Blaupunkt PC105, Instruction Manual

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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 “5th” order), and DUAL-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
name implies a “built-in” acoustical response which has a natural response 30
Hz for example) but also a response suppressing high frequencies (e.g., 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. Advantaaes include simple
installation and adequate performance for most systems.
Disadvantaaes include poor power handling capability and
substandard transient response.
SEALED boxes offer one of the best compromises in
power handling and performance. Because of the “air
spring” provided by the box the advantaaes include simple
box construction, high power handling, excellent transient
response, and smooth low frequency roll-off.
Disadvantaaes 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. Advantaaes
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. Disadvantaaes 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 boxes are relatively new
(about 5 years in the car) but offer some advantages of
both the sealed and vented designs. Advantaaes include
reasonable efficiency, small box volumes, good transient
response, extended low frequency performance, and can
be used with very high power amplifiers. Disadvantaaes
include slightly lower efficiency compared to a vented box
and increased complexity in box design and construction.
DUAL-VENTED boxes vent the sound from the
front and back of the woofer through individually tuned
enclosure on the front and rear of the woofer. The
of this design is its high efficiency over a
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.