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DUAL VOICE COIL ADVANTAGES
The dual voice coil woofer is actually quite old in the home audio industry but still relatively new to the
car audio world. The largest advantage of the DVC woofer is in the flexibility in installation. In order to
raise the sound pressure level (loudness) in a car, you can either add more speakers or add more
amplifier power to drive a single speaker. Many cars cannot fit two subwoofers and their necessary
enclosure volumes but can easily fit large power amplifiers and a single woofer. Simply speaking, the
DVC woofer allows you to make up for speaker deficiencies with additional amplifier power.
SUBWOOFER ENCLOSURE TYPES
Sound is created by the movement of the woofer
cone back and forth. If a woofer cone moves
forward creating a positive pressure wave, this
same motion creates a negative pressure at the
back of the woofer. If these two waves combine
due to the lack of a wall separating the front of the
speaker sound from the back, the output from
the woofer is effectively cancelled thus substan-
tially reducing the bass output of the speaker.
This wall is absolutely necessary and is referred
to as an acoustical „baffle". It can be accom-
plished using a box of some kind or simply the
rear package shelf of an automobile to isolate
the front and back waves of the speaker.
THIELE-SMALL PARAMETERS
Every woofer has its own electromechanical characteristics which are called THIELE-SMALL
parameters. The three most important parameters include RESONANT FREQUENCY („fs"- the
frequency where the speaker moves with the least mechanical resistance), TOTAL Q („Qts"- the
„magnification" of the cone movement at its resonant frequency), and VOLUMETRIC COMPLIANCE
(„Vas"- the equivalent volume of air that the woofer cone can displace for a given power input). Using
these parameters we can then calculate an optimum box volume for a particular woofer and reasonably
predict its frequency response.
COMMON ENCLOSURE TYPES
In the car audio world there are five types of subwoofer enclosures commonly used: INFINITE
BAFFLE, SEALED BOX (closed box), VENTED BOX (bass reflex), SINGLE-VENTED BANDPASS
(often incorrectly referred to as „5th" order), DUAL-VENTED BANDPASS (often incorrectly referred
to as „7th" order). No single design is superior because each has its own compromise in performance,
power handling and design complexity. The bandpass name implies a „built-in" acoustical response
which has a natural highpass response (@ 30 Hz for example) but also a lowpass response
suppressing high frequencies (e.g., > 80 Hz).
FRAME
FRONT PLATE
YOKE
VENT
VOICE COIL
MAGNET
SPIDER
SURROUND
CONE
DUST CAP
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