JBL GT1200 - Manual (Page 5)

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 con-
verted 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 (driving the
speaker past Xmax) should be
avoided. Since speaker-cone
excursion is different for each
type of enclosure, power handling
is different for each enclosure.
• Voice-coil overheating and burn-
ing due to over-excursion is often
caused by overdriving an ampli-
fier into “clipping.” A severely
clipped signal, or squarewave,
contains nearly twice the power
of a clean sine wave at the same
level. Bass that sounds broken up
and distorted at higher volumes
usually indicates that the ampli-
fier is being asked to deliver
power beyond its ability.
• Infinite baffle or “free air”
mounting applications allow for
greater cone excursion than sub-
woofers mounted in an enclosure.
In order to compensate, recognize
that the power-rating value of the
subwoofer will likely be half its
rated power in this application.
• Study the excursion curves on
the enclosed GT Series data
sheet and note the differences
for different enclosure applica-
tions. The type and size of box
used will produce different excur-
sion demands on the enclosed
subwoofer and, consequently,
different levels of power han-
dling. As long as recommended
parameters are used, the sub-
woofer 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 over-
excursion that can eventually
damage the speaker. For
additional help with this issue,
please contact your authorized
JBL dealer.
GTSubwoofers Owner's Manual 7/14/98 2:19 PM Page 5