Bose QC15 / QC25 Bluetooth Module

The newest Bose noise cancelling headset, the QC35, has wireless Bluetooth connection. They are also quite pricey. Many already own a pair of QC15 or QC25. If you’re one of these people and want to upgrade to wireless connection without buying a brand new headset, this might be the solution for you!

This instructable will guide you through how to make your very own Bose Bluetooth module for ~25 USD with chargeable battery, APT-X support and customized casing, among other things. And if you think coding is a chore, you’ll be glad to know that this project is completely coding free! You just assemble the hardware.

This guide originally appeared on our webpage.

You need a 3D printed casing for this project. The casing consists of two parts: the main casing and the lid.

You can download the design below (we supply both STL and STEP files!). You can print it at your own printer or send the files to a 3D printing service (like Shapeways, i.materialise etc..).

If you need to tweak some dimensions, just import the step files into your CAD software and go crazy.

Casing Design

The casing is where all the electronics are kept in place and what keeps everything mounted to the headset with a nice interface.

Note: when describing directions in this step we use the coordinate system where the casing is mounted on the headset.

Casing Design Goals

The main design goals for the casing was to make it as compact as possible as well as providing a good fit to both Bose QC15 and QC25. We also wanted to have the micro-USB charger port towards the back, the power switch towards the front and the Bose cable entry on the underside of the casing. Lastly, we wanted to be able to see the LEDs on the PCBs.

Casing Structure

The battery is in an own compartment on the inside of the “main room” where the two PCBs, power switch, USB port and cable entry reside.

You need the following parts:

• Battery: 3.7V Litium-Polymer 850mAh, package type “703040”, dimensions: 7mm*30mm*40mm . You can easily buy one from eBay.
• Battery charger module: 5V 1A micro USB charging board. You can buy one from eBay (search).
• Power switch: We had a switch from Sparkfun laying around. You can buy the same here.
• CRS8645 Bluetooth breakout module: The heart of the system. There exist several different breakout boards on eBay. Here it’s important to buy the correct one (v4.1). Link to a suitable model you can buy (link to search).
• Headphone cable:
  • Bose QC 15: eBay.
  • Bose QC 25: eBay.
• The 3D printed casing parts from Step 1.

Hot glue works fine when mounting the PCBs.

To mount the switch, apply some hot glue to one of its large sides and slide it into its socket. Afterwards, apply glue around the back of the switch to keep it tightly fastened in the socket. You don’t need all of the switch pins, and one is in the way, so cut one of them off (look at the image to see which).

Cut the cable to a suitable length. Keep in mind that the cord length between the plug and the cable buttons differ between the QC15 and the QC25 cables.

Use a lighter or sanding paper to strip the inner wires. Then apply tin with the soldering iron.

After inserting the cable, apply some glue to create some stress relief for the internal wires.

The systems consists only of three main pieces. The Bluetooth module, battery and battery charger. When we designed this we wanted a long battery lifetime and therefore we selected a battery with 850mAh at 3.7V. In our testing the bluetooth module have at least battery for one work week (8 hours a day, 5 days).

Our Bose headphone cables had the following color / pin out:

• Red: Right output
• Blue: Left ouput
• Brass: Headphones GND
• Green: MIC +
• Brass & Red: MIC –

Follow the schematics in the last chapter and solder.

You can use some of the small wires from the cable for internal wiring.

Make sure the wires on the battery are on the correct side. Also be sure to solder the battery wires after everything else.

Use hot glue, epoxy or similar glue to fasten the lid to the casing.

Then turn on the Bluetooth module and look for a Bluetooth device called CRS8645 on your computer, tablet or mobile phone. This is the one you need to connect to.

That’s it! Enjoy your new wireless Bose headset. :)