Nachiket MhatreJun 04, 2013 19:56:05 IST
I'm generally a fan of open-back headphones. The design prevents cabinet colouration and affords the drivers with a more open, natural sound signature. However, headphones aren't quite portable enough for outdoor usage, where you need smaller earphones for convenience. Unfortunately, due to the limitation of physics, it's impossible to achieve the same natural fidelity from smaller drivers. The fact is, as the transducer (speaker) gets smaller, it costs more to produce the same sound accuracy as its larger equivalent. Therefore, it costs much more to obtain the same level of sound quality from headphones as you'd get from a decent pair of bookshelf speakers. Due to the smaller planar surface of IEMs (In-Ear Monitors), it's still more challenging and expensive for them to match the performance of headphones with larger drivers.
Tragically, since urban India has spread out like a cancer without much in the name of city planning, we have been cursed to spend anywhere between one to three hours of our waking lives commuting to and from work. Despite all of its disadvantages then, it makes perfect sense to invest in a good pair of IEMs that will block out the city's chaos and transport you to your own personal space right in the middle of a crowded locomotive. Mind you, this guide won't merely throw random brands and models. The main objective here is not just to learn which IEMs to purchase, but rather how to go about finding the right one for your needs.
Choosing the correct driver type
There aren't many choices available in IEMs when it comes to the drivers, with dynamic and balanced armature (BA) drivers being the two dominant types. Dynamic drivers are most common because they are the cheapest to manufacture. These drivers are pretty much miniaturised versions of your regular loudspeakers employing a magnet and moving voice coil to oscillate a diaphragm, in order to reproduce sound. Balanced armature drivers employ a similar setup, but the voice coil is stationary. The diaphragm is moved by an armature that's suspended frictionless between two opposing magnets and the voice coil.
A dynamic driver gives excellent bass response, but at the cost of high-frequency detail
Technical mumbo-jumbo aside, this configuration allows the BA driver to have phenomenal electrical efficiency, which allows it to produce a more detailed sound. However, since it doesn't push a large volume of air like dynamic drivers, a BA driver lacks the ability to produce natural bass. To put it in a nutshell, dynamic drivers are cheap and produce great bass, whereas BA drivers are expensive but deliver great high-frequency detail at the cost of a stunted low-end performance.
Having said that, you have examples where multiple BA drivers are combined to produce a greater impact, or even instances where passive crossovers are employed to split high, mid and low frequency ranges across multiple BA drivers. Some expensive IEMs even use a combination of BA and dynamic drivers to deliver the best of both worlds—detailed highs and deep lows.
Getting the specifications right
That technical mumbo-jumbo at the back of the product packaging actually does account for something. If you can read it right, it should allow you to match the IEMs well with your PMP and decide if you should invest in a headphone amplifier. As a thumb rule, most IEMs have nominal impedance between 16-32 ohms, which makes them easy to drive without the need for separate amplification.
Balanced armature drivers have a terrific high-end response and detail, but at the cost of bass
If that sounded Greek and Latin to you, here's an easy example to understand what impedance really is. Imagine sipping a glass of milkshake through a straw, where your lungs are the amplifier, the glass of milkshake the IEM and the straw representing the concept of impedance. The impedance is higher when the straw diameter is small, whereas it gets lower as the diameter increases. It's easier to sip milkshake through a thinner straw, but the volume of milkshake coming through is miniscule. However, you may be able to suck in copious amounts of milkshake through a two-inch PVC pipe, but that will also put a tremendous strain on your lungs.
IEM impedance works in the same way. A high-impedance driver won't put much strain on your PMP, but the maximum volume will be limited. Conversely, a low-impedance IEM will sound louder, but it will put a lot of stress on your PMP's amplifier. Certain balanced armature drivers can be tough on amplifiers due to their very low impedance, whereas some dynamic drivers may sport too high an impedance to provide sufficient volume without amplification. As a rule of thumb, these outliers are better auditioned with and without headphone amplification to see if there's a noticeable improvement in sound quality.
Other important things to consider include sensitivity, frequency response and the type of magnets employed. A high-sensitivity driver will provide greater sound pressure levels per watt, which makes it easier to amplify. Frequency response, although it tells you about the sonic reach of an IEM, it never really gives you an idea of the quantity and quality of impact and authority at those frequencies. Take this spec with a pinch of salt and audition the IEM yourself to be sure. As a rule of thumb, powerful neodymium magnets will provide better bass than regular ferrite ones, so it's an added incentive if an IEM is outfitted with the former.
Just changing ear tips can have a profound effect on sound signature
Ear tips, isolation and sound signature
These tiny cushioning interfaces between your auditory canal and the IEMs may seem to exist for the sole purpose of ensuring better ergonomics, but there's a lot more to the ear tips than it is otherwise apparent. You would be surprised to know what significant a part these tips play in the overall audio signature of the IEMs. In-ear earphones generate a miniscule power output because they have to move a very small column of air in the canal to produce sound. They, however, are at their best efficiency when the seal between the tips and ear canal is perfect. Any amount of leakage leads to a loss in the sound pressure levels, which directly affects the bass performance. It is therefore important to choose a tip that's sized just right for you. Meanwhile, you may want to refer to this handy guide on how to wear IEM effectively.
Ear tips come in three different materials: rubber, silicone and foam. Silicone tips are superior to rubber ones in every single aspect including durability, hygiene and comfort. As such, only the cheapest IEMs will include rubber tips, because any decent brand worth its salt makes it a point to outfit its earphones with silicone tips. These tips themselves are available in varying thicknesses—a factor that can affect sound isolation as well as signature. Thick walled ear tips generally afford better sound isolation, but at the cost of making the sound darker or more bass heavy. Conversely, thinner ear tips may not provide the best isolation, but they are best paired with dark IEMs. Silicone ear tips also ship in double and triple flanged versions, which boost bass and mechanical sound damping by an even larger extent. These multi-flanged ear tips, however, may prove a bit intrusive and uncomfortable to some users.
Using the right sized tip ensures a proper seal, which in turn improves bass response
Finally, you have foam ear tips, which are quite expensive and significantly less durable than their silicone equivalent. However, they are still preferred by audiophiles thanks to an unparalleled level of noise isolation offered. Because foam ear tips practically conform to the natural shape of your auditory canal, they are by far the most comfortable of any ear tips as well. The only problem is that these ear tips tend to attenuate higher frequencies and boost bass by a large degree. They are, therefore, paired the best with brighter sounding earphones, because they can make darker IEMs sound even boomier than they already are.
Instead of just listing out the hottest IEMs in the market, what you have here are all the important parameters that need to be considered before purchasing a pair that's right for you. This not only allows you to choose an IEM with the right type and configuration of drivers, but also check out the box and figure out if you would require a separate headphone amplifier or not. Once you have purchased the IEM of your choice, though, don't forget to experiment with different ear tips to fine tune the sound signature to your liking.
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