INTRODUCTION
Kappa Perfect VQ Series subwoofers 
are unique because they provide 
variable Q. Q adjustments may 
allow the subwoofer to be optimized 
for a particular enclosure or application and may provide the user with 
optimum performance for several 
applications in a single enclosure.
The frequency response of every 
speaker includes three distinct regions 
characterized by flat amplitude (passband), high-frequency attenuation 
(stopband-high) or low-frequency 
attenuation (stopband-low) (see 
Figure 1). Midrange speakers and, to 
a lesser extent, tweeters are used to 
reproduce frequencies in the region 
where they exhibit flat frequency 
response. Subwoofers, on the other 
hand, are used in a region of lowfrequency attenuation, but those low 
frequencies are what we want the 
subwoofer to reproduce. Subwoofer 
system design is almost entirely 
an effort to extend the region of 
flat response to the lowest possible 
frequency or to shape the frequency 
response in the band of reproduced 
frequencies. Qes and, consequently, 
Qts are the parameters that best 
describe the behavior of a subwoofer 
in the range of frequencies it is most 
often used to reproduce.
2
A FEW WORDS ABOUT 
POWER HANDLING
The power-handling capability of any 
woofer is related both to its ability to 
dissipate heat and to the maximum 
excursion limits of its suspension. 
Once the speaker’s voice coil moves 
outside the magnetic gap, power 
can no longer be converted into 
motion and all the amplifier’s power 
is converted into heat in the voice coil. 
Voice-coil heating is the greatest 
detriment to speaker longevity, so 
overexcursion should be avoided. 
Since excursion characteristics are 
very different for each type of 
enclosure, power handling will be 
different for each enclosure type.
Sealed enclosures exert the most 
control over the motion of the subwoofer at the very lowest frequencies 
because the air inside the box acts 
as a spring, opposing the motion 
of the woofer’s cone. Larger boxes 
allow more excursion, providing more 
low-frequency output than the same 
woofer in a smaller box, for any input 
power level. When placed in a sealed 
box much larger than the equivalent 
compliance (Vas) of the subwoofer, 
it will perform as if it were in an 
infinite-baffle application, with the 
attendant lower excursion-limited 
power handling.
Vented and bandpass enclosures allow 
the least excursion for the amount 
of sound output (near and above the 
resonance frequency of the enclosure). 
The mass of air contained in the 
port provides an acoustic load to the 
woofer’s cone at the tuning frequency, 
and this added mass decreases 
excursion so that the subwoofer’s 
motor is, essentially, coupled to the 
air in the port. Vented boxes do not 
provide adequate control below the 
frequency at which the box is tuned, 
so proper design and a subsonic filter 
are important. A vented bandpass box 
will allow the least cone excursion, 
provided a subsonic filter is used.
Infinite-baffle, or “free air,” mounting 
allows for greater excursion than does 
mounting subwoofers in enclosures. 
The power handling of a subwoofer 
mounted in an infinite baffle will be 
reduced by nearly half its rated-powerhandling spec.
Voice-coil overheating and burning 
have only one cause – exposure to too 
much power for too long. An amplifier 
driven into severe clipping or squarewave can output much more average 
power than the average power of a 
clean sine wave of the same level. 
Audible distortion in the sound is a 
clear indication of amplifier clipping 
and should serve as an indication that 
your speakers may be in danger of 
being damaged.
VARIABLE Q (PATENT PENDING)