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Choosing Headphones: A Guide for the Budding Audiophile

Posted by Eric March on February 6, 2008

It’s all in your headLook, if you love music and listen to your iPod virtually everywhere you go, you probably want to get the best quality sound you can while you’re on the go — within your budget, anyway, right? So which ones should you buy? Cans, buds or IEMs? Active noise cancellation or passive noise isolation? Shure or Etymotic? Sennheiser or Grado? Well, that’s what we’re here to discuss. I’m not going to tell you what to buy, but I will arm you with the information you need to make an informed decision about which ones are best for you. None if this is absolutely guaranteed to snag you a top notch pair of cans, but it gets you a lot closer than you would be going in blind. First though, we need to talk about the technology and what it means to your listening experience.

The Terminology
Before we talk about hardware, we need to understand what all of the terms mean so that we can understand what it is we’re looking at when we look at the specs on a set of headphones.

Dynamic Range
This one’s easy. Dynamic range is the range of audio signal that the phones are capable of reproducing. They are typically represented by two numbers, expressed in hertz (Hz) or kilohertz (kHz). A set that lists its dynamic range as 20Hz-20,000Hz means that it is capable of producing low sounds down to 20KHz, and highs up to 20,000Hz, or 20kHz. This is pretty typical for most name-brand phones. Generally speaking, the lower the first number and the higher the second number, the better; we’re looking for the widest dynamic range, and I personally consider 20Hz-20kHz to be my minimum standard. If a pair can exceed that, so much the better.

Signal-to-Noise Ratio (SNR or S/N)
The signal-to-noise ratio, or SNR, is a bit complicated to explain without getting into a bunch of electrical and audio engineering junk, but what it boils down to is how much of the audio signal is getting through to your ears compared to the base level of electrical interference generated by the audio hardware itself (called the “noise floor”). The higher the decibel level listed here, the better — in general, because there are ways to obscure this number to make it look good when it isn’t very. (Just avoid cheap headphones and you’ll run into this problem a lot less.) What it means for you is more sound and less interference (hiss/static) coming from the device.

Impedance
A lot of people ignore this number, and yet I can’t stress how important this number really is. It seems innocent enough, but its impact can be profound. Impedance is the amount of electrical resistance, expressed in Ohms (The Ω symbol) that the headphones possess — or, thought of another way, the amount of power (“load”) that’s needed to drive the headphones. In general, the higher the impedance, the larger the magnets (see below), and the better the sound. This figure can be deceptive though because the impedance depends on the hardware you’re looking at: Full-size headphones generally require more power to drive overall than earbuds or in-ear monitors, so what you’re looking for will depend on that. For full-size cans, you will generally want to look for an impedance of 32Ω or greater. For earbuds and in-ear monitors, 16-20Ω or greater is recommended. Bear in mind however that the more power they require to drive, the more you will need to boost the volume on your iPod to achieve a comfortable listening level.

Magnets
Let’s talk a little about how speakers, and therefore headphones, work. In the main, a speaker consists of a paper or polymer cone or diaphragm (the round, conical part you see when you take off the speaker grille), an electromagnet attached to the back of that cone, and a permanent ring magnet that surrounds the electromagnet. Positive and negative wires are attached to the electromagnet, and when audio signals are sent through these wires, they energize the electromagnet with alternating positive and negative current, which in turn causes the electromagnet to be alternately attracted to and repelled by the permanent magnet. This makes the speaker cone move, which moves the air in front of it and creates sound. I’m sure you’ve looked at a woofer while music was playing to see it vibrating — maybe even held a lit match or lighter in front of it to watch the sound waves from the woofer blow it out. (I know I have.)

Until a few years ago these were all pretty standard magnets. Their size determined their power. However, recent years have seen a greatly increased use of neodymium, or rare-earth magnets. Neodymium magnets are much stronger than conventional permanent magnets — in fact, they are the strongest magnets known to man. (Some of you may have seen instructional pages or YouTube videos on home-made miniature rail guns; they use the same magnets) As a result, speakers have reduced in size and weight because much smaller magnets are needed to achieve the same results of their larger, less powerful brethren.

The ability to greatly reduce the size of magnets while maintaining or even increasing their power has made it possible to build much more high-end headphones and earbuds with even greater dynamic ranges and sound reproduction capabilities.

This is all by way of explaining that the magnet is the thing that’s responsible for reproducing the sound in your headphones, and as such it’s a pretty big deal. The more powerful the magnet, the more power it will require to drive (remember impedance?), the greater the effect it has on the cone, and the richer and more well-rounded the sound your speakers or headphones will be able to reproduce. Ideally, you want to look for headphones that sport neodymium magnets in their drivers, as these will typically produce the best sound.

Driver Size
This one’s pretty simple. The size of the driver (cone) determines how well it can reproduce sound. Larger drivers mean more expressive sound.

The Hardware
Now that we know what it all means, we need to figure out what we can buy to stuff all of that mumbo jumbo into our ears.

Types of Headphones
When it comes to headphones, you have four practical choices: Over-ear (circumaural) headphones, on-ear (supra-aural) headphones, earbuds, or in-ear monitors (IEMs, also sometimes referred to as canalphones). The difference here is in how the units deliver the sound to your ear drums. In order to fully appreciate why this matters, we have to understand how it happens.

Sound is energy. It travels in waves by vibrating molecules of air, dust, water — whatever is handy and in the way. This why sound travels so well through water (lots of water molecules to excite) and not so much through space (not much of anything to vibrate there.) Sound waves expand as they travel — like ripples in a pond — and as a result they get thinner the further they go, resulting in quieter, more attenuated sound the further you are from its source. Therefore, the closer your ears are to the sound, the clearer the sound is and the the quieter it needs to be to be picked up by your ears.

The whole point of headphones is to deliver the sound right to your ears. Headphones can get away with using much less power to deliver loud volume because they only need to move the air between the headphone speakers and your ear drums. That’s a pretty small amount of air when you compare it to conventional speakers, which move air throughout the entire room, which requires a lot more power to do. Herein lies the fundamental and most important differences in the way the four basic types of headphones work, so let’s look at each one:

Full-size headphones (circumaural and supra-aural)
Full-size headphones either fit over your ears or on them. They typically have speaker cones measured in inches because there’s still a fair bit of air between the cones and your ear drums that they need to move. This is why they require more power than buds or IEMs; larger cones, larger magnets to move the amount of air they need to in order to produce good sound. The benefit of full-size phones is that, on the whole, they are typically capable of producing the best and fullest sound available because their large cones allow them to express the greatest range of sound. The down side is their size; good ones tend to be bulky and not really suitable for use on the go. They also tend to leak a lot of sound to the outside world because compared to buds or IEMs, they’re pretty loud. The primary difference between circumaural and supra-aural headphones is that circumaural headphones fit over the ear and typically have much better noise isolation at the expense of bulk and weight, while supra-aural headphones sit on the ear and are much lighter and less bulky at the expense of noise isolation.

Open-Air vs. Sealed
One consideration when looking at full-size cans is whether to buy open-air or enclosed (sealed) models. The hardcore audiophiles feel that open-air headphones, which can pull air from behind the phones to pump into your ears, produce a nicer, richer sound than enclosed, which simply work with whatever air is available around your ears. Open-air phones also leak a lot more sound, so if that is a concern then you probably want to avoid these.

Earbuds
Earbuds fit just inside the canal openings in your ears. They have the benefit of being very small and lightweight, but the drawback is that not everyone can wear buds. I am one of these people; they just don’t fit. They generally require less power because they sit closer to your ear drums than conventional headphones, but they are not the most efficient method of delivering sound as only some of the audio is delivered to your drums; the rest is blocked by the tragus — that flap of skin and cartilage closest to your face that you sometimes push into your ear canals to block out sound just prior to yelling, “NANANA I’M NOT LISTENING!” Earbuds also suffer from poor noise isolation since they typically have no way of creating an effective barrier between your ear canals and the outside world.

In-ear monitors/canalphones
A more recent development in audio technology is the in-ear monitor. These are a lot like earbuds, but are typically angled and designed to fit directly into the ear canal via silicone or foam tips. In so doing, they form a seal. This has several benefits. First and foremost is exceptional noise isolation, usually between 25-35dB or better. When wearing IEMs, outside noise is often reduced to such an extent that you will find it difficult even to hear someone speaking directly to you. Because of this, volume levels can be moderated to a much greater degree, since you do not have to overpower outside noise by boosting the volume. Second, because the audio source is much closer to your ear drums, IEMs only need that tiny pocket of air between the tips and your drums to deliver their sound, which means you tend to get much cleaner sound with less distortion at lower volume levels than with typical buds or headphones. Third, because less power is needed, IEMs are often smaller than typical earbuds while still managing to deliver superior audio quality. Most IEMs will also come with an assortment of types and sizes of tips. Higher end Shure IEMs for example typically come with three sizes of two different types of silicone tips (hard and soft), plus a set of triple-flange tips (silicone tips with three sets of progressively larger radial fins to anchor them in place) and a set of foam tips.

The main drawback to IEMs — as it is to a lesser degree with earbuds — is that your ears do something slightly unpleasant: They produce cerumen. (That’s ear wax to the rest of you.) Because of this, IEMs need to have their tips cleaned on a fairly regular basis. If you keep your ears relatively clean with Q-Tips then this is less of a concern, but you will still need to clean those tips periodically. For foam tips — well, just try and keep your ears as clean as possible and replace them when they get too grungy. I buy them in bags of 10-15 pairs at a time for my Shure E3s, and they typically last me a few months with conscientious aural maintenance.

The other drawback to IEMs — which is not so much a drawback as it is a lack of education — is that a lot of people try them for the first time and think they sound like crap. This is most commonly because they have not inserted them properly. Yes, you actually need to learn how to insert them for them to sound good. IEMs rely on the ability to create a seal in the ear canals to block in the air pocket they need to produce good sound. If you haven’t created a proper seal, then they’re going to sound tinny and attenuated. The best thing to do with these is to try them first with the foam tips; you just compress both tips, shove them as far into your ears as they will go, and then give them a few seconds to expand. They will mold to your ear canals and provide a very good seal — not quite as good as silicone, but almost — and that will allow you to hear what they’re supposed to sound like when you create a proper seal in your ears.

Other Considerations

Active Noise Cancellation (ANC) vs. Noise Isolation
Active Noise Cancellation, or ANC, is an interesting technology. Headphones equipped with ANC typically have two small microphones fitted into the outer housing on either side. These microphones “listen” to the outside noise, pass the sample data on to a noise processor, which then creates an inverse, or polar opposite version of that same noise, and feeds it into the audio stream. I know — what the hell is an “opposite noise?” It’s a bit hard to conceptualize, but yes, every noise has its opposite. Just like colours do — if you had any art classes in school then you know all about complimentary colours, and how green is the opposite (or compliment) of red and such. Sound is the same way, but instead of light waves, we’re dealing with sound waves. Sound waves, when represented visually, are just a bunch lines that make up peaks and troughs on a line. When played back, you get a particular sound. If you want to make another sound that will cancel that sound out, all you have to do is take those bunch of lines and flip them. When played back simultaneously, all of the ascending lines will be cancelled out by the second sound, which will instead play the polar opposite in a descending line, and vice-versa, which has the net effect of attenuating the sound to such a degree that you will have trouble hearing it.

This is what ANC attempts to do with headphones. It takes the outside noise, then creates the polar opposite sound wave of that noise and feeds it into the sound coming out of the headphones, which is supposed to have the net effect of interfering with the outside noise leaking into the headphones enough that it cancels it out to one degree or another. Because of the electronics required, this is typically only available on full-size headphones.

It looks pretty neat on paper, but does it work? To a certain degree, yes — but it is far from perfect. First of all, what the microphones hear on the outside of the headphones, which is unobstructed by anything, is a little different than what you hear on the inside, which is somewhat muffled by the headphone’s padding or cups. This can produce a discrepancy between the outside noise you would have normally heard without ANC, and the outside noise that the ANC is attempting to cancel out. Furthermore, if the noise that the ANC is trying to cancel out happens to correspond to frequencies in the music you are listening to, then it can cancel out parts of the music as well, which can produce undesirable distortions and artifacts, thus degrading your overall listening experience.

And finally, ANC typically either requires its own power source (batteries) or draws extra power from your device, shortening its play duration. Usually this isn’t a big deal, but it’s there just the same.

Noise isolation on the other hand is purely mechanical in nature. This is all about simply sealing your ears off from the outside world by whatever means possible. Whether it’s heavily padded cups on circumaural headphones or the sealing action of in-ear monitors, noise isolation is generally superior to (and cheaper than) its active electronic counterpart for the fact that it does not distort or alter the audio stream in any way, and with the proper materials and methods, as with in-ear monitors, you can achieve a pretty dramatic reduction in overall noise — often greater than that of ANC-bearing cans.

Noise Isolation and Hearing the Outside World
There are times when you do need to hear what’s going on outside — such as when someone is speaking to you. With IEMs, you generally don’t want to have to remove them because of the slight pain in the butt of re-inserting them and recreating that proper seal. There’s something you can do about that though. Shure makes a Push-to-Hear, or PTH module, which is included with its high-end 5-series (E5-PTH, SE530-PTH, etc.), but is also available as a separate purchase. It contains a microphone, and when you push the PTH button, it cuts off the music and lets you listen to the outside world through the mic. When you’re done, release the button and the music comes back. Pretty handy.

Noise Isolation and Your Cell Phone
Along the same lines is when you get a call on your cell while your iPod is blaring. Same problem applies here — but once again, a company called Gear4 has a product called the BluEye, which is essentially a combination wired remote/FM Radio/Bluetooth headset. Pair it with your cell phone, and then whenever an incoming call rings your cell, answer it through the BluEye and you never had to remove your phones. If you have a 5-6G iPod Video or 2-3G Nano, it will even show cal display and last caller information on your screen. (Touch and iPhone display capabilities coming once the SDK is released; for now the BluEye works, there’s no display on your screen.)

Whew. That’s about all my fingers can handle for today. I hope this has been informative and helpful in your quest for a good set of cans. If you have anything else you’d like to see added to this guide, or any questions, please feel free to fire away.

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8 Responses to “Choosing Headphones: A Guide for the Budding Audiophile”

  1. James said

    This is a great summary. I’m currently looking for a pair of in ear sound isolating headphones and this guide has been really interesting reading. Thanks!

    In the end I’ve decided on a pair of Shure SE310’s.

    Below are a few other links I found useful:

    Headphone Guide by Application from http://www.headphone.com
    Guide to Headphone Types from wwww.hifiheadphones.co.uk
    Headphone Buying Tips from wwww.hifiheadphones.co.uk

  2. Eric March said

    I’m glad you found the article useful! If you are interested in iPod Touch and iPhone updates from this blog however, we’ve moved to http://www.touchpodium.com. This version of the blog is no longer being updated.

  3. Khalifa said

    Interesting read, all those complicated-looking specs listed on the headphones box are not so complex afterall. I’m currently using Shure SHR440 on my Sony Walkman CD player DE-J011, because my FLAC-player Cowon J3 Does not work anymore 😦 call me old-school but I refuse to use an iPod and Beats products.

  4. Related,…

    […]Every once in a while we choose blogs that we read. Listed below are the latest sites that we choose[…]…

  5. Hassaan Ahmed said

    I’m strongly into sound quality and durability of the headphones. I want to buy headphones that provide good isolation and great sound without using amps. Can you please recommend a few models. Money is not a problem. Thanks in advance.

  6. sal said

    This is a very informative guide. A really good breakdown and categorization of headphone types.

  7. Nick said

    Eric, great information. Do you by any chance have any information about sensitivity specs? I just bought some earbuds that show a sensitivity response of 110+/-3dB. What does that mean?

  8. May I simply just say what a comfort to uncover an individual who truly understands what they are discussing on the web.
    You certainly understand how to bring a problem to light and make it important.
    A lot more people must check this out and understand this side of your story.
    I was surprised that you’re not more popular since you certainly have the gift.

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