<s>
Acoustic	B-Architecture
suspension	I-Architecture
(	O
air	O
suspension	O
,	O
closed	O
box	O
,	O
sealed	O
box	O
)	O
is	O
a	O
method	O
of	O
loudspeaker	B-Device
cabinet	I-Device
design	O
and	O
utilisation	O
that	O
uses	O
one	O
or	O
more	O
loudspeaker	O
drivers	O
mounted	O
in	O
a	O
sealed	O
box	O
or	O
cabinet	O
.	O
</s>
<s>
Acoustic	B-Architecture
suspension	I-Architecture
systems	O
reduce	O
bass	O
distortion	O
that	O
can	O
be	O
caused	O
by	O
stiff	O
motor	O
suspensions	O
in	O
conventional	O
loudspeakers	O
.	O
</s>
<s>
A	O
compact	O
acoustic	B-Architecture
suspension	I-Architecture
loudspeaker	O
was	O
described	O
in	O
1954	O
by	O
Edgar	O
Villchur	O
,	O
and	O
it	O
was	O
brought	O
to	O
commercial	O
production	O
by	O
Villchur	O
and	O
Henry	O
Kloss	O
with	O
the	O
founding	O
of	O
Acoustic	O
Research	O
in	O
Cambridge	O
,	O
Massachusetts	O
.	O
</s>
<s>
In	O
1960	O
,	O
Villchur	O
reiterated	O
that	O
:	O
The	O
first	O
aim	O
of	O
the	O
acoustic	B-Architecture
suspension	I-Architecture
design	O
,	O
over	O
and	O
above	O
uniformity	O
of	O
frequency	O
response	O
,	O
compactness	O
,	O
and	O
extension	O
of	O
response	O
into	O
the	O
low-bass	O
range	O
,	O
is	O
to	O
reduce	O
significantly	O
the	O
level	O
of	O
bass	O
distortion	O
that	O
had	O
previously	O
been	O
tolerated	O
in	O
loudspeakers	O
.	O
</s>
<s>
Speaker	B-Device
cabinets	I-Device
with	O
acoustic	B-Architecture
suspension	I-Architecture
can	O
provide	O
well-controlled	O
bass	O
response	O
,	O
especially	O
in	O
comparison	O
with	O
an	O
equivalently-sized	O
speaker	B-Device
enclosure	I-Device
that	O
has	O
a	O
bass	O
reflex	O
port	O
or	O
vent	O
.	O
</s>
<s>
Sealed	O
boxes	O
are	O
generally	O
less	O
efficient	O
than	O
a	O
bass-reflex	O
cabinet	O
for	O
the	O
same	O
low-frequency	O
cut-off	O
and	O
cabinet	O
volume	O
,	O
so	O
a	O
sealed-box	O
speaker	B-Device
cabinet	I-Device
will	O
need	O
more	O
electrical	O
power	O
to	O
deliver	O
the	O
same	O
amount	O
of	O
acoustic	O
low-frequency	O
bass	O
output	O
.	O
</s>
<s>
The	O
acoustic	B-Architecture
suspension	I-Architecture
woofer	I-Architecture
uses	O
the	O
elastic	O
cushion	O
of	O
air	O
within	O
a	O
sealed	O
enclosure	O
to	O
provide	O
the	O
restoring	O
force	O
for	O
the	O
woofer	O
diaphragm	B-Device
.	O
</s>
<s>
Unlike	O
the	O
stiff	O
physical	O
suspension	O
built	O
into	O
the	O
driver	O
of	O
conventional	O
speakers	O
,	O
the	O
trapped	O
air	O
inside	O
the	O
sealed-loudspeaker	O
enclosure	O
provides	O
a	O
more	O
linear	O
restoring	O
force	O
for	O
the	O
woofer	O
's	O
diaphragm	B-Device
,	O
enabling	O
it	O
to	O
oscillate	O
a	O
greater	O
distance	O
(	O
excursion	O
)	O
in	O
a	O
linear	O
fashion	O
.	O
</s>
<s>
Even	O
though	O
acoustic	B-Architecture
suspension	I-Architecture
cabinets	O
are	O
often	O
called	O
"	O
sealed	O
box	O
"	O
designs	O
,	O
they	O
are	O
not	O
entirely	O
airtight	O
.	O
</s>
<s>
Acoustic	B-Architecture
suspension	I-Architecture
woofers	I-Architecture
remain	O
popular	O
in	O
hi-fi	O
systems	O
due	O
to	O
their	O
low	O
distortion	O
.	O
</s>
<s>
In	O
the	O
2000s	O
,	O
most	O
subwoofers	B-Application
,	O
bass	O
amplifier	O
cabinets	O
and	O
sound	O
reinforcement	O
system	O
speaker	B-Device
cabinets	I-Device
use	O
bass	O
reflex	O
ports	O
,	O
rather	O
than	O
a	O
sealed-box	O
design	O
,	O
in	O
order	O
to	O
obtain	O
more	O
extended	O
low-frequency	O
response	O
and	O
to	O
get	O
higher	O
sound	O
pressure	O
level	O
(	O
SPL	O
)	O
.	O
</s>
<s>
The	O
speaker	B-Device
enclosure	I-Device
designers	O
and	O
their	O
customers	O
view	O
the	O
risk	O
of	O
increased	O
distortion	O
and	O
phase	O
delay	O
as	O
an	O
acceptable	O
price	O
to	O
pay	O
for	O
increased	O
bass	O
output	O
and	O
higher	O
maximum	O
SPL	O
.	O
</s>
<s>
That	O
said	O
,	O
if	O
one	O
is	O
designing	O
a	O
sound	O
system	O
for	O
a	O
style	O
of	O
music	O
where	O
very	O
accurate	O
,	O
precise	O
bass	O
rhythms	O
are	O
an	O
important	O
part	O
of	O
the	O
genre	O
,	O
one	O
may	O
wish	O
to	O
consider	O
the	O
merits	O
of	O
sealed	O
box	O
woofers	O
and	O
subwoofers	B-Application
.	O
</s>
<s>
The	O
two	O
most	O
common	O
types	O
of	O
speaker	B-Device
enclosure	I-Device
are	O
acoustic	B-Architecture
suspension	I-Architecture
(	O
sometimes	O
called	O
pneumatic	O
suspension	O
)	O
and	O
bass	O
reflex	O
,	O
so	O
they	O
are	O
worth	O
comparing	O
.	O
</s>
<s>
In	O
general	O
,	O
acoustic	B-Architecture
suspension	I-Architecture
systems	O
(	O
driver	O
plus	O
enclosure	O
)	O
have	O
a	O
second-order	O
acoustic	O
(	O
12dB/octave	O
)	O
roll-off	O
below	O
the	O
3dB	O
point	O
.	O
</s>
<s>
This	O
suggests	O
that	O
an	O
acoustic	B-Architecture
suspension	I-Architecture
loudspeaker	O
with	O
the	O
same	O
enclosure	O
volume	O
and	O
low-frequency	O
3dB	O
cut-off	O
as	O
a	O
vented-box	O
system	O
will	O
be	O
up	O
to	O
2.9dB	O
less	O
sensitive	O
than	O
its	O
counterpart	O
.	O
</s>
<s>
Alternatively	O
,	O
if	O
the	O
reference	O
efficiency	O
and	O
cut-off	O
frequency	O
of	O
the	O
two	O
systems	O
is	O
the	O
same	O
,	O
then	O
the	O
enclosure	O
volume	O
of	O
the	O
acoustic	B-Architecture
suspension	I-Architecture
loudspeaker	O
will	O
be	O
approximately	O
twice	O
as	O
large	O
as	O
that	O
of	O
the	O
vented	O
system	O
.	O
</s>
<s>
The	O
acoustic	O
roll-off	O
of	O
acoustic	B-Architecture
suspension	I-Architecture
designs	O
makes	O
them	O
easier	O
to	O
integrate	O
with	O
other	O
drivers	O
with	O
a	O
crossover	O
(	O
passive	O
or	O
active	O
)	O
.	O
</s>
<s>
This	O
makes	O
it	O
an	O
ideal	O
choice	O
for	O
midrange	O
enclosures	O
as	O
well	O
as	O
for	O
satellite	O
speaker	O
and	O
subwoofer	B-Application
systems	O
.	O
</s>
<s>
While	O
boxed	O
hi-fi	O
speakers	O
are	O
often	O
described	O
as	O
being	O
acoustic	B-Architecture
suspension	I-Architecture
or	O
ported	O
(	O
bass	O
reflex	O
)	O
,	O
depending	O
on	O
the	O
absence	O
or	O
presence	O
of	O
a	O
port	O
tube/vent	O
,	O
it	O
is	O
also	O
true	O
that	O
,	O
in	O
typical	O
box	O
speakers	O
with	O
more	O
than	O
two	O
drivers	O
,	O
the	O
midrange	O
drivers	O
between	O
the	O
woofer	O
and	O
tweeter	O
are	O
usually	O
designed	O
as	O
acoustic	B-Architecture
suspension	I-Architecture
,	O
with	O
a	O
separate	O
,	O
sealed	O
air-space	O
,	O
even	O
if	O
the	O
woofer	O
itself	O
is	O
not	O
.	O
</s>
