The speakers associated with Bluetooth helmet systems are all inadequate in our humble opinion. Cardo, Sena, etc all lack enough volume to overcome highway level noise, and do not produce high quality audio for music. Plus, they can move around if not fully secured, and if you pop for a high quality set of speakers, they do not easily move between helmets. Lastly, if your Bluetooth system is not on, you still need ear protection. So earbuds should be the logical alternative right?
Go to any sizeable motorcycle rally, and you will find multiple vendors in this space offering everything from regular inexpensive earbuds to expensive custom molded solutions. If you have one of those ear canals that don't lend themselves to off the shelf earbuds, you get pointed toward the more speedy end of the spectrum. I have always been skeptical of the value proposition, but a friend went high end and suggested that I speak with the PlugUp folks. After being unhappy with all of the solutions attempted, I relented and sat in the booth for the molds to be made, paid the money, and then waited.
A few weeks later, my custom earbuds arrived. They come with their own compact carrying case along with a couple of clips to help manage the leads where they intersect with clothing. The right ear unit also has a red dot so that you can easily identify it, although custom figment means that left and right are not interchangeable. When first inserted, I was immediately struck by how much sound is blocked. You can hear an engine at higher revs, a horn, an ambulance, but most normal ambient sound is gone. Then, the quality of whatever is played is phenomenally better than regular earbuds much less helmet speakers. Music has the full spectrum and excellent stereophonic separation. Phone calls and speech are crystal clear.
When plugged into the Sena 20S, they provide the best of both worlds. Bluetooth for phone, music, audiobooks, and PlugUp for sound quality. A year later, the units continue to perform as new. They are comfortable on a ten hour riding day, and their low profile is a big factor in that equation. The ear protection is great even if you don't pump any audio through them. Lastly, PlugUps now accompany me on any flight, as the same qualities that make them great on the bike, make them great on a plane. Highly recommended.