux to the two halves of the cable you have to repair and lightly tin the ends (360c was good for this application) 
    
14. Cut a small amount of shrink tubing and slide it over one end (I used too much)
15. Use pliers, or ideally self closing ones to hold the two halves of the cable with a bit of overlap and use your soldering iron to melt the solder together. Try not to burn a whole in the ear padding of the other speaker :(
    
16. Let the joint cool sufficiently and then slide the heat shrink tubing over the connection. 
17. Tug on both ends of the cable to make sure you have a solid connection. 
18. Use a heat gun or other source to shrink the tubing over the solder joint.
19. I would also check all the other solder connections at this point and re-solder them if needed. 
    
20. At this point I would test the headphones by plugging in a source, putting in batteries and make sure everything works.
21. Once the test works out, pull the cable out so that only a bit of the housing is left inside the headphones. I used some electrical tape to add some buffer for further fraying.
22. Then use more tape to hold down the cable so it doesn't get in the way of re-assembly. 
23. You now have to re-assemble the armature that holds the speaker unit. First lay out the headphone cable into the cable guide. The slack goes at the head-padding end for extension. 
24. Make sure to place the copper spring in place into the metal armature.
25. Getting the two halves of the speaker holder together while keeping the cable in place was probably the hardest part of re-assembly. I have no advice other than growing another few limbs
26. Then re-assemble the main speaker housing in reverse of how it was taken apart. 

There you have it. If you have any questions feel free to comment below and I'll try to answer them. 

Hopefully PSB has fixed this issue in later production runs or plans to. For what is otherwise an excellent pair of headphones.

Update

Independent of this blog post, I have been in contact with PSB above.  Before I published this info, I sent them a further update via their support forums about the issue that I had found. They have offered to sell me a discounted set of M4U 2s. I am taking them up on their offer. First, these are a great sounding pair of cans with great features. This will allow me to have two pairs, but more importantly, a whole spare set of parts for the one pair I really need.