Getting More Volume from a Handheld Radio

[rwanttaja]

I've got an ICOM handheld permanently installed in my airplane as the primary comm radio. For years, I've used a standard aviation headset with it. I had to crank the volume up all the way, and some folks were STILL hard to understand. Dave Matheny's great column in the newest Sport Aviation also mentions this issue; difficulty hearing a handheld radio in a noisy aircraft when using an aviation headset.

I finally stumbled across the reason earlier this year. Over the past week, I've done some testing in my workshop to get a handle on how bad the problem is and how effective corrective actions can be.

First off, the fundamental reason is an impedance mismatch between the handheld radio audio output and the aviation headset's speakers. The companies making today's handheld radios (ICOM, YAESU, etc.) just adapt their existing product for the aircraft band. This means, like 99.9999% of electronics produced today, it is designed to work with 8 ohm speakers.

Aviation Headsets, on the other hand, are designed to the 1920s Ma Bell headphone standard: 300 ohms.

("Impedance," by the way, is very similar to resistance, except it refers to the effective resistance at given frequencies. Just think of it as resistance for now).

The problem comes when that radio, expecting just 8 ohms of impedance, hits the 150 ohm impedance (two 300 ohm speakers in parallel) of the headset. It can't push as much energy.

I actually ran a test, using three different brands of headsets. I turned on an ICOM handheld, plugged in a consumer-type 8-ohm headphone, and dialed up the volume on the ICOM until I was reading 100 dB in the headphone cup. I then connected the ICOM to the three headsets in turn.

The result?

Headset #1: 89 dB
Headset #2: 94 dB
Headset #3: 92 dB

Between 6 and 11 dB less sound energy hitting one's ears. And sound levels are logarithmic, not linear... a 3 dB reduction in level means HALF THE SOUND ENERGY. A 6 dB reduction means a quarter of the sound energy is available for you to hear.

In other words, these are significant drops. In a J. Mac-class airplane, one just unconsciously ups the volume control a tad. For us poor souls in the open-cockpit machines, there might not be enough volume available.

Fortunately, simple fixes exist, with costs from $5 to $150.

The simplest is to replace the speakers in the aviation headset with 8-ohm models. Rugged Radios (http://www.ruggedradios.com/index.php?main_page=product_info&cPath=1_295&products_id=493) sells 8-ohm headset speakers for $15 each. They might fit your headset. In my case, I actually bought an aviation headset from Rugged on the assumption the speakers have the same wires and attachment. I was right... flew it today, and the volume was good and loud. The drawback here is that the headset can't be used with a "conventional" aircraft radio any more. But then I have two additional headsets....

If you're willing to do a bit more work, you can install an impedance matching transformer that'll let you use your existing headset with no modification. These cost less than $5, and will bring the sound level to within 1-2 dB of the nominal value. You can install the transformers behind the panel, or make a simple plug-in adaptor for your headset, or even install the transformer within the headset itself (although, again, you won't be able to use it with standard radios).

Here's the ordering information and the connections to be made:

http://www.bowersflybaby.com/tech/av_xform2.jpg

I have written the details up in more detail on an article on the Fly Baby web page, Adventures in Amplitude (http://www.bowersflybaby.com/tech/amplitude.html).

Ron Wanttaja

[Byron J. Covey]

Thanks Ron, that is useful info.


BJC

[1600vw]

Ron you are second to none. When I purchased my handheld I did not want the problems you describe. This is why I purchased everything together in a pack type of thing from one company, Icom. They have been great when I needed parts or any replacements. What I like about this everything plays well together right out of the box. I was thinking of using an aviation headset with this system. Thanks for explaining all this and what it takes to use an aviation style headset with a handheld. You do amazing work Ron. Keep at it. I love your radio install for an handheld. Like I said..Second to none....

[rwanttaja]

Ron you are second to none. When I purchased my handheld I did not want the problems you describe. This is why I purchased everything together in a pack type of thing from one company, Icom. They have been great when I needed parts or any replacements. What I like about this everything plays well together right out of the box. I was thinking of using an aviation headset with this system. Thanks for explaining all this and what it takes to use an aviation style headset with a handheld. You do amazing work Ron. Keep at it. I love your radio install for an handheld. Like I said..Second to none....
Thanks a bunch!

Also, your comment reminded me of one thing that I forgot to check. I have a headset adaptor for my ICOM ICA5, and was curious as to whether it included an impedance matcher.

It does not...it just connects the radio's speaker outputs to the built-in 1/4" headset jack. I'm assuming this is same for the headset adaptors for other ICOM aviation handhelds. So even if you use the official adaptor, you need to add the impedance matching device (or change the headset speakers like I did).

I think I have an idea on how to make a compact adaptor. Back when I was working on an under-helmet headset, I made an adaptor inside a pill bottle then filled the bottle with resin casting material:

http://www.bowersflybaby.com/tech/h_mold4.jpg
This particular adaptor, sadly, goes the wrong way (lets me plug in an 8-ohm consumer headset into an aircraft radio jack). But I think a casting like this should work with an ICOM to Aircraft Headset adaptor.

In the immortal words of Commander Montgomery Scott: "I'll let ye know...."

Ron Wanttaja

[FlyingRon]

I think these 3000 watt amplifiers will do the trick. Add this and a big kicker speaker in the back and you can hear well. You can then get a tape of a R-985 and play that to make it sound like you've got some real power in that plane.

http://www.sonicelectronix.com/item_108613_Hifonics-Goliath-Monoblock-Car-Amplifier.html?utm_source=google&utm_medium=cpc&utm_campaign=PLA&scid=scplp11615853&sc_intid=108613&gclid=CjwKEAjwps2_BRC5jduHor-h8xESJADGT-Lt9EyfkPpKIEZVwdSXV_FLLD0j-tjaodSFY661lhY8cRoC2qTw_wcB

[rwanttaja]

I think these 3000 watt amplifiers will do the trick. Add this and a big kicker speaker in the back and you can hear well. You can then get a tape of a R-985 and play that to make it sound like you've got some real power in that plane.
I think I just needed to replace the volume control.
5811
Ron Wanttaja

[Frank Giger]

The simplest is to replace the speakers in the aviation headset with 8-ohm models. Rugged Radios sells 8-ohm headset speakers for $15 each. They might fit your headset. In my case, I actually bought an aviation headset from Rugged on the assumption the speakers have the same wires and attachment. I was right... flew it today, and the volume was good and loud. The drawback here is that the headset can't be used with a "conventional" aircraft radio any more. But then I have two additional headsets....

To be clear, you bought their headset with the 150 ohms impedance speakers and then replaced them with the 8 ohm ones, thinking correctly that all the internal hardware fastening points, size, etc. were the same.

I'd love to have a good "Nieuport Only" headset where I can make out others well. Like most pilots I have three headsets anyway, and so it's not a big deal to have one that only works with my handheld.

Three?

First one given to me by an old pilot no longer flying when I was in lessons - it's a black set with all the logos rubbed off from long use (but works great!).
Second is the bog standard Sigtronics that your Mark One Old Guy On The Field sold me for 25 bucks during a hangar cleaning...I figured I could always use a second.
Third is a David Clark H10-13.4 (again, bog standard) that I saw in a pawn shop under the glass that looked brand new. Knowing that the market isn't great for aviation headsets, I offered 50 bucks to get it off his inventory. He bit. The only bad thing about it is that I wonder if some guy just didn't leave it laying around an FBO....but it could also be from a student pilot that gave it up.

[rwanttaja]

To be clear, you bought their headset with the 150 ohms impedance speakers and then replaced them with the 8 ohm ones, thinking correctly that all the internal hardware fastening points, size, etc. were the same.

Yes, since I'd ordered a Rugged Radios headset, and ordered the replacement speakers from them, I figured it was a good bet that they'd be compatible.

I've never taken another brand apart, and don't really know if there's a "standard" headset speaker design. I suspect not. Here's a shot of my headset and the speakers:

http://www.bowersflybaby.com/tech/av_headset.jpg


I'd love to have a good "Nieuport Only" headset where I can make out others well.
Only have one flight on mine, but I'm happy with the Rugged Radios unit.

It's either my fourth or fifth headset, counting the homemade ones. I've used a Denali ANL as my primary headset for years, and may switch back to it if I come up with a good adaptor solution.

Years ago, I decided I needed a second headset, and ordered one of the "Special" $100 headsets in a magazine ad. It works, but is obviously cheap. The mike boom is just a bent piece of plastic, and the wire rods that hold the ear cups tend to pop off and leave the cup dangling.

I basically expected the same for the Rugged Radios unit, but I was wrong. It seems very solid and well-built. I bought the optional gel cushions, and the passive attenuation is very good. I am very happy with this unit, though like I said, I've only flown with it once.

Here's a helpful hint: When you go to their site, select the 'Clearance' tab. They sell demo units of their headsets there... my RA200 was a demo unit, and cost just $65. It had one or two little scuffs on it, but nothing more than it'd get hanging round the airplane for a month or two.

The speakers are accessed from the inside (ear side) of the cups...see the above picture. Remove the ear seals from the cup. There's a thin sheet of foam over the speaker, just slide it across until you reach the edge and pull it out. Similarly, there's a section of wider foam with a speaker-shaped cutout around the speaker. Again, it's easily removed. Two small Phillips screws, and the speaker is loose. It's sitting on a base of thick foam, which can be moved/rearranged but that really isn't necessary.

Gently pull the speaker free of the ear cup, and the green and black wires will trail after it out of a largish hole in the foam until a pigtailed/soldered junction is found. Pull off the shrink-tube insulation, cut off the wires to the original speakers, solder the wires from the new speakers, cover again with shrink tube (or some other insulation), then tuck the wires back behind the foam as you lead the speaker back into place. Re-install the screws, put the foam back in, and install the ear seal.

Ron Wanttaja

[rwanttaja]

I think I have an idea on how to make a compact adaptor. Back when I was working on an under-helmet headset, I made an adaptor inside a pill bottle then filled the bottle with resin casting material...

In the immortal words of Commander Montgomery Scott: "I'll let ye know...."
And the ghost of Scotty gives a satisfied, "Aye....."

Molded adaptor, using casting resin, worked great. This is a picture of it right out of the mold. Need to clean up some flash, maybe paint it, but I tested it on my ICOM and it works.
http://www.bowersflybaby.com/tech/av_adaptor.jpg
The visible plug is the one that plugs into the panel, direct to the radio. I'd inserted a spare plug into the headset jack on the adaptor, just to verify the jack was clear of casting resin.

Ron Wanttaja

[Jim Heffelfinger]

634863496350

Ron et all.... I was dealing with the same issue the other day - of having a limited volume on a head set/portable - this time for marshaling. So I searched the feeds and ran into your multiple articles.
SO, I ordered the headset and replacement speakers but the wiring looks a bit different now - I thought I would add the photos here for comparison.
There is a 3.5 mm jack on the right ear cup as well.
Jim Heffelfinger
Sacramento

[rwanttaja]

Ron et all.... I was dealing with the same issue the other day - of having a limited volume on a head set/portable - this time for marshaling. So I searched the feeds and ran into your multiple articles.
SO, I ordered the headset and replacement speakers but the wiring looks a bit different now - I thought I would add the photos here for comparison.
There is a 3.5 mm jack on the right ear cup as well.
Wow, that is a bit weird (or maybe wired). Didn't see all the circuit boards in my Rugged Radios headset, but I didn't dig into it very far, either.

Despite the complexity, it's just the speakers that need swapping. Disconnect the wires to the 300-ohm speakers, solder them to the 8-ohm models.

However, gotta ask...it's not an ANL unit, is it? Not sure what a speaker switch would do to an ANL unit...nothing good, I'm sure.

I now have ~10 hours on my converted Rugged Radios headset, and it's been working great. No problem at all, volume-wise.

Ron Wanttaja

[Jim Heffelfinger]

Ron, No not ANR. Same model as you and also "demo". Does yours have a volume control? 3.5mm jack for input. Not sure of levels or impedence. No owner's manual. I will look on the site. Easy solder job. Use a low wattage iron or you will fry the prints on the boards.

[rwanttaja]

Ron, No not ANR. Same model as you and also "demo". Does yours have a volume control? 3.5mm jack for input. Not sure of levels or impedence. No owner's manual. I will look on the site. Easy solder job. Use a low wattage iron or you will fry the prints on the boards.

I don't have it here, but I believe mine has a volume control.

Personally, I wouldn't bother with the boards. Cut the speaker wires and splice in the new speakers.

Ron Wanttaja

[Jim Heffelfinger]

Actually Ron , I just easily unsoldered the 300 ohms and soldered the 8s at the PC boards. - 10 Minutes including letting the station come up to temp and clearing away a spot on the bench. Added an additional sound absorbing layer on the inside of the cups as I put it back together. All good.
Jim
BTW : Thanks for all the great work you do for EAA and us.

[Jim Heffelfinger]

BTW - BTW - I am having a dickens of a time putting on the gel cup seals. I even had the Rugged guys send me a photo tutorial. Still having a hard time......

[DaleB]

10 Minutes including letting the station come up to temp and clearing away a spot on the bench.
Man, I can tell you're not in my workshop. 10 minutes wouldn't even get you down through enough layers to see the top of the bench. I've forgotten what color it is.

[rwanttaja]

BTW - BTW - I am having a dickens of a time putting on the gel cup seals. I even had the Rugged guys send me a photo tutorial. Still having a hard time......
I had a hard time, too...took persistence and a lot of Finnish swear words. I think I got one short bit started, then pinned it in place with my thumb and used a skinny screwdriver to encourage the rest of it.

Ron Wanttaja

[rwanttaja]

I had a hard time, too...took persistence and a lot of Finnish swear words. I think I got one short bit started, then pinned it in place with my thumb and used a skinny screwdriver to encourage the rest of it.
BTW, it occurred to me too late, but...try heat. Use a hair dryer to heat up the cub seal before trying to put it on.

Ron Wanttaja

[Jim Heffelfinger]

RE ear cup seals - I set them out in the sun for 30 minutes - in-sun temps reading 114 today. ( 99 in the shade) I was able to get them on but it was quite a trial. Not for the weak of hand. After all that I was not able to get the 3.5mm input to the speakers. Just nothing coming out. So...... I pulled it all apart looking for a fractured wire or something. Head set worked other than that. At first I was annoyed as the volume was actually weaker than the volume in the regular headset going through the same radio - comparison test - until I realized the on headset volume was turned way down. Pheuw. Have to call tech at Rugged to figure out why I do not have the aux input feature. Apparently they do not have a schematic diagram at hand for the headset. I may have to make one from wire tracing.
FWIW - the speakers are in parallel so I am getting a 4 ohm resistance reading at the plug.

[Sam Buchanan]

Headset volume has been a problem in my very windy and noisy Fokker D.VII replica. I use a Yuasa handheld and Lightspeed QFR ANR headset but still have problems hearing some radio transmissions.

Until today. Following Ron's suggestions, I ordered the 42TL004 miniature audio matching transformer from Mouser and wired it onto the headset adapter. Wow...lots more volume! I was a little concerned about proper matching because the transformer input is 10 ohm and the radio specs say audio is fed to a 16 ohm speaker. But it seems to work fine and I hope there are no long-term issues with the small mis-match.

Highly recommended mod and much appreciated! :)

[rwanttaja]

Headset volume has been a problem in my very windy and noisy Fokker D.VII replica. I use a Yuasa handheld and Lightspeed QFR ANR headset but still have problems hearing some radio transmissions.

Until today. Following Ron's suggestions, I ordered the 42TL004 miniature audio matching transformer from Mouser and wired it onto the headset adapter. Wow...lots more volume! I was a little concerned about proper matching because the transformer input is 10 ohm and the radio specs say audio is fed to a 16 ohm speaker. But it seems to work fine and I hope there are no long-term issues with the small mis-match.

Highly recommended mod and much appreciated! :)
Glad it worked for you, Sam...and appreciate the feedback. I'm trying to get the word out as much as I can...I'm finishing up an article for Kitplanes on the subject. As part of it, I've been on an adaptor-building binge, trying out a number of different approaches.

For those who would like to try this out with minimum effort/minimum cost, here's what you can do: Start with a 1/8" to 1/4" earphone plug adaptor. These allow plugging standard consumer-grade headphones (with a 1/8"/3.5mm plug) into the standard 1/4" headphone socket. They usually come with upscale headphones, or you should be able to find them at places like Best Buy. They sell online for as little as a buck.

Using a drill, put a slight dimple in the insulation between the tip and the first ring. Then use solder to bridge the tip and first ring. Sand down the "bump" from the solder so the plug will still enter a jack.
http://www.bowersflybaby.com/tech/helmet_adapt.jpg

This converts the adaptor to mono...puts the same audio signal into both the left and right channels.

Now: Take an ordinary set of ear buds and plug them into your handheld radio, using the adaptor. You should be notice one heck of a lot more volume.

If you want to try it out in flight, just put your regular headset on over the ear buds, and insert the microphone plug into the headset adaptor. Use tie-wraps or a bit of tape to keep the unused headphone plug out of the way.

You can try this out WITHOUT modifying the adaptor, but you'll have only one ear bud working.

Now, if one has an intercom in the airplane, it's likely you've been able to use the intercom's amplifier to crank up the volume to overcome the mismatch. But I heard from a gent in California who had problems with the levels...with a second headset plugged in, the engine noise would be picked up by the mikes and played over the headsets.

He put the impedance matching transformer between the handheld and the intercom, and the problem went away...he didn't have to run the intercom volume so high.

Ron Wanttaja

[lnuss]

Nice, Ron. But note that they also make adapters that preclude the need to modify like that: Here is (http://www.musiciansfriend.com/accessories/hosa-stereo-mini-f-mono-1-4-m?cntry=us&source=3WWRWXGP&gclid=CjsKDwjw6qnJBRDpoonDwLSeZhIkAIpTR8KFi8Xf-g_vHqES35D_qTzksaJrR2Rbu0rzGrjLRCbsGgII5vD_BwE&kwid=productads-adid^156727059247-device^c-plaid^265306775250-sku^333094000000000@ADL4MF-adType^PLA) a 3.5mm stereo to 1/4" mono adapter, for example.

[Jim Heffelfinger]

Well, after converting the speakers I was trying out the auxiliary jack - nothing coming through. Head scratching - it sat on my bench during the week as a reminder I was stumped. I was trying to figure was it a mis-match in impedance? a broken wire, a shorted jack. There was a 56 ohm resistor across the input. Is it shorted? Since the seller did not have a wiring/schematic diagram I started to trace out on my own. This is not rocket science and we are talking audio frequencies here. I pulled out an ohm meter.... Hum the wires to the PWB/PCB were correct but the ones at the jack itself were reversed - shouldn't matter in this case but I fixed it....checked again - nothing. I pulled out some jumper cables and started to check out the paths jumpering directly to the speaker pads on the PWB. Ta - Da audio. Plugged it back in to the jack - Na-Da. Okay jack shorted - nope, Jumpered to the input pads - Na-Da. Back to my drawing - resistor shorted - nope _ silence. I was so locked up in the impedance mismatch - now 4 ohms ( 8s in parallel) v the 150 (300 in parallel) that I missed a humbling troubleshooting error. I made an assumption. Here is the PWB - can you see the problem???
6362
6363

[rwanttaja]

Jim, I finally remembered to bring my converted RA200 home to do a little experimentation.

I plugged my cell phone into the ("hey, there's a 3.5mm jack here") headset. It worked, but at an extremely low audio level. I had to crank my phone volume up all the way to hear it, getting all sorts of warnings about danger of hearing loss, etc. Even at that, it wasn't very loud. If I hadn't been sitting in my workshop (a shrine to gadgetry, with the appropriate solemn hush and candles burning low in the sconces) I might not have been able to hear it.

They obviously put that 56 ohm resistor in there to attempt some sort of matching to 300-ohm speakers, and possibly, to help act as a mixer. I wonder if that's what's messing you up with the 8-ohm speakers in place? You have, essentially, a 56-ohm minimum on the volume control.

Just shorting out the resistor will do the trick. The only thing is, I'm not sure that that does when the aircraft radio and your tunes device are then basically connected directly in parallel.

Ron "What's burning?" Wanttaja

[Jim Heffelfinger]

Nope, you didn't find the error. Hint green is common...........

I'm going to let this sit for a day or so - somebody will catch it.

[Jim Heffelfinger]

No takers.....Maybe this will help.

6374

[robert l]

OK Ron and Jim, this may not be rocket science but to some of us it's still Greek. Plug the Frugal Shaft into the Thngabob then cross dress the Turbo Incapulator ! Say What ??? I finally figured out some years ago that I'm a visual learner. You can describe it to me, I can read it 47 times and still not get it, especially with electronics. I have an older I-COM but have never used headphones with, I generally just listen to the AWOS while sitting in the truck waiting for my appointed flying time. But this is very interesting.
Bob

[DaleB]

I can see why it doesn't work. I just can't figure out how it ever did work.

[Dana]

How could that board ever work?

[Sam Buchanan]

How could that board ever work?

The signal wires must be crossed somewhere else in the headset. Reminds me of the old British car's wiring....purple wire plugs into green, yellow into red, etc, etc......

[Jim Heffelfinger]

You got it. My assumption was....... wait for it.............. it worked at one time. As noted By Dana and DaleB it could never work as wired. The input from the Aux source just stops. Solution...........

6375

These were "special" and discounted heavily.

In another life - I was an Navy ET. We troubleshot equipment based on the assumption it worked correctly at one time. I then worked for Sanyo building consumer audio equipment. As technicians we assumed it was assembled wrong first and then went to standard troubleshooting methods. This is one of the latter.