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Good speakers are the key to getting the best possible
audio experience from your sound system. You can put together the best
CD or DVD player on the market and the highest-rated AV receiver, but
if you don't have the right speakers, your audio or home theater setup
won't be worth much when it comes to actual sound. Your speakers provide
the interface between your audio system's electronics and the physical
world in which sound is actually played--choosing the right set can make
the difference between cramped, muddy audio and crystal-clear concert-hall
sound.
You can buy a pair of loudspeakers for $50 or you can spend $50,000 and
up. You can buy speakers as small as a baseball or as big as a refrigerator.
There are "bookshelf"-sized speakers costing a few hundred dollars and
others the same size that'll set you back thousands (and are worth every
dollar and then some). There are big speakers that sound anemic and tiny
ones with sound that will hit you so hard they'll knock the wind out of
you. So, how do you know which type of loudspeaker is appropriate for
you?
The "whys" and "hows" of the matter could fill a
book, but one thing's for sure: there's a host of misconceptions about
loudspeakers we need to dispel before we can talk meaningfully about our
subject.
For starters, big speakers don't necessarily play
louder or sound "bigger" than small ones, nor do they necessarily have
better-quality bass. (Contrary to popular thinking, "more" does not always
equal "better.") A three-way, or three-driver, speaker will not necessarily
sound better than a two-way design--in fact, chances are, unless you're
willing to spend a substantial amount of money, the more drivers in the
box, the worse it will sound. A twelve-inch woofer does not necessarily
produce better bass than a ten-inch one. Perhaps you've seen ads for "1000-watt"
speakers--an all-but-meaningless specification.
It takes a lot more than technical specifications
to determine which is the right speaker for you, which is why we perform
hands-on reviews of all our speakers. This guide covers the basic issues
we consider when we're reviewing and discussing loudspeakers--considerations
that might help you choose a set of speakers as well.
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A speaker's frequency range is a measurement of how wide a selection of
sounds it can reproduce. Can it reproduce the lowest bass and the highest
highs? Here's one of the areas where specs can help you out. Keep in mind,
though, that very deep, high-quality bass is usually expensive, and if
you're on a budget and not after high-powered home-theater performance,
you might be more satisfied with good midrange performance since that's
where most of the music is anyway. Extended high-frequency response is
somewhat easier to achieve at reasonable cost, but watch out for "peaky,"
edgy, over-enhanced highs, which can readily induce fatigue.
Bass and treble extension are worth having,
but usually not at the expense of frequency balance--that is, the speaker's
overall tonal neutrality. If the speaker overemphasizes bass frequencies
the sound will be boomy and muddy, the actual notes difficult to distinguish.
If it accentuates high frequencies it may sound bright and harsh. Conversely,
if a speaker de-emphasizes a frequency band, like the upper midrange,
it will sound dry and lifeless. If it short-changes the midbass, it will
likely sound thin and "sucked out."
A great test of a loudspeaker's neutrality
is the human voice; does it sound like a "whole" person, or do you hear
distinct "chesty" and "tizzy" components? Also, make sure the speaker
adequately expresses the difference between soft passages and loud ones.
Keep in mind that most rock music is seriously compressed (the soft passages
are, in effect, boosted to sound nearly as loud as the loud ones), so
other kinds of music like classical and jazz tend to be better for testing
a speaker's dynamic range.
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Another important consideration is stereo imaging or "soundstaging." We
try to evaluate whether a speaker pair can create an accurate soundstage
with adequate width, depth and height.
To appreciate a speaker's soundstaging ability,
we find it's important to sit directly between the speakers and listen
to a simply produced live or "acoustic" recording, rather than a multi-tracked,
artificial studio production. The human ear responds well to spatially
correct "cues" in the form of subtle reflections from surfaces in the
room where music is recorded. When these reflections are faithfully recorded
and played back, the result can be a stunningly real sonic "portrait"
of a musical event.
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Another critical factor in choosing your speakers is how loud you like
to listen and how a given speaker performs at that level. If you live
in a dorm room or an apartment with thin walls, you may be playing your
system at low levels much of the time. Some speakers sound surprisingly
"alive" at low volume while others need to be played loud to get going.
Some speakers start sounding hard, grainy and compressed at higher volumes.
A well-designed speaker will sound good at both low and high volumes.
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When you're evaluating a speaker, you should also keep an ear cocked for
its rhythmic certitude and pacing. Does it "swing"? Does it sound appropriately
snappy and fast, keeping pace with the music, or does it sound sluggish
and constipated no matter what material you give it? These are qualities
you can't measure, though some of what is measurable--sensitivity, for
instance--will have definite effects on a speaker's pacing.
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Your preference in speakers will be strongly affected by your taste in
music. Assuming you're on a budget, if you listen to a lot of rock, you'll
probably be willing to sacrifice some tonal accuracy for more bass. And
you'll probably want a speaker that will play loud without compression,
distortion and "graininess," or a sense of artificial coarseness in the
high frequencies. If, on the other hand, you listen to a great deal of
acoustic music--classical, folk, or jazz--you might be willing to give
up the bottom couple octaves of bass to get smooth, accurate, or liquid-sounding
midrange frequencies.
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The room in which you put your speakers and where in the room you place
them will have a profound effect on the sound you get. Where you sit,
of course, is also a factor. The best sound can usually be heard from
a point directly between the two main speakers. Rooms with reflective
surfaces such as windows, bare walls, and wood or linoleum floors will
produce hard, "confused" sound no matter how much you spend on speakers.
Fortunately, carpeting, drapes or a well-placed tapestry can absorb, reflect,
and diffuse sound.
Moving a speaker just a few inches can greatly
affect the sound--especially for a speaker with strong low-frequency response.
It can mean the difference between no bass and too much bass, or just
the right amount. If you just want to get sound, and if your speakers
are small enough, you can place them on a shelf, but if you'd like to
create and experience a "soundstage" you'll need to move the speakers
into the room, placing smaller ones on specially designed stands at least
six feet apart. This is often not practical in dorm rooms or in small
apartments.
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Most loudspeakers consist of two cones, or drivers (a woofer and a tweeter),
a crossover network, and a cabinet. The cones are the actual producers
of sound--thin funnel-shaped pieces of material (usually plastic) that
vibrate. Each cone produces the frequencies best suited to its size--the
woofer produces bass while the tweeter emits high frequencies. The midrange
falls somewhere between the two and is determined by the crossover network,
which divides the frequencies between the cones.
A well-designed crossover network consists
of a low-pass filter (LPF), which keeps the highs from reaching the woofer,
and a high-pass filter, which keeps the lows from seeping into the tweeter.
The point at which the LPF rolls off the high frequencies and the HPF
rolls off the lows is referred to as the crossover point. A common crossover
point for a two-way system is around 2,300 Hertz (or cycles per second),
but different designs vary the crossover frequency for different effects.
In a three-way design, a dedicated midrange
speaker augments the work of the woofer and tweeter. There are advantages
to such a design, but getting three drivers to work as one can be difficult
and expensive; be wary of three-way designs costing less than a few hundred
dollars each.
The cabinet is a critical component in the
loudspeaker's design, and has a major effect on its sound. A cabinet should
be rigid, well braced and internally damped to avoid sound-coloring resonances.
Plastic cabinets may work fine for computer speakers, but not for serious
audio components. Cabinets should usually be made of wood, or, more commonly,
medium density fiberboard (MDF).
The cabinet design is typically one of two
types: a sealed enclosure, or a "bass-reflex" type with an opening, or
"port," used to provide a longer/deeper resonance cavity for the low frequencies.
When a woofer moves, it pushes air in two directions, forward and back.
Unless dealt with properly, the out-of-phase sound from the back wave
will cancel the front wave, resulting in poor bass. A reflex design's
port gives the back wave a place to go. A properly designed system causes
the two waves to add instead of canceling, resulting in reinforced, rather
than diminished, bass. An alternative and very popular bass reinforcement
methodology is called "acoustic suspension." This design uses a sealed
box wherein the trapped air acts like a spring. The advantage of this
approach is that a smaller box can thereby produce very deep bass; the
disadvantage is lower efficiency, resulting in the need for a more powerful
amplifier.
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When shopping for loudspeakers you'll usually find numerical specifications
along with a written description. Be aware: Measurements and numbers tell
only part of the picture, and any one measurement can be more misleading
than none at all.
For instance, you might get a frequency-response
specification such as "40 Hz-22 kHz," but unless the spec also tells you
the variance within however many decibels (+/- 3 dB, for example), the
numbers are essentially useless. The speaker may well reproduce 20 Hz,
but that tone could be 20 dB "down" from (or below) "flat" response, meaning
you won't really hear 20 Hz from that speaker. Additionally, how a speaker
is measured can affect the response. Was it measured in a room or in a
reflectionless anechoic chamber? Where was the microphone placed to measure
the response? Essentially, a frequency-response measurement by itself,
unaccompanied by a critical review, is pretty much useless!
The specifications will also usually offer
an "impedance" measurement in ohms, which refers to the resistance an
amplifier will encounter when trying to drive a given speaker. Today,
most loudspeakers are rated at 8 ohms, but this is another essentially
meaningless specification since, in reality, the impedance of a loudspeaker
varies with its frequency. Without seeing the impedance "curve" you cannot
know whether the speaker presents an amplifier with an easy or a difficult
load. In any case, today's modern solid-state amplifiers can effectively
drive most properly designed loudspeakers. Still, for reasons too complex
to delve into here, look for loudspeakers with a "nominal" 8-ohm impedance,
though most amplifiers will easily handle a 6-ohm load.
Two more important specs are voltage sensitivity
and power handling. Voltage sensitivity tells you how loud a speaker will
play for a given voltage. This gives you some idea as to how big an amplifier
you'll need to drive the speakers. This measurement is expressed as a
certain number of decibels (dB) per 2.83 V input. For example: "88 dB/2.83V."
Unless you're using a monster amplifier, you probably want speakers with
an efficiency of at least 86 dB, though 88 dB or higher is preferable.
Power handling tells you how much power in
Watts the speakers can take without damage. If a speaker is rated at "100
Watts maximum," don't worry too much if you choose or own a 200-Watt-per-channel
amplifier. Chances are you'll never put that much power into the speakers.
In fact, what usually damages a loudspeaker is using too small an amplifier
and driving it to "clipping" (distortion) levels. The loud-level high
harmonics in the distortion is what does the damage.
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Loudspeakers come in several types, mostly delineated by their frequency
range. A full-frequency-response loudspeaker is one that covers the full
audio band, from approximately 20 to 20,000 Hz. These are always large,
usually expensive, floor-standing designs, neither practical nor priced
within reach of most consumers. But they can offer incredibly realistic,
rich sound.
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The majority of loudspeakers, capable of responding from around 45-20,000
Hz, fall in this category. Prices range from a few hundred dollars to
thousands of dollars a pair. Remember, just because a speaker can cover
this range does not mean it will sound good, or that it will have good
quality bass. Frequency response is but one tiny piece of the sonic
puzzle.
One aspect of the frequency-response spec that
can offer a useful information about a speaker's performance is its variation
from "flat," which is stated as a "+/- x dB." The tighter the variance,
the more flat, or accurate, a speaker's response. Typical variances range
from +/- .5 dB to +/- 3 dB, with the lower figure usually bounding the
frequency extremes. That is, a speaker whose published frequency response
is 50-25 kHz, +/- 3 dB, will be -3 dB below "flat" at 50 Hz and 25 kHz.
This doesn't mean that information below 50 Hz will not be heard, only
that the drop-off after that point may be steep.
Most restricted-frequency-response speakers
are smaller than the floor-standing full-frequency-response products,
and are often known as "bookshelf" speakers. You can usually get stands
to mount bookshelf speakers in the optimal room position (actual bookshelves
are rarely the ideal place to put them).
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The subwoofer's job is to produce the very low tones of your audio system's
dynamic range. A true subwoofer will be able to reproduce a 20 Hz test
tone, which will be felt more than it will be heard (making it great for
home-theater applications), but 30 Hz will do very well in most listening
environments and for most music. Most subwoofers today are "powered,"
meaning that they contain a built-in amplifier and a crossover network
that lets you adjust the sub's upper frequency response so as to more
effectively blend in with your main speakers.
While a full 20 Hz soundwave is 40 feet long,
don't worry if your room is smaller. The wave will fit, though it will
literally bounce off the walls. The problem in smaller rooms is bass pressurization,
where the waves literally pile up and create an ugly, boomy sound. The
solution is to turn the bass volume down to the point where the room doesn't
become too "excited."
Subwoofer performance is greatly affected by
placement. Some locations in a room will cancel the bass entirely. So
where you place the subwoofer and where you sit are critical to getting
the most from it. Subwoofer set-up hint: put the subwoofer in your chair
and play a test CD with a 20 Hz test tone. Walk around the room and you'll
hear places where there's no bass, and other locations where there's great
bass (usually in a corner). That's where you should place your subwoofer.
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While most music is broadcast on two channels (for a stereo effect), home
theater (DVDs and laser discs) uses five-channel audio. A home theater
speaker set consists of two front speakers (sometimes the same ones you'd
normally use for stereo music), two rear or "surround" speakers, a center
channel (used mainly for dialogue), and sometimes a subwoofer.
A pair of high-quality loudspeakers is expensive
enough. Affording five of them is prohibitive for most consumers. So,
for most of us, a five-channel (plus subwoofer) home-theater speaker system
will necessitate a compromise. Buying a high-quality stereo pair and adding
lower-cost center and surround speakers tends to result in disjointed
and uneven performance. Five identical speakers (left, center, right,
and a pair of surrounds) of somewhat lower quality will, in fact, work
better for home theater than a "mix and match" set.
If you have a high-quality stereo pair that
you want to keep and you're turning your stereo into a musical-surround/home-theater
system, consider buying the center channel and surrounds from the same
manufacturer as your original pair. While this will not guarantee sonic
compatibility, it will be a good starting point. Make sure, however, that
the pair, and especially the center channel, are magnetically shielded
so as not to interfere with the image on your television. Serious audiophiles
will likely want two separate systems: one for music (two-channel or six)
and one for home theater. The main impetus for the separation is the television
or video screen; having anything between the main speakers tends to interfere
with the speakers' soundstaging, or imaging.
When multi-channel surround-sound music becomes
more commonplace, as it will with the introduction of DVD-Audio (your
favorite CDs are being remixed for 5.1 channels as you read this), perhaps
the "convergence" of audio and video will become more of a reality. Surround
mixes of major-label artists are already available on DTS (Digital Theater
Sound) compact discs, which can be decoded using any DTS-equipped A/V
receiver. Still, diehards will tend to keep two-channel and multi-channel
entertainment systems separate.
Most reasonably priced home-theater speaker
systems consist of five small, limited-frequency-response speakers (with
bass down to around 60 Hz) and a powered subwoofer. For film surround
sound, bipolar speakers (which radiate sound equally in two directions)
or dipoles are best for the rear channels, but regular "direct radiators"
will work well, too.
These small speakers work for home theater because
the "bass management" systems in most modern A/V receivers permit you
to route the bass from all five channels to the subwoofer, which also
reproduces the separate LFE (low frequency effects) track added to Dolby
Digital and DTS soundtracks (the LFE track is the ".1" in 5.1-channel
surround sound).
Unlike music, which has a basis in reality,
film sound, except for the music track, is usually arbitrary and artificial
(created "after the fact") and therefore tonal accuracy, while important,
is somewhat less critical when choosing low-priced home-theater speaker
systems. More important to good home theater sound are dynamics, the ability
to play loud without compression and/or distortion, and clarity. The latter
is particularly important for the center-channel speaker, which reproduces
most of the dialogue. If you can't understand what the characters are
saying, it's hard to enjoy the movie!
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The price range on loudspeakers is incredibly wide. There are bookshelf-sized
speakers costing a few hundred dollars and others the same size that'll
set you back thousands--and are worth every dollar and then some.
In the $300-and-under range, expect to get a solidly built bookshelf-sized
speaker with optimal performance from 60 Hz (mid-bass) and up. For stronger
and deeper bass (into the 40-Hz region) while keeping a desirable balance
across the audio spectrum, you're probably going to be looking at $300-$600
a pair. Speakers that offer deep bass in lower price ranges are almost
certainly short-changing other important parts of the frequency spectrum
(like the crucial midrange) and, we feel, simply won't be worth your time
and money.
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