Headphones: Part One
Once upon a time, headphones were
heavy clamshells that pinched your head like the claws of an irradiated lobster from a
1950's sci-fi movie -- but that was a long time ago and things have changed. Now you see
people comfortably wearing headphones at malls, parks, offices, schools, and just about
everywhere else. You probably own a pair or two of your own; manufacturers of portable CD
players, MP3 players and boomboxes almost always toss in a pair of cheap headphones with
their products -- and these are mostly what you're seeing in the ears of those plugged-in
folks around town. However, while cheap'n'cheerful headphones might be good enough for
listening to a CD while you're jogging or shopping, they're unlikely to deliver the level
of aural pleasure you get from listening to your two-channel system at home.
In fact, many stereo enthusiasts wonder if it's even
possible for a good pair of 'phones to deliver the same quality of sound as a good pair of
loudspeakers. We'll leave it to the audiophiles to debate that issue, but there's no
argument that it is possible to experience music with extraordinary depth and detail from
a good pair of headphones. And these days there are more choices than ever, so let's get
right to it.
There are two basic types of headphones: dynamic and
electrostatic. The dynamic-driver headphones use the same technology as dynamic-driver
loudspeakers (the most popular type of speakers). That is, they feature cones (also called
diaphragms) made of paper or other material. The cone is attached to a coil of wire called
a voice coil, which is propelled up and down in very rapid, minute, piston-like movements
by a combination of electrical energy (from your amplifier) and the interaction of
magnetic fields. The movements of the voice coil, typically so fast that the eye can't
perceive them, in turn move the cone. The cone's motion displaces air, causing tiny
ripples in air pressure -- sound, in other words. (For more information on speakers and
how they work, look in our "How To" archives for
the four-part series on "Loudspeaker Basics." In fact, if you look at the second article in that series, you'll see an
illustration of an exploded view of a dynamic-driver speaker.)
Just as dynamic-driver speakers and headphones share the
same technology, so do electrostatic speakers and 'phones. In an electrostatic speaker,
the electrical energy from your amplifier (or receiver) again works in conjunction with
magnetic fields to move a diaphragm. In this case, the diaphragm isn't a cone but rather
an extraordinarily thin sheet of Mylar. Like the cone in the dynamic speakers and 'phones,
the Mylar displaces air when it moves and the resulting changes in air pressure cause
sound.
Electrostatic headphones give exceptional detail,
especially in the high end of the sound spectrum, with very low distortion. Why aren't
they more popular? One reason could be that you can't really lay your hands on a set of
electrostat headphones for under $1000. Yeah, that's pretty serious cash for a set of
headphones you might only use when the baby's asleep or when the spousal unit doesn't
share your love of AC/DC, Moby or Bach at full blast. In fact, the world's most expensive
headphones, Sennheiser's Orpheus, are electrostats. Beware: they'll set you back $14,900 a
pop, though they do come with their own tube amp and digital-to-analog converter (which
probably account for about half the cost of the entire rig).
Dynamic headphones can be quite pricey too. There are
headphone "systems," which include dynamic headphones and a dedicated headphone
amplifier, which can cost thousands of dollars. But dynamic-driver 'phones, sans amps, can
be quite cheap as well. You can pick up a pair of headphones for just a few bucks at
megabox discount chain stores.
Though we'd all love to be in a financial position in which
plunking down a few grand for a set of headphones and an amp wouldn't put a dent in our
wallets, let's face it: most of us would rather pay the rent and buy food and other
necessities of life. So, for the purpose of this column, we're going to focus on the more
affordable dynamic-driver headphones.
Let's quickly run through some of the common 'phones
available when you go shopping. (We'll look at more specialized types, as well as amps
that cost less than a year of college, in part two of our series on 'phones.)
Open-air 'phones
These lightweight 'phones sit over your ears and are
acoustically transparent. That is, the sound generated in the headphones isn't contained
entirely within the earcups. One advantage of these 'phones is their lightness, which
makes them quite comfortable, and their typically reasonable prices. Disadvantages include
noise leakage. Wearing open-airs, you'll be leaking noise out, so that those around you,
especially in close quarters, might hear some of what you're hearing. Worse for you is
that you'll hear ambient noises -- conversations, passing cars, the sound of the plane
you're flying on, etc. Another disadvantage of these 'phones is that they tend to be
fragile, so that they're easily broken. Of course, because they're pretty cheap, they can
be easily replaced.
Open-air 'phones often come with over-the-head headbands,
but some now come with behind-the-head headbands. Check out both styles to see which suits
you best.
Sealed 'phones
These are the classic headphones. They come with sealed
earcups; the drivers are encased in an almost airtight soft material. Because they're
sealed, they're heavier than open-airs and might therefore cause listener fatigue sooner.
But the major advantage of the sealed headphones is that they leak far less noise in or
out, though none completely block either. Another advantage: they tend to be sturdier than
open-air 'phones, so they're less likely to break if they're twisted or dropped.
Earbuds
Earbuds are tiny 'phones that fit into your outer ear, held
in place by a lightweight headband or with small clips that attach to your ears. They're
very light and when they fit your ears well, the better sets will give excellent bass
response because you're not only hearing the bass but feeling it as well.
Canal 'phones
These are so small that they fit right into your ear
canals; therefore they require no headband or clips whatsoever. They're very popular
because they form an airtight seal in your canals, greatly reducing outside noise,
allowing you to concentrate on your tunes. Unfortunately, that seal not only blocks
unwanted outside noise, but also sounds you probably should pay attention to -- such as
screeching brakes and shouts of warning. Further, internal noises, such as the
sound of your own breathing, become intensified because you're hearing so very little from
the outside world. One less frequently discussed disadvantage to them is that their small
cushions, which fit into your ear canals, will pick up earwax easily and quickly and so
they must be cleaned or replaced regularly.
Buying tips
When you go out to purchase headphones, there are a number
of things to keep in mind. If you're buying 'phones strictly for use with your system at
home, you probably want a higher level of performance than you're likely to get with the
lightweight open-air 'phones often associated with personal CD and MP3 players. You're
also more likely to tolerate the slightly heavier sealed models because you'll probably be
seated when wearing the 'phones rather than walking or running around, as one does with
the portable players.
The standards you apply to buying headphones are much the
same as those applied when purchasing loudspeakers: you'll want clear sound with good bass
response and as little distortion as possible in the upper frequencies.
You're also going to want to make sure that your headphones
are comfortable. The best 'phones in the world won't do you a bit of good if they don't
fit properly. If you've ever shopped for headphones at one of those megabox stores, you'll
notice that they tend to have their 'phones sealed-up in plastic packages, unavailable for
listening and determining how they fit.
One way around this problem is to patronize audio specialty
shops, which frequently have headphones available to try on and audition. You'll be
listening to the 'phones through what is likely to be expensive gear, so try to listen
through a system that most resembles yours in configuration (separates or integrated
components, power output, etc.), brand name and price. As always, whenever you're shopping
for audio equipment, make sure to take a CD or two from your collection with you to the
store. That way you're listening to music you're very familiar with, not a store-owned CD
you might never have heard, which might have been chosen in order to sonically complement
the equipment being sold.
Hearing damage
No piece on headphones would be complete if it didn't
address one very important issue. Because a pair of really good headphones can give you a
better listening experience than many inexpensive speakers, it's tempting to
"treat" yourself by letting it rip. Don't do it. Your ears can begin to suffer
permanent hearing loss by sustained exposure to sounds over 85dB -- a level easily
exceeded by most home stereos and even a lot of portable music players. How loud is 85dB?
A ringing phone hits 80dB. A hairdryer or lawnmower goes up to 90dB. An ambulance siren
gets up to 120dB -- the same level you're exposed to at rock concerts or when you go to
hear the symphony. So if you're thinking that you want to recreate the volume of a live
performance, think again -- especially if you want to avoid tinnitus (a ringing in the
ears that can become permanent).
In our next segment on headphones, we'll take a look at
some more headphone types -- including surround headphones and noise-reduction models --
as well as headphone accessories that can enhance your listening experience. We'll also
take a closer look at how you can avoid damaging your hearing when enjoying music through
'phones.
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