Sunday, July 15, 2012

Adding Music Speakers to NAC headphones.

Like a lot of other PPG pilots, I fly with NAC intercom/communication speakers on my helmet for in air comms with ground partners, or other pilots.  I've come up with a simple modification to allow me to listen to tunes while flying, without compromising my comms ability.

Many pilots just shove a pair of  noise-cancelling earbuds into their heads before donning these ear-muff style headsets and swear that not only is the sound excellent, but that the additional noise dampening effect of the earbuds is a value added bonus.   I did try the buds, but just didn't find them comfortable with my helmet as I could feel pressure on the earbuds from the headset pressing against them.  And it means extra, loose wires to contend with, that have to go under the earmuff pads, which is less than ideal.

Also, while the earbuds worked okay most of the time, once in a while, one or both buds would shift slightly in my ears, or even fall out, which was getting a little annoying, and not much to do about it once I was off the ground.

My NAC headphones are designated Peltor H520P3 but this mod will probably work on any Peltor headset including simple noise-attenuation, or "ear-defender" style earmuffs.  This modification is very simple, and only requires a drill or a Dremel tool to accomplish.  Or even a small file, since you are only working with plastic.  When completed, the wiring is neat and squared away, and only requires 'on and off' for your music system to work.

You’ll need a set of helmet speakers of the type used for speaker-ing the inside of motorcycle and ski helmets. I picked up this set of knockoffs from an eBay seller "exrell" in China, for $4.39 including shipping. The listing was for "Motorbike Motorcycle Helmet Stereo Speakers Volume Control for MP3/4 Radio iPod."
Or try something like these IMC HS-200's which are sold in bike stores and online for 40 bucks.  

If you use the inexpensive eBay guys, start by tossing the foam covers, and their Velcro backing.  You won’t need them. Or the included 3.5mm male to female extension cable either in all likelihood.

Then pop off the cushioned rubber earpieces on your Peltor headset.  They are designed to open up for battery changes, and they just snap in and out.  However, you may find a sharp tool may help them come off if you’re having any difficulty.  

Then drop in the flat mini-speakers.  Notice that the hard while plastic ovals on the back of the earpieces, have a tiny hole cut drilled in them in the lower-half where the internal NAC speakers sit to let the sound out. 
I used a Dremel with a burr attachment to cut another hole over the new speaker for the same purpose.  The large, sloppy looking hole on the top right is mine, to mate up with the new drop-in speaker beside it.  A drill would have made a cleaner job, but you can't see it when assembled so I took minimal care.  The gray, acoustically permeable material that is glued to the edges of the other side of the white ovals will peel back with relative ease.  You can see the backside of this material through the drill holes.

Then I cut a notch into the plastic cups. I chose the top/rear of the headphones, so the speaker wire will be close to the wires for the comms.  Then I just snapped the headphones back in place.

The hole I drilled below, is actually quite a bit larger than it needs to be, as the speaker wire is pretty thin.  A simple slit cut with a hacksaw blade would probably have sufficed.
These little eBay speakers do have a left and right.  So before you install, plug them into your computer monitor speaker output, and play this youtube test program:

That's it.  The sound from the el cheapo eBay speakers is okay, but not super loud.  About as loud as the earphones that Apple gives you with a new iPod.  You may wish to amp these up to overcome motor noise. 

I ordered a self-powered, mini-amplifier, the FIIO E6 for $23.00 (incl shipping) from Amazon to punch up the volume.  It's super-small, about the size of a book of matches, and although I lack instruments to definitively measure, I'd say that the volume in my speakers is almost doubled.  So much so, that at max volume the headset is uncomfortably loud, and I have to dial it down even when the motor is on.
A nice review here:
An earlier generation of FIIO's amplifiers, the E3 is simpler, and less expensive.  It's a little bigger, because it's powered by a single AAA battery instead of a lithium battery/USB interface, and this might better suit some people.  It only costs ten bucks on eBay with shipping included.

The main difference between the E6 and the E5 is the fact that the E6 is made of plastic and is consequently 15gr lighter than the aluminum E5 at 30gr.

I used Barge all purpose contact cement to attach some hook Velcro to both my IPod Nano and the Fiio amp to the to mate with the Velcro on my FAST helmet.

All I have to do now, is to turn on the iPod, and I'm good to go.

One other thing.  My NAC phones are hardwired to a Garmin radio 2.5 mini-plug.  Another bonus of having a second set of speakers with a connected 3.5 mini-plug, is I that can sometimes opt to fly without music, but rather choose to  monitor the air band of my local airport with my Yaesu 120 scanner instead.  While the private airport I sometimes I fly out of is unmonitored, incoming aircraft give a heads-up that they are on approach about 5 miles out from the runway they're coming in on.

The Yaesu also has a 3.5 mini-plug out connection, like that of my iPod system, so I can fly with a scanner instead of the iPod any time I want, while still having pilot to pilot comms at the same time.

UPDATE: My E6 just fell apart on me.  I had it Velcroed to my helmet, and while peeling it off one day the whole thing split along the seam and a few tiny parts got lost.  E6 owners should watch this, especially if they add Velcro.  The plastic E6 is much lighter construction than the all-aluminum E5 that I bought to replace it, so this petty calamity gave me a chance to compare it to the E5. Unfortunately, the E3 and the E5’s are getting harder to find, and have both gone up in price, (the E3 doubling from $10 with free shipping up to $20) but each variant has some advantages.
Fiio E3
E3 PROs - Inexpensive. You have the convenience of AAA batteries in the field, which is why I bought it to use as a spare, in case I found myself out in the field with a dead amp and no time/facilities to recharge. Still quite small, about the size of a 9v battery - a bit thinner, but slightly longer.
No Brainer operation.  It’s either working or it’s off.

E3 CONs - No on/off switch with the E3.  When connected to a device, a light comes on but unplugging is more hassle than pushing a button. It comes with a very long connection line compared to the other Fiios  This unit distorts more than the E5 and E6 at highest volume.
Fiio E5
E5 PROs - Simple operation. On/Off, Bass Boost On/Off, and a volume control. Same 20 hour power life on a USB charge The aluminum E5 is arguably better looking than the plastic E5 with its shiny plastic fingerprint-attracting surface.

E5 CONs -  Only one level of Bass Boost instead of three on the E6. However, the E6 had a fiddly interface between levels with an On/off that is integrated into level change, so it is easy to accidentally switch levels.  Also the level indicator lights were VERY hard to see in bright sunlight.  The E5 less so.


  1. Great idea...simple & easy to install
    Look forward to trying it.

  2. Thank you. I Will work to your idea.