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Below is the side view of the MX W1s. The big ear piece is the ear bud and the small rubber bit above it helps stabilize the headphones in your ear.

Random-shaped bits of plastic, or sophisticated listening device?

Since Sennheiser is nice, they've provided a helpful diagram of just what all these parts are (it can be found here, if you're curious):

Even with the help of the above diagram, it might not be immediately clear how in tarnation you wear the things. Allow us to elucidate: the big ear piece fits under your tragus like any other in-ear headphone. The small bit at the back leverages the unit against the inside of your concha. Since you're most likely dazzled by our Wikipedia-granted knowledge of ear parts, here's another helpful illustration from Sennheiser.

Next on our journey of the MX W1s is the control pendant.

Once you know how this thing works, it's hard to avoid comparing it to some parasitic alien.

What you do is strap the pendant itself onto your media player, using the rubber band around its midsection. This, of course, increases the girth of your media player, making the entire shebang a bit less portable. From there, just plug it in as normal. On the pendant's top and bottom you'll find a charging port and on/off/connect button respectively. On the pendant's face you can also see a blue LED that will blink at you intermittently when you attempted to connect it.

Once you know how this thing works, it's hard to avoid comparing it to some parasitic alien.

Once you know how this thing works, it's hard to avoid comparing it to some parasitic alien.

The last stop on our tour of the MX W1s is the charging cradle. You can drop the headphones in this, then connect this to the charging cable in order to charge both head phones and the transmitter pendant at the same time. Also, it will hold a charge so you can power up your headphones on the go. The button on its front serves to turn charging on and off.

Witness the charging cradle. When your headphones are charging, the white area around the button will glow orange.

Witness the charging cradle. When your headphones are charging, the white area around the button will glow orange.

Witness the charging cradle. When your headphones are charging, the white area around the button will glow orange.

That's about it for the MX W1s, which can be a bit confusing to the uninitiated, simply because they look nothing like actual headphones. As always, we close with a shot of HATS wearing the headphones, so you can picture what you, noble reader, would look like with them on.

In the MX W1's box is packed full of junk. The astute will find the MX W1s and their receiver, a charging cradle, a leather carrying case, a USB cable, and a plug with four different socket adapters.

The MX W1s don't have a lot to them. They're elongated blobs of plastic with two protrusions and a hatch on their back for the battery. The hatch is kind of tricky to get off and we actually broke a piece on one of our review models (luckily they were broken anyway). In addition to the sleeve over the ear piece, there's a rubbery bit at the back that helps it stay in your ear. If that piece pops off, which it does with greater ease than we would've liked, it becomes nearly impossible to wear these things.

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There's also the charging issue that we ran into. Sennheiser claims the first manufacturer's line had an error that caused the headphones to stop charging properly after a short period of time (we ran into the issue second day we had them). Providing you send them back to Sennheiser, they'll mail you a replacement. While we're glad this return policy is in effect, it doesn't erase the chance there's a pair of busted headphones in any given MX W1 box.

All this being said, the MX W1s also have a big durability advantage: no cord, really. Many cord durability issues stem from the cord being attached to your head. When your media player rolls around in your pocket, it tugs on your ear pieces and you tug back. This can cause wear and tear at the junction between cable and plug. Due to its design, the MX W1 circumvents this issue.

The MX W1s aren't the most attractive set of headphones we've seen. Really, you need to ask yourself if you're willing to look like you're wearing two Bluetooth headsets. Most people can't even pull off a single Bluetooth headset without looking the part of the fool. If you are one of those fortunates, however, we still have doubts you won't look like a sci-fi movie extra from the front view. Really, the only benefit to wearing two Bluetooth headsets is that, should you get a call, you can have a conversation normally without people on one side of you thinking you're insane. Unfortunately, the MX W1s don't have a microphone, so this ideal scenario will never occur. We'd honestly recommend trying these on and checking yourself out in the mirror first.

The MX W1s didn't have the worst frequency response. The bass end is emphasized well; it drops off at the lowest end, which should give a strong base without a lot of boominess. Towards the higher end, however, both lines drop significantly and dance around at our lower limit. They take a small dump up only to dive down past the lower limit, at which point they start getting a bit scribbly.

This loss of the high end is somewhat to be expected, given the odd way these headphones fit into your ears. When they're secure, they don't necessarily fit flush with your ear canal, which not only ruins isolation, but causes you to lose some high end as well.

Again, this isn't necessarily a bad frequency response, but the headphones do handle treble poorly.

The MX W1 actually suffers from less distortion than we would have thought. We expected a ton of distortion because the signal needs to be compressed in order to be wirelessly transferred. Since your music is crunched to a pulp then has to fly through the air before it reaches your ear, it's understandable that some distortion exists.

Regardless of the trials and tribulations that only wireless headphones know, the distortion is definitely high in the low end. Towards the 1kHz mark, however, the distortion falls back down to nominal levels.

The MX W1s don't have perfect tracking, but it's not abysmal either. The main issue with tracking will undoubtedly be positioning errors. If you don't have them just right, one ear piece will generally play slightly louder than the other, and these headphones are really hard to position correctly.

This being said, if you look at the graph and how it wanders from left to right and back again, the slopes are all relatively shallow (no vertical spikes) and the amounts involved aren't particularly noticeable. A four decibel decibel difference isn't going to shock you so profoundly you pop your monocle. We've seen headphones with far better tracking, but again, the MX W1s are wireless in-ears.

The MX W1s were capable of a very loud 117.1dB. We award max points for 120, but anything over that is aural overkill.

The MX W1s did not have the best isolation. The ear buds don't fit really flush with the ear, so there isn't a lot to block out sounds. They don't have active cancellation either.

Because of the barely-there isolation, the MX W1s might not be the best headphones for people on the go. If you're going to walk outside, ambient noise is going to overpower (or at least rudely intrude upon) your playback. We would not recommend these for the average commuter for this reason.

Interestingly enough, considering the poor seal, the MX W1s didn't leak much.

Just look at these things. If you expect them to feel like pillows that just barely kiss your ears, then you are being silly. The ear pieces wedge between flaps of ear skin. This being said, we didn't think the MX W1s were particularly uncomfortable. In fact, we'd go so far to say they're not much less uncomfortable than the average set of in-ears. They stay in really well too, due to their very light-weight design. If you wanted, you could take these to the gym to work out without a cord bouncing around or tucked into your shirt (which results in the cord getting tugged whenever you move your head). Of course, you'll have to deal with looking like you're wearing two Bluetooth headsets, which is typically a bad thing.

Random-shaped bits of plastic, or sophisticated listening device?

These are definitely headphones you'll want to try out before you buy. Two people in our office couldn't even wear these things properly: their ears were too small. Unless you can catch the second part on the inside of your concha, you aren't going to be getting a very good fit: the headphones won't be flush with your ear, and sound a bit tinny. They are actually a bit more comfortable if you don't wear them correctly, strangely enough.

The main issue with wearing the MX W1s for a time period of 6 hours or longer isn't necessarily one of comfort, but one of battery life: the battery won't last a full 6 hours according to our tests. In spite of this shortcoming, we wore the headphones for 6 hours straight anyway. While they certainly get slightly more uncomfortable over time, we were surprised at the relatively slow escalation of discomfort. You will probably have to reposition the headphones slightly as you wear them, to spread the pressure around, but overall, they aren't nearly as uncomfortable as their design would suggest.

The MX W1s might be wireless, but their transmitter gets wired to your headphones. Typically cable connectivity refers to the headphones' ability to hook up to any given jack and we award points for different adapters, etc. The MX W1 transmitter does have a thin plug, which will help you hook up to a recessed jack, but the bulk of the MX W1s' points in this section comes from all the included power adapters.

You could go pretty much anywhere in the world with the MX W1s.

There are plugs for those of you in America, the UK, Europe, and Australia. If you plan on traveling around with these headphones, Sennheiser has you covered. Of course, all that travel means a lot of plane rides, and wireless connectivity isn't allowed on planes.

You could go pretty much anywhere in the world with the MX W1s.

Typically in-ear headphones are very customizable, simple because it's so easy for them to be. All manufacturers have to do is toss in 20 different kinds of sleeves, where they need to be more creative with on-ears or over-ears. This doesn't really apply to the MX W1s, however, which only come with three sizes of sleeve for their bass nozzle. Three sizes of sleeve is standard for in-ears, but fancy (expensive) headphones like the MX W1s typically come with different styles of sleeve. While we understand the MX W1s aren't the typical in-ear design, it doesn't change the fact that they have less customization options than traditional in-ears.

In-ears are the most portable style of headphones. Since they take up such little space, you can simply toss them in your pocket when they're done. We don't think that wirelessness necessarily enhances portability – in fact, the larger ear bud size actually makes them less portable than the average in-ears. The MX W1s are more portable than on-ear headphones that don't have a head band. Although this is a somewhat nebulous category of portability, rest assured: they are easy to cart around.

This is the MX W1s' svelt carrying case. Just pop them in their charging cradle, toss the cradle in here, and you have a nice, snug parcel you can clip to your belt if you so choose.

Other than removing the sleeves, there's really not much you can do to maintain these things. This is typical for in-ears, which are typically just sealed-off plastic bubbles. If your MX W1s break or you want to mod them in any way, you'll have to prepare yourself for a very invasive, likely irreversible procedure.


The MX W1s do connect wirelessly. The transmitter has an 1/8-inch plug and comes with a rubber band that loops around both it and your media player. If you do it right, the transmitter will be latched onto your media player like a parasite.

The MX W1 doesn't have particularly good battery life, however. It lasted just under four hours on a full charge. It seems as though the ear pieces don't necessarily run out at the same time, either: sometimes one lingered for up to 10 minutes after the other had died. Granted, the MX W1s use magical wireless technology, but it doesn't do you any favors when it comes to longevity.


The MX W1s are 100% battery dependent due to their wireless connectivity. They aren't super space-age gizmos that also connect to a power source wirelessly. If they aren't charged, you won't be getting any playback. We had some issues with charging the batteries, namely that every once in a while one of the headpieces wouldn't recognize that it was hooked up to a charge.

These headphones cost $500, don't have pristine audio quality, and aren't made out of a precious metal. While we do think that wireless in-ears are a neat piece of technology, until the costs come down, they're just not feasible for the average consumer.

The MX W1s seem to be more of a tech demo than an actual consumer item. It's the first marriage of Sennheiser and Kleer's wireless technology, and honestly, we can't see someone dropping $500 on these things. Not only do they look silly at best, but they aren't particularly comfortable. Also, while their sound quality is honestly impressive for a set of wireless headphones, let alone in-ears, it can't compete with other headphones. If you're khordephobic and rich, these are the headphones for you.

Meet the tester

Mark Brezinski

Mark Brezinski

Senior Writer


Mark Brezinski is a senior writer with over ten years of experience reviewing consumer tech and home appliances.

See all of Mark Brezinski's reviews

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