Hacking Sena SMH10

Discussion in 'Equipment' started by genka, Sep 23, 2012.

  1. genka

    genka SUV hater

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    My unmodified earbud clamp has no noise issues. Some older units suffered from bad connections between the main unit and the clamp. Mine were replaced under warranty long time ago and it fixed the problem for good.
    #21
  2. StuartV

    StuartV Motorcyclist

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    My earbud clamp does not have a noise issue, either.
    #22
  3. enduro0125

    enduro0125 Sticks and Stones™..

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    I have the first gen. They must have cleaned them up in later runs.
    #23
  4. genka

    genka SUV hater

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    I also modified the factory earbud clamp to use the audio input jack for the "full stereo" mode. I can still use the original output jack for the "no noise mono" mode. After riding for couple of weeks, I prefer good stereo even with the background buzz. The buzz is masked by the engine sound even on idle, but audio quality is considerably better. That mode is simple, just cut 3 traces and solder 2 jumpers.

    [​IMG]

    [​IMG]

    [​IMG]
    #24
  5. bluecrab

    bluecrab ...

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    I just modified my SENA baseplate today, turned out better than I had hoped.

    I pretty much did the modification found here:

    http://waggies.net/Ken/Sena/

    The only difference is I mounted the 3.5mm jack INSIDE the SENA baseplate. I used a Radio Shack 274-246 stereo panel-mount phone jack ($2.69) and wired it to disconnect the internal speakers when the earbuds are plugged in. Everything else is untouched and fully functional (I did not cut any traces on the circuit board).

    Sorry, I didn't take any interior photos. There's just enough room inside the SENA to mount the jack. I did have to cut out some of the plastic on the inside cover plate to get it to fit back together, but as you can see, it turned out great.

    Steve

    [​IMG]
    #25
  6. TXjames

    TXjames High Sider

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    Thanks for the part no. This is exactly how a friend did his. I think I will convert mine as well because I find it extremely difficult to locate the aux input jack with my helmet on. Try plugging in your earbuds with your helmet on and let us know how you like it.
    #26
  7. bluecrab

    bluecrab ...

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    No problem at all. I just felt along the bottom edge and immediately felt the socket.

    I also wanted to say that I didn't install resistors to bring down the sound volume. Everything was fine after a quick spin of the SENA's volume knob. Just need to remember that when using the internal speakers, I'll have to crank up the volume again.

    I'm probably going to do my wife's headset next (I need to get her some earbuds first). If/when I customize her unit, I'll take some detailed photos and post them here.
    #27
  8. enduro0125

    enduro0125 Sticks and Stones™..

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    Cool
    I'm very interested in this mod.

    I was going to buy a new earbud clamp(the buzzing is annoying)but will wait now
    #28
  9. Unscathed

    Unscathed n00b

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    Damn - I was going to get a sena SMH10 just for the earbuds. Looks like now I have the option of the slim model or the Scala!
    Thanks!
    #29
  10. snooker

    snooker AttitudeIsEverything

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    News from Sena, they just announced their new "dual" clamp kits that come both with speakers and an earbud jack so you can connect one or the other. Retails for $60 whereas the old styles were $40. It looks to be about 90% of what most people were hoping for, and is a big improvement. I have not heard any feedback on the relative volume levels or anything reviews at all yet but here's hoping the Hack will now just become an option rather than a necessity :clap

    SMH-A305:
    [​IMG]


    SMH-A306:
    [​IMG]
    #30
  11. ChuBrocka

    ChuBrocka Been here awhile

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    I'm hoping someone can help me out here. I'm attempting bluecrab's mod. I bought a Mode Electronics jack (part 24-391-1):[​IMG]
    My problem is that I have no idea how to wire the jack and I can't find any diagrams online. Anyone familiar with these?
    #31
  12. imarsh

    imarsh Adventurer

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    That plugup.com is absolutely brilliant! Cheers.
    #32
  13. snooker

    snooker AttitudeIsEverything

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    Here I'll google it for you :lol3.

    http://www.mode-elec.com/pdf/audio/24-391.pdf

    You'd have to probably get an ohm meter and take a plug and cut and strip the wires, then do some plugging in and measuring.

    This switch has 2 sets of contacts, as described in the following pdf as having "2 normally closed switches", kinda like a double throw switch in a way. It looks like the Sena output would go to pins 2 and 5, and normally 2 & 5 are connected to pins 3 & 4 (helmet speakers?). Then when you plug in your earbuds it connects pins 2 & 5 to the earbud wires. You have to figure out polarity which is which.

    http://www.mode-elec.com/Products/audio_plugs_jacks(14-18).pdf

    Are you trying to hook up something that normally connects to speakers in the helmet but when you plug in the earbud male end it then connects only to the earbuds???

    If not then maybe the part 24-392-1 looks much simpler. No normally closed connections, more like a single throw switch concept.

    http://www.mode-elec.com/pdf/audio/24-392.pdf
    #33
  14. soloyosh

    soloyosh Dad and husband

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    Wait. So the Sena mount for earbuds is mono?
    #34
  15. StuartV

    StuartV Motorcyclist

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    Not exactly. Genka was referring to the earlier part of the thread that explains how the stereo separation between the channels is really poor. So it's almost the same as mono.
    #35
  16. SnowAviation

    SnowAviation Adventurer

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    I did this mod the other day using the method outlined by TXjames, it works great, great stereo, no buzz and a jack that will long outlive that crappy afterthough extendo jack.

    Thanks to all who posted data on this mod.

    #36
  17. wadenelson

    wadenelson Rider/Writer

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    Is it possible OP has miswired his headset? I'm an electrical engineer....

    If R+, R-, L+ and L- are what they intuitively seem to be, then...

    OP has added an unwanted resistance between the right and left channels, which will damage the stereo sound, make it sound flat, all the things a later poster describes. (Properly mis-wired, it may even effectively remove vocals from stereo recordings...)

    I'd like the chance to discuss this, if OP is still around.

    If it's truly 3-wire, R+, L+, and Common, then a resistor between R+ and C, and another between L+ and C would make more sense.

    It's quite possible I'm missing something with all the cut traces, etc, as I cannot / will not attempt to create a schematic from someone else's circuit from pictures on the internet... of a circuit board for which I also have no schematic.

    If it were MY headset I would have tried wiring a 7.5 ohm between R+ and R-, and another one between L+ and L-.

    7.5, not 75. Could that be another mistake by OP? A 75 ohm resistor placed in parallel with a 2-4 ohm earbud speaker's going to have next to zero effect. Its like placing a garden hose next to an irrigation canal.

    One could simply put a 1-10 ohm (exact level TBD) resistor IN LINE with the common lead if it's a 3-wire headphone circuit. Much simpler.

    As for using a shielded ground lead (later poster), umm yeah. No.

    Umm, ok, read the later post where OP accuses Sena of design flaw. Ummm, No.

    Your attempt to FORCE their circuit board to accept a 3-wire headset cord is where the problem lies, not with Sena's design. In fact their dual amplifier 4-wire design will provide MUCH better stereo sound, separation, and ESPECIALLY VOLUME....

    The solution is to sever your earbud cord where it splits into two separate wires, and HARD wire those to the circuit board, or else use two mono jacks, instead of trying to force a 3-wire cord onto a pair of differential amps.

    OP is to be commended for trailblazing, readers are commended for reading down this far in the thread to find out how to do it correctly.

    Cheers!
    #37
  18. genka

    genka SUV hater

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    There is one mistake in the wiring, it switches left and right channels- which doesn't really affect anything.
    The resistors are in series with the earbuds. They are needed because earbuds work at lower power levels compared to the helmet speakers. Although other users reported that connecting the earbuds directly is not overly loud and acceptable. Sena's own earbud clamp uses 75 Ohm resistors.
    Not even sure what are you trying to accomplish here. The goal of my mod was to convert the helmet speaker clamp for exclusive earbud use.
    Completely wrong, it is never done this way. Such circuit would introduce a crosstalk.
    Umm, Yes.
    I essentially duplicated the circuitry Sena uses in the earbud clamp they sell. It also uses one of the "-" leads as a common for the 3 wire system and suffers from exactly the same problem of poor channel separation. I had an extensive e-mail discussion with Sena, and they agreed that it is an inherent design flow. They added the earbud clamp as an afterthought. The 4 wire system is great, but it only works with speakers.
    I thought about it, and saw no practical way to get it working reliably. First of all, in most cases earbuds can't be converted to a 4 wire circuit. After the L and R wires joint together the common wire has 3 conductors. You could buy 2 pairs of earbuds and cut off one bud from each. Also you need to install another 3.5mm jack in the clamp, and there is not enough room to do it. You can dangle it outside- not a neat and reliable solution.
    #38
  19. ErikMotoMan

    ErikMotoMan Been here awhile

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    Originally Posted by bobframe
    If you tire of doing this yourself or are intimidated to begin....

    You might give Marilyn at Plug Up a call. A friend had her replace the factory speakers with a headphone jack so he could use his own headphones and he reports great results. She has done a bit of work for me...repairing a pair of custom ear phones...reasonably priced and quick.

    She's who I'd use to do something like this.

    PlugUp..http://www.plugup.com/



    Marilyn does have great stuff!
    She had a booth at Laguna last year. I really wanted the molded plugs but was poor, ( still am !) so I got the S-plug instead, basically a sillicone rubber plug with minispeakers. The sound quality is AMAZING. deep, rich bass and clear mid-high tones. Love it. Gripes? The white wiring gets dirty quick - it has a slightly rough surface that allows dirt to imbed.

    'Installing' the plugs requires a solid tug at your earlobe and the plug has to be really shoved deep into the ear canal, otherwise it tends to dislodge. Once in, ambient wind-noise is almost nil. Love it!

    Same plug is also available without speakers.
    #39
  20. wadenelson

    wadenelson Rider/Writer

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    Thanks for the update, OP.

    You seem to have an overriding goal of being able to plug standard earbuds into a stereo mini-jack contained in the Sena unit. I don't. My goal is best quality sound, stereo separation, AND significantly more volume.

    So I'm not using a jack, and no 4-to-3 wire conversion is needed. I've hardwired my earbuds, 2 wires each.

    thanks for the tip on Sena using a 75 ohm shunt. I'll try a 47 ohm for slightly greater volume.

    I really like your idea of cobbling two sets of earbuds into one. Heck, I could mount two minijacks into the side of the helmet itself so I could rapidly unplug when someone starts talking and I need to hear:

    "Yes officer, I can hear you just fine..."

    Again, you pioneered this, led everyone down the road and deserve kudos, even though our audio goals differ. Readers can decide for themselves between the flexibility of wiring up a standard jack plug-in versus highest quality sound.

    W
    #40