66 Audio BTS Pro vs Sennheiser HD 800S

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.

The highs are very clear and revealing, so you will be able to hear even the minute details from the audio that you simply will not be able to pick up with lesser headphones.

The mids are also clear and have nice warmth. They are slightly recessed, yet voices and mid range tones will come out full, so the sound is not lean in any way.

The bass is not boomy but still has enough power for a satisfying thump. Also, due to the bass' tightness and speed, there is no bloat from the lower frequencies.

These headphones sound very immersive. Aside from the highly detailed sound and powerful yet tight bass, the soundstage is very wide, which only a few headphones can match , if any at all.

Despite the massive size of the headphones, Sennheiser was able to keep the weight down by using a special material called Leona, which is very light yet has metal-like toughness.

The HD 800S has one of the widest sound stages of any headphone today. There is excellent separation and you can easily identify where various sounds are coming from and can be very immersive.

These headphones do not make unnecessary creaks or flex when moved or held. Aside from the use of Leona on the ear cups and headband, the size adjuster is made of lightweight metal, with fine yet durable stainless steel mesh covering the drivers.

Out of the box, you get a balanced XLR cable and an unbalanced TRS cable. If you have a balanced headphone amp, then the XLR cable will allow you to maximize your amp's performance with these headphones without the need to buy a different (and expensive) cable.

The ear pads feature high quality memory foam as cushions with the surface being premium quality velours. This material combo is also used on the headband. They feel really soft and conform to the contours of your head. Due to the fabric material, some air can move through the pads, minimizing heat and sweatiness.