Shure SE215 vs 66 Audio BTS Pro

Bass is emphasized so there is a good bit of thump while staying controlled. Mids are rich, highs avoid sibilance, though they're a bit rolled off.
Soundstage is okay--instruments are separated out enough for them to not sound like they're all coming from the same place, but it's not particularly wide.

The memory foam eartips mold to your ear to provide amazing sound isolation, though there's a bit of a learning curve to using them. You have to press them together before putting them in and then allow them to expand in your ear. Once expanded they will take the shape of your ear and that way provide excellent noise isolation.

The earphones also come with silicon tips which are easier to use than the foam ones and also last longer.

The SE215 earphones have a negative profile, optimized nozzle angle, over-ear fit and memory eartips that ensure the earphones stay in place comfortably regardless of situation. You can even lie on your side with them.

6 types of plugs (silicon/ foam: S/M/L).

SE215 earbuds use tough plastic earpiece shells, have a robust kevlar-reinforced cable, a sturdy Y-splitter that's difficult to bend and an L-shaped plug that adds additional strain relief. They won't break if you snag them, drop them or sit on them. They're also completely sweat proof so you can use them while working out without having to worry about damaging them. They're durable enough for professional stage use for which they were specifically designed for.

The SE215's 6.4-ft. cable is very thick, and further reinforced at the left/right split point. Reviews confirm the durability benefits of its heavy-duty design. If it ever does break, the cable is built to detach safely from the earpieces, allowing replacement.

The optimized angle of the earbuds, over-ear fit, and memory ear tips ensure that the earphones stay in place comfortably regardless of situation. These are also sweat-proof, so they're a great option for active use.

Shure provides a warranty against defects in materials or manufacturing for two years.

The BTS Pro is quite robust and can withstand some minor splashes of sweat or rain as these are sweat-proof. They are not completely water-proof though, so you should not get them soaking wet.

There is good detail in the highs and the mids can also be heard clearly with very little muddiness. The lower frequencies are boosted, resulting in a good level of depth and power to each bass thump.

The BTS Pro ear cups sit on the ears with hooks keeping them in place. The flexible connecting band provides good clamping force and can adjust to your head size with continued use. Combined with cushioning on the cups, these are comfortable to wear and will stay in place.

Bluetooth connectivity allows the BTS Pro to connect with smartphones and compatible music players wirelessly, so cables won't be an issue.

66 Audio's Motion Control iOS App gives users added functionality, including EQ control and presets selection, battery status indicator, and even headphone position tracking. These features can improve the listening experience and also minimize the chances of you losing these headphones.

With up to 40 hours of playback time at full charge, it's more than enough for most listening sessions. You won't have to charge these frequently.

A hard shell carrying case is included, which can protect the headphones from minor impact and also make transport much easier. The case also has good aesthetics.

They are easy to bring on the go as the ear cups can be folded into the headband. This further reduces the already slim and compact size, making them easy to chuck into a bag when on the go.

The right ear cup of the BTS Pro features buttons for controlling headphone features. You can play/pause tracks, increase/decrease volume as well as answer/end calls by pressing the corresponding buttons, negating the need to pull out your phone to do so.

You do not need to take the BTS Pro off in order to answer incoming calls. There is a built-in microphone which allows you to easily take or make calls in the middle of your run or workout.