<s>
A	O
speaker	B-Device
enclosure	I-Device
using	O
a	O
passive	B-Architecture
radiator	I-Architecture
(	O
PR	O
)	O
usually	O
contains	O
an	O
"	O
active	O
loudspeaker	O
"	O
(	O
or	O
main	O
driver	O
)	O
,	O
and	O
a	O
passive	B-Architecture
radiator	I-Architecture
(	O
also	O
known	O
as	O
a	O
"	O
drone	O
cone	O
"	O
)	O
.	O
</s>
<s>
The	O
active	O
loudspeaker	O
is	O
a	O
normal	O
driver	O
,	O
and	O
the	O
passive	B-Architecture
radiator	I-Architecture
is	O
of	O
similar	O
construction	O
,	O
but	O
without	O
a	O
voice	B-Device
coil	I-Device
and	O
magnet	O
assembly	O
.	O
</s>
<s>
It	O
is	O
not	O
attached	O
to	O
a	O
voice	B-Device
coil	I-Device
or	O
wired	O
to	O
an	O
electrical	O
circuit	O
or	O
power	O
amplifier	O
.	O
</s>
<s>
In	O
the	O
same	O
way	O
as	O
a	O
ported	O
loudspeaker	O
,	O
a	O
passive	B-Architecture
radiator	I-Architecture
system	O
uses	O
the	O
sound	O
pressure	O
otherwise	O
trapped	O
in	O
the	O
enclosure	O
to	O
excite	O
a	O
resonance	O
that	O
makes	O
it	O
easier	O
for	O
the	O
speaker	O
system	O
to	O
create	O
the	O
deepest	O
pitches	O
(	O
e.g.	O
,	O
basslines	O
)	O
.	O
</s>
<s>
The	O
passive	B-Architecture
radiator	I-Architecture
resonates	O
at	O
a	O
frequency	O
determined	O
by	O
its	O
mass	O
and	O
the	O
springiness	O
(	O
compliance	O
)	O
of	O
the	O
air	O
in	O
the	O
enclosure	O
.	O
</s>
<s>
Internal	O
air	O
pressure	O
produced	O
by	O
movements	O
of	O
the	O
active	O
driver	O
cone	O
moves	O
the	O
passive	B-Architecture
radiator	I-Architecture
cone	O
.	O
</s>
<s>
Passive	B-Architecture
radiators	I-Architecture
are	O
used	O
instead	O
of	O
a	O
reflex	O
port	O
for	O
several	O
reasons	O
.	O
</s>
<s>
To	O
a	O
first-order	O
approximation	O
,	O
the	O
passive	B-Architecture
radiator	I-Architecture
works	O
identically	O
to	O
a	O
port	O
.	O
</s>
<s>
Passive	B-Architecture
radiators	I-Architecture
are	O
tuned	O
by	O
mass	O
variations	O
(	O
Mmp	O
)	O
,	O
changing	O
the	O
way	O
that	O
they	O
interact	O
with	O
the	O
compliance	O
of	O
the	O
air	O
in	O
the	O
box	O
.	O
</s>
<s>
The	O
weight	O
of	O
the	O
cone	O
of	O
the	O
passive	B-Architecture
radiator	I-Architecture
should	O
be	O
approximately	O
equivalent	O
to	O
the	O
mass	O
of	O
the	O
air	O
that	O
would	O
have	O
filled	O
the	O
port	O
which	O
might	O
have	O
been	O
used	O
for	O
that	O
design	O
.	O
</s>
<s>
If	O
the	O
passive	B-Architecture
radiator	I-Architecture
's	O
acoustic	O
mass	O
equals	O
that	O
of	O
the	O
port	O
,	O
and	O
the	O
PR	O
's	O
compliance	O
is	O
negligible	O
,	O
then	O
the	O
frequency	O
response	O
behaviour	O
of	O
these	O
two	O
types	O
of	O
systems	O
will	O
be	O
virtually	O
identical	O
.	O
</s>
<s>
Although	O
the	O
frequency	O
response	O
of	O
a	O
passive	B-Architecture
radiator	I-Architecture
will	O
be	O
similar	O
to	O
that	O
of	O
a	O
ported	O
cabinet	O
,	O
the	O
system	O
low-frequency	O
roll-off	O
will	O
be	O
slightly	O
steeper	O
(	O
5th-order	O
rather	O
than	O
4th-order	O
)	O
,	O
due	O
to	O
a	O
notch	O
(	O
dip	O
)	O
in	O
the	O
frequency	O
response	O
caused	O
by	O
the	O
Vap	O
(	O
compliance	O
or	O
stiffness	O
)	O
of	O
the	O
passive	B-Architecture
radiator	I-Architecture
.	O
</s>
<s>
Passive	B-Architecture
radiators	I-Architecture
are	O
used	O
in	O
Bluetooth	B-Protocol
speakers	O
,	O
home	O
stereo	O
speakers	O
,	O
subwoofer	B-Application
cabinets	O
and	O
car	O
audio	O
speaker	O
systems	O
,	O
particularly	O
in	O
cases	O
where	O
there	O
is	O
not	O
enough	O
space	O
for	O
a	O
port	O
or	O
vent	O
system	O
.	O
</s>
<s>
While	O
most	O
studio	B-Device
monitor	I-Device
speakers	I-Device
are	O
either	O
ported	O
bass	O
reflex	O
designs	O
,	O
or	O
closed-back	O
without	O
a	O
vent	O
or	O
passive	B-Architecture
radiator	I-Architecture
,	O
Mackie	O
's	O
HR824	O
and	O
HR624	O
monitor	O
speakers	O
have	O
a	O
passive	B-Architecture
radiator	I-Architecture
installed	O
on	O
the	O
rear	O
of	O
the	O
cabinet	O
.	O
</s>
<s>
Focal	O
also	O
sells	O
a	O
studio	B-Device
monitor	I-Device
with	O
a	O
passive	B-Architecture
radiator	I-Architecture
called	O
the	O
SM9	O
.	O
</s>
<s>
Respective	O
examples	O
of	O
a	O
smart	B-Device
speaker	I-Device
and	O
a	O
portable	O
Bluetooth	B-Protocol
Speaker	O
utilizing	O
passive	B-Architecture
radiators	I-Architecture
are	O
Apple	O
's	O
HomePod	B-Device
mini	I-Device
and	O
Ultimate	O
Ears	O
 '	O
UE	B-Application
Boom	I-Application
.	O
</s>
