In 2014 H-D® started installing their 6.5GT Boom!™ systems as standard equipment in some bikes, and as an option on others. For some reason they did not include a wireless headset interface specification even though they were selling wireless headsets. Needless to say, H-D® received a lot of grief due to this oversight. The only way to control the functions of the Boom!™ system was to buy a corded headset and use the installed 7-pin DIN connector in the console (if your bike came with one) or to buy the #69200865 Audio Music & Communications Kit (Which added the required 7-pin DIN plug.) that allowed you to plug-in an H-D® compatible corded headset. It wasn't an ideal solution, but it was all Harley (or anyone else) offered for the next two years.
While Harley was working on a solution, Sena (Who makes Harley's headsets for them.) came up with an interim solution - their Freewire™ wireless module. It allows wireless control of the 6.5GT Boom!™ system through the 7-pin DIN connector of the Communicatioins Kit. So you've eliminated the wire to the headset, but gained a wire connecting the Freewire™ to the 7-pin DIN plug. Not exactly the most elegant solution, not to mention it leaves the Freewire™ exposed to being stolen.
In 2017 Harley finally announced their solution - the Wireless Headset Interface Module, or WHiM. It was designed by Sena under contract from Harley, and it connects directly to the 6.5GT Boom!™ Infotainment System's wiring harness and allows full wireless control.
For 2019 Harley introduced their Boom! GTS Infotainment system with Apple CarPlay, but still no wireless headset connectivity - You still need to purchase a WHiM module. (The Sena Freewire™ should work with the new GTS system, but I have no idea if it will work with the GTS's Apple CarPlay.)
Great! Now it's easy to add wireless bluetooth control and just go buy a bluetooth headset, right? Not so fast there Kemosabe! There are caveats...
So what's all this talk about CODECs, eh? CODECs are enCOder-DECoder's, or the method of how they convert the audio to a digital stream to transmit, and back again. Most Bluetooth headsets use Low Complexity Subband Coding (SBC) to compress the (stereo) audio. SBC is geared towards low power use and was designed to transmit high definition audio, but introduces a bit of latency. Sena uses SBC in their Freewire™ and their headsets, as does Cardo. Harley went a step further with their WHiM and headsets, and included a newer CODEC called aptX that is supposed to allow CD quality audio and be backwards compatible with SBC CODEC components. (This supports the thought about why non-Harley branded headsets only work in monaural, since the aptX CODEC should fall back to an SBC connection (which supports stereo audio) if aptX support isn't found.)
One major point when deciding on a wireless system is "Do you ride with a pasenger?" If you do, the cheapest wireless solution is the WHiM because it supports both a rider and passenger in one unit, while the Freewire™ only supports one - two Freewires™ are required for a rider/passenger to gain full Boom!™ control. I greyed that out because I personally don't have any experience with rider/passenger communications, so I can't really say if this is true. Maybe it was for headsets that only used Bluetooth, but the new headsets use Bluetooth Mesh, so if you get, say, two Sena 30K headsets, you'd really only need one Freewire™ - (for the rider) because the passenger doesn't need to control the Infotainment System, and while the rider is connected to it with bluetooth, the passenger can communicate to the rider through the Mesh network independently. (This won't work if the rider's 30K headset is paired to a WHiM because Mesh networking will be disabled on that headset - a problem the Freewire doesn't exibit.)
A second major point is prior investment in prior wireless headsets...
Some riders already own a Sena headset that works fine. For them the only way to obtain voice control and listen to stereo music from the Boom!™ System would be to discard or sell their present headset(s) and buy the Harley-branded version. Of course, if they're fine with monaural audio from the Boom!™ System - GPS, CB, Phone calls, & Radio - then staying with their Sena-branded wireless headset shouldn't be a problem. Likewise if they already have a Sena-branded headset and want stereo audio they can go with the Freewire™.
Some riders already own a Cardo headset that works fine. For them the only way to obtain voice control and listen to stereo music from the Boom!™ System would be to discard or sell their present headset(s) and buy the Harley-branded version. Of course, if they're fine with monaural audio from the Boom!™ System - GPS, CB, Phone calls, & Radio - then staying with their Cardo-branded wireless headset shouldn't be a problem.
NOTE #1: I've modified the flowchart to include the Cardo Packtalk headsets which the WHiM recognizes and pairs to, so you have another option. Like the Sena, the Cardo will give you monaural audio when playing through the WHiM, but unlike the Sena, the Cardo unit will allow you to use it's Mesh Technology while paired to the WHiM!
NOTE #2: Please read the complete Addendum sections if you are thinking about adding wireless comm. to your bike.
Here's some additional information I've discovered in working with both the WHiM and the Freewire™ connecting to the Sena 30K Mesh headset...