Hard hat mounted headphones

Because commercially made ones are too #### expensive.

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Retrofitting some MSA hat-attached earmuffs with speakers from a broken pair of headphones, without drilling any new holes.

Some time back I needed a hard hat for work. Being that I'm in the Sunshine State, I figured something full brim was the better option, although these are rare beasts here in Brisbane.

It later gained some velcro dots for mounting a headlight and battery. In that regard, it replaced my old "hat lamp" that I built some 8 years before (when 1W LED modules were considered "bright").

Fast forward a few years, we had bought one of these cheap hard cap/earmuff/visor combos from Bunnings for a brush cutter, and after about 9 months, the harness on it crapped out. So I went looking around to see if I could retrofit this old one from work with the necessary bits.

Turns out the hats are rare but becoming more common, the accessories are next to impossible to source. There are plenty for the cap-style, but not full brim ones like this one and they generally don't co-operate with the detachable brims that are also common. The 40mm brim isn't much, but it sure beats nothing and goes all the way around!

The linked earmuffs work with the TA-440 hat I have, they're designed to work on MSA's range which you can buy here. The visor (made by ERB) and the earmuffs were sourced from Amazon.

Looking at the earmuffs this afternoon, it dawned on me that the ear cups could accommodate headphones very easily. I just had to feed the wires in through the back of the cup. I do emergency communications work for Brisbane Area WICEN, and they do the International Rally of Queensland annually. I just pop the visor off, rip the headlight off my bike helmet, slap it on the hard hat and I'm ready to go.

With the headlight mounting points and speakers in the earmuffs, I'd have the perfect tool for hearing the radio traffic near the noisy cars, seeing my way in the early hours of the morning and avoiding my neck getting burned to a crisp in the middle of the day.

I have chosen to use RCA connectors in spite of the relatively low insertion force for two reasons:

  • They're a fairly hardy connector with little that can go wrong with them.
  • The connectors are widely available both as bare plugs and pre-made assemblies.

A microphone is the only other useful bit, but at least now I can listen to music whilst mowing the lawn. I'm thinking this will be a detachable affair, and I'll make a wiring harness up to suit my radio equipment.

When not being used, the cable can be detached from the earmuffs, there's nothing dangling to get snagged or cause nuisance. When in use, one can run the cable in from the back so that tugging on the cable does not pull the plugs out.

  • Adding a microphone

    Stuart Longland02/18/2017 at 07:30 0 comments

    So, late last year I actually went to the trouble of adding a microphone to the rig. Not a difficult proposition, but I discovered there is a right way, and a wrong way, to go about it.

    No prises as to what one I unwittingly chose first.

    On my bicycle, I have a headset embedded in the helmet there. It's an open face motorcycle helmet (I don't trust bicycle helmets, see #Improved Helmets). There, I took ear cups from a broken Heil Traveler headset, stuck velcro pads to the back of them, and stuffed those in the side cavities of the helmet.

    Yes, over time the padding on the ear cup fell to bits. It is on my ever growing TO-DO list to see if I can figure out an alternative. I'm thinking a piece of foam padding cut into a toroid shape and a cloth cover cut from scrap, sewn around the toroid, clamped between the two halves of the ear cup -- just need to ensure the screws are still accessible.

    For the microphone, I used a spare electret capsule scavenged from a mobile phone hands free kit. In a length of 1.5mm diamaeter solid copper wire about 30cm long, I made a loop around the electret capsule half way along the wire to hold it in place, then twisted the two lengths of copper to form the boom.

    Shielded cable and a small capacitor is soldered to the microphone, and this is loosely wound around the copper boom.

    A small plastic bag is placed over the microphone and tape wound tightly around the open end for weather proofing (I've lost too many electret capsules to count due to rain ingress) and a foam windsock placed over that.

    Finally, a length of plastic sheath is fed over the top of the boom and cabling. This can be rammed into the helmet in between the inner liner and the outer shell.

    This works for a motorcycle helmet quite well. Been using this arrangement for years on the bicycle. This is what the arrangement looks like:

    I tried a similar arrangement for the first attempt at a headset microphone boom. However, two mistakes:

    • I used only a single short length of copper wire, rather than doubling it up
    • The earmuffs attach to a small coupling via a small tubular section of rubber: I attached the boom by looping the wire around that.

    The former mistake meant the microphone would bounce around… it really needs to be stiffer than what the single piece of copper would permit. Secondly, winding it round that tubular section meant it cut into said tubular section! The earmuff hasn't fallen off yet, but there is damage.

    So what's the right way? A better way is to use a short M5 bolt, washer and lock-nut. The earmuffs are attached to brackets that are way longer than they need to be.

    I used coat hanger wire for this version, but then forgot to put a sheath over it, so I wound some electrical tape around it instead. Not as nice looking, but it's functional:

    Here I used an off-the-shelf wind sock. I repeated the construction exercise with a second hard hat that normally lives on my desk at work. (Not that I've actually needed it for work yet.)

    Originally I was going to use speakers out of a broken Logitech USB headset, but then managed to rip the little PCB off the back of one speaker. Oops!

    The headset speakers I did use came from a still sort-of-working but uncomfortable to wear pair of headphones that I decided to rip apart. Unlike the previous pair, the mounting plate was just a bit big to fit, so out came the cutting tool to cut it down to size.

    The mounting plate featured a small PCB where the connections were made between the speaker, outgoing cable and a small volume pot. I opted to connect to this PCB instead of directly to the speaker after my previous destructive effort. ;-)

    For the microphone boom, I used one off a Garmin Rino GPS/CB radio headset, as it's again another terribly uncomfortable headset, plus it's a single-sided one (I hate that). I found though the microphone seemed non-functional, so replaced that with one I ripped off a kit FM wireless microphone PCB, installing a 100nF capacitor across the terminals for EMC,...

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  • 1
    Step 1

    Mounting tip for 6-point hats like the TA-440: You might have to experiment a bit with location so that the middle two points don't interfere with the earmuffs, but I find slightly behind the harness mount points worked best.

    Use the supplied templates to guide you on drilling the two holes for mounting the earmuffs.

  • 2
    Step 2

    Put two fingers in behind the black plastic attached to the cushioning pad, grab hold of the ear cup and pull the ear cup apart. Remove the foam padding.

  • 3
    Step 3

    At this point you should be able to easily access the mounting point at the back of the cup. Use your fingers to pull the cup to one side, then using needle nose pliers, insert the twisted pair in as far as you can get it.

    Then, switch sides, use your thumb to pull the plug out of the way and the pliers to yank the cable through the hole.

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Bharbour wrote 02/20/2019 at 02:53 point

Be careful riding in traffic with those muffs on! I almost dusted some kid riding with his headphones on. I don't think he knew I was coming up behind him (at about 60kph) and he turned straight in front of me. It was a really near thing. From personal experience, I don't even like to be out walking in public with earphones on. Too much situational awareness  comes from what you hear.

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Stuart Longland wrote 02/20/2019 at 03:25 point

Agreed, but at this time, it's illegal to ride a bicycle wearing one of these anyway as hard hats do not confirm to AS/NZS 2063 which is required of any cyclist.

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