Audio Reproduction Systems
Ever wanted
to know all about audio reproduction, but were afraid to ask? Do Watts and
SPL sound like terms normal people would never use in public? You're in luck!
The head audio geek at TargetPC, or Bill as I'm known to some, has decided
to put fingers to the keyboard to demystify the wonderfully confusing world
of sound. Why not follow along as I tackle a few difficult concepts and simplify
manufacturer specifications that leave most of the world reaching for an air
sickness bag.
Terminology
What would
technology be without its beloved technobabble? Specifications, or geakspeak
to many, is just the verbage that must be used when conveying complex ideas
so all is clear between engineers. Inner audio circles label their language
as "dB." In my 20 years in professional audio, I've actually had
people come up to me and spout, "Yeah man, just got a hot new 24 channel
console, let's talk dB." Without touching on the social ramifications
of such cryptic communication, here's a very condensed list of words and abbreviations
to get anyone noticed in a crowd. Use these sparingly as prolonged exposure
can do odd things, like increase the distance between you and your spouse
or worse, attract more dB'ers.
|
Term
|
Definition
|
|
dB
|
Decibel
or 1/10th of a Bell
|
|
SPL
|
Sound Pressure Level
(measured in dB)
|
|
Volt
|
Unit of Pressure (denoted as E or V)
|
|
Watt
|
Unit
of Power (denoted as P or W)
|
|
Amp
|
Unit
of Current (Amperage, denoted as I)
|
|
THD
|
Total
Harmonic Distortion (a percentage)
|
|
S/N
|
Signal
to Noise Ratio (measured in dB)
|
|
FR
|
Frequency
Response (measured in Hz & dB)
|
|
Hz
|
Hertz
(frequency or recurrence)
|
|
Z
|
Impedance
(measured in Ohms)
|
A few modifiers
are necessary as well. If I want one thousand of something, I'd say "kilo"
as in kilohertz (1000 Hz). If I'd want one thousandth of something,
I'd say "milli" as in millivolt (mV). Glance at a wider range if
you prefer; this list is far from exhaustive.
|
Abbreviation
|
Fraction
or Multiplier
|
|
p
|
pico
(0.000000000001)
|
|
u
|
micro
(0.000001)
|
|
m
|
milli
(0.001)
|
|
k
|
kilo
(1,000)
|
|
M
|
Mega
(1,000,000)
|
|
G
|
Giga
(1,000,000,000,000)
|
Amplifiers
The last
time you requested someone to "turn it up," you could have said,
"hey man, amplify that sound." An amplifier is a set of components
designed to make something "more" or louder if you prefer. Similar
to an automobile accelerator pedal, punching it equates to crankin' the knob
off. So what's important when browsing your local electronic retailer? Is
more always better?
Power
Output
Watts are easy as
PIE. No, not the fork and plate kind, the physics kind. Power (in Watts)
equals current (I or A) times voltage (E or V). Since the formula is a
linear ratio, increasing the power would mean an increase in voltage and/or
current. All power amplifiers generate distortion, which are errors created
when boosting the signal from a lower state to a higher state.
