Helmet Headphone Electronics Tutorial - Hearing Enhancement

CrimsonViper97

Active Member
Member DIN
S097
Communication is difficult on the con floor, so why make it harder than it has to be.

The following guide will help you take an off-the-shelf pair of ear protection and adapt them to your helmet of choice. I first saw this technique used by PapaBraus on his MK VI helmet here: 3-D Printed MK VI helmet assembly and paint.

Thanks to NobleofDeath16 for peer pressuring me to write this tutorial, proofreading, and helping me take photos.

Disclaimers: This tutorial assumes/requires a basic competency in soldering and electronics. Even so, there is a possibility of damaging the circuit in following this tutorial, so proceed at your own risk. Be sure to read and understand this tutorial fully before starting work. Please be cautious when handling any glues, circuit components, or other materials inside the headphones. They may contain or be coated with harmful chemicals. It is recommended that you wear gloves and wash your hands after handling said materials. Work in a room with adequate ventilation and use a fume extractor or respirator when soldering.

The cheap circuit in the Zohan headphones picks up a lot of EMF, so expect to occasionally hear some noise (eg. when walking near a wireless router). Additionally, anything that vibrates your helmet, like fan noise, will be picked up by the microphones. All this to say- it's not perfect but it's better than nothing.

Parts:
22AWG Stranded wire, at least two colors
Zohan Headphones: Amazon.com
Battery Holder, 2xAAA: Amazon.com

Tools:
Scissors
Small flathead screwdriver
Small Phillips screwdriver
Side cutters
Soldering Iron and solder
Solder sucker and/or solder wick
3rd hand
Wire strippers


Step 1: Disassemble the Headset
Remove the headset from the box.
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Remove the black earpads from each side. They are held in with small clips and should pop out with a light application of force. Save these for later.
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Separate the earphones from the headband. Cut a slit along the top of the headband, making sure not to cut the cable inside. The headband can be discarded.
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You should now have just the earphones connected by a black cable. Remove the battery door to get it out of the way.
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Take a small flathead screwdriver and slide it between the green plastic housing and the black plastic ring from which we removed the ear pads. Apply a gentle prying motion and they should separate. Save the black rings and foam pads, as we will use them to create the headphones for the inside of the helmet.


You should now be looking at the interior of the headphones. Remove the foam filler and discard it. With a small phillips head screwdriver, remove the speakers and the PCB (Printed Circuit Board). The electret microphones and 3.5mm jack are secured with an unidentified hot glue. Please use caution and I recommend gloves/wash your hands after handling unidentified glue. This can be peeled away, allowing the mics to be pulled out and the jack unscrewed. You will also want to remove the hot glue from around the circuit board, especially where it meets the volume knob. Side cutters can be extremely helpful for this, allowing you to use a pinch and twist motion. A flathead screwdriver can be useful as well. Be careful not to scrape or stab the PCB. Once you have removed the glue from around the PCB, it should slide out sideways. Save the knob to reuse, as the stem of the potentiometer can be difficult to turn. With your side cutters, cut away plastic to remove the cable from the plastic shell. If you haven’t already, remove the nut from the 3.5mm jack and pull it out of the shell. Cut the wire connections to the battery box.
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You should now have just the electronic “nervous system” of the headphones. If you don’t want to mess around with any custom wiring and the length of the premade wires works with your helmet you may attach the battery box and proceed to installation. Check all the wiring, especially the solder joints as they are often poorly connected and come loose during disassembly of the headphones. Resolder any broken wiring and skip to step 4. If you would like to clean u or extend the wiring, proceed to step 2.
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Cont.
 

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Step 2: Cleaning up the PCB
Remove the hot glue covering the solder connections on the PCB. While pulling gently on the cabling, heat the solder joints one-by-one with a tinned soldering iron until they pull loose. Remove the speakers from their plastic holders. Desolder the speakers and the microphones loose from their wiring.
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You should now have the following components: PCB, battery holder, 3.5mm jack, 2 microphones, and two speakers. Using a soldering iron and solder sucker (and soldering wick or whatever desoldering tools you prefer, clear out the holes in the PCB where the wiring was attached. This will allow you to pass the wire through before soldering, giving you a sturdier connection than the factory wiring.
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Step 3: Preparing the microphones and Speakers

Now that we have the PCB cleaned up we’re going to estimate the length of our wiring. The first thing we’re going to do is decide on a location for our microphones. You want one on either side of the helmet in a location where it won’t be too obvious. On my MK VII (produced by EVAKura if you are looking to source the same helmet), I chose a spot right behind the visor where the helmet was going to be painted black. Take into consideration that you will need to access this location from inside the helmet to insert the microphone. Carefully drill a hole matching the diameter of the microphone.
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Next, decide where you would like to mount the PCB. From this location, unroll some wire and run it to one of your mic locations, leaving a little extra, and cut. Measure some wire of a different color to the same length and cut. We used red for positive and black for negative, but the idea here is to differentiate positive and negative, so any two colors will do. For a clean look, chuck these wires into a drill and twist them together. If you do so, leave some additional length as the wires will shorten as they twist together.
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On the back of one electret microphone, solder your negative wire to the pad with traces running to the outer ring and your positive wire to the semicircular pad beside it.
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Repeat this process for the second microphone.

In the same manner as the microphones, cut one set of wire for each speaker. It doesn’t matter which pads you use for positive and negative, so long as you are consistent from speaker to speaker. Otherwise, they will be out of phase (it’ll sound weird, trust me).
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Step 4: Prepare the headphones

Because helmets are so unique from one to the next, there isn’t a one size fits all method for making the headphones. If you have an inch or more of room between your ears and the sides of the helmet, you may proceed with the following steps.


Insert the black earpad into the ring from which it was removed. Trace the outline of this assembly onto a piece of thin foam and cut it out. In the center of the foam piece, trace the outline of the circular speaker grill and cut that out as well. Stick the speaker grill through the hole in the foam and glue it in place with some hot glue.
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Take the earpad assembly and place the foam that was originally covering the speakers (black on one side and gray on the other) roughly centered on its back, gray side up. Lightly tack the foam in place with hot glue. Lay hot glue around the perimeter of the back side of the ear pad assembly and place the speaker grill assembly on top (grill side down so the speaker can still be inserted). Press firmly until hot glue is cool. Place the speaker into the circular grill holder.
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Cut a piece of 2mm foam to the shape of your new headphone assembly and stick it to the back with contact cement. Do not spread contact cement on the speaker.
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To compensate for wider or narrower helmets, you can increase the thickness of this layer of foam, or create foam spacer blocks like we did here.
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I prefer using 3M industrial strength velcro to attach my headphones because it allows for some adjustability inside the helmet. It’s hard to get them in the right place without doing some trial and error.

IF YOUR HELMET IS A TIGHT SQUEEZE:

You might have to get creative, so proceed at your own risk. The important thing is that the speaker cones are protected from damage and that they can move freely. Avoid getting glue on the cone, and try to keep them out of direct contact with anything. I’m excited to see what you guys come up with, so please share in this thread!


Step 5: Extend the 3.5mm jack

If you would like, cut and solder new wiring for the 3.5mm jack. I used blue for AUX R, black for GND, and red for AUX L.
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Step 6: Solder it all back together

For each component lead, stick the wire through its corresponding hole in the PCB and apply solder. Pay careful attention to which speakers and microphones are for right and left. I chose to put hot glue over my connections to protect them from shorting.

PCB Connection Labeling:
PHL-: Left microphone negative
PHL+: Left microphone positive
SPL-: Left speaker negative
SPL+: Left speaker positive
VCC: Battery positive
GND: Battery Negative

SPR+: Right speaker positive
SPR-: Right speaker negative

AUXR: 3.5mm jack right
GND: 3.5mm jack ground
AUX_L: 3.5mm jack left

PHR+: Right microphone positive
PHR-: Right microphone negative

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Step 7: Mounting it in your helmet

Use hot glue to mount the PCB in your desired location. We used a half inch block of foam to make the volume knob easier to access. If your battery holder has a switch, make sure it’s accessible or set to the on position and then velcro or hot glue in place. Stick the microphones through their holes so that they are flush with the outside of the helmet and apply hot glue on the inside of the helmet to secure them in place. Clean the inside surface where you wish to mount your headphones with isopropyl alcohol and apply the adhesive side of your velcro. Mount the 3.5mm jack in a convenient location, making sure that a cable can still be plugged in. If your helmet is thin enough, you can drill a hole in which to mount the jack so that a cable can be plugged in from the outside.
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And that’s about it! I would suggest being conservative with the volume; crowd noise can easily become a deafening roar. Enjoy higher quality conversations and better situational awareness!
 

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Quick question, on the parts, list you say 2x AA battery holder but the link is to a AAA battery holder, can you confirm what size battery this uses?
 

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