The cutaway cross-section view reveals a speaker’s hidden components.
“I DON’T KNOW—ASK MY TECH.” IT’S
a response I’ve gotten in more BASS PLAYER
interviews than I care to admit when the conversation
has turned to the technical aspects
of bass gear. Fair enough—I know my earliest
motivation for playing had absolutely nothing
to do with things like damping factor,
the Fletcher-Munson effect, or any other
kind of highfalutin tech terms. But allow
me to enumerate a few facts for those of
us who can’t afford to hire gear geeks to
think for us:
1. There’s more to being a bass player
than playing bass.
2. Gear can be expensive, and when it
breaks or doesn’t work right, it sucks.
3. Learning some general principles of
electronics and acoustics will result in
your playing better, sounding smarter,
and looking hotter.
Okay, so m aybe I’m getting a little carried
away. But bumping up basic knowledge of
how your gear works will go a long way in
making yourself a more well-rounded bass
player. For now, let’s take a closer look at
one of the most crucial components in sound
production for amplified bass: speakers.
First of all, what exactly is sound? Sound
is “mechanical radiant energy transmitted
by longitudinal pressure waves in a material
medium (as air),” according to the good
folks at Merriam-Webster. In bass amplification, the loudspeaker, or driver, is the key
agent in converting an amplifier’s radiant
energy into airborne pressure waves. It does
this through the process of excursion, the
back-and-forth motion of a speaker’s cone
(or diaphragm), driven by the electromagnetic
interaction of a speaker’s movable
voice coil with a fixed magnet [see Fig. 1].
NEO, ARE YOU THE ONE?
From Alexander Graham Bell’s first patented
telephone loudspeaker in 1876 through the
moving-coil speakers of Magnavox in 1917
and the high-tech drivers of the modern day,
the materials used to fabricate loudspeakers
have changed quite a bit. In the early
days of amplification, drivers typically featured
paper cones and magnets made of
alnico, a composite of aluminum, nickel,
and cobalt. As the cost of alnico shot skyward
in the ’60s, speaker magnets were made
increasingly of ceramic ferrite. Nowadays,
a number of manufacturers have begun to
favor lightweight neodymium as a magnet
material, a choice that cuts the net weight
of a 10" driver roughly in half. While some
players are suspicious of neodymium drivers,
claiming they introduce an unwelcome
spike in the midrange frequencies, many
others are quick to go neo on the grounds
of weight alone.
THE CONE ZONE
In the diaphragm department, Larry Hartke
flipped the speaker world on its conehead
when he built his first aluminum-cone driver
for bassist Jaco Pastorius in the early ’80s.
Hartke’s reputation grew through the ’80s
and ’90s on the merits of the aluminum
driver’s fast, snappy response. Hartke Systems
recently re-upped the ante with the
release of its HyDrive hybrid cones made of
both paper and aluminum [Fig. 2]. Alternative
materials ranging from hemp to Kevlar
have also begun to gain some traction in
the cone field.
SIZE DOESN’T MATTER
(BUT SIZE MATTERS)
From the booty-full bite of Phil Jones’s 5"
Piranha speakers [Fig. 3] to the bowel-battering
“brown sound” of the AccuGroove
Whappo Grande’s 21" super-sub [Fig. 4],
drivers come in sizes big and small. While
it’s true an 18" speaker is capable of moving
more air than a 10" driver by virtue of its
speaker cone’s greater surface area, the calculation
gets more complicated when you
begin to factor in the design of the cabinet
itself and the number of speakers within.
WATTS UP, OHMS?
Power handling and impedance—the resistance
presented in a circuit containing alternating
current (AC)—is where things can get
a bit harder for the average Joe to grok. A
popular analogy to help illustrate the way
electrical current flows is to imagine the circuit
as a garden hose, where the current is
the flow of water through the hose, voltage
is the water pressure as it exits the nozzle,
and impedance is the nozzle (or thumb)
controlling the flow of current.
The mathematical equation used to
determine the relationship between current,
voltage, and impedance is known as
Ohm’s law, which states: current (measured
in amperes) equals voltage (in volts)
divided by impedance (in ohms). To calculate
impedance, you can simply switch
around the equation to read: impedance
equals voltage divided by current.
When it comes to speakers and amps, if a
speaker or combination of speakers puts up
too much resistance, the potential energy from
the amplifier won’t be efficiently translated into
sound. But perhaps a larger problem is when
a group of speakers offers too little resistance,
forcing the amplifier to pump out more current
that it should, ultimately frying it.
The calculation of impedance is pretty
straightforward when you’re dealing with a
single speaker—say, a 15" rated at 4Ω. Paired
with a Markbass F 500 head, which puts out
500 watts at 4Ω, you’re in good shape. If you
add an identical 1x15 cab to the mix, you
effectively double the load to the amplifier by
halving the speakers’ impedance 2Ω. While
some heads can operate safely at 2Ω, others
can’t. This is where the calculation of total
impedance (or load) becomes really important.
We’ll dig deeper into the subject of impedance
in a future column. In the meantime,
take a second to familiarize yourself with
all the specs listed on your heads and cabinets.
Hopefully all the numbers and calculations
don’t make your head explode, and
with any luck, you can use those numbers
and calculations to keep your head from
exploding. In the meantime, play well, study
hard, and look sharp!