•
Voice-coil overheating and burning due
to overexcursion are often caused by over-
driving an amplifier 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 amplifier
is clipping (i.e., being asked to deliver
power beyond its rated power).
•
Infinite baffle or “free air” mounting
applications allow for greater cone excur-
sion than subwoofers mounted in an enclo-
sure. In order to compensate, recognize
that the power-rating value of the sub-
woofer 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, conse-
quently, different levels of power handling.
As long as recommended 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 sub-
ject the subwoofer to overexcursion (i.e.,
where the voice coil leaves the gap) that
can eventually damage the speaker. For
additional help with this issue, please con-
tact your authorized Infinity dealer.
S
PECIFICATIONS
Reference 811w
Configuration:
8" woofer
Nominal Impedance:
4 ohms
Power Handling:
200W
Sensitivity @ 2.83V/1m:
91dB
Frequency Response:
50Hz – 1kHz
Mounting Depth:
4-3/8" (112mm)
Cut-out Diameter:
7-1/8" (181mm)
Reference 1011w
Configuration:
10" subwoofer
Nominal Impedance:
4 ohms
Power Handling:
225W
Sensitivity @ 2.83V/1m:
92dB
Frequency Response:
40Hz – 500Hz
Mounting Depth:
4-5/8" (118mm)
Cut-out Diameter:
9-1/8" (232mm)
Reference 1211w
Configuration:
12" subwoofer
Nominal Impedance:
4 ohms
Power Handling:
250W
Sensitivity @ 2.83V/1m:
93dB
Frequency Response:
30Hz – 500Hz
Mounting Depth:
5" (127mm)
Cut-out Diameter:
12-1/8" (308mm)
P
OWER
-H
ANDLING
L
IMITATIONS
The power-handling capability of any
woofer is related to both its ability to dissi-
pate heat and the maximum excursion lim-
its 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 longevi-
ty, so overexcursion should be avoided.
Since speaker-cone excursion is different
for each type of enclosure, power handling
is different 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 larger than the Vas of the
subwoofer, it will perform as if it were in
an infinite baffle installation.
Vented enclosures have the lowest
amount of excursion for the amount of
sound output. This is a result of port output
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 port tuning range, so proper
design is important. A vented bandpass box
will have the lowest overall cone excursion,
provided a subsonic filter is used.
Reference 811w,1011w,1211w OM 7/14/98 10:31 AM Page 3
