INTRODUCTION
A FEW WORDS ABOUT of the wooferOs cone. Larger boxesso proper design and a subsonic filter
POWER HANDLINGallow more excursion, providing moreare important. A vented bandpass box
low-frequency output than the samewill allow the least cone excursion,
The power-handling capability of any
woofer in a smaller box, for any inputprovided a subsonic filter is used.
woofer is related both to its ability to
power level. When placed in a sealed
dissipate heat and to the maximum Infinite-baffle, or Ofree air,� mounting
box much larger than the equivalent
excursion limits of its suspension.allows for greater excursion than does
compliance (Vas) of the subwoofer,
Once the speakerOs voice coil movesmounting subwoofers in enclosures.
it will perform as if it were in an
outside the magnetic gap, power The power handling of a subwoofer
infinite-baffle application, with the
can no longer be converted intomounted in an infinite baffle will be
attendant lower excursion-limited
motion and all the amplifierOs power reduced by nearly half its rated-power-
power handling.
is converted into heat in the voice coil. handling spec.
Voice-coil heating is the greatest Vented and bandpass enclosures allow
Voice-coil overheating and burning
detriment to speaker longevity, sothe least excursion for the amount
have only one cause � exposure to too
overexcursion should be avoided.of sound output (near and above the
much power for too long. An amplifier
Since excursion characteristics areresonance frequency of the enclosure).
driven into severe clipping or square-
very different for each type of The mass of air contained in the
wave can output much more average
enclosure, power handling will be port provides an acoustic load to the
power than the average power of a
different for each enclosure type.wooferOs cone at the tuning frequency,
clean sine wave of the same level.
and this added mass decreases
Sealed enclosures exert the most Audible distortion in the sound is a
excursion so that the subwooferOs
control over the motion of the sub-clear indication of amplifier clipping
motor is, essentially, coupled to the
woofer at the very lowest frequenciesand should serve as an indication that
air in the port. Vented boxes do not
because the air inside the box acts your speakers may be in danger of
provide adequate control below the
as a spring, opposing the motion being damaged.
frequency at which the box is tuned,
VARIABLE Q (PATENTPENDING)
Kappa Perfect VQ Series subwoofersfrequency or to shape the frequency
are unique because they provide response in the band of reproduced
variable Q. Q adjustments may frequencies. Qes and, consequently,
allow the subwoofer to be optimizedQts are the parameters that best
for a particular enclosure or applica-describe the behavior of a subwoofer
tion and may provide the user within the range of frequencies it is most
optimum performance for severaloften used to reproduce.
applications in a single enclosure.
dBSPLSPL vs Frequency Deg
�10 180
The frequency response of every
�15 150
speaker includes three distinct regions
LOW-FREQUENCY
characterized by flat amplitude (pass-�20ATTENUATIONFLAT AMPLITUDEHIGH- 120
FREQUENCY
band), high-frequency attenuationATTENUATION
�25 90
(stopband-high) or low-frequency
attenuation (stopband-low) (see �30 60
Figure 1). Midrange speakers and, to
�35 30
a lesser extent, tweeters are used to
�40 0
reproduce frequencies in the region
where they exhibit flat frequency�45�30
response. Subwoofers, on the other
�50�60
hand, are used in a region of low-
frequency attenuation, but those low�55�90
frequencies are what we want the
�60�120
subwoofer to reproduce. Subwoofer
�65�150
system design is almost entirely
an effort to extend the region of �70�180
30 Hz 501002005001K2K5K10K
flat response to the lowest possible
Figure 1. Frequency response of a speaker.
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