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ZAMM Fanatic
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2,730 Posts
Discussion Starter #1 (Edited)
I'm cutting off the speakers and soldering in earbuds on my SMH-10. My beautiful new helmet has sat unworn on the kitchen table long enough.

I just wanted to walk away from it having spent all those dollars and STILL NOT able to hear my favorite tunes out on the open road at an enjoyable volume.

So I've played with one of my OTHER helmets, with the HARD (radar visual remote) system instead for awhile. Got it working...flawlessly.... giving me a LED visual warning when my V-1 "breaks squelch..."

So back to the "tunes and calls" helmet....

The speakers were simply unable to supply sufficient volume and overcome wind noise in my Bell Mag9. Over 60mph I couldn't even discern what tune was playing unless the .mp3 had been "mastered" at a fairly high volume.

After several rounds of back and forth with Sena and doing a lot of Internet research it appears earbuds are the only answer. Unfortunately the clamp kit specific to the Mag9 doesn't have an earbud jack.

Anyone here already done this? I seem to recall a post about adding a resistor in series so as not to blow out the earbuds.

I've got a decade resistor box so I cant alligator clamp it all together and dial it down to the right resistance/volume.

Ok, I found the post on another forum. The OP is, with all due respect, NOT a qualified circuit designer. I'm gonna re-do the conversion from scratch because his "design" is fatally flawed, leading to loss of stereo separation, blah, blah, blah. Updates to follow.

http://www.advrider.com/forums/showthread.php?p=25082278#post25082278
 

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ZAMM Fanatic
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2,730 Posts
Discussion Starter #2
Update. SMH-10 Speakers are 29 ohms, earbuds measure 19 ohms meaning they should work even without any added resistors -- but will be appx 50% louder AS IS.

However, since IN the ear is probably perceived as at least 4X as loud as a nearby speaker, probably need to raise them up to around 50 ohms by adding resistor.

Measuring the resistance of the earbuds was a challenge. One copper-colored wire on each bud, red on R, green on L.

Well I KNEW that the green varnish is insulating, ditto for red, and you have to scrape it off or apply a flame to get it off in order to get a good contact. Well, there was also a CLEAR varnish on the copper wire, lol, that slowed me down a few minutes!
 

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ZAMM Fanatic
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2,730 Posts
Discussion Starter #3 (Edited)
Ok, job is complete, including the microscopic soldering which is always a challenge!

I ordered a box of assorted resistors from Ebay thinking I needed either a 47 ohm or possibly 100 ohm in series to cut the volume down to the earbuds.

But when I tried it using my decade resistor box...guess what, earbuds worked GREAT connected directly. I started at 200 ohms and worked my way down... expecting overload/distortion at some point....

Volume is excellent. I don't have to dial it up to full volume anymore.

Ok, some pictures.

I'm just today learning to use FLICKR for off-site storage of images rather than IMGUR because my Macintosh's Iphoto will automatically upload to FLICKER but not IMGUR...

Heres the finished product, ready to snap back into my Bell Mag9

Untitled by wadenelson1, on Flickr



CLICK ON IMAGES FOR LARGER

Here are the leftover speakers. Want to put speakers in your helmet? $20, shipped.



Untitled by wadenelson1, on Flickr

Here is a Sena boom/clamp that INCLUDES an earbud jack and an input audio jack...

Untitled by wadenelson1, on Flickr

here's the decade resistor box I used to determine the correct value resistor to put inline with the earbuds (zero!). I used to use this to "fake out" airbag ECM's for testing purposes.

Untitled by wadenelson1, on Flickr

Measuring the resistance of the earbuds (19.2 ohms) versus the speakers (29 ohms)

Untitled by wadenelson1, on Flickr

Untitled by wadenelson1, on Flickr

Ok and now I see I can choose the size on Imgur before copying the link...

Untitled by wadenelson1, on Flickr


Ok, next project, linking radar detector to Bluetooth transmitter to send to headset.
 
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