Headphones: Part Two
In the first part
of our two-part series on headphones, we discussed the two major categories of headphones
-- electrostatic and dynamic -- and how they work. We also explored a variety of the most
common headphone types, from open-air 'phones to canal 'phones, and we also touched on
hearing damage, which can easily take place when listening to headphones. So if you're
looking for a good starting place for your search for a good pair of headphones, please
take a look at that article before continuing with this one.
In this second half of our series, we're going to look at
some exciting technologies that might well improve your headphone listening: wireless
'phones, surround-sound headphones, and cans that cancel unwanted noise when you're
listening to music or when you want to hear nothing at all. We'll also go over some
headphone accessories that can enhance your listening experience: jacks, cables, and amps
designed especially for 'phones.
One of the problems with the headphones we looked at in the
first half of this series is that they all reproduce sound in stereo (two channels). Music
from the left channel is fed into your left ear and music from the right channel is fed
into your right ear. Most people hear music reproduced this way as though it were coming
from inside their heads. You probably know this feeling well -- the sound seems as
though it's being generated in the center of your brain rather than in front of you, as it
does when you listen to your stereo at home, or from all around you, as when you listen to
a home-theater system.
Isn't that spatial?
One headphone technology that has made real strides in its
ability to realistically reproduce sound -- get it outside of your head -- is spatial
simulation. Several headphones attempt to accomplish this through locating the earspeakers
in front of the ear, instead of firing directly into it.
The German manufacturer Ultrasone puts out a line of
in-front 'phones, ranging in price from about $100 to about $600. These headphones deliver
two- or four-channel sound by positioning the transducers off-center and in front of your
ears so that the sound seems to radiate from somewhere in front of your head rather than
inside it.
Surround 'phones represent another way of eliminating that
center-of-the-head sensation. Surround 'phones, as you've probably guessed, are designed
to replicate the multichannel experience you get when watching a DVD in a home theater.
These headphones generally come with a processor, which can either synthesize surround
sound from two-channel sources or channel true surround to your headphones' small drivers.
Acoustic Research's $229 900MHz wireless headphones have a
built-in Dolby Digital processor "virtually identical to that of a movie theater or a
live musical performance," according to the manufacturer. We haven't tested these
particular 'phones so we can't determine the validity of the claim, but we do know that
many similar types of cans, even with all of their processors and psychoacoustic tricks,
still fall quite a bit short of what a home theater can deliver. On the other hand, what
they do accomplish can be satisfying in its own right.
A lot of new A/V receivers can give you a hint of what
these surround 'phones can sound like. Take a look at your receiver and see if you have
digital signal processing (DSP) modes, such as Concert Hall, Cathedral, Nightclub,
or Singing in the Shower modes. Notice how many of them, when engaged, give a sense
of artificial spaciousness to your music? Simple algorithms in the digital processor move
the sound back and forth between the left and right channels, add time delays to parts of
the sound (giving it a bit of echo), or employ other, similar digital tricks that affect
how your brain perceives sound.
A popular offshoot of the surround 'phones is the new
noise-cancellation headphone. The problem, as with the surrounds, is that the engineers of
these things have lots of pretty descriptions of how they work, but the fact is they
usually don't live up to the techno-hype. Noise-cancellation 'phones are often purchased
by folks who travel a lot on planes and buses or who have small, bipedal noise-generators
of the organic variety (kids). The noise-cancellation 'phones have small microphones
built-in to receive outside noises, which are then analyzed by signal-processing
electronics, which then generate out-of-phase (and, therefore, canceling) soundwaves
inside your headphones. Some of the higher-priced models ($100 and up) certainly reduce
the amount of noise leaking into your ears from the outside, especially on the low end of
the aural spectrum where the disturbing rumbles of airplane engines lurk. Unfortunately,
they can also cancel out some of the bass in your music, making your tunes sound
abnormally bright due to the lack of low-frequency notes, leaving you with
muffled-sounding or unbalanced music. Don't dismiss noise-canceling 'phones, however. Even
a 10dB reduction in steady-state noise on a cross-country flight can pay huge dividends in
how well rested you feel at the end of the day. Compared with making travel easier and
more comfortable, reduced fidelity may seem a small price to pay.
Yet another headphone innovation that has gained popularity
in recent years is wireless technology. The two types of wireless 'phones are those that
use RF (radio frequency) signals and those that use infrared signals. The former can
transmit further (about 100', though manufacturers often claim much greater distances) and
don't have to be in the line of sight of the unit's base. The latter transmits up to 30'
and do have to be in the line of sight of the base. The sound of some models of wireless
headphones can be quite good, but definitely try before you buy -- and pay close attention
to how well balanced the headsets are. Much of the convenience offered by wireless
headphones can be offset by a bulky, poorly balanced headset that makes you sit in one
position all night or risk having it fall off your head.
No matter which type of headphones you decide to get --
straightforward dynamic-driver 'phones, surrounds, noise canceling, or wireless cans --
you might well be able to improve the sound of them with some properly chosen accessories.
I think, therefore I amp
Perhaps the most important accessory, and no doubt the most
expensive, for your headphones is a separate, dedicated amp. The vast majority are solid
state, just like the vast majority of receivers and amps for home audio, but there are a
few tube amps out there. (Sennheiser Orpheus headphones come with a tube amp -- the combo
will set you back $15,000, however.)
Why would anyone buy an amp when most receivers,
preamp-tuners, and integrated amps come with a handy headphone jack on the front panel?
That good question is answered by another one: how many people buy a receiver based on how
the music sounds coming out of the headphone jack? Answer: virtually no one. Therefore,
manufacturers tend to regard headphone jacks and related electronics to be, at best, an
afterthought. Even high-end gear can have surprisingly shoddy hookups for cans.
In addition, many fine headphones have massive power
demands -- demands not even remotely met by the tiny little op-amps attached to most
headphone jacks. AKG's phenomenal K 1000 model, for instance, requires a whopping 7
watts! A separate headphone amp is required if you want to hear what these headphones are
capable of.
And if you listen to a lot of music through a portable
device, consider that most portables limit the amount of power devoted to the headphone
output (mainly to conserve battery power). So if you spend quite a bit of time listening
to music through headphones at home or on the run, you might very well do yourself a favor
by considering an amp.
Possibly the best reason for employing a headphone
amplifier, however, is our old problem, that center-of-the-head sound. Many of the best
headphone amplifiers utilize special electronic circuits that mimic the way we hear in
free space. They add a little of the left channel's signal to the right and a little of
the right channel's signal to the left, add some delay and equalization (which is based on
the way sound wraps around our heads in normal hearing) and voila, natural
from-the-front sound. Since everyone's hearing is different, no single approximation of
natural sound works for everybody, however, so always listen to a spatial-restoration
circuit before committing to buy it.
Headphone amps are available for portable devices (the
HeadRoom AirHead amp is $119) and for at home (Musical Fidelity's X-Can V2 goes for $295),
but you can also find models that cost a lot more.
Cable, guys
Everyone who has ever wired their stereo system with a
spool of wire from a nationwide electronics dumporium, and then, later, gone out and
purchased higher-quality cables, knows the good stuff does make a noticeable
difference in the sound. The same can be true of headphone cables.
Of course, as soon as you open the infamous can of cable
worms, phrases like "oxygen-free copper conductors and pure polyethylene
dielectrics" come crawling out. No worries. Look up "What You Need to Know About
Loudspeaker Cables" in our How To
section and that'll give you some good ideas about speaker cable that'll help guide you
through the purchase of headphone cables as well.
Big jacks and little jacks
If you find that you like the sound of the open-air
headphones that came with your Walkman and you want to use them in your living room,
plugged into your receiver, you're probably going to have to head back to that nationwide
electronics dumporium. You're going to need a 1/4" (standard size on home audio gear)
to 1/8" (standard on portable devices) adapter (also known as a miniplug to phonoplug
adapter). And you'll need an adapter to go the other way if you want to use those big,
comfy, good-sounding sealed headphones on your portable device.
The choices of headphones and accessories are plentiful. As
always, try to get in as much auditioning time as possible before making your purchase.
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