I will get straight to the point. What hifi rated the Sennheiser Momentum M2 in-ear headphones as the product of the year 2016. I own those and these sound marginally better than those with a very similar sound signature.

The main characteristics of this headphone is lush detailed sound, great dynamics and tight, full bodied bass. These are not bass heavy, but these are not bass shy either. Its a bit hard to explain but I will try. My stereo setup consists of a pair of KEF LS50 speakers. I was extremely happy with it, till one day I added a HSU Subwoofer from the home theater system to the mix. The KEF's sounded the same but suddenly I was aware of what I was missing. Think of these headphones as a similar set up where a superb stereo speaker has an amazing subwoofer added to it. The bass never over powers the mids and highs like other bass heavy headphones do. It just adds the extension that you wont notice until you hear it.

There is no noise cancelling feature here, I am fine with that. The passive noise cancelling did not bother me at all during a 4 hour flight.
What this headphone does is deliver musicality and details in spades. Compared to my Shure SE846 (4X the price) these lack maybe a very thin veil of transparency and detail. But you will be hard pressed to find the differences in an A/B test. All that over bluetooth !!!

Not sure why a previous customer complained about bluetooth range, these have a better range than Urbanite XL's that I also own. I was able to keep a steady connection to my Laptop inside the house while planting perennials outside today. That's at least a 50 feet range. When the connection does go out of range, the sq doesn't deteriorate, it simply drops out. I like it, this means I am not constantly trying to be as close to the source as possible to eke out the best possible sound from these.

Charging is via a micro usb cable. I would have preferred USB-C but that's just me. One nice touch, if you are listening to music via PC and run out of juice, you can plug these in to the PC and it becomes a USB powered headphone while it charges. Sure the USB cable is inconvenient, but it keeps you listening to the music without interruption. There is no difference sonically between a wireless or a wired connection. This isnt a new feature, other bluetooth headphones by sennheiser have this feature as well, but I find it a nice feature to have.

There are a couple of things I do not like about these headphones:
1) The cables come out from the bottom of the neck piece. This adds a bit of length to the headphone cables and it simply makes no sense ergonomically
2) The headphone cables are flat, but I would have much preferred them to be braided as well. Nylon braiding will add some tensile strength to the cables and will give them a longer life, also I find the rubber very slightly sticky on my neck. Nylon or hybrid braiding usually feels a little better.
Then again, if you keep a beard, nylon braiding will be scratchy.
3) Out of the box, you get 4 sizes of silicone tips (Xsmall, small, medium, large). My $ 9 Apie earbuds came with 6 sizes. I needed something between small and medium for the right fit. The comply foam tips for momentum fit on these just fine, so thats what I am using. Come on sennheiser, at this price, I expect a few more tips and a few foam ones as well.
4) These headphones are bright out of the box and need at least 20 hours of break in to approach their actual sound quality. I wont ding these for that. But seemed like a longer than usual time to break them in.
5) No aptX™ HD.

There are a few things I do like about these headphones
1) Incredible sound quality. I have quite a few bluetooth headphones including Sennheiser made ones as well as the Sony MDR-1000X and the B&W P7 Wireless. These headphones sound better to me than any of those.
2) Improved bluetooth range. If you arent getting a good range or poor sound, check your bluetooth set up, these headphones have a better range than the ones mentioned above.
3) Classy, understated design with a premium finish that oozes luxury.
4) The switch to lower the volume is towards the outside. Easy to reach if you need to reduce the volume in a hurry.
5) 15+ hours battery life.
6) Unobtrusive neckband that easily hides inside the shirt collar.
7) Built in USB DAC.
8) Qualcomm® apt-X™ bluetooth setup. No discernible lag while watching a movie.
9) Sensitive microphone. Everyone hears me clearly and I dont have to shout during my conversation. These will also catch a lot of the external noises, but not any more than your phones built in mic.
10)Included case is quite nice and can hold an extra pair of IEM's.

All in all, until Sennheiser releases a truly over ear headphone that can cover my entire ear and supports aptX™ HD, these will remain my go to headphones for listening on the go and at work. (My serious listening headphone is lately a Sennheiser HD 700), sure this headphone isnt for everyone. It doesnt have noise cancelling, isnt flashy and doesnt have a rapper or a dj attached to its development, (though I hear Sennheiser is trying that as well). If music is what you seek and are willing to take on the relative comprise of going bluetooth over wired, these headphones are heartily recommended for you.

This one is tough for me because I love Sennheiser as a company and they produce awesome products. I purchased these understanding some of the flaws, thinking that they wouldn't really be a big deal and that I could overlook them, but after using them for a bit, there are just some gripes I can't see past. Before going further, let me say that this will be a review based on the use of these as an everyday wireless headset for your phone, which is what I believe most people shopping in this segment are looking for.

If listening to music and sheer audio quality was the only thing that mattered, I would probably give these 5-stars since I think they do about as well as can be expected from any Bluetooth earbuds—the limiting factor being the quality of the Bluetooth audio signal rather than the earbuds themselves.

As a headset for general use, though, I have three primary gripes.

1. The Ear Buds REALLY Should Have Been Designed To Retract.
This is something that I obviously knew about prior to purchase, but it's not until I started to wear these everyday and use them on a regular basis that I began to really understand how annoying this oversight in design could be. I generally have these around my neck almost all day, but it's not as if I'm making phone calls or listening to music the entire day so when I'm not, the ear buds just dangle precariously and I'm aware that I have this pretty delicate, but fairly pricey thing just waiting to get caught on something and ripped off.

The alternative would really be to remove the band from my person and store it securely in the very nice protective case that Sennheiser provides, but I feel like that sort of goes against the idea of a headset since doing so would effectively cut me off from the hands-free call receiving benefits. So it seems to be either use it the way I would use my normal headphones for listening to music (although my normal headphones are far more robust) or have my earbuds get caught on everything from my seatbelt to the straps of my backpack.

So this is one of those things that I simply underestimated the annoyance of going into it, but Sennheiser should really do better next time.

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2. The Mic Needs Some Sort of Noise Cancellation
Part of the reason one would purchase a headset like this is for the combined ability to listen to audio and make phone calls. With the average wired headset, you often notice people moving the mic portion closer to their mouth during their phone calls. The reason for this is pretty obvious—it essentially reduces the signal-to-noise ratio by making your voice louder than the ambient noise. The location of the mic on the neckband, however, means that without some sort of technology to reduce the ambient noise—something that doesn't seem to be present—the person on the other end of your phone call is going to hear a whole lot of what's going on around you.

So while you will hear the other person well thanks to the great audio quality, this quirk of the microphone means that the other person may not hear you so well without you having to raise your voice louder than normal.

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3. Bluetooth Can Be Finnicky

This isn't so much a specific knock against this headset (although, I feel like it's performance in this regard is not as good as some other headsets I've tried), but Bluetooth can be a finnicky thing with connection being unexpectedly lost between the device and your phone. I was actually on a walk where the headset simply disconnected and refused to reconnect with the phone despite all of my attempts. I'm not sure what prevented the pairing (maybe it overheated?), but a few hours later, it suddenly started working again without a hiccup. This hasn't been a consistent problem for me so it's been difficult to really pin down the cause, but I would just put it out there that you might purchase these and suddenly find yourself in situations where they may not be pairing with your device for periods of time.

I suppose that's a risk with all wireless technology to a degree, but as I noted above, I have other Bluetooth headphones and headsets that I've used that haven't suffered from the quirks that I've experienced with this particular headset... That having been said, I guess take this last one with a grain of salt.

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So now that we're done with the gripes, I'll bring up some positives. I find the controls on the neckband to be logically laid out and easy to use. The battery life has been very good for me and I've never had a situation where I was even close to running out of battery. The audio quality is, of course, excellent. And the headset looks pretty good in my opinion.

I've replaced the stock ear bud tips with Comply Foam tips simply because I find them to be more comfortable, but that's personal preference rather than a knock on the stock ear bud tips.

I hope this has provided a little bit of insight to help you make an informed decision. Frankly, there doesn't seem to be any standout in this category that performs excellently in all aspects so at the moment, it's going to come down to where you are willing to take your compromises. For me, even despite that grievances that I've mentioned, audio quality is still paramount to me, so I will continue to use them and if I could go back and do it again, I would have still purchased them.

Love this IEM and I'm a guy who hates IEMs in general. The comfort is the best so far from this type of HPs, and the sound is very full and competitive to some of my full size cans. Great connectivity and very stable. Aptx is great if your source device support it. Battery lasts 2 days easily.Sounds great for phone calls too, on both ends. The dual usage [music and hands free phone calls] makes it a valuable product for me.
Wish the buds had magnets to stick to one another when not in the ear so they don't dangle.

sound is good. Design needs work. The earbuds have no way to secure them to the neck strap (such as a clip or magnetic attachment). So they just dangle there when not in your ears getting caught on everything from backpacks, jackets, lanyards, or anything else that may come near the front of your personage. For a pair of $200 buds, this is an unforgivable oversight.

Update:

It looks like the latency when playing video occurs in rare scenarios but it does occur.

I use sennheiser for nearly 6 years and always appreciated the quality of the sound when compared to other head phones(including Bose).

Having said that, the quality of the sound is top notch in this wireless headset as well, it is not bass heavy but still delivers a true sound with good quality bass. The Bluetooth pairing is seamless with iPhone(haven't tried with Android).

The problem I have is the gap in audio sync when playing videos. The audio picks up late when playing video which is not a huge problem for me cos i mostly listen to audio but still it is not acceptable when i paid 200$ for something where a basic function is missing.

I will have to probably return it.