Audio-Technica ATH-M40x vs 66 Audio BTS Pro

Sound signature is quite accurate, almost flat. Bass is much more controlled instead of boomy, while there is a slight elevation on the highs, resulting in extra energy and detail up top. These offer a nice middle ground between a fun sound and a more reference/analytical sound signature. This sound quality makes the headphones quite versatile as music enjoyment headphones or studio-use cans.

The M40xs feel solid and are known to be quite durable. The plastics used in the build do not easily flex or make creaks, giving the impression that these can last quite a long time.

The over-ear, closed back design along with the thick pleather ear pads can block out quite a lot of ambient noise, and will help users to focus in on the music. These make the headphones great for travel or for mixing/monitoring use.

The headphones come with a straight cable and a coiled cable, making them useful in the studio or while walking.

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.