<s>
A	O
subwoofer	B-Application
(	O
or	O
sub	O
)	O
is	O
a	O
loudspeaker	O
designed	O
to	O
reproduce	O
low-pitched	O
audio	O
frequencies	O
known	O
as	O
bass	O
and	O
sub-bass	O
,	O
lower	O
in	O
frequency	O
than	O
those	O
which	O
can	O
be	O
(	O
optimally	O
)	O
generated	O
by	O
a	O
woofer	B-Device
.	O
</s>
<s>
The	O
typical	O
frequency	O
range	O
for	O
a	O
subwoofer	B-Application
is	O
about	O
20	O
–	O
200Hz	O
for	O
consumer	O
products	O
,	O
below	O
100Hz	O
for	O
professional	O
live	O
sound	O
,	O
and	O
below	O
80Hz	O
in	O
THX-certified	O
systems	O
.	O
</s>
<s>
Subwoofers	B-Application
are	O
never	O
used	O
alone	O
,	O
as	O
they	O
are	O
intended	O
to	O
augment	O
the	O
low-frequency	O
range	O
of	O
loudspeakers	O
that	O
cover	O
the	O
higher	O
frequency	O
bands	O
.	O
</s>
<s>
While	O
the	O
term	O
"	O
subwoofer	B-Application
"	O
technically	O
only	O
refers	O
to	O
the	O
speaker	B-Device
driver	I-Device
,	O
in	O
common	O
parlance	O
,	O
the	O
term	O
often	O
refers	O
to	O
a	O
subwoofer	B-Application
driver	B-Device
mounted	O
in	O
a	O
speaker	B-Device
enclosure	I-Device
(	O
cabinet	O
)	O
,	O
often	O
with	O
a	O
built-in	O
amplifier	O
.	O
</s>
<s>
Subwoofers	B-Application
are	O
made	O
up	O
of	O
one	O
or	O
more	O
woofers	B-Device
mounted	O
in	O
a	O
loudspeaker	B-Device
enclosure	I-Device
—	O
often	O
made	O
of	O
wood	O
—	O
capable	O
of	O
withstanding	O
air	O
pressure	O
while	O
resisting	O
deformation	O
.	O
</s>
<s>
Subwoofer	B-Device
enclosures	I-Device
come	O
in	O
a	O
variety	O
of	O
designs	O
,	O
including	O
bass	O
reflex	O
(	O
with	O
a	O
port	O
or	O
vent	O
)	O
,	O
using	O
a	O
subwoofer	B-Application
and	O
one	O
or	O
more	O
passive	B-Architecture
radiator	I-Architecture
speakers	I-Architecture
in	O
the	O
enclosure	B-Device
,	O
acoustic	B-Architecture
suspension	I-Architecture
(	O
sealed	O
enclosure	B-Device
)	O
,	O
infinite	O
baffle	O
,	O
horn-loaded	B-Device
,	O
tapped	O
horn	O
,	O
transmission	O
line	O
,	O
bandpass	O
or	O
isobaric	B-Device
designs	O
.	O
</s>
<s>
Passive	O
subwoofers	B-Application
have	O
a	O
subwoofer	B-Application
driver	B-Device
and	O
enclosure	B-Device
and	O
they	O
are	O
powered	O
by	O
an	O
external	O
amplifier	O
.	O
</s>
<s>
Active	O
subwoofers	B-Application
include	O
a	O
built-in	O
amplifier	O
.	O
</s>
<s>
The	O
first	O
home	O
audio	O
subwoofers	B-Application
were	O
developed	O
in	O
the	O
1960s	O
to	O
add	O
bass	O
response	O
to	O
home	O
stereo	O
systems	O
.	O
</s>
<s>
Subwoofers	B-Application
came	O
into	O
greater	O
popular	O
consciousness	O
in	O
the	O
1970s	O
with	O
the	O
introduction	O
of	O
Sensurround	O
in	O
movies	O
such	O
as	O
Earthquake	O
,	O
which	O
produced	O
loud	O
low-frequency	O
sounds	O
through	O
large	O
subwoofers	B-Application
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
the	O
compact	B-Device
cassette	I-Device
and	O
the	O
compact	O
disc	O
in	O
the	O
1980s	O
,	O
the	O
reproduction	O
of	O
deep	O
and	O
loud	O
bass	O
was	O
no	O
longer	O
limited	O
by	O
the	O
ability	O
of	O
a	O
phonograph	O
record	O
stylus	O
to	O
track	O
a	O
groove	O
,	O
and	O
producers	O
could	O
add	O
more	O
low-frequency	O
content	O
to	O
recordings	O
.	O
</s>
<s>
As	O
well	O
,	O
during	O
the	O
1990s	O
,	O
DVDs	O
were	O
increasingly	O
recorded	O
with	O
"	O
surround	O
sound	O
"	O
processes	O
that	O
included	O
a	O
low-frequency	O
effects	O
(	O
LFE	O
)	O
channel	O
,	O
which	O
could	O
be	O
heard	O
using	O
the	O
subwoofer	B-Application
in	O
home	O
theater	O
systems	O
.	O
</s>
<s>
During	O
the	O
1990s	O
,	O
subwoofers	B-Application
also	O
became	O
increasingly	O
popular	O
in	O
home	O
stereo	O
systems	O
,	O
custom	O
car	O
audio	O
installations	O
,	O
and	O
in	O
PA	O
systems	O
.	O
</s>
<s>
By	O
the	O
2000s	O
,	O
subwoofers	B-Application
became	O
almost	O
universal	O
in	O
sound	O
reinforcement	O
systems	O
in	O
nightclubs	O
and	O
concert	O
venues	O
.	O
</s>
<s>
In	O
1933	O
,	O
the	O
head	O
of	O
MGM	O
's	O
sound	O
department	O
,	O
Douglas	O
Shearer	O
,	O
worked	O
with	O
John	O
Hilliard	O
and	O
James	O
B	O
.	O
Lansing	O
(	O
who	O
would	O
later	O
found	O
Altec	O
Lansing	O
in	O
1941	O
and	O
JBL	O
in	O
1946	O
)	O
to	O
develop	O
a	O
new	O
speaker	O
system	O
that	O
used	O
a	O
two-way	O
enclosure	B-Device
with	O
a	O
W-shaped	O
bass	O
horn	O
that	O
could	O
go	O
as	O
low	O
as	O
40Hz	O
.	O
</s>
<s>
In	O
the	O
late	O
1930s	O
,	O
Lansing	O
created	O
a	O
smaller	O
two-way	O
speaker	O
with	O
a	O
woofer	B-Device
in	O
a	O
vented	O
enclosure	B-Device
,	O
which	O
he	O
called	O
the	O
Iconic	O
system	O
;	O
it	O
was	O
used	O
as	O
a	O
studio	O
monitor	O
and	O
in	O
high-end	O
home	O
hi-fi	O
set-ups	O
.	O
</s>
<s>
During	O
the	O
1940s	O
swing	O
era	O
,	O
to	O
get	O
deeper	O
bass	O
,	O
"	O
pipelike	O
opening[s]	O
 "	O
were	O
cut	O
into	O
speaker	B-Device
enclosures	I-Device
,	O
creating	O
bass	O
reflex	O
enclosures	O
,	O
as	O
it	O
was	O
found	O
that	O
even	O
a	O
fairly	O
inexpensive	O
speaker	B-Device
enclosure	I-Device
,	O
once	O
modified	O
in	O
this	O
way	O
,	O
could	O
"	O
transmit	O
the	O
driving	O
power	O
of	O
a	O
heavy	O
...	O
drumbeat	O
—	O
and	O
sometimes	O
not	O
much	O
else	O
—	O
to	O
a	O
crowded	O
dancefloor.	O
"	O
</s>
<s>
Prior	O
to	O
the	O
development	O
of	O
the	O
first	O
subwoofers	B-Application
,	O
woofers	B-Device
were	O
used	O
to	O
reproduce	O
bass	O
frequencies	O
,	O
usually	O
with	O
a	O
crossover	B-Algorithm
point	O
set	O
at	O
500Hz	O
and	O
a	O
loudspeaker	O
in	O
an	O
infinite	O
baffle	O
or	O
in	O
professional	O
sound	O
applications	O
,	O
a	O
"	O
hybrid	O
horn-loaded	B-Device
"	O
bass	O
reflex	O
enclosure	B-Device
(	O
such	O
as	O
the	O
15-inch	O
Altec	O
Lansing	O
A-7	O
enclosure	B-Device
nicknamed	O
the	O
"	O
Voice	O
of	O
the	O
Theater	O
"	O
,	O
which	O
was	O
introduced	O
in	O
1946	O
)	O
.	O
</s>
<s>
In	O
September	O
1964	O
,	O
Raymon	O
Dones	O
,	O
of	O
El	O
Cerrito	O
,	O
California	O
,	O
received	O
the	O
first	O
patent	O
for	O
a	O
subwoofer	B-Application
specifically	O
designed	O
to	O
augment	O
omnidirectionally	O
the	O
low	O
frequency	O
range	O
of	O
modern	O
stereo	O
systems	O
(	O
US	O
patent	O
3150739	O
)	O
.	O
</s>
<s>
The	O
Octavium	O
speaker	O
and	O
Dones	O
's	O
subwoofer	B-Application
technology	O
were	O
also	O
utilized	O
,	O
in	O
a	O
few	O
select	O
theaters	O
,	O
to	O
reproduce	O
low	O
pitch	O
frequencies	O
for	O
the	O
1974	O
blockbuster	O
movie	O
Earthquake	O
.	O
</s>
<s>
Another	O
early	O
subwoofer	B-Device
enclosure	I-Device
made	O
for	O
home	O
and	O
studio	O
use	O
was	O
the	O
separate	O
bass	O
speaker	O
for	O
the	O
Servo	O
Statik	O
1	O
by	O
New	O
Technology	O
Enterprises	O
.	O
</s>
<s>
Designed	O
as	O
a	O
prototype	O
in	O
1966	O
by	O
physicist	O
Arnold	O
Nudell	O
and	O
airline	O
pilot	O
Cary	O
Christie	O
in	O
Nudell	O
's	O
garage	O
,	O
it	O
used	O
a	O
second	O
winding	O
around	O
a	O
custom	O
Cerwin-Vega	O
18-inch	O
(	O
45cm	O
)	O
driver	B-Device
to	O
provide	O
servo	O
control	O
information	O
to	O
the	O
amplifier	O
,	O
and	O
it	O
was	O
offered	O
for	O
sale	O
at	O
$1795	O
,	O
some	O
40%	O
more	O
expensive	O
than	O
any	O
other	O
complete	O
loudspeaker	O
listed	O
at	O
Stereo	O
Review	O
.	O
</s>
<s>
The	O
subwoofer	B-Application
was	O
reviewed	O
positively	O
in	O
Stereophile	O
magazine	O
's	O
winter	O
1968	O
issue	O
as	O
the	O
SS-1	O
by	O
Infinity	O
.	O
</s>
<s>
Another	O
of	O
the	O
early	O
subwoofers	B-Application
was	O
developed	O
during	O
the	O
late	O
1960s	O
by	O
Ken	O
Kreisel	O
,	O
the	O
former	O
president	O
of	O
the	O
Miller	O
&	O
Kreisel	O
Sound	O
Corporation	O
in	O
Los	O
Angeles	O
.	O
</s>
<s>
When	O
Kreisel	O
's	O
business	O
partner	O
,	O
Jonas	O
Miller	O
,	O
who	O
owned	O
a	O
high-end	O
audio	O
store	O
in	O
Los	O
Angeles	O
,	O
told	O
Kreisel	O
that	O
some	O
purchasers	O
of	O
the	O
store	O
's	O
high-end	O
electrostatic	B-Device
speakers	I-Device
had	O
complained	O
about	O
a	O
lack	O
of	O
bass	O
response	O
in	O
the	O
electrostatics	O
,	O
Kreisel	O
designed	O
a	O
powered	O
woofer	B-Device
that	O
would	O
reproduce	O
only	O
those	O
frequencies	O
that	O
were	O
too	O
low	O
for	O
the	O
electrostatic	B-Device
speakers	I-Device
to	O
convey	O
.	O
</s>
<s>
Infinity	O
's	O
full	O
range	O
electrostatic	B-Device
speaker	I-Device
system	O
that	O
was	O
developed	O
during	O
the	O
1960s	O
also	O
used	O
a	O
woofer	B-Device
to	O
cover	O
the	O
lower	O
frequency	O
range	O
that	O
its	O
electrostatic	O
arrays	O
did	O
not	O
handle	O
adequately	O
.	O
</s>
<s>
The	O
first	O
use	O
of	O
a	O
subwoofer	B-Application
in	O
a	O
recording	O
session	O
was	O
in	O
1973	O
for	O
mixing	O
the	O
Steely	O
Dan	O
album	O
Pretzel	O
Logic	O
,	O
when	O
recording	O
engineer	O
Roger	O
Nichols	O
arranged	O
for	O
Kreisel	O
to	O
bring	O
a	O
prototype	O
of	O
his	O
subwoofer	B-Application
to	O
Village	O
Recorders	O
.	O
</s>
<s>
Further	O
design	O
modifications	O
were	O
made	O
by	O
Kreisel	O
over	O
the	O
next	O
ten	O
years	O
,	O
and	O
in	O
the	O
1970s	O
and	O
1980s	O
by	O
engineer	O
John	O
P	O
.	O
D'Arcy	O
;	O
record	O
producer	O
Daniel	O
Levitin	O
served	O
as	O
a	O
consultant	O
and	O
"	O
golden	O
ears	O
"	O
for	O
the	O
design	O
of	O
the	O
crossover	B-Algorithm
network	I-Algorithm
(	O
used	O
to	O
partition	O
the	O
frequency	O
spectrum	O
so	O
that	O
the	O
subwoofer	B-Application
would	O
not	O
attempt	O
to	O
reproduce	O
frequencies	O
too	O
high	O
for	O
its	O
effective	O
range	O
,	O
and	O
so	O
that	O
the	O
main	O
speakers	O
would	O
not	O
need	O
to	O
handle	O
frequencies	O
too	O
low	O
for	O
their	O
effective	O
range	O
)	O
.	O
</s>
<s>
In	O
1976	O
,	O
Kreisel	O
created	O
the	O
first	O
satellite	O
speakers	O
and	O
subwoofer	B-Application
system	O
,	O
named	O
"	O
David	O
and	O
Goliath	O
"	O
.	O
</s>
<s>
Subwoofers	B-Application
received	O
a	O
great	O
deal	O
of	O
publicity	O
in	O
1974	O
with	O
the	O
movie	O
Earthquake	O
,	O
which	O
was	O
released	O
in	O
Sensurround	O
.	O
</s>
<s>
Initially	O
installed	O
in	O
17	O
U.S.	O
theaters	O
,	O
the	O
Cerwin-Vega	O
"	O
Sensurround	O
"	O
system	O
used	O
large	O
subwoofers	B-Application
that	O
were	O
driven	O
by	O
racks	O
of	O
500	O
watt	O
amplifiers	O
,	O
triggered	O
by	O
control	O
tones	O
printed	O
on	O
one	O
of	O
the	O
audio	O
tracks	O
on	O
the	O
film	O
.	O
</s>
<s>
Four	O
of	O
the	O
subwoofers	B-Application
were	O
positioned	O
in	O
front	O
of	O
the	O
audience	O
under	O
(	O
or	O
behind	O
)	O
the	O
film	O
screen	O
and	O
two	O
more	O
were	O
placed	O
together	O
at	O
the	O
rear	O
of	O
the	O
audience	O
on	O
a	O
platform	O
.	O
</s>
<s>
While	O
some	O
hi-fi	O
aficionados	O
had	O
solved	O
the	O
problem	O
by	O
using	O
other	O
playback	O
sources	O
,	O
such	O
as	O
reel-to-reel	O
tape	O
players	O
which	O
were	O
capable	O
of	O
delivering	O
accurate	O
,	O
naturally	O
deep	O
bass	O
from	O
acoustic	O
sources	O
,	O
or	O
synthetic	O
bass	O
not	O
found	O
in	O
nature	O
,	O
with	O
the	O
popular	O
introduction	O
of	O
the	O
compact	B-Device
cassette	I-Device
in	O
the	O
late	O
1960s	O
it	O
became	O
possible	O
to	O
add	O
more	O
low	O
frequency	O
content	O
to	O
recordings	O
.	O
</s>
<s>
By	O
the	O
mid-1970s	O
,	O
12-inch	O
vinyl	O
singles	O
,	O
which	O
allowed	O
for	O
"	O
more	O
bass	O
volume	O
"	O
,	O
were	O
used	O
to	O
record	O
disco	O
,	O
reggae	O
,	O
dub	O
and	O
hip-hop	O
tracks	O
;	O
dance	O
club	O
DJs	O
played	O
these	O
records	O
in	O
clubs	O
with	O
subwoofers	B-Application
to	O
achieve	O
"	O
physical	O
and	O
emotional	O
"	O
reactions	O
from	O
dancers	O
.	O
</s>
<s>
In	O
the	O
early	O
1970s	O
,	O
David	O
Mancuso	O
hired	O
sound	O
engineer	O
Alex	O
Rosner	O
to	O
design	O
additional	O
subwoofers	B-Application
for	O
his	O
disco	O
dance	O
events	O
,	O
along	O
with	O
"	O
tweeter	B-Device
arrays	O
"	O
to	O
"	O
boost	O
the	O
treble	O
and	O
bass	O
at	O
opportune	O
moments	O
"	O
at	O
his	O
private	O
,	O
underground	O
parties	O
at	O
The	O
Loft	O
.	O
</s>
<s>
The	O
demand	O
for	O
sub-bass	O
sound	O
reinforcement	O
in	O
the	O
1970s	O
was	O
driven	O
by	O
the	O
important	O
role	O
of	O
"	O
powerful	O
bass	O
drum	O
"	O
in	O
disco	O
,	O
as	O
compared	O
with	O
rock	O
and	O
pop	O
;	O
to	O
provide	O
this	O
deeper	O
range	O
,	O
a	O
third	O
crossover	B-Algorithm
point	O
from	O
40	O
to	O
120Hz	O
(	O
centering	O
on	O
80Hz	O
)	O
was	O
added	O
.	O
</s>
<s>
By	O
the	O
end	O
of	O
the	O
1970s	O
,	O
subwoofers	B-Application
were	O
used	O
in	O
dance	O
venue	O
sound	O
systems	O
to	O
enable	O
the	O
playing	O
of	O
"[b]ass-heavy	O
dance	O
music	O
"	O
that	O
we	O
"	O
do	O
not	O
'	O
hear	O
 '	O
with	O
our	O
ears	O
but	O
with	O
our	O
entire	O
body	O
"	O
.	O
</s>
<s>
By	O
the	O
later	O
1970s	O
,	O
disco	O
club	O
sound	O
engineers	O
were	O
using	O
the	O
same	O
large	O
Cerwin-Vega	O
Sensurround-style	O
folded	B-Device
horn	I-Device
subwoofers	B-Application
that	O
were	O
used	O
in	O
Earthquake	O
and	O
similar	O
movies	O
in	O
dance	O
club	O
system	O
installations	O
.	O
</s>
<s>
In	O
the	O
early	O
1980s	O
,	O
Long	O
designed	O
a	O
sound	O
system	O
for	O
the	O
Warehouse	O
dance	O
club	O
,	O
with	O
"	O
huge	O
stacks	O
of	O
subwoofers	B-Application
"	O
which	O
created	O
"	O
deep	O
and	O
intense	O
"	O
bass	O
frequencies	O
that	O
"pound[ed]	O
through	O
your	O
system	O
"	O
and	O
"	O
entire	O
body	O
"	O
,	O
enabling	O
clubgoers	O
to	O
"	O
viscerally	O
experience	O
"	O
the	O
DJs	O
 '	O
house	O
music	O
mixes	O
.	O
</s>
<s>
In	O
Jamaica	O
in	O
the	O
1970s	O
and	O
1980s	O
,	O
sound	O
engineers	O
for	O
reggae	O
sound	O
systems	O
began	O
creating	O
"	O
heavily	O
customized	O
"	O
subwoofer	B-Device
enclosures	I-Device
by	O
adding	O
foam	O
and	O
tuning	O
the	O
cabinets	O
to	O
achieve	O
"	O
rich	O
and	O
articulate	O
speaker	O
output	O
below	O
100	O
Hz	O
"	O
.	O
</s>
<s>
The	O
sound	O
engineers	O
for	O
Stone	O
Love	O
Movement	O
(	O
a	O
sound	O
system	O
crew	O
)	O
,	O
for	O
example	O
,	O
modified	O
folded	B-Device
horn	I-Device
subwoofers	B-Application
they	O
imported	O
from	O
the	O
US	O
to	O
get	O
more	O
of	O
a	O
bass	O
reflex	O
sound	O
that	O
suited	O
local	O
tone	O
preferences	O
for	O
dancehall	O
audiences	O
,	O
as	O
the	O
unmodified	O
folded	B-Device
horn	I-Device
was	O
found	O
to	O
be	O
"	O
too	O
aggressive	O
"	O
sounding	O
and	O
"	O
not	O
deep	O
enough	O
for	O
Jamaican	O
listeners	O
"	O
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
the	O
Bose	O
Acoustimass	O
AM-5	O
became	O
a	O
popular	O
subwoofer	B-Application
and	O
small	O
high-range	O
satellite	O
speaker	O
system	O
for	O
home	O
listening	O
.	O
</s>
<s>
The	O
success	O
of	O
the	O
AM-5	O
led	O
to	O
other	O
makers	O
launching	O
subwoofer-satellite	O
speaker	O
systems	O
,	O
including	O
Boston	O
Acoustics	O
Sub	O
Sat	O
6	O
and	O
7	O
,	O
and	O
the	O
Cambridge	O
SoundWorks	O
Ensemble	O
systems	O
(	O
by	O
Kloss	O
)	O
.	O
</s>
<s>
Claims	O
that	O
these	O
sub-satellite	O
systems	O
showed	O
manufacturers	O
and	O
designers	O
that	O
home	O
theater	O
systems	O
with	O
a	O
hidden	O
subwoofer	B-Application
could	O
be	O
"	O
feasible	O
and	O
workable	O
in	O
a	O
normal	O
living	O
room	O
"	O
for	O
mainstream	O
consumers	O
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
Origin	O
Acoustics	O
developed	O
the	O
first	O
residential	O
in-wall	O
subwoofer	B-Application
named	O
Composer	O
.	O
</s>
<s>
It	O
used	O
an	O
aluminum	O
10-inch	O
(	O
25.4cm	O
)	O
driver	B-Device
and	O
a	O
foam-lined	O
enclosure	B-Device
designed	O
to	O
be	O
mounted	O
directly	O
into	O
wall	O
studs	O
during	O
the	O
construction	O
of	O
a	O
new	O
home	O
.	O
</s>
<s>
An	O
example	O
of	O
1990s	O
subwoofer	B-Application
use	O
in	O
sound	O
reinforcement	O
is	O
the	O
Ministry	O
of	O
Sound	O
dance	O
club	O
which	O
opened	O
in	O
1991	O
in	O
London	O
.	O
</s>
<s>
The	O
club	O
spent	O
about	O
£	O
500,000	O
on	O
a	O
sound	O
system	O
that	O
used	O
Martin	O
Audio	O
components	O
in	O
custom-built	O
cabinets	O
,	O
including	O
twelve	O
21	O
"	O
9,500	O
watt	O
active	O
subwoofers	B-Application
,	O
twelve	O
18-inch	O
subwoofers	B-Application
and	O
twelve	O
Martin	O
Audio	O
W8C	O
mid-high	O
speakers	O
.	O
</s>
<s>
Home	O
subwoofers	B-Application
grew	O
in	O
popularity	O
,	O
as	O
they	O
were	O
easy	O
to	O
add	O
to	O
existing	O
multimedia	O
speaker	O
setups	O
and	O
they	O
were	O
easy	O
to	O
position	O
or	O
hide	O
.	O
</s>
<s>
In	O
2018	O
,	O
some	O
electronic	O
dance	O
music	O
(	O
EDM	O
)	O
sound	O
systems	O
for	O
venues	O
that	O
play	O
hardcore	O
bass	O
have	O
multiple	O
subwoofer	B-Application
arrays	O
to	O
deal	O
with	O
mid-bass	O
(	O
80	O
–	O
150Hz	O
)	O
,	O
bass	O
(	O
40	O
–	O
80Hz	O
)	O
,	O
and	O
"	O
infra-bass	O
"	O
(	O
20	O
–	O
40Hz	O
)	O
.	O
</s>
<s>
In	O
2015	O
,	O
Damon	O
Krukowski	O
wrote	O
an	O
article	O
entitled	O
"	O
Drop	O
the	O
Bass	O
:	O
A	O
Case	O
Against	O
Subwoofers	B-Application
"	O
for	O
Pitchfork	O
magazine	O
,	O
based	O
on	O
his	O
performing	O
experience	O
with	O
Galaxie	O
500	O
;	O
he	O
argues	O
that	O
"	O
for	O
certain	O
styles	O
of	O
music	O
"	O
,	O
especially	O
acoustic	O
music	O
genres	O
,	O
"	O
these	O
low-end	O
behemoths	O
are	O
actually	O
ruining	O
our	O
listening	O
experience	O
"	O
by	O
reducing	O
the	O
clarity	O
of	O
the	O
low	O
end	O
.	O
</s>
<s>
In	O
2015	O
,	O
John	O
Hunter	O
from	O
REL	O
Acoustics	O
stated	O
that	O
audiophiles	O
tend	O
to	O
"	O
have	O
a	O
love/hate	O
relationship	O
with	O
subwoofers	B-Application
"	O
because	O
most	O
subs	O
have	O
"	O
awful	O
"	O
,	O
"	O
entry-level	O
"	O
sound	O
quality	O
and	O
they	O
are	O
used	O
in	O
an	O
"	O
inappropriate	O
way	O
"	O
,	O
without	O
integrating	O
the	O
bass	O
seamlessly	O
.	O
</s>
<s>
Subwoofers	B-Application
use	O
speaker	B-Device
drivers	I-Device
(	O
woofers	B-Device
)	O
typically	O
between	O
8-inch	O
(	O
20cm	O
)	O
and	O
21-inch	O
(	O
53cm	O
)	O
in	O
diameter	O
.	O
</s>
<s>
Some	O
uncommon	O
subwoofers	B-Application
use	O
larger	O
drivers	O
,	O
and	O
single	O
prototype	O
subwoofers	B-Application
as	O
large	O
as	O
60-inch	O
(	O
152cm	O
)	O
have	O
been	O
fabricated	O
.	O
</s>
<s>
On	O
the	O
smaller	O
end	O
of	O
the	O
spectrum	O
,	O
subwoofer	B-Application
drivers	O
as	O
small	O
as	O
4-inch	O
(	O
10cm	O
)	O
may	O
be	O
used	O
.	O
</s>
<s>
Small	O
subwoofer	B-Application
drivers	O
in	O
the	O
4-inch	O
range	O
are	O
typically	O
used	O
in	O
small	O
computer	O
speaker	O
systems	O
and	O
compact	O
home	O
theatre	O
subwoofer	B-Application
cabinets	O
.	O
</s>
<s>
The	O
size	O
of	O
the	O
driver	B-Device
and	O
number	O
of	O
drivers	O
in	O
a	O
cabinet	O
depends	O
on	O
the	O
design	O
of	O
the	O
loudspeaker	B-Device
enclosure	I-Device
,	O
the	O
size	O
of	O
the	O
cabinet	O
,	O
the	O
desired	O
sound	O
pressure	O
level	O
,	O
the	O
lowest	O
frequency	O
targeted	O
and	O
the	O
level	O
of	O
permitted	O
distortion	O
.	O
</s>
<s>
The	O
most	O
common	O
subwoofer	B-Application
driver	B-Device
sizes	O
used	O
for	O
sound	O
reinforcement	O
in	O
nightclubs	O
,	O
raves	O
and	O
pop/rock	O
concerts	O
are	O
10-	O
,	O
12-	O
,	O
15	O
-	O
and	O
18-inch	O
models	O
(	O
25cm	O
,	O
30cm	O
,	O
38cm	O
,	O
and	O
45cm	O
respectively	O
)	O
.	O
</s>
<s>
The	O
largest	O
available	O
sound	O
reinforcement	O
subwoofers	B-Application
,	O
21-inch	O
(	O
53cm	O
)	O
drivers	O
,	O
are	O
less	O
commonly	O
seen	O
.	O
</s>
<s>
The	O
efficiency	O
of	O
a	O
speaker	B-Device
driver	I-Device
is	O
given	O
by	O
:	O
</s>
<s>
where	O
the	O
variables	O
are	O
Thiele/Small	B-Device
parameters	I-Device
.	O
</s>
<s>
Deep	O
low-frequency	O
extension	O
is	O
a	O
common	O
goal	O
for	O
a	O
subwoofer	B-Application
and	O
small	O
box	O
volumes	O
are	O
also	O
considered	O
desirable	O
,	O
to	O
save	O
space	O
and	O
reduce	O
the	O
size	O
for	O
ease	O
of	O
transportation	O
(	O
in	O
the	O
case	O
of	O
sound	O
reinforcement	O
and	O
DJ	O
subwoofers	B-Application
)	O
.	O
</s>
<s>
Hofmann	O
's	O
"	O
Iron	O
Law	O
"	O
therefore	O
mandates	O
low	O
efficiency	O
under	O
those	O
constraints	O
,	O
and	O
indeed	O
most	O
subwoofers	B-Application
require	O
considerable	O
power	O
,	O
much	O
more	O
than	O
other	O
individual	O
drivers	O
.	O
</s>
<s>
So	O
,	O
for	O
the	O
example	O
of	O
a	O
sealed	O
speaker	B-Device
box	I-Device
,	O
the	O
box	O
volume	O
to	O
achieve	O
a	O
given	O
is	O
proportional	O
to	O
:	O
</s>
<s>
Therefore	O
,	O
a	O
decrease	O
in	O
box	O
volume	O
(	O
i.e.	O
,	O
a	O
smaller	O
speaker	B-Device
cabinet	I-Device
)	O
and	O
the	O
same	O
will	O
decrease	O
the	O
efficiency	O
of	O
the	O
subwoofer	B-Application
.	O
</s>
<s>
As	O
the	O
efficiency	O
is	O
proportional	O
to	O
,	O
small	O
improvements	O
in	O
low-frequency	O
extension	O
with	O
the	O
same	O
driver	B-Device
and	O
box	O
volume	O
will	O
result	O
in	O
very	O
significant	O
reductions	O
in	O
efficiency	O
.	O
</s>
<s>
For	O
these	O
reasons	O
,	O
subwoofers	B-Application
are	O
typically	O
very	O
inefficient	O
at	O
converting	O
electrical	O
energy	O
into	O
sound	O
energy	O
.	O
</s>
<s>
This	O
combination	O
of	O
factors	O
accounts	O
for	O
the	O
higher	O
amplifier	O
power	O
required	O
to	O
drive	O
subwoofers	B-Application
,	O
and	O
the	O
requirement	O
for	O
greater	O
power	O
handling	O
for	O
subwoofer	B-Application
drivers	O
.	O
</s>
<s>
Enclosure	B-Device
variations	O
(	O
e.g.	O
,	O
bass	O
reflex	O
designs	O
with	O
a	O
port	O
in	O
the	O
cabinet	O
)	O
are	O
often	O
used	O
for	O
subwoofers	B-Application
to	O
increase	O
the	O
efficiency	O
of	O
the	O
driver/enclosure	O
system	O
,	O
helping	O
to	O
reduce	O
the	O
amplifier	O
power	O
requirements	O
.	O
</s>
<s>
Subwoofers	B-Application
are	O
typically	O
constructed	O
by	O
mounting	O
one	O
or	O
more	O
woofers	B-Device
in	O
a	O
cabinet	O
of	O
medium-density	O
fibreboard	O
(	O
MDF	O
)	O
,	O
oriented	O
strand	O
board	O
(	O
OSB	O
)	O
,	O
plywood	O
,	O
fiberglass	O
,	O
aluminum	O
or	O
other	O
stiff	O
materials	O
.	O
</s>
<s>
Because	O
of	O
the	O
high	O
air	O
pressure	O
they	O
produce	O
in	O
the	O
cabinet	O
,	O
subwoofer	B-Device
enclosures	I-Device
often	O
require	O
internal	O
bracing	O
to	O
distribute	O
the	O
resulting	O
forces	O
.	O
</s>
<s>
Subwoofers	B-Application
have	O
been	O
designed	O
using	O
a	O
number	O
of	O
enclosure	B-Device
approaches	O
:	O
bass	O
reflex	O
(	O
with	O
a	O
port	O
or	O
vent	O
)	O
,	O
using	O
a	O
subwoofer	B-Application
and	O
one	O
or	O
more	O
passive	B-Architecture
radiator	I-Architecture
speakers	I-Architecture
in	O
the	O
enclosure	B-Device
,	O
acoustic	B-Architecture
suspension	I-Architecture
(	O
sealed	O
enclosure	B-Device
)	O
,	O
infinite	O
baffle	O
,	O
horn-loaded	B-Device
,	O
tapped	O
horn	O
,	O
transmission	O
line	O
and	O
bandpass	O
.	O
</s>
<s>
Each	O
enclosure	B-Device
type	O
has	O
advantages	O
and	O
disadvantages	O
in	O
terms	O
of	O
efficiency	O
increase	O
,	O
bass	O
extension	O
,	O
cabinet	O
size	O
,	O
distortion	O
,	O
and	O
cost	O
.	O
</s>
<s>
Multiple	O
enclosure	B-Device
types	O
may	O
even	O
be	O
combined	O
in	O
a	O
single	O
design	O
,	O
such	O
as	O
in	O
computer	O
audio	O
with	O
the	O
subwoofer	B-Application
design	O
of	O
the	O
Labtec	B-Device
LCS-2424	O
(	O
later	O
acquired	O
by	O
Logitech	O
and	O
used	O
for	O
their	O
Z340/Z540/Z640/Z3/Z4	O
)	O
,	O
which	O
is	O
a	O
(	O
primitive	O
)	O
passive	B-Architecture
radiator	I-Architecture
bandpass	O
enclosure	B-Device
with	O
a	O
bass	O
reflex	O
dividing	O
chamber	O
.	O
</s>
<s>
While	O
not	O
necessarily	O
an	O
enclosure	B-Device
type	O
,	O
isobaric	B-Device
(	O
such	O
as	O
push-pull	O
)	O
coupled	O
loading	O
of	O
two	O
drivers	O
has	O
sometimes	O
been	O
used	O
in	O
subwoofer	B-Application
products	O
of	O
computer	O
,	O
home	O
cinema	O
and	O
sound	O
reinforcement	O
class	O
,	O
and	O
also	O
DIY	O
versions	O
in	O
automotive	O
applications	O
,	O
to	O
provide	O
relatively	O
deep	O
bass	O
for	O
their	O
size	O
.	O
</s>
<s>
Self-contained	O
"	O
isobaric-like	O
"	O
driver	B-Device
assemblies	O
have	O
been	O
manufactured	O
since	O
the	O
2010s	O
.	O
</s>
<s>
The	O
smallest	O
subwoofers	B-Application
are	O
typically	O
those	O
designed	O
for	O
desktop	O
multimedia	O
systems	O
.	O
</s>
<s>
The	O
largest	O
common	O
subwoofer	B-Device
enclosures	I-Device
are	O
those	O
used	O
for	O
concert	O
sound	O
reinforcement	O
systems	O
or	O
dance	O
club	O
sound	O
systems	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
large	O
concert	O
subwoofer	B-Device
enclosure	I-Device
is	O
the	O
1980s-era	O
Electro-Voice	O
MT-4	O
"	O
Bass	O
Cube	O
"	O
system	O
,	O
which	O
used	O
four	O
18-inch	O
(	O
45cm	O
)	O
drivers	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
subwoofer	B-Application
that	O
uses	O
a	O
bass	O
horn	O
is	O
the	O
Bassmaxx	O
B-Two	O
,	O
which	O
loads	O
an	O
18-inch	O
(	O
45cm	O
)	O
driver	B-Device
onto	O
an	O
long	O
folded	B-Device
horn	I-Device
.	O
</s>
<s>
Folded	O
horn-type	O
subwoofers	B-Application
can	O
typically	O
produce	O
a	O
deeper	O
range	O
with	O
greater	O
efficiency	O
than	O
the	O
same	O
driver	B-Device
in	O
an	O
enclosure	B-Device
that	O
lacks	O
a	O
horn	O
.	O
</s>
<s>
However	O
,	O
folded	B-Device
horn	I-Device
cabinets	O
are	O
typically	O
larger	O
and	O
heavier	O
than	O
front-firing	O
enclosures	O
,	O
so	O
folded	B-Device
horns	I-Device
are	O
less	O
commonly	O
used	O
.	O
</s>
<s>
Some	O
experimental	O
fixed-installation	O
subwoofer	B-Application
horns	O
have	O
been	O
constructed	O
using	O
brick	O
and	O
concrete	O
to	O
produce	O
a	O
very	O
long	O
horn	O
that	O
allows	O
a	O
very	O
deep	O
sub-bass	O
extension	O
.	O
</s>
<s>
Subwoofer	B-Application
output	O
level	O
can	O
be	O
increased	O
by	O
increasing	O
cone	O
surface	O
area	O
or	O
by	O
increasing	O
cone	O
excursion	O
.	O
</s>
<s>
Since	O
large	O
drivers	O
require	O
undesirably	O
large	O
cabinets	O
,	O
most	O
subwoofer	B-Application
drivers	O
have	O
large	O
excursions	O
.	O
</s>
<s>
The	O
conflict	O
between	O
assorted	O
goals	O
can	O
never	O
be	O
fully	O
resolved	O
;	O
subwoofer	B-Application
designs	O
necessarily	O
involve	O
tradeoffs	O
and	O
compromises	O
.	O
</s>
<s>
Hofmann	O
's	O
Iron	O
Law	O
(	O
the	O
efficiency	O
of	O
a	O
woofer	B-Device
system	O
is	O
directly	O
proportional	O
to	O
its	O
cabinet	O
volume	O
(	O
as	O
in	O
size	O
)	O
and	O
to	O
the	O
cube	O
of	O
its	O
cutoff	O
frequency	O
,	O
that	O
is	O
how	O
low	O
in	O
pitch	O
it	O
will	O
go	O
)	O
applies	O
to	O
subwoofers	B-Application
just	O
as	O
it	O
does	O
to	O
all	O
loudspeakers	O
.	O
</s>
<s>
Thus	O
a	O
subwoofer	B-Device
enclosure	I-Device
designer	O
aiming	O
at	O
the	O
deepest-pitched	O
bass	O
will	O
probably	O
have	O
to	O
consider	O
using	O
a	O
large	O
enclosure	B-Device
size	O
;	O
a	O
subwoofer	B-Device
enclosure	I-Device
designer	O
instructed	O
to	O
create	O
the	O
smallest	O
possible	O
cabinet	O
(	O
to	O
make	O
transportation	O
easier	O
)	O
will	O
need	O
to	O
compromise	O
how	O
low	O
in	O
pitch	O
their	O
cabinet	O
will	O
go	O
.	O
</s>
<s>
The	O
typical	O
frequency	O
range	O
for	O
a	O
subwoofer	B-Application
is	O
between	O
20	O
–	O
200Hz	O
.	O
</s>
<s>
Professional	O
concert	O
sound	O
system	O
subwoofers	B-Application
typically	O
operate	O
below	O
100Hz	O
,	O
and	O
THX-certified	O
systems	O
operate	O
below	O
80Hz	O
.	O
</s>
<s>
Subwoofers	B-Application
vary	O
in	O
terms	O
of	O
the	O
range	O
of	O
pitches	O
that	O
they	O
can	O
reproduce	O
,	O
depending	O
on	O
a	O
number	O
of	O
factors	O
such	O
as	O
the	O
size	O
of	O
the	O
cabinet	O
and	O
the	O
construction	O
and	O
design	O
of	O
the	O
enclosure	B-Device
and	O
driver(s )	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
JBL	O
4688	O
TCB	O
Subwoofer	B-Application
System	O
,	O
a	O
now-discontinued	O
system	O
which	O
was	O
designed	O
for	O
movie	O
theaters	O
,	O
had	O
a	O
frequency	O
response	O
of	O
23	O
–	O
350Hz	O
when	O
measured	O
within	O
a	O
10-decibel	O
boundary	O
(	O
0dB	O
to	O
10dB	O
)	O
and	O
a	O
narrower	O
frequency	O
response	O
of	O
28	O
–	O
120Hz	O
when	O
measured	O
within	O
a	O
6-decibel	O
boundary	O
( ±3dB	O
)	O
.	O
</s>
<s>
Subwoofers	B-Application
also	O
vary	O
in	O
regard	O
to	O
the	O
sound	O
pressure	O
levels	O
achievable	O
and	O
the	O
distortion	O
levels	O
that	O
they	O
produce	O
over	O
their	O
range	O
.	O
</s>
<s>
Some	O
subwoofers	B-Application
,	O
such	O
as	O
"	O
The	O
Abyss	O
"	O
by	O
MartinLogan	O
for	O
example	O
,	O
can	O
reproduce	O
pitches	O
down	O
to	O
around	O
18Hz	O
(	O
which	O
is	O
about	O
the	O
pitch	O
of	O
the	O
lowest	O
rumbling	O
notes	O
on	O
a	O
huge	O
pipe	O
organ	O
with	O
16Hz	O
bass	O
pipes	O
)	O
to	O
120Hz	O
( ±3dB	O
)	O
.	O
</s>
<s>
Nevertheless	O
,	O
even	O
though	O
the	O
Abyss	O
subwoofer	B-Application
can	O
go	O
down	O
to	O
18Hz	O
,	O
its	O
lowest	O
frequency	O
and	O
maximum	O
SPL	O
with	O
a	O
limit	O
of	O
10%	O
distortion	O
is	O
35.5Hz	O
and	O
79.8dB	O
at	O
2	O
meters	O
.	O
</s>
<s>
This	O
means	O
that	O
a	O
person	O
choosing	O
a	O
subwoofer	B-Application
needs	O
to	O
consider	O
more	O
than	O
just	O
the	O
lowest	O
pitch	O
that	O
the	O
subwoofer	B-Application
can	O
reproduce	O
.	O
</s>
<s>
'	O
Active	O
subwoofers	B-Application
 '	O
include	O
their	O
own	O
dedicated	O
amplifiers	O
within	O
the	O
cabinet	O
.	O
</s>
<s>
Some	O
such	O
systems	O
are	O
even	O
supplied	O
with	O
a	O
calibrated	O
microphone	O
to	O
measure	O
the	O
subwoofer	B-Application
's	O
in-room	O
response	O
,	O
so	O
the	O
automatic	O
equalizer	O
can	O
correct	O
the	O
combination	O
of	O
subwoofer	B-Application
,	O
subwoofer	B-Application
location	O
,	O
and	O
room	O
response	O
to	O
minimize	O
the	O
effects	O
of	O
room	O
modes	O
and	O
improve	O
low-frequency	O
performance	O
.	O
</s>
<s>
'	O
Passive	O
subwoofers	B-Application
 '	O
have	O
a	O
subwoofer	B-Application
driver	B-Device
and	O
enclosure	B-Device
,	O
but	O
they	O
do	O
not	O
include	O
an	O
amplifier	O
.	O
</s>
<s>
They	O
sometimes	O
incorporate	O
internal	O
passive	O
crossovers	B-Algorithm
,	O
with	O
the	O
filter	O
frequency	O
determined	O
at	O
the	O
factory	O
.	O
</s>
<s>
These	O
are	O
generally	O
used	O
with	O
third-party	O
power	O
amplifiers	O
,	O
taking	O
their	O
inputs	O
from	O
active	B-Algorithm
crossovers	I-Algorithm
earlier	O
in	O
the	O
signal	O
chain	O
.	O
</s>
<s>
Inexpensive	O
Home	O
Theatre	O
in	O
a	O
Box	O
packages	O
often	O
come	O
with	O
a	O
passive	O
subwoofer	B-Application
cabinet	O
that	O
is	O
amplified	O
by	O
the	O
multi-channel	O
amplifier	O
.	O
</s>
<s>
While	O
few	O
high-end	O
home-theater	O
systems	O
use	O
passive	O
subwoofers	B-Application
,	O
this	O
format	O
is	O
still	O
popular	O
in	O
the	O
professional	O
sound	O
industry	O
.	O
</s>
<s>
Equalization	O
can	O
be	O
used	O
to	O
adjust	O
the	O
in-room	O
response	O
of	O
a	O
subwoofer	B-Application
system	O
.	O
</s>
<s>
Designers	O
of	O
active	O
subwoofers	B-Application
sometimes	O
include	O
a	O
degree	O
of	O
corrective	O
equalization	O
to	O
compensate	O
for	O
known	O
performance	O
issues	O
(	O
e.g.	O
,	O
a	O
steeper	O
than	O
desired	O
low	O
end	O
roll-off	B-Algorithm
rate	O
)	O
.	O
</s>
<s>
In	O
addition	O
,	O
many	O
amplifiers	O
include	O
an	O
adjustable	O
low-pass	O
filter	O
,	O
which	O
prevents	O
undesired	O
higher	O
frequencies	O
from	O
reaching	O
the	O
subwoofer	B-Application
driver	B-Device
.	O
</s>
<s>
For	O
example	O
,	O
if	O
a	O
listener	O
's	O
main	O
speakers	O
are	O
usable	O
down	O
to	O
80Hz	O
,	O
then	O
the	O
subwoofer	B-Application
filter	O
can	O
be	O
set	O
so	O
the	O
subwoofer	B-Application
only	O
works	O
below	O
80Hz	O
.	O
</s>
<s>
Typical	O
filters	O
involve	O
some	O
overlap	O
in	O
frequency	O
ranges	O
;	O
a	O
steep	O
4th-order	O
24dB/octave	O
low-pass	O
filter	O
is	O
generally	O
desired	O
for	O
subwoofers	B-Application
in	O
order	O
to	O
minimize	O
the	O
overlap	O
region	O
.	O
</s>
<s>
The	O
filter	O
section	O
may	O
also	O
include	O
a	O
high-pass	O
"	O
infrasonic	O
"	O
or	O
"	O
subsonic	O
"	O
filter	O
,	O
which	O
prevents	O
the	O
subwoofer	B-Application
driver	B-Device
from	O
attempting	O
to	O
reproduce	O
frequencies	O
below	O
its	O
safe	O
capabilities	O
.	O
</s>
<s>
Setting	O
an	O
infrasonic	O
filter	O
is	O
important	O
on	O
bass	O
reflex	O
subwoofer	B-Application
cabinets	O
,	O
as	O
the	O
bass	O
reflex	O
design	O
tends	O
to	O
create	O
the	O
risk	O
of	O
cone	O
overexcursion	O
at	O
pitches	O
below	O
those	O
of	O
the	O
port	O
tuning	O
,	O
which	O
can	O
cause	O
distortion	O
and	O
damage	O
the	O
subwoofer	B-Application
driver	B-Device
.	O
</s>
<s>
For	O
example	O
,	O
in	O
a	O
ported	O
subwoofer	B-Device
enclosure	I-Device
tuned	O
to	O
30Hz	O
,	O
one	O
may	O
wish	O
to	O
filter	O
out	O
pitches	O
below	O
the	O
tuning	O
frequency	O
;	O
that	O
is	O
,	O
frequencies	O
below	O
30Hz	O
.	O
</s>
<s>
Careful	O
positioning	O
of	O
the	O
subwoofer	B-Application
within	O
the	O
room	O
can	O
also	O
help	O
flatten	O
the	O
frequency	O
response	O
.	O
</s>
<s>
Multiple	O
subwoofers	B-Application
can	O
manage	O
a	O
flatter	O
general	O
response	O
since	O
they	O
can	O
often	O
be	O
arranged	O
to	O
excite	O
room	O
modes	O
more	O
evenly	O
than	O
a	O
single	O
subwoofer	B-Application
,	O
allowing	O
equalization	O
to	O
be	O
more	O
effective	O
.	O
</s>
<s>
Changing	O
the	O
relative	O
phase	O
of	O
the	O
subwoofer	B-Application
with	O
respect	O
to	O
the	O
woofers	B-Device
in	O
other	O
speakers	O
may	O
or	O
may	O
not	O
help	O
to	O
minimize	O
unwanted	O
destructive	O
acoustic	O
interference	O
in	O
the	O
frequency	O
region	O
covered	O
by	O
both	O
the	O
subwoofer	B-Application
and	O
the	O
main	O
speakers	O
.	O
</s>
<s>
It	O
may	O
not	O
help	O
at	O
all	O
frequencies	O
,	O
and	O
may	O
create	O
further	O
problems	O
with	O
frequency	O
response	O
,	O
but	O
even	O
so	O
is	O
generally	O
provided	O
as	O
an	O
adjustment	O
for	O
subwoofer	B-Application
amplifiers	O
.	O
</s>
<s>
Continuously	O
variable	O
phase	O
control	O
circuits	O
are	O
common	O
in	O
subwoofer	B-Application
amplifiers	O
,	O
and	O
may	O
be	O
found	O
in	O
crossovers	B-Algorithm
and	O
as	O
do-it-yourself	O
electronics	O
projects	O
.	O
</s>
<s>
Phase	O
controls	O
allow	O
the	O
listener	O
to	O
change	O
the	O
arrival	O
time	O
of	O
the	O
subwoofer	B-Application
sound	O
waves	O
relative	O
to	O
the	O
same	O
frequencies	O
from	O
the	O
main	O
speakers	O
(	O
i.e.	O
,	O
at	O
and	O
around	O
the	O
crossover	B-Algorithm
point	O
to	O
the	O
subwoofer	B-Application
)	O
.	O
</s>
<s>
The	O
subwoofer	B-Application
phase	O
control	O
found	O
on	O
many	O
subwoofer	B-Application
amplifiers	O
is	O
actually	O
a	O
polarity	O
inversion	O
switch	O
.	O
</s>
<s>
It	O
allows	O
users	O
to	O
reverse	O
the	O
polarity	O
of	O
the	O
subwoofer	B-Application
relative	O
to	O
the	O
audio	O
signal	O
it	O
is	O
being	O
given	O
.	O
</s>
<s>
This	O
type	O
of	O
control	O
allows	O
the	O
subwoofer	B-Application
to	O
either	O
be	O
in	O
phase	O
with	O
the	O
source	O
signal	O
,	O
or	O
180	O
degrees	O
out	O
of	O
phase	O
.	O
</s>
<s>
The	O
subwoofer	B-Application
phase	O
can	O
still	O
be	O
changed	O
by	O
moving	O
the	O
subwoofer	B-Application
closer	O
to	O
or	O
further	O
from	O
the	O
listening	O
position	O
,	O
however	O
this	O
may	O
not	O
be	O
always	O
practical	O
.	O
</s>
<s>
Some	O
active	O
subwoofers	B-Application
use	O
a	O
servo	O
feedback	O
mechanism	O
based	O
on	O
cone	O
movement	O
that	O
modifies	O
the	O
signal	O
sent	O
to	O
the	O
voice	O
coil	O
.	O
</s>
<s>
An	O
advantage	O
of	O
a	O
well-implemented	O
servo	O
subwoofer	B-Application
design	O
is	O
reduced	O
distortion	O
making	O
smaller	O
enclosure	B-Device
sizes	O
possible	O
.	O
</s>
<s>
Servo-controlled	O
subwoofers	B-Application
are	O
not	O
the	O
same	O
as	O
Tom	O
Danley	O
's	O
ServoDrive	O
subwoofers	B-Application
,	O
whose	O
primary	O
mechanism	O
of	O
sound	O
reproduction	O
avoids	O
the	O
normal	O
voice	O
coil	O
and	O
magnet	O
combination	O
in	O
favor	O
of	O
a	O
high-speed	O
belt-driven	O
servomotor	B-Algorithm
.	O
</s>
<s>
The	O
ServoDrive	O
design	O
increases	O
output	O
power	O
,	O
reduces	O
harmonic	O
distortion	O
and	O
virtually	O
eliminates	O
power	B-Architecture
compression	I-Architecture
,	O
the	O
loss	O
of	O
loudspeaker	O
output	O
that	O
results	O
from	O
an	O
increase	O
in	O
voice	O
coil	O
impedance	O
due	O
to	O
overheating	O
of	O
the	O
voice	O
coil	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
subwoofer	B-Application
augments	O
the	O
bass	O
capability	O
of	O
the	O
main	O
speakers	O
,	O
and	O
allows	O
them	O
to	O
be	O
smaller	O
without	O
sacrificing	O
low-frequency	O
capability	O
.	O
</s>
<s>
A	O
subwoofer	B-Application
does	O
not	O
necessarily	O
provide	O
superior	O
bass	O
performance	O
in	O
comparison	O
to	O
large	O
conventional	O
loudspeakers	O
on	O
ordinary	O
music	O
recordings	O
due	O
to	O
the	O
typical	O
lack	O
of	O
very	O
low	O
frequency	O
content	O
on	O
such	O
sources	O
.	O
</s>
<s>
However	O
,	O
there	O
are	O
recordings	O
with	O
substantial	O
low-frequency	O
content	O
that	O
most	O
conventional	O
loudspeakers	O
are	O
ill-equipped	O
to	O
handle	O
without	O
the	O
help	O
of	O
a	O
subwoofer	B-Application
,	O
especially	O
at	O
high	O
playback	O
levels	O
,	O
such	O
as	O
music	O
for	O
pipe	O
organs	O
with	O
32	O
 '	O
(	O
9.75	O
meter	O
)	O
bass	O
pipes	O
(	O
16Hz	O
)	O
,	O
very	O
large	O
bass	O
drums	O
on	O
symphony	O
orchestra	O
recordings	O
and	O
electronic	O
music	O
with	O
extremely	O
low	O
synth	O
bass	O
parts	O
,	O
such	O
as	O
bass	O
tests	O
or	O
bass	O
songs	O
.	O
</s>
<s>
Frequencies	O
which	O
are	O
sufficiently	O
low	O
are	O
not	O
easily	O
localized	O
by	O
humans	O
,	O
hence	O
many	O
stereo	O
and	O
multichannel	O
audio	O
systems	O
feature	O
only	O
one	O
subwoofer	B-Application
channel	O
and	O
a	O
single	O
subwoofer	B-Application
can	O
be	O
placed	O
off-center	O
without	O
affecting	O
the	O
perceived	O
sound	O
stage	O
,	O
since	O
the	O
sound	O
that	O
it	O
produces	O
will	O
be	O
difficult	O
to	O
localize	O
.	O
</s>
<s>
The	O
intention	O
in	O
a	O
system	O
with	O
a	O
subwoofer	B-Application
is	O
often	O
to	O
use	O
small	O
main	O
speakers	O
(	O
of	O
which	O
there	O
are	O
two	O
for	O
stereo	O
and	O
five	O
or	O
more	O
for	O
surround	O
sound	O
or	O
movie	O
tracks	O
)	O
and	O
to	O
hide	O
the	O
subwoofer	B-Application
elsewhere	O
(	O
e.g.	O
</s>
<s>
behind	O
furniture	O
or	O
under	O
a	O
table	O
)	O
,	O
or	O
to	O
augment	O
an	O
existing	O
speaker	O
to	O
save	O
it	O
from	O
having	O
to	O
handle	O
woofer-destroying	O
low	O
frequencies	O
at	O
high	O
levels	O
.	O
</s>
<s>
This	O
effect	O
is	O
possible	O
only	O
if	O
the	O
subwoofer	B-Application
is	O
restricted	O
to	O
quite	O
low	O
frequencies	O
,	O
usually	O
taken	O
to	O
be	O
,	O
say	O
,	O
100Hz	O
and	O
below	O
—	O
still	O
less	O
localization	O
is	O
possible	O
if	O
restricted	O
to	O
even	O
lower	O
maximum	O
frequencies	O
.	O
</s>
<s>
Higher	O
upper	O
limits	O
for	O
the	O
subwoofer	B-Application
(	O
e.g.	O
,	O
125Hz	O
)	O
are	O
much	O
more	O
easily	O
localized	O
,	O
making	O
a	O
single	O
subwoofer	B-Application
impractical	O
.	O
</s>
<s>
Home	O
theatre	O
systems	O
typically	O
use	O
one	O
subwoofer	B-Application
cabinet	O
(	O
the	O
"	O
1	O
"	O
in	O
5.1	O
surround	O
sound	O
)	O
.	O
</s>
<s>
However	O
,	O
to	O
"	O
improve	O
bass	O
distribution	O
in	O
a	O
room	O
that	O
has	O
multiple	O
seating	O
locations	O
,	O
and	O
prevent	O
"	O
node	O
"	O
or	O
"	O
null	O
points	O
"	O
with	O
weakened	O
bass	O
response	O
,	O
some	O
home	O
cinema	O
enthusiasts	O
use	O
"	O
5.2	O
"	O
or	O
"	O
7.2	O
"	O
surround	O
sound	O
systems	O
with	O
two	O
subwoofer	B-Application
cabinets	O
in	O
the	O
same	O
room	O
.	O
</s>
<s>
Some	O
users	O
add	O
a	O
subwoofer	B-Application
because	O
high	O
levels	O
of	O
low-frequency	O
bass	O
are	O
desired	O
,	O
even	O
beyond	O
what	O
is	O
in	O
the	O
original	O
recording	O
,	O
as	O
in	O
the	O
case	O
of	O
house	O
music	O
enthusiasts	O
.	O
</s>
<s>
Thus	O
,	O
subwoofers	B-Application
may	O
be	O
part	O
of	O
a	O
package	O
that	O
includes	O
satellite	O
speakers	O
,	O
may	O
be	O
purchased	O
separately	O
,	O
or	O
may	O
be	O
built	O
into	O
the	O
same	O
cabinet	O
as	O
a	O
conventional	O
speaker	O
system	O
.	O
</s>
<s>
For	O
instance	O
,	O
some	O
floor-standing	O
tower	O
speakers	O
include	O
a	O
subwoofer	B-Application
driver	B-Device
in	O
the	O
lower	O
portion	O
of	O
the	O
same	O
cabinet	O
.	O
</s>
<s>
Physical	O
separation	O
of	O
subwoofer	B-Application
and	O
"	O
satellite	O
"	O
speakers	O
not	O
only	O
allows	O
placement	O
in	O
an	O
inconspicuous	O
location	O
,	O
but	O
since	O
sub-bass	O
frequencies	O
are	O
particularly	O
sensitive	O
to	O
room	O
location	O
(	O
due	O
to	O
room	O
resonances	O
and	O
reverberation	O
'	O
modes	O
 '	O
)	O
,	O
the	O
best	O
position	O
for	O
the	O
subwoofer	B-Application
is	O
not	O
likely	O
to	O
be	O
where	O
the	O
"	O
satellite	O
"	O
speakers	O
are	O
located	O
.	O
</s>
<s>
Higher	O
end	O
home	O
theater	O
systems	O
and	O
enthusiasts	O
may	O
also	O
opt	O
to	O
take	O
low-frequency	O
bass	O
reproduction	O
even	O
further	O
by	O
incorporating	O
2	O
or	O
more	O
external	O
subwoofers	B-Application
.	O
</s>
<s>
Having	O
two	O
subwoofers	B-Application
placed	O
around	O
the	O
living	O
room	O
ensures	O
even	O
distribution	O
of	O
bass	O
,	O
reducing	O
subwoofer	B-Application
localization	O
and	O
pressurizing	O
the	O
room	O
with	O
low	O
frequency	O
notes	O
that	O
can	O
be	O
felt	O
,	O
just	O
like	O
the	O
cinemas	O
.	O
</s>
<s>
For	O
greatest	O
efficiency	O
and	O
best	O
coupling	O
to	O
the	O
room	O
's	O
air	O
volume	O
,	O
subwoofers	B-Application
can	O
be	O
placed	O
in	O
a	O
corner	O
of	O
the	O
room	O
,	O
far	O
from	O
large	O
room	O
openings	O
,	O
and	O
closer	O
to	O
the	O
listener	O
.	O
</s>
<s>
All	O
low-frequency	O
information	O
is	O
sent	O
to	O
the	O
subwoofer	B-Application
.	O
</s>
<s>
However	O
,	O
unless	O
the	O
sound	O
tracks	O
have	O
been	O
carefully	O
mixed	O
for	O
a	O
single	O
subwoofer	B-Application
channel	O
,	O
it	O
is	O
possible	O
to	O
have	O
some	O
cancellation	O
of	O
low	O
frequencies	O
if	O
bass	O
information	O
in	O
one	O
channel	O
's	O
speaker	O
is	O
out	O
of	O
phase	O
with	O
another	O
.	O
</s>
<s>
The	O
physically	O
separate	O
subwoofer/satellite	O
arrangement	O
,	O
with	O
small	O
satellite	O
speakers	O
and	O
a	O
large	O
subwoofer	B-Application
cabinet	O
that	O
can	O
be	O
hidden	O
behind	O
furniture	O
,	O
has	O
been	O
popularized	O
by	O
multimedia	O
speaker	O
systems	O
such	O
as	O
Bose	O
Acoustimass	O
Home	O
Entertainment	O
Systems	O
,	O
Polk	O
Audio	O
RM2008	O
Series	O
and	O
Klipsch	O
Audio	O
Technologies	O
ProMedia	O
,	O
among	O
many	O
others	O
.	O
</s>
<s>
Particularly	O
among	O
lower	O
cost	O
"	O
Home	O
Theater	O
in	O
a	O
Box	O
"	O
systems	O
and	O
with	O
"	O
boom	O
boxes	O
"	O
,	O
however	O
,	O
the	O
inclusion	O
of	O
a	O
subwoofer	B-Application
may	O
be	O
little	O
more	O
than	O
a	O
marketing	O
technique	O
.	O
</s>
<s>
It	O
is	O
unlikely	O
that	O
a	O
small	O
woofer	B-Device
in	O
an	O
inexpensively-built	O
compact	O
plastic	O
cabinet	O
will	O
have	O
better	O
bass	O
performance	O
than	O
well-designed	O
conventional	O
(	O
and	O
typically	O
larger	O
)	O
speakers	O
in	O
a	O
plywood	O
or	O
MDF	O
cabinet	O
.	O
</s>
<s>
Mere	O
use	O
of	O
the	O
term	O
"	O
subwoofer	B-Application
"	O
is	O
no	O
guarantee	O
of	O
good	O
or	O
extended	O
bass	O
performance	O
.	O
</s>
<s>
Many	O
multimedia	O
"	O
subwoofers	B-Application
"	O
might	O
better	O
be	O
termed	O
"	O
mid	O
bass	O
cabinets	O
"	O
(	O
60	O
to	O
160Hz	O
)	O
,	O
as	O
they	O
are	O
too	O
small	O
to	O
produce	O
deep	O
bass	O
in	O
the	O
30	O
to	O
59Hz	O
range	O
.	O
</s>
<s>
Further	O
,	O
poorly-designed	O
systems	O
often	O
leave	O
everything	O
below	O
about	O
120Hz	O
(	O
or	O
even	O
higher	O
)	O
to	O
the	O
subwoofer	B-Application
,	O
meaning	O
that	O
the	O
subwoofer	B-Application
handles	O
frequencies	O
which	O
the	O
ear	O
can	O
use	O
for	O
sound	O
source	O
localization	O
,	O
thus	O
introducing	O
an	O
undesirable	O
subwoofer	B-Application
"	O
localization	O
effect	O
"	O
.	O
</s>
<s>
This	O
is	O
usually	O
due	O
to	O
poor	O
crossover	B-Algorithm
designs	O
or	O
choices	O
(	O
too	O
high	O
a	O
crossover	B-Algorithm
point	O
or	O
insufficient	O
crossover	B-Algorithm
slope	O
)	O
used	O
in	O
many	O
computer	O
and	O
home	O
theater	O
systems	O
;	O
localization	O
also	O
comes	O
from	O
port	O
noise	O
and	O
from	O
typically	O
large	O
amounts	O
of	O
harmonic	O
distortion	O
in	O
the	O
subwoofer	B-Application
design	O
.	O
</s>
<s>
Home	O
subwoofers	B-Application
sold	O
individually	O
usually	O
include	O
crossover	B-Algorithm
circuitry	O
to	O
assist	O
with	O
the	O
integration	O
of	O
the	O
subwoofer	B-Application
into	O
an	O
existing	O
system	O
.	O
</s>
<s>
Automobiles	O
are	O
not	O
well	O
suited	O
for	O
the	O
"	O
hidden	O
"	O
subwoofer	B-Application
approach	O
due	O
to	O
space	O
limitations	O
in	O
the	O
passenger	O
compartments	O
.	O
</s>
<s>
It	O
is	O
not	O
possible	O
,	O
in	O
most	O
circumstances	O
,	O
to	O
fit	O
such	O
large	O
drivers	O
and	O
enclosures	O
into	O
doors	O
or	O
dashboards	O
,	O
so	O
subwoofers	B-Application
are	O
installed	O
in	O
the	O
trunk	O
or	O
back	O
seat	O
space	O
.	O
</s>
<s>
The	O
"	O
SPL	O
wars	O
"	O
have	O
drawn	O
much	O
attention	O
to	O
subwoofers	B-Application
in	O
general	O
,	O
but	O
subjective	O
competitions	O
in	O
sound	O
quality	O
(	O
"	O
SQ	O
"	O
)	O
have	O
not	O
gained	O
equivalent	O
popularity	O
.	O
</s>
<s>
Many	O
non-competition	O
subwoofers	B-Application
are	O
also	O
capable	O
of	O
generating	O
high	O
levels	O
in	O
cars	O
due	O
to	O
the	O
small	O
volume	O
of	O
a	O
typical	O
car	O
interior	O
.	O
</s>
<s>
In	O
the	O
2000s	O
,	O
several	O
car	O
audio	O
manufacturers	O
produced	O
subwoofers	B-Application
using	O
non-circular	O
shapes	O
,	O
including	O
Boston	O
Acoustic	O
,	O
Kicker	O
,	O
Sony	O
,	O
Bazooka	O
,	O
and	O
X-Tant	O
.	O
</s>
<s>
Other	O
major	O
car	O
audio	O
manufacturers	O
like	O
Rockford	O
Fosgate	O
did	O
not	O
follow	O
suit	O
since	O
non-circular	O
subwoofer	B-Application
shapes	O
typically	O
carry	O
some	O
sort	O
of	O
distortion	O
penalties	O
.	O
</s>
<s>
An	O
important	O
factor	O
in	O
the	O
"	O
square	O
sub	O
vs	O
round	O
sub	O
"	O
argument	O
is	O
the	O
effects	O
of	O
the	O
enclosure	B-Device
used	O
.	O
</s>
<s>
Sd	O
is	O
the	O
cone	O
area	O
of	O
the	O
subwoofer	B-Application
(	O
in	O
m2	O
)	O
.	O
</s>
<s>
These	O
are	O
some	O
of	O
the	O
Thiele/Small	B-Device
parameters	I-Device
which	O
can	O
either	O
be	O
measured	O
or	O
found	O
with	O
the	O
driver	B-Device
specifications	O
.	O
</s>
<s>
After	O
the	O
introduction	O
of	O
Sensurround	O
,	O
movie	O
theater	O
owners	O
began	O
installing	O
permanent	O
subwoofer	B-Application
systems	O
.	O
</s>
<s>
Dolby	O
Stereo	O
70	O
mm	O
Six	O
Track	O
was	O
a	O
six-channel	O
film	O
sound	O
format	O
introduced	O
in	O
1976	O
that	O
used	O
two	O
subwoofer	B-Application
channels	O
for	O
stereo	O
reproduction	O
of	O
low	O
frequencies	O
.	O
</s>
<s>
In	O
1981	O
,	O
Altec	O
introduced	O
a	O
dedicated	O
cinema	O
subwoofer	B-Application
model	O
tuned	O
to	O
around	O
20Hz	O
:	O
the	O
8182	O
.	O
</s>
<s>
Starting	O
in	O
1983	O
,	O
THX	O
certification	O
of	O
the	O
cinema	O
sound	O
experience	O
quantified	O
the	O
parameters	O
of	O
good	O
audio	O
for	O
watching	O
films	O
,	O
including	O
requirements	O
for	O
subwoofer	B-Application
performance	O
levels	O
and	O
enough	O
isolation	O
from	O
outside	O
sounds	O
so	O
that	O
noise	O
did	O
not	O
interfere	O
with	O
the	O
listening	O
experience	O
.	O
</s>
<s>
This	O
helped	O
provide	O
guidelines	O
for	O
multiplex	O
cinema	O
owners	O
who	O
wanted	O
to	O
isolate	O
each	O
individual	O
cinema	O
from	O
its	O
neighbors	O
,	O
even	O
as	O
louder	O
subwoofers	B-Application
were	O
making	O
isolation	O
more	O
difficult	O
.	O
</s>
<s>
Specific	O
cinema	O
subwoofer	B-Application
models	O
appeared	O
from	O
JBL	O
,	O
Electro-Voice	O
,	O
Eastern	O
Acoustic	O
Works	O
,	O
Kintek	O
,	O
Meyer	O
Sound	O
Laboratories	O
and	O
BGW	O
Systems	O
in	O
the	O
early	O
1990s	O
.	O
</s>
<s>
Tom	O
Horral	O
,	O
a	O
Boston-based	O
acoustician	O
,	O
blames	O
complaints	O
about	O
modern	O
movies	O
being	O
too	O
loud	O
on	O
subwoofers	B-Application
.	O
</s>
<s>
He	O
says	O
that	O
before	O
subwoofers	B-Application
made	O
it	O
possible	O
to	O
have	O
loud	O
,	O
relatively	O
undistorted	O
bass	O
,	O
movie	O
sound	O
levels	O
were	O
limited	O
by	O
the	O
distortion	O
in	O
less	O
capable	O
systems	O
at	O
low	O
frequency	O
and	O
high	O
levels	O
.	O
</s>
<s>
Professional	O
audio	O
subwoofers	B-Application
used	O
in	O
rock	O
concerts	O
in	O
stadia	O
,	O
DJ	O
performances	O
at	O
dance	O
music	O
venues	O
(	O
e.g.	O
,	O
electronic	O
dance	O
music	O
)	O
and	O
similar	O
events	O
must	O
be	O
capable	O
of	O
very	O
high	O
bass	O
output	O
levels	O
,	O
at	O
very	O
low	O
frequencies	O
,	O
with	O
low	O
distortion	O
.	O
</s>
<s>
This	O
is	O
reflected	O
in	O
the	O
design	O
attention	O
given	O
in	O
the	O
2010s	O
to	O
the	O
subwoofer	B-Application
applications	O
for	O
sound	O
reinforcement	O
,	O
public	O
address	O
systems	O
,	O
dance	O
club	O
systems	O
and	O
concert	O
systems	O
.	O
</s>
<s>
Cerwin-Vega	O
states	O
that	O
when	O
a	O
subwoofer	B-Application
cabinet	O
is	O
added	O
to	O
an	O
existing	O
full-range	O
speaker	O
system	O
,	O
this	O
is	O
advantageous	O
,	O
as	O
it	O
moves	O
the	O
"	O
lowest	O
...	O
frequencies	O
from	O
your	O
main	O
 [ full-range ] 	O
PA	O
speakers	O
"	O
thus	O
eliminat	O
...	O
a	O
large	O
amount	O
of	O
the	O
excess	O
work	O
that	O
your	O
main	O
top	O
 [ full-range ] 	O
box	O
was	O
trying	O
to	O
reproduce	O
.	O
</s>
<s>
A	O
different	O
argument	O
for	O
adding	O
subwoofer	B-Application
cabinets	O
is	O
that	O
they	O
may	O
increase	O
the	O
"	O
level	O
of	O
clarity	O
"	O
and	O
"	O
perceived	O
loudness	O
"	O
of	O
an	O
overall	O
PA	O
system	O
,	O
even	O
if	O
the	O
SPL	O
is	O
not	O
actually	O
increased	O
.	O
</s>
<s>
Sound	O
on	O
Sound	O
states	O
that	O
adding	O
a	O
subwoofer	B-Device
enclosure	I-Device
to	O
a	O
full-range	O
system	O
will	O
reduce	O
"	O
cone	O
excursion	O
"	O
,	O
thus	O
lowering	O
distortion	O
,	O
leading	O
to	O
an	O
overall	O
cleaner	O
sound	O
.	O
</s>
<s>
Subwoofers	B-Application
are	O
now	O
almost	O
universal	O
in	O
professional	O
sound	O
applications	O
such	O
as	O
live	O
concert	O
sound	O
,	O
churches	O
,	O
nightclubs	O
,	O
and	O
theme	O
parks	O
.	O
</s>
<s>
Movie	O
theatres	O
certified	O
to	O
the	O
THX	O
standard	O
for	O
playback	O
always	O
include	O
high-capability	O
subwoofers	B-Application
.	O
</s>
<s>
Some	O
professional	O
applications	O
require	O
subwoofers	B-Application
designed	O
for	O
very	O
high	O
sound	O
levels	O
,	O
using	O
multiple	O
12-	O
,	O
15-	O
,	O
18	O
-	O
or	O
21-inch	O
drivers	O
(	O
30cm	O
,	O
40cm	O
,	O
45cm	O
,	O
53cm	O
respectively	O
)	O
.	O
</s>
<s>
Drivers	O
as	O
small	O
as	O
10-inch	O
(	O
25cm	O
)	O
are	O
occasionally	O
used	O
,	O
generally	O
in	O
horn-loaded	B-Device
enclosures	O
.	O
</s>
<s>
The	O
number	O
of	O
subwoofer	B-Device
enclosures	I-Device
used	O
in	O
a	O
concert	O
depends	O
on	O
a	O
number	O
of	O
factors	O
,	O
including	O
the	O
size	O
of	O
the	O
venue	O
,	O
whether	O
it	O
is	O
indoors	O
or	O
outdoors	O
,	O
the	O
amount	O
of	O
low-frequency	O
content	O
in	O
the	O
band	O
's	O
sound	O
,	O
the	O
desired	O
volume	O
of	O
the	O
concert	O
,	O
and	O
the	O
design	O
and	O
construction	O
of	O
the	O
enclosures	O
(	O
e.g.	O
,	O
direct-radiating	O
versus	O
horn-loaded	B-Device
)	O
.	O
</s>
<s>
A	O
tiny	O
coffeehouse	O
may	O
only	O
need	O
a	O
single	O
10-inch	O
subwoofer	B-Application
cabinet	O
to	O
augment	O
the	O
bass	O
provided	O
by	O
the	O
full-range	O
speakers	O
.	O
</s>
<s>
A	O
small	O
bar	O
may	O
use	O
one	O
or	O
two	O
direct-radiating	O
15-inch	O
(	O
40cm	O
)	O
subwoofer	B-Application
cabinets	O
.	O
</s>
<s>
A	O
large	O
dance	O
club	O
may	O
have	O
a	O
row	O
of	O
four	O
or	O
five	O
twin	O
18-inch	O
(	O
45cm	O
)	O
subwoofer	B-Application
cabinets	O
,	O
or	O
more	O
.	O
</s>
<s>
In	O
the	O
largest	O
stadium	O
venues	O
,	O
there	O
may	O
be	O
a	O
very	O
large	O
number	O
of	O
subwoofer	B-Device
enclosures	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
the	O
2009	O
–	O
2010	O
U2	O
360°	O
Tour	O
used	O
24	O
Clair	O
Brothers	O
BT-218	O
subwoofers	B-Application
(	O
a	O
double	O
18-inch	O
(	O
45cm	O
)	O
box	O
)	O
around	O
the	O
perimeter	O
of	O
the	O
central	O
circular	O
stage	O
,	O
and	O
72	O
proprietary	O
Clair	O
Brothers	O
cardioid	O
S4	O
subwoofers	B-Application
placed	O
underneath	O
the	O
ring-shaped	O
"	O
B	O
"	O
stage	O
which	O
encircles	O
the	O
central	O
main	O
stage	O
.	O
</s>
<s>
The	O
main	O
speakers	O
may	O
be	O
'	O
flown	O
 '	O
from	O
the	O
ceiling	O
of	O
a	O
venue	O
on	O
chain	O
hoists	O
,	O
and	O
'	O
flying	O
points	O
 '	O
(	O
i.e.	O
,	O
attachment	O
points	O
)	O
are	O
built	O
into	O
many	O
professional	O
loudspeaker	B-Device
enclosures	I-Device
.	O
</s>
<s>
Subwoofers	B-Application
can	O
be	O
flown	O
or	O
stacked	O
on	O
the	O
ground	O
near	O
the	O
stage	O
.	O
</s>
<s>
One	O
of	O
the	O
reasons	O
subwoofers	B-Application
may	O
be	O
installed	O
on	O
the	O
ground	O
is	O
that	O
on-the-ground	O
installation	O
can	O
increase	O
the	O
bass	O
performance	O
,	O
particularly	O
if	O
the	O
subwoofer	B-Application
is	O
placed	O
in	O
the	O
corner	O
of	O
a	O
room	O
(	O
conversely	O
,	O
if	O
a	O
subwoofer	B-Application
cabinet	O
is	O
perceived	O
as	O
too	O
loud	O
,	O
alternatives	O
to	O
on-the-ground	O
or	O
in-corner	O
installation	O
may	O
be	O
considered	O
)	O
.	O
</s>
<s>
Just	O
as	O
consumer	O
subwoofer	B-Device
enclosures	I-Device
can	O
be	O
made	O
of	O
medium-density	O
fibreboard	O
(	O
MDF	O
)	O
,	O
oriented	O
strand	O
board	O
(	O
OSB	O
)	O
,	O
plywood	O
,	O
plastic	O
or	O
other	O
dense	O
material	O
,	O
professional	O
subwoofer	B-Device
enclosures	I-Device
can	O
be	O
built	O
from	O
the	O
same	O
materials	O
.	O
</s>
<s>
MDF	O
is	O
commonly	O
used	O
to	O
construct	O
subwoofers	B-Application
for	O
permanent	O
installations	O
as	O
its	O
density	O
is	O
relatively	O
high	O
and	O
weatherproofing	O
is	O
not	O
a	O
concern	O
.	O
</s>
<s>
Other	O
permanent	O
installation	O
subwoofers	B-Application
have	O
used	O
very	O
thick	O
plywood	O
:	O
the	O
Altec	O
8182	O
(	O
1981	O
)	O
used	O
7-ply	O
28mm	O
birch-faced	O
oak	O
plywood	O
.	O
</s>
<s>
Touring	O
subwoofers	B-Application
are	O
typically	O
built	O
from	O
18	O
–	O
20mm	O
thick	O
void-free	O
Baltic	O
birch	O
(	O
Betula	O
pendula	O
or	O
Betula	O
pubescens	O
)	O
plywood	O
from	O
Finland	O
,	O
Estonia	O
or	O
Russia	O
;	O
such	O
plywood	O
affords	O
greater	O
strength	O
for	O
frequently	O
transported	O
enclosures	O
.	O
</s>
<s>
Not	O
naturally	O
weatherproof	O
,	O
Baltic	O
birch	O
is	O
coated	O
with	O
carpet	O
,	O
thick	O
paint	O
or	O
spray-on	O
truck	O
bedliner	O
to	O
give	O
the	O
subwoofer	B-Device
enclosures	I-Device
greater	O
durability	O
.	O
</s>
<s>
Touring	O
subwoofer	B-Application
cabinets	O
are	O
typically	O
designed	O
with	O
features	O
that	O
facilitate	O
moving	O
the	O
enclosure	B-Device
(	O
e.g.	O
,	O
wheels	O
,	O
a	O
"	O
towel	O
bar	O
"	O
handle	O
and	O
recessed	O
handles	O
)	O
,	O
a	O
protective	O
grille	O
for	O
the	O
speaker	O
(	O
in	O
direct	O
radiating-style	O
cabinets	O
)	O
,	O
metal	O
or	O
plastic	O
protection	O
for	O
the	O
cabinets	O
to	O
protect	O
the	O
finish	O
as	O
the	O
cabinets	O
are	O
being	O
slid	O
one	O
on	O
top	O
of	O
another	O
,	O
and	O
hardware	O
to	O
facilitate	O
stacking	O
the	O
cabinets	O
(	O
e.g.	O
,	O
interlocking	O
corners	O
)	O
and	O
for	O
"	O
flying	O
"	O
the	O
cabinets	O
from	O
stage	O
rigging	O
.	O
</s>
<s>
In	O
the	O
2000s	O
,	O
many	O
small	O
-	O
to	O
mid-size	O
subwoofers	B-Application
designed	O
for	O
bands	O
 '	O
live	O
sound	O
use	O
and	O
DJ	O
applications	O
are	O
"	O
powered	O
subs	O
"	O
;	O
that	O
is	O
,	O
they	O
have	O
an	O
integrated	O
power	O
amplifier	O
.	O
</s>
<s>
These	O
models	O
typically	O
have	O
a	O
built-in	O
crossover	B-Algorithm
.	O
</s>
<s>
In	O
professional	O
concert	O
sound	O
system	O
design	O
,	O
subwoofers	B-Application
can	O
be	O
incorporated	O
seamlessly	O
with	O
the	O
main	O
speakers	O
into	O
a	O
stereo	O
or	O
mono	O
full-range	O
system	O
by	O
using	O
an	O
active	B-Algorithm
crossover	I-Algorithm
.	O
</s>
<s>
The	O
audio	O
engineer	O
typically	O
adjusts	O
the	O
frequency	O
point	O
at	O
which	O
lower	O
frequency	O
sounds	O
are	O
routed	O
to	O
the	O
subwoofer	B-Application
speaker(s )	O
,	O
and	O
mid-frequency	O
and	O
higher	O
frequency	O
sounds	O
are	O
sent	O
to	O
the	O
full-range	O
speakers	O
.	O
</s>
<s>
If	O
the	O
main	O
sound	O
system	O
is	O
stereo	O
,	O
the	O
subwoofers	B-Application
can	O
also	O
be	O
in	O
stereo	O
.	O
</s>
<s>
Otherwise	O
,	O
a	O
mono	O
subwoofer	B-Application
channel	O
can	O
be	O
derived	O
within	O
the	O
crossover	B-Algorithm
from	O
a	O
stereo	O
mix	O
,	O
depending	O
on	O
the	O
crossover	B-Algorithm
make	O
and	O
model	O
.	O
</s>
<s>
While	O
2010-era	O
subwoofer	B-Application
cabinet	O
manufacturers	O
suggest	O
placing	O
subwoofers	B-Application
on	O
either	O
side	O
of	O
a	O
stage	O
(	O
as	O
implied	O
by	O
the	O
inclusion	O
of	O
pole	O
cups	O
for	O
the	O
full-range	O
PA	O
cabinets	O
)	O
,	O
Dave	O
Purton	O
argues	O
that	O
for	O
club	O
gigs	O
,	O
having	O
two	O
subwoofer	B-Application
cabinets	O
on	O
either	O
side	O
of	O
a	O
stage	O
will	O
lead	O
to	O
gaps	O
in	O
bass	O
coverage	O
in	O
the	O
venue	O
;	O
he	O
states	O
that	O
putting	O
the	O
two	O
subwoofer	B-Application
cabinets	O
together	O
will	O
create	O
a	O
more	O
even	O
,	O
omnidirectional	O
sub-bass	O
tone	O
.	O
</s>
<s>
Instead	O
of	O
being	O
incorporated	O
into	O
a	O
full-range	O
system	O
,	O
concert	O
subwoofers	B-Application
can	O
be	O
supplied	O
with	O
their	O
own	O
signal	O
from	O
a	O
separate	O
mix	O
bus	O
on	O
the	O
mixing	O
console	O
;	O
often	O
one	O
of	O
the	O
auxiliary	O
sends	O
(	O
"	O
aux	O
"	O
or	O
"	O
auxes	O
"	O
)	O
is	O
used	O
.	O
</s>
<s>
This	O
configuration	O
is	O
called	O
"	O
aux-fed	O
subwoofers	B-Application
"	O
,	O
and	O
has	O
been	O
observed	O
to	O
significantly	O
reduce	O
low-frequency	O
"	O
muddiness	O
"	O
that	O
can	O
build	O
up	O
in	O
a	O
concert	O
sound	O
system	O
which	O
has	O
on	O
stage	O
a	O
number	O
of	O
microphones	O
each	O
picking	O
up	O
low	O
frequencies	O
and	O
each	O
having	O
different	O
phase	O
relationships	O
of	O
those	O
low	O
frequencies	O
.	O
</s>
<s>
The	O
aux-fed	O
subwoofers	B-Application
method	O
greatly	O
reduces	O
the	O
number	O
of	O
sources	O
feeding	O
the	O
subwoofers	B-Application
to	O
include	O
only	O
those	O
instruments	O
that	O
have	O
desired	O
low-frequency	O
information	O
;	O
sources	O
such	O
as	O
kick	O
drum	O
,	O
bass	O
guitar	O
,	O
samplers	O
and	O
keyboard	O
instruments	O
.	O
</s>
<s>
This	O
simplifies	O
the	O
signal	O
sent	O
to	O
the	O
subwoofers	B-Application
and	O
makes	O
for	O
greater	O
clarity	O
and	O
low	O
punch	O
.	O
</s>
<s>
Aux-fed	O
subwoofers	B-Application
can	O
even	O
be	O
stereo	O
,	O
if	O
desired	O
,	O
using	O
two	O
auxiliary	O
mix	O
buses	O
.	O
</s>
<s>
To	O
keep	O
low-frequency	O
sound	O
focused	O
on	O
the	O
audience	O
area	O
and	O
not	O
on	O
the	O
stage	O
,	O
and	O
to	O
keep	O
low	O
frequencies	O
from	O
bothering	O
people	O
outside	O
of	O
the	O
event	O
space	O
,	O
a	O
variety	O
of	O
techniques	O
have	O
been	O
developed	O
in	O
concert	O
sound	O
to	O
turn	O
the	O
naturally	O
omnidirectional	O
radiation	O
of	O
subwoofers	B-Application
into	O
a	O
more	O
directional	O
pattern	O
.	O
</s>
<s>
These	O
techniques	O
include	O
:	O
setting	O
up	O
subwoofers	B-Application
in	O
a	O
vertical	O
array	O
;	O
using	O
combinations	O
of	O
delay	O
and	O
polarity	O
inversion	O
;	O
and	O
setting	O
up	O
a	O
delay-shaded	O
system	O
.	O
</s>
<s>
With	O
a	O
cardioid	O
dispersion	O
pattern	O
,	O
two	O
end-fire	O
subwoofers	B-Application
can	O
be	O
placed	O
one	O
in	O
front	O
of	O
the	O
other	O
.	O
</s>
<s>
The	O
enclosure	B-Device
nearest	O
the	O
listener	O
is	O
delayed	O
by	O
a	O
few	O
milliseconds	O
.	O
</s>
<s>
The	O
second	O
subwoofer	B-Application
is	O
delayed	O
a	O
precise	O
amount	O
corresponding	O
to	O
the	O
time	O
it	O
takes	O
sound	O
to	O
traverse	O
the	O
distance	O
between	O
speaker	O
grilles	O
.	O
</s>
<s>
Stacking	O
or	O
rigging	O
the	O
subwoofers	B-Application
in	O
a	O
vertical	O
array	O
focuses	O
the	O
low	O
frequencies	O
forward	O
to	O
a	O
greater	O
or	O
lesser	O
extent	O
depending	O
on	O
the	O
physical	O
length	O
of	O
the	O
array	O
.	O
</s>
<s>
Another	O
cardioid	O
subwoofer	B-Application
array	O
pattern	O
can	O
be	O
used	O
horizontally	O
,	O
one	O
which	O
takes	O
few	O
channels	O
of	O
processing	O
and	O
no	O
change	O
in	O
required	O
physical	O
space	O
.	O
</s>
<s>
This	O
method	O
is	O
often	O
called	O
"	O
cardioid	O
subwoofer	B-Application
array	O
"	O
or	O
"	O
CSA	O
"	O
even	O
though	O
the	O
pattern	O
of	O
all	O
directional	O
subwoofer	B-Application
methods	O
is	O
cardioid	O
.	O
</s>
<s>
The	O
CSA	O
method	O
reverses	O
the	O
enclosure	B-Device
orientation	O
and	O
inverts	O
the	O
polarity	O
of	O
one	O
out	O
of	O
every	O
three	O
subwoofers	B-Application
across	O
the	O
front	O
of	O
the	O
stage	O
,	O
and	O
delays	O
those	O
enclosures	O
for	O
maximum	O
cancellation	O
of	O
the	O
target	O
frequency	O
on	O
stage	O
.	O
</s>
<s>
Polarity	O
inversion	O
can	O
be	O
implemented	O
electronically	O
,	O
by	O
reversing	O
the	O
wiring	O
polarity	O
,	O
or	O
by	O
physically	O
positioning	O
the	O
enclosure	B-Device
to	O
face	O
rearward	O
.	O
</s>
<s>
This	O
method	O
reduces	O
forward	O
output	O
relative	O
to	O
a	O
tight-packed	O
,	O
flat-fronted	O
array	O
of	O
subwoofers	B-Application
,	O
but	O
can	O
solve	O
problems	O
of	O
unwanted	O
low-frequency	O
energy	O
coming	O
into	O
microphones	O
on	O
stage	O
.	O
</s>
<s>
A	O
second	O
method	O
of	O
rear	O
delay	O
array	O
combines	O
end-fire	O
topology	O
with	O
polarity	O
reversal	O
,	O
using	O
two	O
subwoofers	B-Application
positioned	O
front	O
to	O
back	O
,	O
the	O
drivers	O
spaced	O
one-quarter	O
wavelength	O
apart	O
,	O
the	O
rear	O
enclosure	B-Device
inverted	O
in	O
polarity	O
and	O
delayed	O
by	O
a	O
few	O
milliseconds	O
for	O
maximum	O
cancellation	O
on	O
stage	O
of	O
the	O
target	O
frequency	O
.	O
</s>
<s>
The	O
end-fire	O
subwoofer	B-Application
method	O
,	O
also	O
called	O
"	O
forward	O
steered	O
arrays	O
"	O
,	O
places	O
subwoofer	B-Application
drivers	O
co-axially	O
in	O
one	O
or	O
more	O
rows	O
,	O
using	O
destructive	O
interference	O
to	O
reduce	O
emissions	O
to	O
the	O
sides	O
and	O
rear	O
.	O
</s>
<s>
This	O
can	O
be	O
done	O
with	O
separate	O
subwoofer	B-Device
enclosures	I-Device
positioned	O
front	O
to	O
back	O
with	O
a	O
spacing	O
between	O
them	O
of	O
one-quarter	O
wavelength	O
of	O
the	O
target	O
frequency	O
,	O
the	O
frequency	O
that	O
is	O
least	O
wanted	O
on	O
stage	O
or	O
most	O
desired	O
in	O
the	O
audience	O
.	O
</s>
<s>
The	O
arrival	O
time	O
of	O
sound	O
energy	O
from	O
all	O
the	O
subwoofers	B-Application
is	O
near-simultaneous	O
from	O
the	O
audience	O
's	O
perspective	O
,	O
but	O
is	O
canceled	O
out	O
to	O
a	O
large	O
degree	O
behind	O
the	O
subwoofers	B-Application
because	O
of	O
offset	O
sound	O
wave	O
arrival	O
times	O
.	O
</s>
<s>
Directionality	O
of	O
the	O
target	O
frequency	O
can	O
achieve	O
as	O
much	O
as	O
25dB	O
rear	O
attenuation	O
,	O
and	O
the	O
forward	O
sound	O
is	O
coherently	O
summed	O
in	O
line	O
with	O
the	O
subwoofers	B-Application
.	O
</s>
<s>
The	O
positional	O
technique	O
of	O
end-fire	O
subwoofers	B-Application
came	O
into	O
widespread	O
use	O
in	O
European	O
live	O
concert	O
sound	O
in	O
2006	O
.	O
</s>
<s>
The	O
output	O
pattern	O
suffers	O
from	O
comb-filtering	O
off-axis	O
,	O
but	O
can	O
be	O
further	O
shaped	O
by	O
adjusting	O
the	O
frequency	O
response	O
of	O
each	O
row	O
of	O
subwoofers	B-Application
.	O
</s>
<s>
A	O
long	O
line	O
of	O
subwoofers	B-Application
placed	O
horizontally	O
along	O
the	O
front	O
edge	O
of	O
the	O
stage	O
can	O
be	O
delayed	O
such	O
that	O
the	O
center	O
subwoofers	B-Application
fire	O
several	O
milliseconds	O
prior	O
to	O
the	O
ones	O
flanking	O
them	O
,	O
which	O
fire	O
several	O
milliseconds	O
prior	O
to	O
their	O
neighbors	O
,	O
continuing	O
in	O
this	O
fashion	O
until	O
the	O
last	O
subwoofers	B-Application
are	O
reached	O
at	O
the	O
outside	O
ends	O
of	O
the	O
subwoofer	B-Application
row	O
(	O
beamforming	B-Algorithm
)	O
.	O
</s>
<s>
This	O
method	O
helps	O
to	O
counteract	O
the	O
extreme	O
narrowing	O
of	O
the	O
horizontal	O
dispersion	O
pattern	O
seen	O
with	O
a	O
horizontal	O
subwoofer	B-Application
array	O
.	O
</s>
<s>
Some	O
subwoofer	B-Device
enclosure	I-Device
designs	O
rely	O
on	O
drivers	O
facing	O
to	O
the	O
sides	O
or	O
to	O
the	O
rear	O
in	O
order	O
to	O
achieve	O
a	O
degree	O
of	O
directionality	O
.	O
</s>
<s>
End-fire	O
drivers	O
can	O
be	O
positioned	O
within	O
a	O
single	O
enclosure	B-Device
that	O
houses	O
more	O
than	O
one	O
driver	B-Device
.	O
</s>
<s>
Some	O
less	O
commonly-used	O
bass	O
enclosures	O
are	O
variants	O
of	O
the	O
subwoofer	B-Device
enclosure	I-Device
's	O
normal	O
range	O
,	O
such	O
as	O
the	O
mid-bass	O
cabinet	O
(	O
60	O
–	O
160Hz	O
)	O
and	O
the	O
infrasonic	O
(	O
extra	O
low	O
)	O
subwoofer	B-Application
(	O
below	O
30Hz	O
)	O
.	O
</s>
<s>
Front-loaded	O
subwoofers	B-Application
have	O
one	O
or	O
more	O
subwoofer	B-Application
speakers	O
in	O
a	O
cabinet	O
,	O
typically	O
with	O
a	O
grille	O
to	O
protect	O
the	O
speakers	O
.	O
</s>
<s>
In	O
practice	O
,	O
many	O
front-loaded	O
subwoofer	B-Application
cabinets	O
have	O
a	O
vent	O
or	O
port	O
in	O
the	O
speaker	B-Device
cabinet	I-Device
,	O
thus	O
creating	O
a	O
bass	O
reflex	O
enclosure	B-Device
.	O
</s>
<s>
As	O
such	O
,	O
non-vented	O
front-firing	O
subwoofer	B-Application
cabinets	O
are	O
rare	O
in	O
pro	O
audio	O
applications	O
.	O
</s>
<s>
Horn-loaded	B-Device
subwoofers	B-Application
have	O
a	O
subwoofer	B-Application
speaker	O
that	O
has	O
a	O
pathway	O
following	O
the	O
loudspeaker	O
.	O
</s>
<s>
Cerwin-Vega	O
states	O
that	O
its	O
folded	B-Device
horn	I-Device
subwoofer	B-Application
cabinets	O
,	O
"	O
on	O
...	O
average	O
,	O
produce	O
6dB	O
more	O
output	O
at	O
1	O
watt	O
than	O
a	O
dual	O
18[-inch]	O
vented	O
box	O
"	O
giving	O
"	O
four	O
times	O
the	O
output	O
with	O
half	O
the	O
number	O
of	O
drivers	O
"	O
.	O
</s>
<s>
The	O
Cerwin-Vega	O
JE-36C	O
has	O
a	O
five	O
feet	O
long	O
folded	B-Device
horn	I-Device
chamber	O
length	O
in	O
the	O
wooden	O
cabinet	O
.	O
</s>
<s>
Manifold	O
subwoofers	B-Application
have	O
two	O
or	O
more	O
subwoofer	B-Application
speakers	O
that	O
feed	O
the	O
throat	O
of	O
a	O
single	O
horn	O
.	O
</s>
<s>
This	O
increases	O
SPL	O
for	O
the	O
subwoofer	B-Application
,	O
at	O
the	O
cost	O
of	O
increased	O
distortion	O
.	O
</s>
<s>
EV	O
has	O
a	O
manifold	O
speaker	B-Device
cabinet	I-Device
in	O
which	O
four	O
drivers	O
are	O
mounted	O
as	O
close	O
together	O
as	O
practical	O
.	O
</s>
<s>
An	O
unusual	O
example	O
of	O
manifold	O
subwoofer	B-Application
design	O
is	O
the	O
Thomas	O
Mundorf	O
(	O
TM	O
)	O
approach	O
of	O
having	O
four	O
subwoofers	B-Application
facing	O
each	O
other	O
and	O
sitting	O
close	O
together	O
,	O
which	O
is	O
used	O
for	O
theatre	O
in	O
the	O
round	O
shows	O
,	O
where	O
the	O
audience	O
surrounds	O
the	O
performers	O
in	O
a	O
big	O
circle	O
(	O
e.g.	O
,	O
Metallica	O
has	O
used	O
this	O
in	O
some	O
concerts	O
)	O
.	O
</s>
<s>
Cerwin-Vega	O
defines	O
a	O
manifold	O
enclosure	B-Device
as	O
one	O
in	O
which	O
"	O
the	O
...	O
driver	B-Device
faces	O
into	O
a	O
tuned	O
ported	O
cavity	O
.	O
</s>
<s>
You	O
hear	O
sound	O
directly	O
from	O
the	O
back	O
of	O
the	O
driver	B-Device
in	O
addition	O
to	O
the	O
sound	O
that	O
emanates	O
out	O
of	O
the	O
port	O
.	O
</s>
<s>
This	O
type	O
of	O
enclosure	B-Device
design	O
extends	O
the	O
frequency	O
capability	O
of	O
the	O
driver	B-Device
lower	O
than	O
it	O
would	O
reproduce	O
by	O
itself.	O
"	O
</s>
<s>
Bandpass	O
subwoofers	B-Application
have	O
a	O
sealed	O
cabinet	O
within	O
another	O
cabinet	O
,	O
with	O
the	O
"	O
outer	O
"	O
cabinet	O
typically	O
having	O
a	O
vent	O
or	O
port	O
.	O
</s>
<s>
In	O
rare	O
cases	O
,	O
sound	O
reinforcement	O
subwoofer	B-Device
enclosures	I-Device
are	O
also	O
used	O
for	O
bass	O
instrument	O
amplification	O
by	O
electric	O
bass	O
players	O
and	O
synth	O
bass	O
players	O
.	O
</s>
<s>
For	O
most	O
bands	O
and	O
most	O
small	O
-	O
to	O
mid-size	O
venues	O
(	O
e.g.	O
,	O
nightclubs	O
and	O
bars	O
)	O
,	O
standard	O
bass	O
guitar	O
speaker	B-Device
enclosures	I-Device
or	O
keyboard	O
amplifiers	O
will	O
provide	O
sufficient	O
sound	O
pressure	O
levels	O
for	O
onstage	O
monitoring	O
.	O
</s>
<s>
However	O
,	O
in	O
some	O
cases	O
,	O
performers	O
wish	O
to	O
have	O
extended	O
sub-bass	O
response	O
that	O
is	O
not	O
available	O
from	O
standard	O
instrument	O
speaker	B-Device
enclosures	I-Device
,	O
so	O
they	O
use	O
subwoofer	B-Application
cabinets	O
.	O
</s>
<s>
Just	O
as	O
some	O
electric	O
guitarists	O
add	O
huge	O
stacks	O
of	O
guitar	O
cabinets	O
mainly	O
for	O
show	O
,	O
some	O
bassists	O
will	O
add	O
immense	O
subwoofer	B-Application
cabinets	O
with	O
18-inch	O
woofers	B-Device
mainly	O
for	O
show	O
,	O
and	O
the	O
extension	O
subwoofer	B-Application
cabinets	O
will	O
be	O
operated	O
at	O
a	O
lower	O
volume	O
than	O
the	O
main	O
bass	O
cabinets	O
.	O
</s>
<s>
Bass	O
guitar	O
players	O
who	O
may	O
use	O
subwoofer	B-Application
cabinets	O
include	O
performers	O
who	O
play	O
with	O
extended	O
range	O
basses	O
that	O
include	O
a	O
low	O
"	O
B	O
"	O
string	O
(	O
about	O
31Hz	O
)	O
,	O
bassists	O
who	O
play	O
in	O
styles	O
where	O
a	O
very	O
powerful	O
sub-bass	O
response	O
is	O
an	O
important	O
part	O
of	O
the	O
sound	O
(	O
e.g.	O
,	O
funk	O
,	O
Latin	O
,	O
gospel	O
,	O
R	O
&	O
B	O
,	O
etc	O
.	O
</s>
<s>
Keyboard	O
players	O
who	O
use	O
subwoofers	B-Application
for	O
on-stage	O
monitoring	O
include	O
electric	O
organ	O
players	O
who	O
use	O
bass	O
pedal	O
keyboards	O
(	O
which	O
go	O
down	O
to	O
a	O
low	O
"	O
C	O
"	O
which	O
is	O
about	O
33Hz	O
)	O
and	O
synth	O
bass	O
players	O
who	O
play	O
rumbling	O
sub-bass	O
parts	O
that	O
go	O
as	O
low	O
as	O
18Hz	O
.	O
</s>
<s>
Several	O
concert	O
sound	O
subwoofer	B-Application
manufacturers	O
suggest	O
that	O
their	O
subs	O
can	O
be	O
used	O
for	O
bass	O
instrument	O
amplification	O
.	O
</s>
<s>
Meyer	O
Sound	O
suggests	O
that	O
its	O
650-R2	O
Concert	O
Series	O
Subwoofer	B-Application
,	O
a	O
enclosure	B-Device
with	O
two	O
18-inch	O
drivers	O
(	O
45cm	O
)	O
,	O
can	O
be	O
used	O
for	O
bass	O
instrument	O
amplification	O
.	O
</s>
<s>
While	O
performers	O
who	O
use	O
concert	O
sound	O
subwoofers	B-Application
for	O
onstage	O
monitoring	O
may	O
like	O
the	O
powerful	O
sub-bass	O
sound	O
that	O
they	O
get	O
onstage	O
,	O
sound	O
engineers	O
may	O
find	O
the	O
use	O
of	O
large	O
subwoofers	B-Application
(	O
e.g.	O
,	O
two	O
18-inch	O
drivers	O
(	O
45cm	O
)	O
)	O
for	O
onstage	O
instrument	O
monitoring	O
to	O
be	O
problematic	O
,	O
because	O
it	O
may	O
interfere	O
with	O
the	O
"	O
Front	O
of	O
House	O
"	O
sub-bass	O
sound	O
.	O
</s>
<s>
Unlike	O
a	O
typical	O
subwoofer	B-Application
driver	B-Device
,	O
which	O
produces	O
audible	O
vibrations	O
,	O
tactile	O
transducers	O
produce	O
low-frequency	O
vibrations	O
that	O
are	O
designed	O
to	O
be	O
felt	O
by	O
individuals	O
who	O
are	O
touching	O
the	O
transducer	O
or	O
indirectly	O
through	O
a	O
piece	O
of	O
furniture	O
or	O
a	O
wooden	O
floor	O
.	O
</s>
<s>
They	O
are	O
attached	O
to	O
a	O
seat	O
,	O
for	O
instance	O
a	O
drummer	O
's	O
stool	O
(	O
"	O
throne	O
"	O
)	O
or	O
gamer	O
's	O
chair	O
,	O
car	O
seat	O
or	O
home	O
theater	O
seating	O
,	O
and	O
the	O
vibrations	O
of	O
the	O
driver	B-Device
are	O
transmitted	O
to	O
the	O
body	O
then	O
to	O
the	O
ear	O
in	O
a	O
manner	O
similar	O
to	O
bone	O
conduction	O
.	O
</s>
<s>
They	O
connect	O
to	O
an	O
amplifier	O
like	O
a	O
normal	O
subwoofer	B-Application
.	O
</s>
<s>
This	O
helps	O
the	O
drummer	O
in	O
a	O
rock	O
music	O
band	O
to	O
monitor	O
their	O
kick	O
drum	O
performance	O
without	O
filling	O
the	O
stage	O
with	O
powerful	O
,	O
loud	O
low-frequency	O
sound	O
from	O
a	O
15-inch	O
(	O
40cm	O
)	O
subwoofer	B-Application
monitor	O
and	O
an	O
amplifier	O
,	O
which	O
can	O
"	O
leak	O
"	O
into	O
other	O
drum	O
mics	O
and	O
lower	O
the	O
quality	O
of	O
the	O
sound	O
mix	O
.	O
</s>
<s>
By	O
not	O
having	O
a	O
large	O
,	O
powerful	O
subwoofer	B-Application
monitor	O
,	O
a	O
bass	O
shaker	O
also	O
enables	O
a	O
drummer	O
to	O
lower	O
the	O
sound	O
pressure	O
levels	O
that	O
they	O
are	O
exposed	O
to	O
during	O
a	O
performance	O
,	O
reducing	O
the	O
risk	O
of	O
hearing	O
damage	O
.	O
</s>
<s>
With	O
varying	O
measures	O
upon	O
which	O
to	O
base	O
claims	O
,	O
several	O
subwoofers	B-Application
have	O
been	O
said	O
to	O
be	O
the	O
world	O
's	O
largest	O
,	O
loudest	O
or	O
lowest	O
.	O
</s>
<s>
The	O
Matterhorn	O
is	O
a	O
subwoofer	B-Application
model	O
completed	O
in	O
March	O
2007	O
by	O
Danley	O
Sound	O
Labs	O
in	O
Gainesville	O
,	O
Georgia	O
after	O
a	O
U.S.	O
military	O
request	O
for	O
a	O
loudspeaker	O
that	O
could	O
project	O
infrasonic	O
waves	O
over	O
a	O
distance	O
.	O
</s>
<s>
The	O
subwoofer	B-Application
has	O
a	O
flat	O
frequency	O
response	O
from	O
15	O
to	O
80Hz	O
,	O
and	O
is	O
down	O
3dB	O
at	O
12Hz	O
.	O
</s>
<s>
The	O
container	O
doors	O
swing	O
open	O
to	O
reveal	O
a	O
tapped	O
horn	O
driven	O
by	O
40	O
long-throw	O
15-inch	O
(	O
40cm	O
)	O
MTX	O
speaker	B-Device
drivers	I-Device
each	O
powered	O
by	O
its	O
own	O
1000-watt	O
amplifier	O
.	O
</s>
<s>
A	O
diesel	B-Algorithm
generator	I-Algorithm
is	O
housed	O
within	O
the	O
enclosure	B-Device
to	O
supply	O
electricity	O
when	O
external	O
power	O
is	O
unavailable	O
.	O
</s>
<s>
Instead	O
,	O
using	O
only	O
a	O
single	O
20	O
amp	O
electrical	O
circuit	O
for	O
safety	O
,	O
visitors	O
were	O
allowed	O
to	O
step	O
inside	O
the	O
horn	O
of	O
the	O
subwoofer	B-Application
for	O
an	O
"	O
acoustic	O
massage	O
"	O
as	O
the	O
fractionally	O
powered	O
Matterhorn	O
reproduced	O
low	O
level	O
10	O
–	O
15Hz	O
waves	O
.	O
</s>
<s>
Another	O
subwoofer	B-Application
claimed	O
to	O
be	O
the	O
world	O
's	O
biggest	O
is	O
a	O
custom	O
installation	O
in	O
Italy	O
made	O
by	O
Royal	O
Device	O
primarily	O
of	O
bricks	O
,	O
concrete	O
and	O
sound-deadening	O
material	O
consisting	O
of	O
two	O
subwoofers	B-Application
embedded	O
in	O
the	O
foundation	O
of	O
a	O
listening	O
room	O
.	O
</s>
<s>
The	O
horn-loaded	B-Device
subwoofers	B-Application
each	O
have	O
a	O
floor	O
mouth	O
that	O
is	O
,	O
and	O
a	O
horn	O
length	O
that	O
is	O
,	O
in	O
a	O
cavity	O
under	O
the	O
floor	O
of	O
the	O
listening	O
room	O
.	O
</s>
<s>
Each	O
subwoofer	B-Application
is	O
driven	O
by	O
eight	O
18-inch	O
subwoofer	B-Application
drivers	O
with	O
voice	O
coils	O
.	O
</s>
<s>
A	O
single	O
diameter	O
subwoofer	B-Application
driver	B-Device
was	O
designed	O
by	O
Richard	O
Clark	O
and	O
David	O
Navone	O
with	O
the	O
help	O
of	O
Dr.	O
Eugene	O
Patronis	O
of	O
the	O
Georgia	O
Institute	O
of	O
Technology	O
.	O
</s>
<s>
The	O
driver	B-Device
was	O
intended	O
to	O
break	O
sound	O
pressure	O
level	O
records	O
when	O
mounted	O
in	O
a	O
road	O
vehicle	O
,	O
calculated	O
to	O
be	O
able	O
to	O
achieve	O
more	O
than	O
180dBSPL	O
.	O
</s>
<s>
The	O
driver	B-Device
was	O
mounted	O
in	O
a	O
stepvan	O
owned	O
by	O
Tim	O
Maynor	O
but	O
was	O
too	O
powerful	O
for	O
the	O
amount	O
of	O
applied	O
reinforcement	O
and	O
damaged	O
the	O
vehicle	O
.	O
</s>
<s>
MTX	O
's	O
Loyd	O
Ivey	O
helped	O
underwrite	O
the	O
project	O
and	O
the	O
driver	B-Device
was	O
then	O
called	O
the	O
MTX	O
"	O
Thunder	O
1000000	O
"	O
(	O
one	O
million	O
)	O
.	O
</s>
<s>
The	O
heaviest	O
production	O
subwoofer	B-Application
intended	O
for	O
use	O
in	O
automobiles	O
is	O
the	O
MTX	O
Jackhammer	O
by	O
MTX	O
Audio	O
,	O
which	O
features	O
a	O
diameter	O
cone	O
.	O
</s>
<s>
The	O
Jackhammer	O
has	O
been	O
featured	O
on	O
the	O
reality	O
TV	O
show	O
Pimp	B-Device
My	I-Device
Ride	I-Device
.	O
</s>
