VARIABLE Q (CONTINUED)INSTALLINGAND REMOVINGTHE INSERTS
Kappa Perfect VQ woofers are designedthe LowQ insert installed; with the MidQYour Kappa Perfect VQ subwoofer is
to provide optimum system Q and insert installed; and without an insertshipped from the factory without an
frequency response in infinite-baffleinstalled (HighQ). The difference in theinsert installed. After determining
applications or in very large enclosuresperformance of the woofer with its which application and enclosure is
with no insert installed in the polepiece.various adjustments is increased outputmost suitable for your system, install
The smaller of the two inserts is at and slightly above system resonancethe appropriate insert in the wooferOs
intended to be used with woofers(Fc) with increasing Q, but reduced polepiece by aligning the insert with
mounted in medium-sized sealed boxesoutput at the lowest reproduced the hole in the wooferOs polepiece and
and vented boxes. The largest insert isfrequencies. The reduced motor forcesimply dropping the insert into place
intended to provide optimum Q for verysupplied by the lower-Q designs results(see Figure 5).
small sealed or vented boxes or for usein reduced sensitivity (SPL 2.83V/1m),
Figure 5. Installing the insert.
with woofers used in SPL competition,but the effects of that reduced
where the enclosure is designed to sensitivity are greatest above 100Hz.
provide the highest output possible Subwoofers in cars are typically used
at a single frequency.for frequencies below 100Hz, so the
reduced sensitivity is inconsequential.
While it may seem that the most
The difference in behavior for vented
forceful motor will provide the best
and bandpass enclosures is similar, but
performance in all applications, in
the enclosure design is more complex
reality that is not the case. When a
and should be given special attention.
woofer is mounted in an enclosure, the
resonance of the woofer becomes theAlthough Kappa Perfect VQ subwoofers
resonance of the combination of the airwere designed with specific uses for the
inside the box and the woofer, and Qtsinserts in mind, there are many different
(speaker Q) becomes Qtc (system Q).enclosure and insert combinations
For example, Figure 4 shows thethat may suit your taste. The intended To remove the insert, squeeze the
response of a Kappa Perfect VQ combinations are highlighted as insert tool to compress the area
subwoofer in a sealed box optimized forOoptimum� on the charts in the sectionbetween the two tabs, insert the end
use with the MidQ insert. Pictured ontitled OChoosing an Application andof the tool into the vent in the center
the graph are the responses of theEnclosure�; several other applicationsof the insert and align the two tabs
woofer and enclosure combination withare also included.with the two small holes inside the
vent. The tabs should lock into the two
holes. Pull firmly on the tool to
dBEffects of Variable Q
95
remove the insert (See Figure 6).
SYSTEM RESONANCE (Fc)
REDUCED SENSITIVITY
90Figure 6. Removing the insert.
85
Step 1
TYPICAL LOW-PASS-
CROSSOVER FREQUENCY
80
Step 2
75
70
65
60
55
20Frequency50100Hz2005001K2K
lowQ
Figure 4. Effects of Variable Q.
midQ
highQNote: Magnetic force holds the insert in
place. DonOt be afraid to pull hard on the
insert to remove it.
4 |
ACEC
