https://www.quietridemuffs.com/
Wow. What a difference. Finally have the helmet speakers on the proper side of the hearing protection.
Pros
Quieter than any ear plugs I've tried
Don't have to do the helmet off-on any more because I forgot the earplugs
Can listen to music at about 1/2 volume, even at high speeds
No more having to blast the music through the earplugs, which never worked worth a damn for me
Good vendor, reportedly cooperative if you need advice or to return the kit
Cons
Not a trivial installation job
Not cheap, but great value in my opinion
May not be feasible for folks with big heads
Tough to figure out if they'll fit until you try
Might be warm for some, but was OK at 25C for me
It's definitely a different sensation riding with these things. I remember my first ride with earplugs, and the detached feeling that took a few rides to get used to. The Quiet Ride muffs add an additional level of detachment. After two rides I was used to it though. If you've ever worn an aviation headset in a light aircraft, you know what to expect. The sound is sort of a muffled din. If I duck down completely into the bubble behind my windshield, the din disappears.
Some helmets might make for an easier installation, and some folks can surely work faster, but it took me about a day's work on my modular. About 2 hours to decipher the helmet components, and carve out enough foam little by little to get the first muff into an acceptable position. It was tougher than I expected to figure out where my ears are.
If you like the concept but are squeamish about the helmet surgery, Quiet Ride sells helmets that incorporate the muffs.
I have a basic bluetooth intercom https://www.ebay.ca/itm/1x-1200M-BT-Intercom-Bluetooth-Interphone-Motorcycle-Helmet-Headset-FM-5-Riders-/261515289551?pt=Intercoms_Access_Controls&hash=item3ce386a3cf and had no trouble installing its speakers in the muffs. I assume that more expensive intercoms would sound better, but I'm very satisfied with the sound quality of mine now.
I wear a size small helmet and mine had sufficient space. It's about time I got some benefit from having a shell that's so much bigger than my head. The lower, removable piece of foam I was carving out actually has some additional space between it and the shell that I could have used, but I didn't have to carve that deep. I did the rough carving with a knife, and sort of machined the muff area flat with a triangular sanding rasp on an oscillating tool. To judge the depth, I drilled a few holes about a quarter inch deep, used a sharpie to color the bottom of the holes, and sanded until I hit the marked area. It's still a bit tight since I can almost get by without pumping up the bladders. In fact, some people might be able to do without the bladders if they can get an acceptable compromise between putting on the helmet easily and having a decent seal on the muffs.
I cut shallow grooves in the main helmet foam to accommodate the hoses and wiring, and taped those into place. Did some whittling on the cheek pads, and added some velcro on one leg to make up for the absence of the attachment clip I had to cut away. BTW, I did a test ride without those cheek pads and was surprised at how much more air and noise was present.
Very happy with the end result. The muffs work so well that music, phone, and nav directions are all very practical. And now any time I get bored I can chat with Google Assistant.