Recabling Sennheiser HD 457 Headphones

I purchased my first pair of Sennheisers around five years back and they served me well for the time I've owned them.

Until this week.

One side of the headphones stopped working all together. If I moved the cord just right, the other side would cut out as well. So, It's time to disassemble them and repair the cord.

Here's how I repaired my headphones.

Required Materials

• Sennheiser HD 457 Headphones
• #1 Philips Screwdriver
• #1 Straight Blade Screwdriver
• Heatshrink Tubing - 1/8" and 3/16"
• Soldering Iron
• Solder
• Desoldering Braid
• 6' Stereo Extension Cable
• Multi-Meter

Step 1 - Disassembly

Start off by popping of the earphone covers. They come off with a little pressure around the edges. They secure to the gray plastic housing with two plastic hooks and with a little pressure, they release their grip.

Step 2 - Seperating the housing from the headband.

My headphones were pretty well warn so this next step may be a little easier for me than you. The gray plastic housing secures to the headphone band with a ball and channel. The ball is on the housing and the headband contains the channel. If you slide the housing up to the top (like sizing them for a very small head) there is a small v-notch at the very top of the channel. Gently pull the the headphones straight back from the headband, all the time supporting the headband with equal pressure backwards. They should come out fairly easily. You need to pull straight back or else you'll break the ball off, rendering the headphones useless.

Repeat the process again for the other side. You should have the headphone housings seperate from the headband now.

Step 3 - Removing the drivers

There are four Philips #1 screws that hold each driver in the gray plastic housing. Take a small jewelers screwdriver and unscrew the four screws, being careful not to lose them. Now the driver should come out if you tip the gray plastic housing over.

Step 4 - Seperate the drivers from the housings

This is where the drivers and housing part their respective ways. First take note of which wire goes to which terminal. I took a continuity tester and mapped out which was the signal and ground wire from the jack. My signal wire was attached to the terminal with a number above it and the ground was the terminal with no markings. As a note, the signal wire is colored red or green.

Move the foam layer away from your working area. Hot soldering irons and this layer don't mix well. Take a soldering iron and desolder the two wires from the driver. Clean up the factory solder with desoldering braid or a desolder iron. Set the driver aside. We're going to be working on the housing next.

Step 5 - Removing the wire from the housing

There is a small metal U shaped piece of metal that holds the strain relief boot and wire to the terminal. I ended up using a small flat bladed jewelers screwdriver and a fine tipped pliers to remove the piece of metal. Set the part aside.

You should now be able to wiggle the strain relief boot and wire out of the housing. Separate the two and set the housing aside. We are now going to be separating the strain relief boot from the wire. Take a scalpel and cut the boot lengthwise down the middle, exposing the wire and a metal clip. The wire is glued into the bottom of the strain relief boot. I ended up taking a fine tipped pliers and pulling out the insulation from the wire. After you are done, you will be left with a strain relief boot to be used in the upcoming step.

Step 6 - Adding new cable

Cut the female end off the stereo extension cable. The next step is to separate the cable to go to each housing. Split the cable 14" - 18" from the end. The distance is up to you, base it on personal taste for how you want your headphones to feel.

*Important step*

Slip a piece of heat shrink tubing over both wires now. This will be how you stop the wire splitting further than you need it to at a later step.

You're wire will have a coating over the pair of internal wires. Strip 2"-3" off the wire pair, exposing the grounding layer and internal signal wire. Next, twist the ground layer strands into a wire. This makes wiring a little easier. Finally, strip 1/2" of insulation from the signal wire and twist the strands. It makes the next step easier.

*Imporatant Step*

Place another peice of heat shrink tubing over both wires here. This keeps the strain off the wires for the next step.

Step 7 - Tinning the wires and replacing the strain relief boot

Take the wires that you just twisted and tin the ends of both wires. This step is a lot easier when the wire is free of the housing as space starts becoming tight in the next steps.

Next we are going to place the strain relief boot on the new wire. I slipped a piece of heat shrink tubing on the wire to be used to secure the strain relief boot to the wire before putting the boot on the wire. Open the cut your used to remove the strain relief boot from the wire and slip the wire into the cut on the boot. The boot should end up 2"- 2.5" from the end of the wire, with the square end facing the bare wires. Slide the heat shrink tubing over the boot and shrink closed. This will keep the boot from moving on you and secure the wire and strain relief boot together for the next step.

Step 8 - Hooking up the wire to the driver

Slide the wire and strain relief boot back into the gray plastic housing. It takes a bit of wiggling to get the locking channel past the housing. When you have the wire aligned and positioned back in its original spot, place the metal U shaped retaining clip back on the gray plastic housing with a fine tipped pliers. You should now have the wires, strain relief boot and housing all together now.

Take the driver and tin the two pads that you cleaned off in a previous step. This makes the next step easier. I used a third hand to hold the wire and held the driver in my hand in the next step. Solder the wires back to their respective terminals. I chose to leave the foam layer off up until now. Slip it back over the driver and connect it back in the orginal spot. There is a notch in the foam and a raised notch on the gray plastic housing. Align them. Screw the driver back into the gray plastic housing and reattach the headphone pad that your removed in Step 1.

Congratulations, you now have 1/2 of the project complete. The process is the same for the other channel when you have both of them rewired, snap them back into the headband. You are now finished. Plug them in and test them out and you should now have a working pair of headphones. If you notice that they do not work, check your solder joints. You either have a short or a cold joint. Reheat the joint and check for continuity.

I did find out why the headphones failed during this project. Sennheiser places a metal clip around the cables under the strain boot and the place where the two wires split to each ear. This breaks the wire over time. See photo for the offending part.