I'd disconnect the tweeters, and listen to the system just to separate / troubleshoot the system.
This is going to sound crazy, but if you pull your fairing off, the rear of your speakers should be exposed. you can GENTLY push on the cones and feel if they "scrape" at all, that is a rough way to feel if the coils have burnt / de-laminated.

If you want to try an ohm meter, you can, but it depends on what speakers you're running. Aftermarket are -usually- 4 or 8 ohm. I think the stock HD are 2 ohm. I think they have a plug to disconnect.

Maybe someone else can chime in too.
My setup is with the Hawg Wired 5.25" to 6.5" speaker adapters. The speakers blew [DX..?] so I tried Infinity Kappas as they were well regarded on this forum. They work pretty great. Funny thin, the ones I have has a little on/off push button to adjust the high frequency cutoffs. I could look for the manual, but it kept me from installing the speaker grills so I could use this feature. Just be careful when washing...

I had good luck with Hawg Wired's amplifier, but some say it's not that great. It's what I had, so it's all I know. I've heard good reports about Biketronics, but then others have said stay away...

I also have an Aquatic AV. It had to go back for warrantee-d work, but they fixed it. I have to install it once I get some time in the garage.

Good Luck

H

 

This won't work, speakers are measured by impedance not resistance which is what an ohmmeter measures. A 2, 4 or 8 ohm speaker is an impedance measurement made at 1 kHz, it is usually a totally higher or lower number anywhere else in the audio spectrum.