<s>
In	O
a	O
loudspeaker	O
,	O
power	B-Architecture
compression	I-Architecture
or	O
thermal	B-Architecture
compression	I-Architecture
is	O
a	O
loss	O
of	O
efficiency	O
observed	O
as	O
the	O
voice	B-Device
coil	I-Device
heats	O
up	O
under	O
operation	O
,	O
increasing	O
the	O
DC	O
resistance	O
of	O
the	O
voice	B-Device
coil	I-Device
and	O
decreasing	O
the	O
effective	O
available	O
power	O
of	O
the	O
audio	O
amplifier	O
.	O
</s>
<s>
Two	O
main	O
pathways	O
exist	O
to	O
mitigate	O
the	O
problem	O
:	O
to	O
design	O
a	O
way	O
for	O
the	O
voice	B-Device
coil	I-Device
to	O
dissipate	O
more	O
heat	O
during	O
operation	O
,	O
and	O
to	O
design	O
a	O
more	O
efficient	O
transducer	O
that	O
generates	O
less	O
heat	O
for	O
a	O
given	O
sound	O
output	O
level	O
.	O
</s>
<s>
The	O
other	O
95%	O
or	O
more	O
of	O
the	O
electrical	O
energy	O
is	O
turned	O
into	O
unwanted	O
heat	O
,	O
which	O
causes	O
the	O
voice	B-Device
coil	I-Device
to	O
increase	O
in	O
temperature	O
.	O
</s>
<s>
Too	O
much	O
heat	O
–	O
more	O
than	O
–	O
can	O
destroy	O
the	O
voice	B-Device
coil	I-Device
,	O
but	O
long	O
before	O
that	O
happens	O
the	O
loudspeaker	O
will	O
experience	O
power	B-Architecture
compression	I-Architecture
.	O
</s>
<s>
A	O
voice	B-Device
coil	I-Device
made	O
of	O
copper	O
wire	O
will	O
have	O
its	O
DC	O
resistance	O
increase	O
by	O
about	O
72%	O
when	O
heating	O
up	O
from	O
20°	O
C	O
(	O
room	O
temperature	O
)	O
to	O
200°	O
C	O
,	O
and	O
its	O
sensitivity	O
will	O
decrease	O
by	O
4.7	O
decibels	O
.	O
</s>
<s>
Silver	O
wire	O
has	O
a	O
slightly	O
worse	O
problem	O
with	O
power	B-Architecture
compression	I-Architecture
,	O
while	O
aluminum	O
wire	O
is	O
slightly	O
better	O
.	O
</s>
<s>
In	O
multi-way	O
systems	O
,	O
power	B-Architecture
compression	I-Architecture
is	O
often	O
observed	O
to	O
occur	O
first	O
in	O
one	O
of	O
the	O
low	O
frequency	O
bandpasses	O
.	O
</s>
<s>
In	O
passive	O
loudspeakers	O
with	O
internal	O
crossover	O
components	O
,	O
power	B-Architecture
compression	I-Architecture
will	O
change	O
the	O
electrical	O
characteristics	O
of	O
the	O
crossover	O
filters	O
,	O
and	O
the	O
crossover	O
point	O
can	O
shift	O
,	O
introducing	O
distortions	O
related	O
to	O
an	O
incorrect	O
crossover	O
filter	O
.	O
</s>
<s>
To	O
counteract	O
power	B-Architecture
compression	I-Architecture
,	O
one	O
solution	O
is	O
to	O
increase	O
heat	O
dissipation	O
.	O
</s>
<s>
Typical	O
methods	O
include	O
cooling	O
fins	O
on	O
the	O
magnet	O
housing	O
,	O
a	O
larger	O
diameter	O
voice	B-Device
coil	I-Device
,	O
ferrofluid	O
in	O
the	O
gap	O
between	O
voice	B-Device
coil	I-Device
and	O
magnet	O
,	O
venting	O
of	O
the	O
pole	O
piece	O
,	O
metal	O
parts	O
that	O
conduct	O
heat	O
to	O
the	O
outside	O
,	O
increasing	O
the	O
enclosure	O
's	O
internal	O
chamber	O
volume	O
behind	O
the	O
magnet	O
,	O
and	O
electric	O
cooling	O
fans	O
.	O
</s>
<s>
Another	O
solution	O
is	O
to	O
design	O
a	O
system	O
that	O
increases	O
efficiency	O
,	O
such	O
as	O
by	O
using	O
a	O
horn	B-Device
loudspeaker	I-Device
rather	O
than	O
a	O
direct-radiating	O
design	O
.	O
</s>
<s>
Or	O
by	O
choosing	O
a	O
transducer	O
other	O
than	O
the	O
voice	B-Device
coil	I-Device
,	O
such	O
as	O
Bruce	O
Thigpen	O
's	O
rotary	B-Device
woofer	I-Device
(	O
1974	O
)	O
or	O
Tom	O
Danley	O
's	O
servo-motor	O
subwoofer	O
(	O
1983	O
)	O
.	O
</s>
<s>
Power	B-Architecture
compression	I-Architecture
is	O
usually	O
considered	O
a	O
long-term	O
problem	O
,	O
arising	O
over	O
time	O
with	O
extended	O
strong	O
signal	O
sent	O
to	O
the	O
loudspeaker	O
.	O
</s>
