larryandelly
trampgeo
This post is about modifying your Sena and possibly other brands of helmet speakers to make the sound volume louder. This post now includes Parts 1 & 2 plus an addendum that contains a correction.
I have been working on helmet speaker mods for a few years and there is quite a bit to report here, so I’ve broken it down into 4 sections: background/warning, summary, testing and build details. This post goes through the testing section. I’ll finish up in a few days. I need to take a few photos that will help with soldering and construction.
CONSTRUCTION, PART 2 HAS BEEN ADDED BELOW
AN ADDENDUM, PART 3 HAS BEEN ADDED AT THE END
I know that helmet sound, especially music is a hot topic. I don’t listen to music in town or in congested traffic. I do listen to music on long slab trips, but curiously, not as much as I used to. I’ve posted this on the MOA Gear forum although there is not much about actual motorcycling in it. It’s here because I like the MOA and it seems to have more polite thoughtful conversations than some of the other forums. So here it goes. I’d like to get some feedback before I do the second half of this article so I can include things I haven’t thought of.
BACKGROUND
In the fall of 2008 I went to a Monday night Arizona Cardinals football game against the San Francisco 49ers. There were two Cardinals goal line stands and the Cardinals had a come back win, all on national television. The enclosed stadium home crowd was incredibly loud and I left the game with permanent hearing damage. Since then I have needed hearing aids in order to have a normal conversation. I was already experimenting using different speakers with my Sena SMH-10 helmet communication and audio system and my hearing damage made me work harder on it. BTW, the Sena unit works very well with the audio system on my 2014 R1200RT. Anyway, having experimented and tested various audio components I have settled on a system that I have used for a year and I am pretty happy with.
OK, here’s the warning. You can make your in-helmet speakers VERY LOUD. These very loud speakers are meant to be used with ear plugs. In its current configuration, I never turn on my Sena unit while wearing my helmet unless I have earplugs in. (I like the green Howard Leight MAX LITE foam ear plugs best. I can trim the rear sides of the plug to let in just the right amount of outside noise.) I suspect that Big Bad Voodoo Daddy at 113dB could itself do some hearing damage without earplugs! So here’s my legal caveat: Do the mods described herein at your own risk. If the mods described below make you nervous, don’t do it. I’m not saying what you should do, just what I did, blah, blah, blah.
SUMMARY
Switching from a Sena OEM 28 ohm helmet speaker to an 8 ohm helmet speaker increases measured speaker volume by about 8 dB (decibels, measured with a sound level meter). The 8 ohm speaker draws more power from the Sena audio amplifier due to the speaker’s lower impedance (Impedance is the same as resistance except that it includes resistance due to speaker coil inductance, in case you ask.). This drives the speaker louder. Please note that it is possible that the higher current output of the Sena unit may shorten its life. I’m also willing to guess that once you hook up a low impedance speaker, the manufacturers warranty is out the window.
The second mod is to put a 2.5 watt chip amp between the Sena output and the helmet speaker. Doing this in conjunction with the 8 ohm speaker can yield a further measured gain of 13 dB. The chip amp is small, about the size of two stacked quarters, but it requires that a somewhat larger than AA size battery be stuck on the helmet. There is a possible advantage to using the chip amp because it presents a very high impedance load to the Sena amplifier, relieving the Sena unit of the task of driving an 8 ohm load and reducing the drain on the Sena battery.
So I’ve ridden with both mods, and the speaker only mod raises the volume with earplugs so I can understand bike-to-bike communication easily, even at high speed. At 70+ mph, music is not super loud, but usually loud enough for me if I am familiar with the music. This is on an RT with the windshield up where I don’t have to deal with a lot of wind noise. Using the chip amp plus the 8 ohm speakers raises the volume a somewhat over the speaker only option, but subjectively it doesn’t seem like an extra 13 dB. I should add that the Visaton 8 ohm miniature speakers are optimized for speech. I like the sound I get but they are not the same as you get listening to stereo headphones in a quiet room. Driving them with the Sena unit or the chip amp probably pushes them to their limit, and if you measured the distortion levels they would be high. But hey, this is motorcycle riding we’re talking about.
If you are going to try these mods, the speaker only solution is the easiest and cheapest to try first. Ordering a pair of Visaton 8 ohm miniature speakers from Germany on Ebay is about $23 as of January, 2017. Parts and soldering instructions are listed in the build section.
TESTING
OK boys and girls, here’s where we really get “into the weeds”. I found that trying different speakers and amp setups required removing and replacing components from inside my helmet, and by the time I got done all the swapping I wasn’t sure I remembered the sound level well enough to compare an old and new configuration. So I used a Radio Shack sound meter and a simple jig to hold each speaker under test exactly one inch from the sound meter microphone. The speakers were tested in “free air”, not on a baffle or in a box. The sound source was a very loud pink noise MP3 sound file on my phone which was sent to the Sena SMH-10 via Bluetooth. Pink noise is a type of random noise that supposedly sends acoustic energy to all frequencies. So the test setup was the same for all speaker and amp configurations. And boy did I test! Here are the speakers that were tested, numbered in the same order as in the results table:
1) Sena speaker, 28 ohms, supplied with the SMH-10.
2) J&M DynaPort helmet speaker, 48 ohms. No longer available, these speakers are sealed with a 1” bass port to enhance bass response. They do have a nice sound. Interesting design.
3) Koss headphone drivers broken out of a pair if Koss PortaPro stereo headphones, 55 ohms.
4) Visaton K40 miniature speaker, 40mm diameter, 50 ohms.
5) Visaton K50 FLS miniature speaker, 50mm diameter, 50 ohms.
6) Visaton K40 miniature speaker, 40mm diameter, 8 ohms.
7) Visaton K50 FLS miniature speaker, 50mm diameter, 8 ohms.
Visaton speakers are made in Germany and are the only helmet sized speakers I could find that have 8 ohms impedance. More details and pictures are in the build section. The Sena helmet speakers are similar to regular headphone speakers which usually have 25 to 50 ohms impedance.
Sound level measurement results for the speakers listed above are given in the table below with and without using the chip amplifier to boost sound levels.
The tests show that the Visaton 8 ohm helmet speakers give the “most boost for the buck” so to speak. The Visaton 40mm and 50 mm diameter speakers show the same loudness, but the 50mm driver is supposed to have better bass although I’m not sure I can hear it. Regarding the amplified speaker results, the chip amp has jumper settings for 6, 9, 12, 15 and 18 dB gain. I only have used and tested the amp at the 12 dB gain setting. In theory, another 6 dB gain is available at the 18 dB setting but I have not tried it. At some point a speaker can be driven to its maximum excursion and adding more power does not add more volume but just more distortion.
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So you want LOUD helmet speakers, PART 2
This post is about how I modified my Sena helmet speakers to get louder sound – the parts and soldering.
Before I begin I would like to thank everyone who commented on my original post. SiReese has a good point, one that I should have addressed. Positioning of the speakers is very important. Yesterday I spent a couple of hours cutting pieces of rigid foam and Velcro in order to move the speakers in my helmet closer to my ears without causing any discomfort. Making a spacer wedge that was thicker toward the bottom front of the speaker helped increase the volume in my unamplified Visaton K40 version. So, thanks Si!
SPEAKER ONLY MOD
This section is about swapping out the OEM speakers for lower impedance Visaton K40 or K50 FLS speakers. This involves connectors, soldering, a little Velcro tape and a small plumbing part. Photo 1 shows the plain vanilla Visaton K40 and K50 speakers. Photos 2 and 3 show the same speakers ready to mount in the helmet.
The first step is to go to Home Depot and buy 2 ‘PartsmasterPro Snap-in Strainers’, shown in Photo 7. These are cheap sink strainers that will be used as speaker grill covers. The 1-5/8” size fits the K40 speaker and the 1-7/8” size fits the K50 speaker. Cut off the three metal tabs and then epoxy the strainer to the front of the speaker. I bent the smaller strainer into a small dome shape in order to keep the speaker diaphragm from touching the strainer. Be careful to epoxy the grill only on the edge of the speaker and not get any epoxy on the diaphragm. I’m a fan of ‘J-B Weld Steel Epoxy’, which will glue just about anything to anything.
Next solder a connector pigtail onto the back of each speaker. The connector I like to use is called a JST connector and has 6”-8” of red and black 20 AWG wire attached to each connector. Photo 6 shows the connector. I don’t like male and female designation in this case because it is confusing. I have labeled them pin and socket in the photo. You can see the little metal pins on the pin side. Solder the socket connector wires to the speakers. An Amazon link for the connectors is provided below. After soldering, the soldered area needs to be covered with an electrical insulator. Really sticky tape is OK, but I prefer a couple of coats of ‘GB Liquid Tape’, available at Home Depot or Amazon. It is available in colors, but I prefer basic black for most occasions. Liquid Tape makes a broken connection hard to repair though. I haven’t discussed whether to leave the pigtail full length or to trim it. Length depends on how your wires are routed in your helmet and whether you will be using a chip amp, so it’s hard to say. Just “measure twice, cut once.”
Now for the fun part, voiding your warranty and soldering those tiny little wires. Void your warranty by cutting the speaker wires to your OEM speakers. Strip off about ½” of outer insulation from the wires that go back to the Sena unit. Strip back about ¼” insulation from the two inner wires. You can strip the insulation off of the two inner speaker wires or just burn off the insulation with your soldering iron. Photo 5 shows this.
Now solder JST pin connector pigtails to the speaker wires that go back to the Sena unit. Be sure to use pin connectors this time. Strip back ¼” insulation from the red and black pigtail ends. Slide two pieces of heat shrink tubing over each pigtail wire and another over the black Sena speaker wire. You only need a small pencil soldering iron. Harbor Freight has a 30-watt unit for $4. Harbor Freight and Amazon have heat shrink tubing kits for under $10. The easiest way to solder thin wires is to put solder onto the wires and then place them side by side and solder them together without adding more solder (again Photo 5). The trick to soldering is to make sure that you melt fresh solder onto the soldering tip just before you use it. You can tap off any excess. Fresh solder has fresh flux that isn’t oxidized. Having a ‘third hand’ helps too (see photo and parts list below). After the wires are soldered, slip the heat shrink over the wires and shrink the tubing by holding the soldering iron close to the wire.
If you want to, solder the socket JST connector pigtails to your OEM speaker wires so you can compare the new and old helmet speakers. Put some Velcro tape on the back of your new speakers, connect the speakers to the Sena wires at the JST connectors, and fit your new speakers back into your helmet. The K40 speakers are the same diameter and possibly a bit thinner than the original speakers. You can use the foam covers that came with the Sena speakers to cover the K40 metal speaker grill if you wish.
Just remember, socket connectors on the speaker wires and pin connectors on the Sena wires.
SPEAKER MOD PLUS CHIP AMP
Adding a chip amp between the Sena unit and the speakers can add a lot more loudness to your speakers, as demonstrated in the TESTING section of my first post. I’ll give more general directions here as I assume this mod will be tackled by those with some tinkering experience.
The chip amp I used is from a company called Adafruit (ay-duh-fruit), adafruit.com. There are plenty of other 5 watt chip amps out there similar to the one I used that are probably just as good. I just like and trust Adafruit. They have plush toys of Cappy the capacitor and Hans the 555 Timer IC that I got for my granddaughters. Check out Lady Ada if you dare! Photo 8 shows the little chip amp with all of the connections, 4 wires input from the Sena unit, 4 wires out to the speakers and two wires to 5 volts power. All of the wires are pigtails from JST connectors. The input wires have socket connectors and the output wires have pin connectors. In the photo none of the gain jumpers are connected, so the gain is at the default of 6 dB. When I was done I put some large diameter heat shrink tubing around the amp board and shrank it down so the wires stuck out each end.
Photo 9 shows a little external cell phone recharging battery that you can use for power. You just have to cut a micro USB cable and attach JST connector pigtails to the +5 volts and ground wires of the cable. I used a lithium battery and separate charger from Adafruit, but I think the cell phone charger is easier. I don’t know the pinouts of a micro USB connector, so you will have to look that up. The battery can also be used to power or recharge your Sena unit. My battery lasts 2 or 3 full days between charges. Photo 10 shows the wire from my amp to the battery that is velcroed to the back of my helmet. I attached some yellow heat shrink around wires on both sides of the power connector to make sure I plug the battery into only the amp power supply wires. I turn amp power on and off by plugging and unplugging the JST connector. The battery weighs about 2-1/2 ounces.
Photos 11 and 12 show the mods with and without the amp inserted. You can do the whole setup with just pigtail wire and the wire that already goes to the speakers. The amp and wires are hidden behind helmet padding and only the wire to the battery is exposed. (The wire lengths from the amp to the speakers in Photo 12 are wrong as one wire will need to be longer in order to reach the far side of the helmet.)
Whew. That’s it for now. What I have described here is just one solution for making the sound louder for my failing ears. I did this less out of necessity but more because I am retired with plenty of time and it was a fun hobby thing. So, I guess my advice is try these mods only if you would enjoy doing it too. Oh yes, and don’t blame me if you burn a hole in your finger or your helmet catches fire.
I hope I will get some more replies to this post. I have sent away for another pair of helmet speakers to test and I will post the test results if they are positive. Also, if anyone knows of small connectors with thinner (but strong) wire pigtails that can be used for this project, I’d like to hear about it. 20 gauge is definitely overkill. I've listed some 22 gauge that I haven't tried in the parts list.
-Larry Johnson 1/20/2018
Parts Sources
Visaton K40 8 ohm speaker: https://www.ebay.com/itm/Visaton-K-...681325&hash=item2373a1378e:g:ZnUAAOxyLN9SiPm3
Visaton K50 FLS 8 ohm Speaker: https://www.ebay.com/p/VISATON-K-50-FLS-8-Ohm-070506/1489740855?_trksid=p2047675.l2644
Speaker grill: https://www.homedepot.com/p/PartsmasterPro-1-5-8-in-Snap-In-Strainer-58124B/206849054
JST connectors, 20 gauge: https://www.amazon.com/dp/B01M5AHF0Z/_encoding=UTF8?coliid=I3K2DR9T6LURHP&colid=92W2L7I131UX&psc=0
JST connectors, 22 gauge, haven’t tried them, but thinner wires might be better: https://www.amazon.com/eBoot-Pairs-...sr=8-1-spons&keywords=jst+connectors+24&psc=1
Heat shrink tubing: https://www.amazon.com/dp/B00EXLPLTW/_encoding=UTF8?coliid=IBA02IQSS9HC7&colid=92W2L7I131UX&psc=0
GB Liquid Tape: https://www.amazon.com/dp/B000FPAN2K/_encoding=UTF8?coliid=IMEP5TTD9AXVV&colid=92W2L7I131UX&psc=1
Adafruit chip amp: https://www.adafruit.com/product/987
Cell phone battery: https://www.amazon.com/gp/product/B01N5XTZFC/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Third hand: https://www.amazon.com/dp/B000RB38X8/_encoding=UTF8?coliid=I2VEJRWYUZFPJ9&colid=92W2L7I131UX&psc=0
Cappy the Capacitor - Circuit Playground Plush Toy (character from ‘Circuit Playground’ kids show at adafruit.com): https://www.adafruit.com/product/1021
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So you want LOUD helmet speakers, Addendum PART 3
I am adding a bit more here for a correction and an additional speaker option.
- A correction to parts 1 and 2: The Visaton 50mm 8 ohm speaker that I tested was model K50 FLS, not model K50FL. I have corrected the error in the text, text table and parts list above. The K50 FL is about 5 dB less loud in my testing than the K50 FLS. Both of the K50 speakers were a little too large anyway, and the 40mm diameter K40 speakers fit better into the Arai and Shoei helmets that I have. Sorry about the error.
- I found a another speaker sourced in the U.S. that is very interesting. The speaker is the Peerless HPD-40N16PET00-32 Headphone Driver sold by www.parts-express.com. This is a 32 ohm headphone driver, not a miniature speaker like the Visaton unit. Even though it has 32 ohms impedance, the sound level is only 1 or 2 decibels less than the 8 ohm Visaton K40. It may or may not provide a significant loudness improvement over the existing Sena speakers in your helmet. What I did was to use this speaker with the chip amp set to 18 dB gain. I think that the quality of the sound is a little better than the Visaton units, unless my Sena volume is cranked up all the way and I get distortion from the speaker being driven too hard (same as Visaton speakers). For a cost of $10 each, including the metal grill, the Peerles speakers might be worth a try first.
The Peerless driver is the same diameter as the Sena and Visaton K40 speakers. It uses the smaller 1-5/8" drain cover for a speaker grill.
Peerless, along with other Danish speaker component manufacturing companies like Scan-Speak and Vifa, pioneered the standard for high fidelity dynamic drivers back in the 1970s and 1980s. Some very expensive speakers were made (possibly still are?) using Peerless drivers. Dunlavy comes to mind. Now, of course, Peerless is owned by Tympany, a Hong Kong based company. The Peerless driver listed above is made in China.
I have been working on helmet speaker mods for a few years and there is quite a bit to report here, so I’ve broken it down into 4 sections: background/warning, summary, testing and build details. This post goes through the testing section. I’ll finish up in a few days. I need to take a few photos that will help with soldering and construction.
CONSTRUCTION, PART 2 HAS BEEN ADDED BELOW
AN ADDENDUM, PART 3 HAS BEEN ADDED AT THE END
I know that helmet sound, especially music is a hot topic. I don’t listen to music in town or in congested traffic. I do listen to music on long slab trips, but curiously, not as much as I used to. I’ve posted this on the MOA Gear forum although there is not much about actual motorcycling in it. It’s here because I like the MOA and it seems to have more polite thoughtful conversations than some of the other forums. So here it goes. I’d like to get some feedback before I do the second half of this article so I can include things I haven’t thought of.
BACKGROUND
In the fall of 2008 I went to a Monday night Arizona Cardinals football game against the San Francisco 49ers. There were two Cardinals goal line stands and the Cardinals had a come back win, all on national television. The enclosed stadium home crowd was incredibly loud and I left the game with permanent hearing damage. Since then I have needed hearing aids in order to have a normal conversation. I was already experimenting using different speakers with my Sena SMH-10 helmet communication and audio system and my hearing damage made me work harder on it. BTW, the Sena unit works very well with the audio system on my 2014 R1200RT. Anyway, having experimented and tested various audio components I have settled on a system that I have used for a year and I am pretty happy with.
OK, here’s the warning. You can make your in-helmet speakers VERY LOUD. These very loud speakers are meant to be used with ear plugs. In its current configuration, I never turn on my Sena unit while wearing my helmet unless I have earplugs in. (I like the green Howard Leight MAX LITE foam ear plugs best. I can trim the rear sides of the plug to let in just the right amount of outside noise.) I suspect that Big Bad Voodoo Daddy at 113dB could itself do some hearing damage without earplugs! So here’s my legal caveat: Do the mods described herein at your own risk. If the mods described below make you nervous, don’t do it. I’m not saying what you should do, just what I did, blah, blah, blah.
SUMMARY
Switching from a Sena OEM 28 ohm helmet speaker to an 8 ohm helmet speaker increases measured speaker volume by about 8 dB (decibels, measured with a sound level meter). The 8 ohm speaker draws more power from the Sena audio amplifier due to the speaker’s lower impedance (Impedance is the same as resistance except that it includes resistance due to speaker coil inductance, in case you ask.). This drives the speaker louder. Please note that it is possible that the higher current output of the Sena unit may shorten its life. I’m also willing to guess that once you hook up a low impedance speaker, the manufacturers warranty is out the window.
The second mod is to put a 2.5 watt chip amp between the Sena output and the helmet speaker. Doing this in conjunction with the 8 ohm speaker can yield a further measured gain of 13 dB. The chip amp is small, about the size of two stacked quarters, but it requires that a somewhat larger than AA size battery be stuck on the helmet. There is a possible advantage to using the chip amp because it presents a very high impedance load to the Sena amplifier, relieving the Sena unit of the task of driving an 8 ohm load and reducing the drain on the Sena battery.
So I’ve ridden with both mods, and the speaker only mod raises the volume with earplugs so I can understand bike-to-bike communication easily, even at high speed. At 70+ mph, music is not super loud, but usually loud enough for me if I am familiar with the music. This is on an RT with the windshield up where I don’t have to deal with a lot of wind noise. Using the chip amp plus the 8 ohm speakers raises the volume a somewhat over the speaker only option, but subjectively it doesn’t seem like an extra 13 dB. I should add that the Visaton 8 ohm miniature speakers are optimized for speech. I like the sound I get but they are not the same as you get listening to stereo headphones in a quiet room. Driving them with the Sena unit or the chip amp probably pushes them to their limit, and if you measured the distortion levels they would be high. But hey, this is motorcycle riding we’re talking about.
If you are going to try these mods, the speaker only solution is the easiest and cheapest to try first. Ordering a pair of Visaton 8 ohm miniature speakers from Germany on Ebay is about $23 as of January, 2017. Parts and soldering instructions are listed in the build section.
TESTING
OK boys and girls, here’s where we really get “into the weeds”. I found that trying different speakers and amp setups required removing and replacing components from inside my helmet, and by the time I got done all the swapping I wasn’t sure I remembered the sound level well enough to compare an old and new configuration. So I used a Radio Shack sound meter and a simple jig to hold each speaker under test exactly one inch from the sound meter microphone. The speakers were tested in “free air”, not on a baffle or in a box. The sound source was a very loud pink noise MP3 sound file on my phone which was sent to the Sena SMH-10 via Bluetooth. Pink noise is a type of random noise that supposedly sends acoustic energy to all frequencies. So the test setup was the same for all speaker and amp configurations. And boy did I test! Here are the speakers that were tested, numbered in the same order as in the results table:
1) Sena speaker, 28 ohms, supplied with the SMH-10.
2) J&M DynaPort helmet speaker, 48 ohms. No longer available, these speakers are sealed with a 1” bass port to enhance bass response. They do have a nice sound. Interesting design.
3) Koss headphone drivers broken out of a pair if Koss PortaPro stereo headphones, 55 ohms.
4) Visaton K40 miniature speaker, 40mm diameter, 50 ohms.
5) Visaton K50 FLS miniature speaker, 50mm diameter, 50 ohms.
6) Visaton K40 miniature speaker, 40mm diameter, 8 ohms.
7) Visaton K50 FLS miniature speaker, 50mm diameter, 8 ohms.
Visaton speakers are made in Germany and are the only helmet sized speakers I could find that have 8 ohms impedance. More details and pictures are in the build section. The Sena helmet speakers are similar to regular headphone speakers which usually have 25 to 50 ohms impedance.
Sound level measurement results for the speakers listed above are given in the table below with and without using the chip amplifier to boost sound levels.
The tests show that the Visaton 8 ohm helmet speakers give the “most boost for the buck” so to speak. The Visaton 40mm and 50 mm diameter speakers show the same loudness, but the 50mm driver is supposed to have better bass although I’m not sure I can hear it. Regarding the amplified speaker results, the chip amp has jumper settings for 6, 9, 12, 15 and 18 dB gain. I only have used and tested the amp at the 12 dB gain setting. In theory, another 6 dB gain is available at the 18 dB setting but I have not tried it. At some point a speaker can be driven to its maximum excursion and adding more power does not add more volume but just more distortion.
----------------------------------------------------
So you want LOUD helmet speakers, PART 2
This post is about how I modified my Sena helmet speakers to get louder sound – the parts and soldering.
Before I begin I would like to thank everyone who commented on my original post. SiReese has a good point, one that I should have addressed. Positioning of the speakers is very important. Yesterday I spent a couple of hours cutting pieces of rigid foam and Velcro in order to move the speakers in my helmet closer to my ears without causing any discomfort. Making a spacer wedge that was thicker toward the bottom front of the speaker helped increase the volume in my unamplified Visaton K40 version. So, thanks Si!
SPEAKER ONLY MOD
This section is about swapping out the OEM speakers for lower impedance Visaton K40 or K50 FLS speakers. This involves connectors, soldering, a little Velcro tape and a small plumbing part. Photo 1 shows the plain vanilla Visaton K40 and K50 speakers. Photos 2 and 3 show the same speakers ready to mount in the helmet.
The first step is to go to Home Depot and buy 2 ‘PartsmasterPro Snap-in Strainers’, shown in Photo 7. These are cheap sink strainers that will be used as speaker grill covers. The 1-5/8” size fits the K40 speaker and the 1-7/8” size fits the K50 speaker. Cut off the three metal tabs and then epoxy the strainer to the front of the speaker. I bent the smaller strainer into a small dome shape in order to keep the speaker diaphragm from touching the strainer. Be careful to epoxy the grill only on the edge of the speaker and not get any epoxy on the diaphragm. I’m a fan of ‘J-B Weld Steel Epoxy’, which will glue just about anything to anything.
Next solder a connector pigtail onto the back of each speaker. The connector I like to use is called a JST connector and has 6”-8” of red and black 20 AWG wire attached to each connector. Photo 6 shows the connector. I don’t like male and female designation in this case because it is confusing. I have labeled them pin and socket in the photo. You can see the little metal pins on the pin side. Solder the socket connector wires to the speakers. An Amazon link for the connectors is provided below. After soldering, the soldered area needs to be covered with an electrical insulator. Really sticky tape is OK, but I prefer a couple of coats of ‘GB Liquid Tape’, available at Home Depot or Amazon. It is available in colors, but I prefer basic black for most occasions. Liquid Tape makes a broken connection hard to repair though. I haven’t discussed whether to leave the pigtail full length or to trim it. Length depends on how your wires are routed in your helmet and whether you will be using a chip amp, so it’s hard to say. Just “measure twice, cut once.”
Now for the fun part, voiding your warranty and soldering those tiny little wires. Void your warranty by cutting the speaker wires to your OEM speakers. Strip off about ½” of outer insulation from the wires that go back to the Sena unit. Strip back about ¼” insulation from the two inner wires. You can strip the insulation off of the two inner speaker wires or just burn off the insulation with your soldering iron. Photo 5 shows this.
Now solder JST pin connector pigtails to the speaker wires that go back to the Sena unit. Be sure to use pin connectors this time. Strip back ¼” insulation from the red and black pigtail ends. Slide two pieces of heat shrink tubing over each pigtail wire and another over the black Sena speaker wire. You only need a small pencil soldering iron. Harbor Freight has a 30-watt unit for $4. Harbor Freight and Amazon have heat shrink tubing kits for under $10. The easiest way to solder thin wires is to put solder onto the wires and then place them side by side and solder them together without adding more solder (again Photo 5). The trick to soldering is to make sure that you melt fresh solder onto the soldering tip just before you use it. You can tap off any excess. Fresh solder has fresh flux that isn’t oxidized. Having a ‘third hand’ helps too (see photo and parts list below). After the wires are soldered, slip the heat shrink over the wires and shrink the tubing by holding the soldering iron close to the wire.
If you want to, solder the socket JST connector pigtails to your OEM speaker wires so you can compare the new and old helmet speakers. Put some Velcro tape on the back of your new speakers, connect the speakers to the Sena wires at the JST connectors, and fit your new speakers back into your helmet. The K40 speakers are the same diameter and possibly a bit thinner than the original speakers. You can use the foam covers that came with the Sena speakers to cover the K40 metal speaker grill if you wish.
Just remember, socket connectors on the speaker wires and pin connectors on the Sena wires.
SPEAKER MOD PLUS CHIP AMP
Adding a chip amp between the Sena unit and the speakers can add a lot more loudness to your speakers, as demonstrated in the TESTING section of my first post. I’ll give more general directions here as I assume this mod will be tackled by those with some tinkering experience.
The chip amp I used is from a company called Adafruit (ay-duh-fruit), adafruit.com. There are plenty of other 5 watt chip amps out there similar to the one I used that are probably just as good. I just like and trust Adafruit. They have plush toys of Cappy the capacitor and Hans the 555 Timer IC that I got for my granddaughters. Check out Lady Ada if you dare! Photo 8 shows the little chip amp with all of the connections, 4 wires input from the Sena unit, 4 wires out to the speakers and two wires to 5 volts power. All of the wires are pigtails from JST connectors. The input wires have socket connectors and the output wires have pin connectors. In the photo none of the gain jumpers are connected, so the gain is at the default of 6 dB. When I was done I put some large diameter heat shrink tubing around the amp board and shrank it down so the wires stuck out each end.
Photo 9 shows a little external cell phone recharging battery that you can use for power. You just have to cut a micro USB cable and attach JST connector pigtails to the +5 volts and ground wires of the cable. I used a lithium battery and separate charger from Adafruit, but I think the cell phone charger is easier. I don’t know the pinouts of a micro USB connector, so you will have to look that up. The battery can also be used to power or recharge your Sena unit. My battery lasts 2 or 3 full days between charges. Photo 10 shows the wire from my amp to the battery that is velcroed to the back of my helmet. I attached some yellow heat shrink around wires on both sides of the power connector to make sure I plug the battery into only the amp power supply wires. I turn amp power on and off by plugging and unplugging the JST connector. The battery weighs about 2-1/2 ounces.
Photos 11 and 12 show the mods with and without the amp inserted. You can do the whole setup with just pigtail wire and the wire that already goes to the speakers. The amp and wires are hidden behind helmet padding and only the wire to the battery is exposed. (The wire lengths from the amp to the speakers in Photo 12 are wrong as one wire will need to be longer in order to reach the far side of the helmet.)
Whew. That’s it for now. What I have described here is just one solution for making the sound louder for my failing ears. I did this less out of necessity but more because I am retired with plenty of time and it was a fun hobby thing. So, I guess my advice is try these mods only if you would enjoy doing it too. Oh yes, and don’t blame me if you burn a hole in your finger or your helmet catches fire.
I hope I will get some more replies to this post. I have sent away for another pair of helmet speakers to test and I will post the test results if they are positive. Also, if anyone knows of small connectors with thinner (but strong) wire pigtails that can be used for this project, I’d like to hear about it. 20 gauge is definitely overkill. I've listed some 22 gauge that I haven't tried in the parts list.
-Larry Johnson 1/20/2018
Parts Sources
Visaton K40 8 ohm speaker: https://www.ebay.com/itm/Visaton-K-...681325&hash=item2373a1378e:g:ZnUAAOxyLN9SiPm3
Visaton K50 FLS 8 ohm Speaker: https://www.ebay.com/p/VISATON-K-50-FLS-8-Ohm-070506/1489740855?_trksid=p2047675.l2644
Speaker grill: https://www.homedepot.com/p/PartsmasterPro-1-5-8-in-Snap-In-Strainer-58124B/206849054
JST connectors, 20 gauge: https://www.amazon.com/dp/B01M5AHF0Z/_encoding=UTF8?coliid=I3K2DR9T6LURHP&colid=92W2L7I131UX&psc=0
JST connectors, 22 gauge, haven’t tried them, but thinner wires might be better: https://www.amazon.com/eBoot-Pairs-...sr=8-1-spons&keywords=jst+connectors+24&psc=1
Heat shrink tubing: https://www.amazon.com/dp/B00EXLPLTW/_encoding=UTF8?coliid=IBA02IQSS9HC7&colid=92W2L7I131UX&psc=0
GB Liquid Tape: https://www.amazon.com/dp/B000FPAN2K/_encoding=UTF8?coliid=IMEP5TTD9AXVV&colid=92W2L7I131UX&psc=1
Adafruit chip amp: https://www.adafruit.com/product/987
Cell phone battery: https://www.amazon.com/gp/product/B01N5XTZFC/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Third hand: https://www.amazon.com/dp/B000RB38X8/_encoding=UTF8?coliid=I2VEJRWYUZFPJ9&colid=92W2L7I131UX&psc=0
Cappy the Capacitor - Circuit Playground Plush Toy (character from ‘Circuit Playground’ kids show at adafruit.com): https://www.adafruit.com/product/1021
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So you want LOUD helmet speakers, Addendum PART 3
I am adding a bit more here for a correction and an additional speaker option.
- A correction to parts 1 and 2: The Visaton 50mm 8 ohm speaker that I tested was model K50 FLS, not model K50FL. I have corrected the error in the text, text table and parts list above. The K50 FL is about 5 dB less loud in my testing than the K50 FLS. Both of the K50 speakers were a little too large anyway, and the 40mm diameter K40 speakers fit better into the Arai and Shoei helmets that I have. Sorry about the error.
- I found a another speaker sourced in the U.S. that is very interesting. The speaker is the Peerless HPD-40N16PET00-32 Headphone Driver sold by www.parts-express.com. This is a 32 ohm headphone driver, not a miniature speaker like the Visaton unit. Even though it has 32 ohms impedance, the sound level is only 1 or 2 decibels less than the 8 ohm Visaton K40. It may or may not provide a significant loudness improvement over the existing Sena speakers in your helmet. What I did was to use this speaker with the chip amp set to 18 dB gain. I think that the quality of the sound is a little better than the Visaton units, unless my Sena volume is cranked up all the way and I get distortion from the speaker being driven too hard (same as Visaton speakers). For a cost of $10 each, including the metal grill, the Peerles speakers might be worth a try first.
The Peerless driver is the same diameter as the Sena and Visaton K40 speakers. It uses the smaller 1-5/8" drain cover for a speaker grill.
Peerless, along with other Danish speaker component manufacturing companies like Scan-Speak and Vifa, pioneered the standard for high fidelity dynamic drivers back in the 1970s and 1980s. Some very expensive speakers were made (possibly still are?) using Peerless drivers. Dunlavy comes to mind. Now, of course, Peerless is owned by Tympany, a Hong Kong based company. The Peerless driver listed above is made in China.
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