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The Shure SE420s' ear buds are one part sparkling gray and one part slightly-darker sparkling gray. The ear buds themselves have nozles that protrude at an angle. The tips of these nozzles are open to the air, but there is a guard at the very bottom. The headphones are meant to be worn with the cord around the back of the ear, as indicated by the 'L' and 'R' markings on the back of each ear bud.

***As you can see, wearing these right-side-up means

you'll have to wrap the cord around your ear. ***



The cord is dark gray, and truncates at a heavy-duty junction where the two channels meet. This split has a 1/8-inch plug, which you can connect to a media player or the included extension cord for additional length.

***This is quite the robust cord guard.

Click for a bigger image.***

**In the Box**

In the box is a treasure trove of sleeves (4 sets of foams in three sizes, 3 sets of soft plastic in three sizes, and a set of triple-flanged). You'll also find the headphones, their extension cord, an optional in-line volume switch, a 1/4-inch adapter, an airplane adapter, and a firm-covered carrying case.


In terms of durability, the Shure SE420s seem to be in good shape. The cord is thick, has robust junctions with the ear buds and plug, and seems to be well constructed overall. The one, somewhat minor issue we found was with the neck split slide-adjuster. As on the SE210s, the slider ripped quite easily. The cord guards tend to whiten with stress, which might not bode well for durability. Another issue is the open nozzles. The nozzles don't have a guard at their front, which exposes their interior to all kinds of gross stuff. While there's a cleaning tool included, it won't reach far into the nozzle. This means the bottom of the nozzle could accrue rogue ear wax and dust which, over time, will both decrease audio quality and just be really gross in general.

***This sliding adjuster will rip easily if you're not

careful. Click for a bigger image.***

These issues aside, however, these headphones look and feel quite rugged. You don't feel like you need to treat the SE420s with kid gloves, which is definitely a good attribute. As long as you watch for the issues mentioned above, then your Shure SE420s should stay healthy.


In-ear headphones don't have a lot of space to work with. Even a really great design is likely to go unnoticed due to their innocuous size. This being said, the Shure SE420s look nice. These headphones have the typical Shure bent nozzle, which means you either have to loop the cord around your ears or the headphones will stick straight out of your ears (which isn't particularly flattering). The headphones themselves look fine enough, however. They're different from the iPod headphones out there, but they just aren't particularly attractive or unattractive. Like the Shure SE210s, these might not look overly fancy, but they look nice enough.

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About our testing:

Our testing rig consists of the very same hardware and software that manufacturers use for testing audio quality. The hardware is, literally, a hearing machine. HATS, our head and torso simulator, has a humanoid shape to it and precise microphones installed in its ears. For more information on our tests, read this article.

**Frequency Response**   *(4.02)*     

How the test works:

This test measures the emphasis the headphones place on any given frequency. Once we outfit HATS with the headphones,  we play back a frequency sweep that spans everything from 100Hz to 20kHz. Each frequency is played at the same decibel level. HATS listens to the playback and reports a detailed map of what it heard. SoundCheck then interprets that data and gives us a nifty graph of how the headphones emphasize each frequency.  The green line is the left channel, red is right, the dotted lines represent the limits of the area we score, the left side of the graph is decibel level, and the bottom of the graph runs across the frequencies we tested. For more info, click the orange 'i' button above.

What we found:

The Shure SE420s had a pretty good frequency response result. As you can see, these headphones put some emphasis on the bass frequencies but trail off towards the higher end. The lines dip a bit below the lower limit here, but overall the line progressed evenly. If there were any sharp peaks or long furloughs far outside the limits, then it would have been an issue. As it is, the Shure SE420 wasn't perfect, but still performed pretty well.

How the Shure SE420 compares:

The SE420s' managed to score ever so slightly above average here compared to the comparison headphones. As you can see, the SE420s managed to perform better than the SE210s, although the general shape of the curve was about the same. The MM 50 iPs scored a bit better, because they barely strayed outside the scoring limits at all (the bass was a bit loud, but we don't score on the extreme low or high end). The other set of headphones that did better than the SE420s was the 6isolators, which had a very even kiel to their frequency response. This is great for music purists who want a faithful representation of their music. Again, overall a good showing from the SE420s, but not particularly outstanding.

**Distortion**   *(3.82)*     

How the test works:

Our distortion test checks for any differences between the original sound wave and whatever's coming out of the headphones. We again run a frequency sweep through the headphones, HATS listens, and SoundCheck spits out a graph. The green and red lines again represent the left and right channels respectively, and the bottom represents the frequencies we tested. The left side of the graph, however, represents the distortion levels. The big number on this test is 3%: this is the distortion level at which you'll really notice something is off. Ideally the both channels would just sit along the zero line.

What we found:

While it wasn't terrible, the Shure SE420s did show a bit of distortion. Most of it was in very low amounts across the whole spectrum, but it did have a small bump around the 1kHz mark. Overall, it stayed below 1% the entire time, which means it'll be less noticeable than a brief spike in distortion.

How the Shure SE420 compares:

The only set of headphones the SE420 had less distortion than were the Audio-Technica ATH-ANC3s. If you check out the graph you can see why. The other headphones might be less obvious due to the small increments involved and the minute size of the thumbnails. You can click the links to check a larger graph and our full review, or you can trust us when we say that all the other graphs have lines that run closer to the origin. Most have slightly bumpier lines, but the bumps are brief and, most of the time, involve a lower distortion level than the SE420 at its max.

**Tracking**   *(10.10)*     

How the test works:

Our tracking test looks at the relative volume of the cups. If they're playing some sounds louder than others, that can be an issue; if one cup is playing some sounds louder than the other cup, that's a separate issue entirely. We again send our frequency sweep through the headphones, and SoundCheck measures each instance where one channel was being played a bit louder than the other. One thing to keep in mind: the extreme left and right of this graph aren't totally accurate and aren't calculated towards this section's score. We leave in those bits so you can get a good picture of what happens in these areas, but don't treat the actual decibel measurement as gospel.

What we found:

The SE420s had great overall tracking. Again, what we look for here are any sharp hikes or plummets. We don't score the far high or low end, which renders those spikes around and after 10kHz moot. The response is very, very flat across virtually the entire stretch, meaning the audio will be very balanced. In the results pictured at here, the right channel was about 2dB louder virtually the entire way. This imbalance is so small it's almost insignificant, and could likely just be remedied by adjusting the ear buds.

How the Shure SE420 compares:

The Shure SE420s had a very flat tracking score. It managed to do better than just about every other set of the comparison headphones. Some of the headphones pictured below have seemingly flatter graphs, but keep in mind that these graphs are normalized: there was probably some brief spike that got flattened out somewhere along the line. Really, though, anything above 8 is really well balanced, to the point where the typical users probably wouldn't notice. The Shure SE420s simply manage to be better than they need to be.

**Maximum Usable Volume**   *(10.00)*      

How the test works:

This test is essentially a series of distortion tests. In it, however, the volume is increased after each pass. As volume increases, so does distortion. We keep bumping the volume until we find the point at which any more juice will result in 3% distortion. Although you technically can use volumes that exceed this number, the music will sound a bit blown out and the audio quality will be noticeably diminished.

What we found:

The headphones were able to squeeze out 122.54dB before the distortion got bad. This garners the SE420s maximum points for this score. Any more than 120dB is dangerous to anyone without pre-existing hearing problems. It can also have adverse affects on your headphones. In the SE420s case, however, anyone who likes it loud will be very pleased.

**Isolation**   *(10.12)*     

How the test works:

Our isolation test is a bit different than our other tests. Instead of bothering with frequency sweeps, we simply bombard HATS (and the headphones it's wearing) with pink noise. Pink noise is what you get when you play each frequency at a decibel level that's proportional to its frequency. This means bass sounds will be played louder than high-frequency sounds and, in the end, will result is each frequency being played at equal power. It sounds a lot like airplane ambience. The graph below depicts how much of this noise at each frequency was blocked out.

What we found:

The Shure SE420s have an amazing capability to drown out external noise, partially due to their wide selection of sleeves (the bits that stick onto the ear bud to protect it from the nastiness that hides in your ears). We tested out the three types of sleeves and found that, contrary to our initial beliefs, the foam sleeves were able to block out more sound than our previous pick for best isolators, the triple-flange sleeves. This makes sense, because actual ear plugs nowadays are made of foam, not little plastic Christmas trees. To the triple-flanged sleeves' defense, however, they came in a very close second place.

In any case, these foam ear buds were able to block out an impressive amount of noise. Like most in-ears, the majority of this blockage happened towards the higher frequencies, but it did block out an impressive chunk towards the lower end too.

How the Shure SE420 compares:

The Shure SE420 is, at the time of this writing, the best set of headphones for isolation. The Etymotic Research 6isolators, one of our first reviews, has finally been dethroned, and active-cacellers out there lie prostrate before its attenuating might. The SE420s are excellent for blocking out sound.

**Leakage**   *(10.00)*     

How the test works:

We test leakage by playing pink noise through the headphones at a set decibel level. We have a microphone set up six inches from HATS that will record anything that manages to leak out.

What we found:

These headphones barely let out a whisper. You should have no fear of anyone ever hearing your playback. These headphones would be great for hipsters that don't want to continually say they're listening to Chiptunes or La Bouche ironically.


First of all, we have to give our standard caveat: the people in our office who tried out these headphones, in all liklihood, have heads and ears shaped far differently than yours. We highly recommend you try on these or any headphones for at least a few hours before you decide to keep them.

We're not huge fans of Shure's in-ear headphone design. If you wear them the correct way, the cord has to loop around your ears, which we don't find particularly comfortable. If you invery them 180 degrees so the cord hangs downward, they jut out and away from your ears. Not only does this look a bit silly, but it just felt a bit odd since the cord was falling away from the ear buds at an odd angle. Also, the sleeves aren't particularly comfortable. Other soft plastic sleeves are made out of a thinner material and therefore don't put as much pressure on our ear canals.

**Extended Use***(4.50)*

Once we wore the headphones for a bit, we didn't mind the weird fit quite as much. This increase in overall comfort was diminished somewhat by the thick sleeves causing slight discomfort over time. Overall, they're of average comfort, but if you don't like in-ears you won't like these headphones.

**Cable Connectivity***(6.12)*

The Shure SE420s have a short cord, which is just long enough to reach the media player in your athletic/trendy arm band. With the extension cord, the headphones stretch to almost 5 feet in length, which is above average for in-ear headphones. We like the extra inches, but the SE420s aren't stretching across the room any time soon.

***Without this cord your SE420s will just be a few feet long.

You'll use this cord more often than not.***

The Shure SE420s also come with two adapters: 1/4-inch and airplane. The 1/4-inch adapter is to make your headphones compatible with a wider range of stereos and amps.

***The 1/4-inch and airplane adapters are a standard

inclusion for most mid-to-high-range headphones.***


The Shure SE420s are very portable, despite the thickness of their cord. The reason for this, of course, is due to their ridiculously short length. Since they're just over two feet in length without their extension cord, they have the potential to be more portable than typical in-ear headphones. If you're not using an arm band, then they're slightly less portable compared to other in-ears (the cord is a thicker and longer than average). The headphones do come with a carrying case, but it's not particularly fancy. It doesn't have any pockets or anything inside, which is unfortunate; many in-ear headphones, like the Etymotic Research 6isolators or Audio-Technica ATH-ANC3, have several pouches in their carrying cases for corralling all their sleeves. With the Shures you'll have to be careful, lest you comically spill all 24 individual sleeves every time you open the case.


The Shure SE420s have a fair bit of customability inherent in the packed-in selection of sleeves. There are three types to choose from: foam, soft plastic, or triple flange. There are two pairs of small-sized foam sleeves, two mediums, and one large. There are small, medium, and large offerings for the soft plastic sleeves, one pair per size. Alas, there's only one pair of triple-flanged sleeves.

***Pictured above: foam sleeves, soft plastic sleeves,

triple-flanged sleeves, and the cleaning tool.***

There's also an included accessory, the volume dial attachment. This customization option (obviously) gives you an easier way to control your playback volume. This functionality isn't remarkable, but it's a great inclusion we typically don't see offered.

***The volume dial can be attached before or after the extension cord,

depending on your preference. It can also be used to add a few

inches to cord length.***


Like other in-ear headphones, there isn't a lot you can do in terms of taking the headphones apart to fix issues. The SE420s will let you take off the sleeves for better cleaning. They also come with a cleaning tool, which is basically a loop of metal in a plastic stick. This is a great inclusion, but the reason it's included is because the headphones' nozzles are totally open to the air. That means that the inside of the nozzle is in constant peril from all the gross stuff in your ears as well as external dust, grime, or tiny insects (in particular look out for ear wigs or the terrifying miniature ear-eating scorpion). Though we realize the open nozzles are why the tool was included, we think the open nozzles themselves create a bit of a maintenance issue where there might not have been one previously. The tool also doesn't reach particularly far down the nozzle because Shure obviously doesn't want you poking anything vital. This does mean, however, that stuff will get buried at the bottom of the nozzle, then laugh at you as your tiny cleaning tool fails to exhume it.

**Other Features***(5.00)*

Battery Dependence

The Shure SE420s dont' require any batteries. Since fancier headphones can sometimes need batteries, we think those than don't deserve some points. Batteries are a pain to maintain, especially when dead batteries mean you can't listen to your freshly-charged media player. Really, when you're listening to music, the only battery you should have to worry about is that of your media player.


The Shure SE420s are a touch expensive, but not absurdly so. For the most part the SE420s have a cost that's proportional to what they offer. If you're looking for a budget option, check out the Shure SE210s, which offer proportionally the same deal but cost less (and therefore offer less). If you're looking for a flat-out deal, check out the Sennheiser MM50 iPs or the Denon AH-C351s, both of which cost a lot less. The MM 50 iP headphones also offer a bit better audio quality and a totally different wear experience. The AH-C351s have a similar short-cord design, but use a lighter cable gauge. They also don't come with as many extras and offer poorer audio quality. If you're a commuter, however, we think the SE420s are a good enough value to merit consideration.


Shure SE210]( - The Shure SE210 costs less and offers less than the SE420s. Therefore, the main decision in this match-up comes down to your budget. If you're looking for the better pair of headphones, then pick  up the SE420s. If your main concern is price, then rest assured the SE210s will offer you the same quality-to-price ratio as the SE420s. Our recommendation is the SE420s, especially if you're a commuter or have to be in noisy environments; the SE420s have crazy good isolation.


Sennheiser MM 50 iP]( - This match-up is not in the SE420s favor. The MM 50 iP headphones have better audio quality and are a much better deal than the SE420s. The entire case for the SE420s hinges on isolation and leakage. As you're probably aware if you read this review so far, the SE420s have remarkable isolation and leakage control. If those factors are important to you, the SE420s win hands-down. In all other cases, however, we'd default to the MM 50 iPs




Audio-Technica ATH-ANC3]( - The ATH-ANC3 headphones are a confusing package. They have active cancellation, but when it's on they block out far less sound than non-noise-cancelling in-ears. They also performed a lot better on our audio tests when the feature is turned off. The ATH-ANC3s' strong point is their unique sound. Their frequency response graph shows a clear emphasis on bass, and they really emphasize 7kHz, which is around where the attack of a drum is. Therefore, if you like music with a heavy beat, at least give the ATH-ANC3s a listen. For our choice, however, we'd lean towards the SE420s in this match-up.

Denon AH-C351 - The Denon AH-C351s are the clear pick for anyone on a budget. For $50 they offer solid audio quality, a good wear experience, and, like the 420s, have a short cord and extension. The Shure SE420s did have better audio quality and much better isolation and leakage control, but they also cost considerably more. You therefore have to ask yourself what's more important: performance or keeping your money.

Etymotic Research 6isolator - The SE420s have trumped the 6isolators at their namesake capability: isolation. Without this, the best asset the 6isolators have is their portability, followed closely by their better overall audio quality. They're also a bit less expensive. If you want total isolation, get the SE420s. If you want a slightly better deal, or just don't want to spend as much money, the 6isolators have an edge.


The Shure SE420s are a solid pair of headphones. Their frequency response graph wasn't bad, their distortion was fairly low (to the point of not being noticeable unless you were looking for it), and they can isolate better than any other headphones we've reiewed. If you've been getting annoyed at how loud your commute is, or if your desk at work is right near the squeeky air conditioner, the SE420s can offer you the silence you seek. They are great isolators, both for you and those around you. What they aren't, however, is cheap or particularly special-sounding. If you're buying based on your wallet's contents then we'd point you at any of the other five comparison headphones, especially the MM 50 iPs or Denon AH-C351s. The former is a better overall set that can't isolate nearly as well, but retail for half the SE420s' price; the latter is good for what it costs, which isn't a lot. While the SE420s should be taken into consideration if you're looking for in-ears, they're a shoe-in for isolating its users from everything.

Audiophiles probably aren't looking for the best isolation since they plan on listening in an ideal environment. Therefore the most important quality is audio performance. While the tracking is impressive, distortion was a bit high and the frequency response wasn't particularly breath-taking.

Portable users are who these headphones were made for. They're in-ears which means they're hardly a burden to lug around. They also have excellent isolation and leakage control to keep the morning commute and your music separate.

Despite them not being the most comfortable set of in-ears (which could make a difference on a long flight), the SE420s block out so much sound that we can't not recommend them here.

In-ears are just not ideal for the home theater. The tiny, closed-off sound puts in-ears below on-ear or over-ear headphones in this category, unless the entry is absolutely remarkable. The Shure SE420s are not remarkable in this way.

Meet the tester

Mark Brezinski

Mark Brezinski

Senior Writer


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

See all of Mark Brezinski's reviews

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