Drivers: 2x Dayton Audio CE38MB-32 drivers. Available from Parts Express
Ear Cushions: Bose QuietComfort QC15 QC2 replacements, available from Amazon, eBay or AliExpress. If you want to make it a bit more funky, use these: https://amzn.to/3JlS9rM
Bluetooth Module: I recommend CSR8645 based modules without an on board amplifier. DO NOT get one of the commonly available 5W amplifer ones – they are way over powered. This one from AliExpress will work well. The housing has been designed to take newer (and much more expensive) CSR8675 modules, although they don’t have the microphone input.
If you have Autodesk Fusion 360 and want to customise the design, the source CAD files can be accessed here.
Print the headband with the channel facing up, covers with the outer face on the bed and baffles with the ear side on the bed.
The parts used in these instructions have been coated in filler, sanded back and painted to give a smooth finish. I will post detailed instructions for this in due course.
1. Mount The Drivers
Making sure you don’t damage the fragile diaphram of the drivers, place them in the baffles as oriented in the picture below (yellow circles).
Apply 4 ‘blob’s of glue to each (red circles) and leave to dry. Gluing around the full perimeter will adversely affect the sound.
2. Prepare Up The Headband
Cut 2 sets of wires, approx 60cm (24″) long. Label each end of each set – ‘p’ (power) and ‘a’ (audio).
Run the wires through the headband channel. To minimise the risk of splitting, the channel was designed to be a bit shallow, so if necessary, hold the wiring in place with tape.
I find that if the headband is not covered, they break after a few weeks of use. I am yet to have a covered one break, so am 99% sure the cause is chemical attack. If you don’t have a heat gun, gaffer tape works ok. Wrap the tape over from the top and put a strip on the inside. Otherwise…
Cut the heatshrink to approx 40cm (16″) and slide onto the headband.
Working from the top centre, shrink the heatshrink using a heat gun.
3. Lengthen Microphone Pigtails If Necessary
You’ll need approx 60mm of wire on the microphone, so lengthen if necessary.
Break off two tabs along the same side of each switch and insert the switches into the baffle.
Place the bluetooth module into its slot and solder a length of red wire into the ‘1V8’ hole. See picture below for bluetooth module orientation.
Route the wire around to each swich and using a marker, mark off where it crosses one tab from each switch.
Remove the bluetooth module and wire, then using a scalpel or knive, strip the wire around the marked off locations. Cut near the last one and strip the end.
Apply some solder to the stripped sections.
Apply some solder to each tab on each switch. This will make attaching the wires easier.
5. Tune The Sound
By now the glue on the drivers should be dry. If not pause for a bit!
These drivers in this configuration are way too bass heavy and lack high end detail, so to make them sound more balanced, we need to attenuate some of the bass. Even if you are a bass-nut, trust me on this, they sound mediocre without this step.
Look carefully and you’ll notice that there are holes in the frame of the rear of the drivers (covered by the black cloth). Roll up a piece of plasticine into a sausage and cover all except one of these holes on each driver.
6. Wire Everyting Up
Wire everything up as per the following wiring diagram, following the sprcific tips below:
A few tips:
The headband is ‘handed’, so to get the sides correct, match ‘L’ on the headband with the baffle marked ‘L’ above the headband slot. This will result in the control buttons being on the LHS (so that right handed people can use them while writing, mousing etc) and so that the volume buttons are hidden on the rear. Other than that, the sides of don’t matter.
Wire the drivers up first. LP = Left Positive, LN = Left Neutral etc on the bluetooth board
Mount the bluetooth and BCM boards before wiring to them. You should NOT need to glue the bluetooth board in
Mount the bluetooth board with the two small microphone solder pads, labelled M+ and M- facing up (not visible in the photo above). Solder the microphone to these
To solder to the bluetooth board, dab a bit of solder onto the striped wires and holding the soldering iron on the solder, slide the wire into the board. If it needs a bit more solder, solder from the top. You shouldn’t need to solder from the underside.
For the BCM, which has larger through holes, fill the holes with solder, then re-melt with the tip of the soldering iron and silde the wire in
The longer terminal on the LED is the positive
If you use a different LED, the minimum value of the resistor should be R = (3.7 – Vf)/If, where Vf is the rated forward voltage of the LED, If the rated forward current of the LED and 3.7 is the nominal battery voltage. Double or triple the value as the LED doesn’t have to be at its full brightness.
Wire the battery in last to minimise the risk of shorting it
Make sure the wires into the BCM are not contacting the driver
When wiring on the postive supply rail for the switches and resistor for the LED, put a bit of eletrical tape or heatshrink on any areas that may be at risk of shorting to the negative (yellow circles below)
The microphone sits in the slot shown by the red circle below
For the power switch, wire onto the two terminals on the side you want to be ‘on’ (blue circle below).
The completed wiring should look like this:
Slot the headband in place. This is a good point to test that everyting is working.
Peel the adhesive and attach the piece of fabric that came with the cushions to the baffles. NOTE: to make cushion fitment easier, one side of the flange is shorter than the other (green arrow below). I recommend either remembering which side this is or marking it by putting the cutout on the fabric on this side.
Sliding over the short flange last (green arrow above), attach the cushions:
Fit the covers. To pair, turn them on and search for them in ‘bluetooth devices’. They will be labelled CSR8645.
If you start to notice white residue on the insides that looks like you’ve shorted something, don’t worry, this is most likely residue from the glue.
Crank ’em up and enjoy your new headphones! I find they seem to sound better after 10-20 minutes of listening.
If you have any feedback or questions I would love to hear from you – I can be contacted via [email protected]. I hope you enjoy your new headphones!
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