Sound systems
So I went down the rabbit hole a few times, looking for better music (without a headset). Thought I'd discuss some options, here, although it pertains to any model in general, there's a LOT of solutions I found that are specific to the model I was long to improve.
First, the different years have different factory hardware. I believe it was starting in 2020, they went to 'power band' systems. BTW, if I say radio, I mean infotainment system, I'm just old school. Those stock systems sound much better than the earlier ones, and are generally not plug and play compatible with earlier systems. (You can make anything work with enough fiddling, but different physical size and mounting, electric specs, software) I do not have much experience with power band, other than to say a lot of the annoying quirks I've discovered, have been addressed by Indian.
Second, a lot of the older (pre 2020) parts are getting hard to find. While oem vehicle parts are available, after market accessory add ons are not being made any more.
So-
Discussion 1: easy upgrades
It turns out, the factory speakers are a bit of a disappointment. In fact, the software for the 2016 and earlier, will literally blow the speakers. If you turn it loud when going slow, and have the automatic volume control turned on, it will turn it up, when you go fast, beyond 100%. I don't use that feature anymore, even though they supposedly fixed the problem.
I changed the speakers to Polk DB522. These are much higher wattage, and won't blow from anything the factory amp can toss at them. They sound much better, and are less than $100 a pair. (I have a few factory speakers if anyone wants them. ) The install is pretty easy, and I'd say this would be the go to (except see below) for quick audio improvent.
In these bikes, and I think still in the power band, there is no actual speaker enclosure. The sound just goes where it wants, and more than half is wasted toward the front or ground. Speaker baffles, or boom mats, are foam rubber bits to solve this. Crutchfield has a pair that fit well, and are pretty cheap. (I seem to recall $5, but maybe $10.) The ones shaped like the speaker are trimmed to fit in the mount space, you poke a hole for the wire, and simply lay them in place before you mount your speaker.
These 2 upgrades, for less than a hundred bucks and a couple hours work, produce probably a 20% improvement in sound quality, and maybe a 5% improvement in volume.
Next: saddle bag speaker craziness!
Satellite radio:
I know. I told you I went down a deep rabbit hole...
I decided I needed satellite radio. I was done losing signal, I didn't have enough room for a ton of CDs, and I really didn't have much of a digital collection.
There are a few ways to hook this up. 1) run the satellite radio app on your phone, and BT direct to the Head unit. This was unacceptable, I probably lost cell signal almost as much as radio. This isn't a bad idea for local riding, though. 2) use the satellite receiver unit, and broadcast on an FM channel, for the head unit to pick up. I didn't want to lose sound quality, though. And it wasn't worth buying the only receiver that broadcast BT, especially since I already decided I didn't want to lose sound quality. (See below, though.) 3) hard wire the signal to the Head unit. I bought the adapter that plugs in between the antenna leads, and plays on an FM channel. It is now hard wired and works well.
Now looking into things for the sidecar bike... I discovered they have a new product. I would need a new cradle to mount the reciever, I'd just swap it from bike to bike. They now make a BT cradle that's something like $2 more than a plain one. A little research, and I discovered I was way off about sound quality. BT actually can broadcast, about 3x more sound quality than satellite radio does. (Yes they have a lot of bandwidth, but they use it for 200 channels, not quality.) I also discovered they have a USB power converter. Using the USB plug I was going to install anyway, and ordering the right cradle I was going to anyway... I could have satellite radio into those 45 mm headset speakers Rick likes, for less than $10. I also found a waterproof case for the reciever for $5. Now all I need to do is get the new handlebars on, so I can mount everything! And maybe later, an amp and a pair of JL Audio speaker pods...