Sennheiser HD 650 vs Jaybird X2

The sound signature is near neutral but with a little emphasis on the lower frequencies. The bass is slightly forward with good punch and tightness. Explosions will have good rumble, without overpowering the other frequencies.
The mids are warm and clear, adding extra body to the sound. Game dialogue will be easy to hear.
Highs have good clarity, but are not forward in any way, so harshness is minimized.

The H650 is popular for its near neutral sound, which makes it quite versatile. The headphones can give a great casual listening, gaming, and movie watching experience yet are accurate enough for pro audio mixing. They are also lightweight and comfortable so you won't have any issues wearing them for hours.

Clamping force is not too tight. The ear pads and headband feature memory foam which are covered by velour material. The pads feel really soft on the head and allow airflow for minimized heat build-up/sweat.
The headband also features similar cushioning materials and minimizes pressure spots on the head.

The open ear cup design allows the sound to blend with your surroundings, giving it a natural width. It will also be easier to identify the direction of sounds, which can really help immersion.

The HD-650s do not feel heavy at all. They are usable for long music listening, movie or gaming sessions without feeling pain or strain on their head and neck.

While the cable connectors are proprietary, they can easily be removed from the ear cups with a firm pull. The popularity of these headphones means that there are a lot of aftermarket cables that can be bought.

The X2 comes with wing tips that you can attach to the earpieces. The tips enhance the grip of the headphones in the ear, and will help keep them secure even while you are running.

The highs are crisp, airy and forward so detail presentation is very good. Bass is fast and controlled instead of boomy, so it does not muddy up the overall sound.

This sound signature works well with a wide range of genres and rock, pop, hip-hop and EDM will definitely sound great with these headphones.

Integrated into the remote is a microphone, so you do not need to pull out your phone should a call come in. Mic quality is pretty decent, and your voice should be easy to understand on the other line.

Signal quality is pretty stable with minimal distortion or drops, even if you are on the move.

The in-line remote will allow you to control music playback, adjust volume as well as answer/end calls.

You get standard silicone ear tips in different sizes, along with a carrying case, different sized wing tips, premium Comply foam ear tips in different sizes, cable management clips as well as the micro-USB charging cable.

Exposure to drops or small splashes of rain or sweat won't easily damage these.