Band-pass enclosures often provide the most
output available from any amplifier and sub-
woofer combination at the expense
of sonic accuracy. If sheer SPL (sound-
pressure level) is what you desire most,
choose a band-pass enclosure. Band-pass-
enclosure design is very tricky, and the
aid of a computer and enclosure design soft-
ware is necessary. If you are an
experienced installer or have some wood-
working experience, you may wish to build
the enclosure described in the enclosure
design sheet included with this woofer.
Fortunately, there are many prefabricated
band-pass boxes available and they are
all optimized to extract the most output pos-
sible from any woofer. Band-pass
enclosures can be quite large and may
require a lot of space inside your vehicle.
POWER HANDLING
LIMITATIONS
The power handling capability of any woofer
is related to both its ability to dissipate heat
and the maximum excursion limits of its
cone. 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.This voice coil heating is the
largest detriment to speaker longevity, so
overexcursion should be avoided. Since
speaker-cone excursion is different for each
type of enclosure, power handling is differ-
ent for each enclosure.
Sealed enclosures exert the most control
over the motion of a subwoofer because the
air inside the box acts like a spring against
the motion of the woofer cone. Larger boxes
allow for more excursion, thus providing
more low-frequency output for the amount
of power used.When placed in a sealed box
much larger than the Vas of the subwoofer, it
will perform as if it were in an infinite-baf-
fle installation.
Vented and band-pass enclosures have the
lowest amount of excursion for the amount
of sound output.This is a result of port out-
put reinforcing the sound output from the
woofer. The mass of the air contained in the
port provides an acoustic load on the
woofer’s cone at the tuning frequency, and
this added mass decreases woofer-cone
excursion.Vented boxes do not provide
adequate woofer control when driven below
the tuned frequency (Fb), so proper design is
important.A vented band-pass box will have
the lowest overall cone excursion,
provided a subsonic filter is used.
• Voice coil overheating and burning due to
overexcursion are often caused by over-
driving an amplifier into “clipping.”A
severely clipped signal, or square wave,
contains nearly twice the power of a clean
sine wave at the same level. Bass that
sounds broken up and distorted at higher
volumes is usually indicative of an
amplifier that is clipping and being asked
to deliver power beyond its ability.
• Infinite-baffle or “free air” mounting
applications allow for greater cone
excursion than subwoofers mounted in
an enclosure. In order to compensate,
the power handling of the subwoofer
will likely be half its rated power in this
application.
• Study the excursion curves on the enclosed
Reference Series data sheet
and note the differences for different
enclosure applications.The type and
size of box used will produce different
excursion demands on the enclosed
subwoofer and, consequently, different lev-
els of power handling.As long as the rec-
ommended enclosure parameters are used,
the subwoofer will perform properly in its
enclosed environment. However, any
design deviation may result in less than
optimum performance, and may also
subject the subwoofer to overexcursion
(i.e., the voice coil leaving the gap), which
can eventually damage the speaker. For
additional help with this issue, please
contact your authorized Infinity dealer.
38545_Ref_Inf_woofer_860W_OM 22/08/08 9:29 Side 4
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