 By
conventional speakers, we mean speakers that use traditional woofers and tweeters, andcome
in boxes that range in size from models that fit nicely on a bookshelf all the way up to
coffin sized models! |
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Here we'll focus on the technologies used today to build a quality speaker and
how to go about selecting a model that suits your taste, your space and your budget. Since
several of our speaker brands use proprietary technology to achieve their sonic goals, we
will occasionally mention specific brands here as a guide for where you might look for
specific features.
 The only thing you
want vibrating in a speaker system is the speakers themselves... if the box vibrates, it
also creates unwanted sounds and resonances. For this reason, most manufacturers make
their boxes of high density particle board
of at least 1/2 inch thickness (the thicker the better). Particle board is more resistant
to vibration than real wood which has natural flex along the grain. Better speakers will
also feature braced internal cavities to prevent vibration. Veneers may be real wood or
other materials but they do not affect the sound.
Some boxes are ported with a vent and
others are sealed air tight based on the
speaker designers goals. Ported boxes tend
to play more loudly for a given amount of power input and ports are often used to enhance
bass response. Sealed systems tend to
provide a smoother, deeper bass but not play with the same efficiency since some of the
acoustic energy is trapped inside the box. Excellent, accurate speakers of both designs
can be made. Another design similar to a ported design is the transmission line which can
be compared to a maze inside the speaker cabinet which channels the bass energy to a port.
This can allow a relatively small and light woofer to produce excellent deep bass.
Speakers with ports on the back need a little breathing room and are therefore not a good
choice for wall or bookshelf mounting.
Boxes can also reflect the sound being produced from the speakers with their surface
baffle and their edges. These reflections cause the speaker to have a "boxy"
rather than open sound. Some manufacturer's overcome this with felt padding on the front
baffle, others make very narrow speakers with rounded edges to avoid reflections.
Tweeters must be able to move back and
forth over 20,000 times per second... stopping and starting very quickly to insure that
the music sounds crisp and clear. They also cannot flex as they do this or you'd hear
distortion. So the ideal tweeter is both small, lightweight and very stiff. That paper
cone tweeter in a pair of $49 speakers may go out to 20,000 Hz... but you'll also get
distortion and a lack of clarity as it flexes and struggles to stop and start quickly!
- JBL®
attacks this problem with their series of speakers using Titanium drivers for speed and
strength.
- Infinity®
uses their famous EMIT tweeter in their Kappa series speakers which eliminates weight with
a mylar/aluminum driver and have recently introduced a composite silk dome tweeter in
their Compositions series.
- DCM®
uses a very small piezo element housed in a horn structure to enhance dispersion and
loudness.
Midrange drivers are responsible for
covering roughly 70% of the sound we hear so, as you might imagine, exotic materials tend
to show up here  as well.... Infinity® Kappa's
(seen to the right) use a foam dome that looks a bit like a snowball, other brands use
graphite reinforcement for added stiffness or composite plastics or specially treated
paper. While midranges don't have to vibrate as quickly, they must move larger masses of
air than tweeters so lack of flex is important in these drivers. In better speakers, most
manufacturers build the midrange driver it's own box within the speaker box so that it
does not get affected by pressure waves from the woofer. You may see this feature called a
"sealed midrange" and this is desirable if you are looking for accurate sound.
Woofers must move massive amounts of air
to produce deep and loud bass notes. They must stand up to many "G"'s of force
without flexing and distorting yet they have to be able to be light enough to stop and
start quickly or your bass will sound "muddy". This is quite a challenge
especially when you are designing 10 or 12 or even 15" woofers! Some manufacturer's
us multiple smaller drivers to move masses of air while each driver stays relatively small
and light. (Two 12" woofers have 28% more surface area than a single 15"
woofer... but are also more expensive to manufacture and install!) Others go to special
designs, for example:
- Infinity's®
IMG graphite/polymer woofer.
- JBL's®
"aquaplas" cement like compound.
- Velodynes®
composite spun aluminum drivers.
- DCM®
uses impregnated paper drivers with special reinforcing ribs
- Bose's®
famous 901 speaker uses nine 4.5" drivers and an electronic equalizer to develop
massive bass while keeping transients crisp and clean with small drivers!
So there are many ways to achieve good, crisp, clear, loud and deep bass but it pays to
listen carefully when you shop. Many inexperienced people are fooled into thinking that
more bass is good bass. Some inexpensive speakers offer lots of mid-bass but very little
deep bass and do not provide bass that is crisp and clean. Insist on hearing some
"quick" bass riffs when you are comparing two different speakers... listen to
the differences in quality of the bass and not just which is louder (that's what bass
& treble controls are for... but you can't fix "slow" bass!).
  
Most speakers are direct radiating in
that all their sound comes from the front and hits your  ears directly. Bi-polar
designs have rear mounted speakers which also produce sound which is sent out into the
room and reaches your ears a bit later in time and can give a more spacious and open
sound. (Some people like this - others prefer the sharp focus of a direct radiating
design. Bi-polars need breathing room so they are not a good choice if you need your
speakers close to the wall in back of them.) Back in the 1960's, Bose® pioneered the
use of direct-reflecting® speakers with the introduction of the famous Bose® 901 (seen below).
This speaker, (901 series VI today), uses one direct radiating speaker and 8  speakers mounted on angled back panels
which provides an envelope of sound throughout the room (see illustration to right). This
makes where you sit completely unimportant which Bose® calls 'stereo everywhere'. (See illustration
to the right.) Again, some people like this and others don't but it is necessary to have a
good reflecting surface behind a pair of 901's for them to do their job properly. All Bose® '01 series
speakers use this direct reflecting design philosophy in some measure. We don't endorse
any particular design philosophy since your room set-up and personal tastes should be the
guiding factor in your purchase decision... but we thought you'd like to be aware of the
basic differences.
The crossover network is an electronic
circuit that acts as a traffic cop inside your speaker box, sending the high notes to the
tweeter and the low notes to the woofer and so on. Careful attention to crossover design
is necessary to help compensate for time delays in sounds reaching your ears from each of
the speakers and to preserve a great stereo image. Manufacturer's of better speakers spend
a lot of time and energy on the design of this unseen part of your speaker but the end
result is a speaker that seems to disappear leaving only the music and the players. Some
designs give the user the option to wire in two pairs of speaker wires from their amp to a
set of double binding posts on the back of the speaker. This Bi-wiring is claimed by some
to enhance the overall sound quality by promoting a better transfer of electricity. At the
very high end, some people use separate external electronic crossovers and amps for each
of the speaker components... a separate amp for the woofer and a separate amp for the
tweeter. This is said to avoid crossover irregularities and provide more accurate sound...
but it is so expensive to that most people avoid it! Speakers that are compatible with
Bi-amping & bi-wiring are easily identifiable by the dual set of wire terminals on
their rear panel and a small metal "jumper" plate that joins them together for
normal operation.
If conventional bookshelf or tower speakers seem like the right choice for you, the
next step is to shop and listen! If you want to do some critical listening and comparing,
it's best to go on a weekday or evening when the crowds are smaller and we can give you
our undivided attention. It's also a good idea to bring along a well recorded and dynamic
CD that you are familiar with. You should be able to listen to deep, fast bass, natural
male and female vocals and shimmering cymbals. (If you don't have anything suitable - our
sales counselors always have some good material on hand - but it is best if you are
familiar with the material). If you have size constraints for your speakers, bring those
measurements with you and be prepared to talk about your other audio equipment so we can
insure a proper match. If you have a budget in mind, it's helpful to know that as well but
remember that your speakers should be the most expensive component you own as they affect
sound quality the most. Before you start to listen to speakers in your price/size range,
ask to listen to the best speakers in the sound room. No... this isn't some kind of sales
ploy! Listening to the best speakers will make you sensitive to what specific things you
are not getting in a lesser speaker. The ear/brain has no memory for sound quality so
establishing a reference point for "great" is helpful in choosing between two
more modest speakers.
OK... ready, get set.... listen!!
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