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COMMON ENCLOSURE TYPES
In the car audio world there are 5 types of subwoofer enclosures commonly used; INFINITE
BAFFLE, SEALED BOX (closed box), VENTED BOX (bass reflex), SINGLE-VENTED
(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).
INFINITE BAFFLE designs simply use the trunk of the car
for its acoustical enclosure and the rear deck to isolate the
front and rear sound paths. Advantages include simple
installation and adequate performance for most systems.
Disadvantanes include poor power handling capability and
substandard transient response.
ED boxes offer one of the best compromises in
handling and performance. Because of the "air
box construction, high power handling, excellent transient
response, and smooth low frequency roll-off.
Disadvantaqes include only moderate efficiencies at low
frequencies and the need for large box volumes.
VENTED boxes extend the low frequency response below
that of the sealed box by using a port tube. Advantaqes
include extended low frequency response, lower distortion
due to smaller cone movements in its passband, good
efficiency, good transient response, moderate size boxes,
and high power capacity. Disadvantages include increased
complexity in box design and possible woofer damage due
to over-excursion of the woofer cone below the cut-off
frequency of the vented box.
SINGLE-VENTED BANDPASS boxes are relatively new
(about 5 years in the car) but offer some advantages of
both the sealed and vented designs. Advantaqes include
reasonable efficiency, small box volumes, good transient
response, extended low frequency performance, and can
be used with very high power amplifiers. Disadvantaqes
include slightly lower efficiency compared to a vented box
and increased complexity in box design and construction.
DUAL-VENTED BANDPASS boxes vent the sound from the
front and back of the woofer through individually tuned
osure on the front and rear of the woofer. The
narrow frequency band. Disadvantaaes include complex
design and construction, large box volumes, poor transient
response, and susceptibilities to cone over-excursions
(damage) for sound outside its primary frequency band.
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