<s>
In	O
a	O
loudspeaker	O
,	O
a	O
phase	B-Architecture
plug	I-Architecture
,	O
phasing	B-Architecture
plug	I-Architecture
or	O
acoustical	O
transformer	O
is	O
a	O
mechanical	O
interface	O
between	O
a	O
speaker	B-Device
driver	I-Device
and	O
the	O
audience	O
.	O
</s>
<s>
The	O
phase	B-Architecture
plug	I-Architecture
extends	O
high	O
frequency	O
response	O
because	O
it	O
guides	O
waves	O
outward	O
toward	O
the	O
listener	O
rather	O
than	O
allowing	O
them	O
to	O
interact	O
destructively	O
near	O
the	O
driver	O
.	O
</s>
<s>
Phase	B-Architecture
plugs	I-Architecture
are	O
commonly	O
found	O
in	O
high-powered	O
horn	B-Device
loudspeakers	I-Device
used	O
in	O
professional	O
audio	O
,	O
in	O
the	O
mid	O
-	O
and	O
high-frequency	O
bandpasses	O
,	O
positioned	O
between	O
the	O
compression	B-Device
driver	I-Device
diaphragm	O
and	O
the	O
acoustic	O
horn	O
.	O
</s>
<s>
They	O
may	O
also	O
be	O
present	O
in	O
front	O
of	O
woofer	B-Device
cones	O
in	O
some	O
loudspeaker	O
designs	O
.	O
</s>
<s>
The	O
phase	B-Architecture
plug	I-Architecture
can	O
be	O
considered	O
a	O
further	O
narrowing	O
of	O
the	O
horn	O
throat	O
,	O
becoming	O
an	O
extension	O
of	O
the	O
horn	O
to	O
the	O
surface	O
of	O
the	O
diaphragm	O
.	O
</s>
<s>
Various	O
loudspeaker	O
designs	O
were	O
produced	O
in	O
the	O
1920s	O
,	O
including	O
General	O
Electric	O
engineers	O
Chester	O
W	O
.	O
Rice	O
and	O
Edward	O
W	O
.	O
Kellogg	O
mating	O
an	O
acoustic	O
horn	O
to	O
the	O
speaker	B-Device
driver	I-Device
in	O
1925	O
.	O
</s>
<s>
In	O
1926	O
,	O
Bell	O
System	O
engineers	O
Albert	O
L	O
.	O
Thuras	O
and	O
Edward	O
C	O
.	O
Wente	O
modified	O
the	O
horn	B-Device
loudspeaker	I-Device
by	O
inserting	O
the	O
first	O
phase	B-Architecture
plug	I-Architecture
between	O
the	O
driver	O
and	O
the	O
horn	O
.	O
</s>
<s>
This	O
phase	B-Architecture
plug	I-Architecture
directed	O
sound	O
waves	O
into	O
the	O
horn	O
throat	O
from	O
the	O
center	O
of	O
the	O
diaphragm	O
and	O
from	O
a	O
ring	O
around	O
the	O
perimeter	O
of	O
the	O
diaphragm	O
,	O
by	O
way	O
of	O
center	O
hole	O
and	O
annular	O
slot	O
,	O
for	O
the	O
purpose	O
of	O
improving	O
"	O
the	O
transmission	O
characteristics	O
"	O
of	O
the	O
loudspeaker	O
"	O
at	O
the	O
upper	O
portion	O
of	O
the	O
sound	O
frequency	O
range.	O
"	O
</s>
<s>
Based	O
on	O
their	O
joint	O
research	O
,	O
the	O
two	O
engineers	O
were	O
awarded	O
consecutive	O
U.S.	O
patents	O
:	O
Thuras	O
filed	O
a	O
patent	O
for	O
a	O
novel	O
electrodynamic	O
diaphragm	O
design	O
,	O
and	O
Wente	O
filed	O
a	O
patent	O
for	O
the	O
first	O
phase	B-Architecture
plug	I-Architecture
.	O
</s>
<s>
The	O
principles	O
laid	O
out	O
by	O
Thuras	O
and	O
Wente	O
have	O
influenced	O
every	O
subsequent	O
phase	B-Architecture
plug	I-Architecture
design	O
.	O
</s>
<s>
In	O
horn	B-Device
loudspeakers	I-Device
,	O
the	O
phase	B-Architecture
plug	I-Architecture
serves	O
to	O
carry	O
sound	O
waves	O
out	O
from	O
all	O
areas	O
of	O
the	O
compression	B-Device
driver	I-Device
diaphragm	O
through	O
the	O
compression	O
chamber	O
to	O
the	O
horn	O
throat	O
such	O
that	O
each	O
pulse	O
of	O
sound	O
reaches	O
the	O
throat	O
as	O
one	O
coherent	O
wave	O
front	O
.	O
</s>
<s>
The	O
phase	B-Architecture
plug	I-Architecture
is	O
a	O
complex	O
and	O
expensive	O
element	O
of	O
the	O
compression	B-Device
driver	I-Device
.	O
</s>
<s>
Phase	B-Architecture
plugs	I-Architecture
are	O
machined	O
in	O
metals	O
such	O
as	O
aluminum	O
,	O
or	O
cast	O
in	O
hard	O
plastic	O
or	O
Bakelite	O
.	O
</s>
<s>
Many	O
variations	O
exist	O
in	O
phase	B-Architecture
plug	I-Architecture
design	O
,	O
but	O
two	O
types	O
have	O
evolved	O
to	O
match	O
two	O
major	O
diaphragm	O
types	O
:	O
dome	O
and	O
ring	O
.	O
</s>
<s>
Phase	B-Architecture
plugs	I-Architecture
that	O
interface	O
with	O
dome-type	O
diaphragms	O
include	O
a	O
wide	O
variety	O
:	O
designs	O
with	O
radial	O
slots	O
,	O
designs	O
with	O
concentric	O
annular	O
ring	O
slots	O
,	O
and	O
hybrid	O
designs	O
with	O
a	O
combination	O
of	O
annular	O
and	O
radial	O
slots	O
.	O
</s>
<s>
Altec	O
engineer	O
Clifford	O
A	O
.	O
Henricksen	O
reported	O
on	O
the	O
differences	O
between	O
radial	O
and	O
"	O
circumferential	O
"	O
types	O
of	O
phase	B-Architecture
plugs	I-Architecture
at	O
Audio	O
Engineering	O
Society	O
conventions	O
in	O
1976	O
and	O
1978	O
.	O
</s>
<s>
Radial	O
slots	O
in	O
the	O
phase	B-Architecture
plug	I-Architecture
do	O
not	O
correct	O
for	O
this	O
small	O
time	O
difference	O
,	O
which	O
affects	O
the	O
highest	O
frequencies	O
.	O
</s>
<s>
Circular	O
slots	O
may	O
allow	O
resonances	O
to	O
build	O
up	O
between	O
the	O
diaphragm	O
and	O
the	O
phase	B-Architecture
plug	I-Architecture
—	O
resonances	O
which	O
cause	O
wave	O
cancellations	O
and	O
a	O
corresponding	O
reduction	O
in	O
frequency	O
response	O
at	O
the	O
resonance	O
frequency	O
.	O
</s>
<s>
This	O
design	O
requires	O
a	O
radically	O
different	O
shape	O
of	O
phase	B-Architecture
plug	I-Architecture
,	O
but	O
radial	O
slots	O
and	O
concentric	O
rings	O
may	O
still	O
play	O
a	O
part	O
.	O
</s>
<s>
The	O
combined	O
area	O
of	O
the	O
phase	B-Architecture
plug	I-Architecture
slots	O
is	O
typically	O
about	O
one-eighth	O
to	O
one-tenth	O
of	O
the	O
area	O
of	O
the	O
diaphragm	O
.	O
</s>
<s>
A	O
smaller	O
slot	O
area	O
traps	O
more	O
wave	O
energy	O
between	O
the	O
phase	B-Architecture
plug	I-Architecture
and	O
the	O
diaphragm	O
.	O
</s>
<s>
In	O
researching	O
the	O
diaphragm/phase	O
plug	O
interface	O
,	O
David	O
Gunness	O
found	O
that	O
only	O
half	O
the	O
wave	O
energy	O
,	O
at	O
best	O
,	O
travels	O
directly	O
from	O
the	O
diaphragm	O
through	O
the	O
phase	B-Architecture
plug	I-Architecture
slots	O
and	O
out	O
to	O
the	O
listener	O
.	O
</s>
<s>
The	O
other	O
half	O
(	O
or	O
more	O
)	O
causes	O
cancellations	O
within	O
the	O
space	O
between	O
the	O
diaphragm	O
and	O
the	O
phase	B-Architecture
plug	I-Architecture
,	O
or	O
causes	O
temporal	O
anomalies	O
(	O
time	O
smear	O
)	O
upon	O
leaving	O
the	O
phase	B-Architecture
plug	I-Architecture
later	O
than	O
the	O
direct	O
sound	O
.	O
</s>
<s>
To	O
minimize	O
the	O
problem	O
,	O
Gunness	O
modeled	O
the	O
behavior	O
mathematically	O
and	O
used	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
to	O
apply	O
a	O
polarity-reversed	O
version	O
of	O
the	O
undesired	O
wave	O
behavior	O
to	O
the	O
original	O
audio	O
signal	O
.	O
</s>
<s>
Phase	B-Architecture
plugs	I-Architecture
may	O
be	O
placed	O
in	O
front	O
of	O
woofer	B-Device
cones	O
,	O
especially	O
in	O
horn-loaded	O
loudspeaker	O
designs	O
.	O
</s>
<s>
In	O
the	O
same	O
fashion	O
as	O
compression	B-Device
driver	I-Device
phase	B-Architecture
plugs	I-Architecture
,	O
the	O
intent	O
is	O
to	O
minimize	O
higher-frequency	O
wave	O
interference	O
near	O
the	O
driver	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
"	O
high	O
frequency	O
"	O
is	O
relative	O
to	O
the	O
intended	O
bandpass	O
;	O
for	O
example	O
,	O
a	O
cone	O
woofer	B-Device
might	O
be	O
expected	O
to	O
reproduce	O
550Hz	O
energy	O
near	O
the	O
top	O
of	O
its	O
intended	O
range	O
,	O
however	O
,	O
the	O
wavelength	O
of	O
550Hz	O
is	O
approximately	O
twice	O
the	O
diameter	O
of	O
the	O
woofer	B-Device
,	O
so	O
wave	O
energy	O
at	O
that	O
frequency	O
traveling	O
laterally	O
from	O
one	O
side	O
to	O
the	O
other	O
will	O
be	O
out	O
of	O
phase	O
and	O
will	O
cancel	O
.	O
</s>
<s>
With	O
a	O
phase	B-Architecture
plug	I-Architecture
in	O
the	O
center	O
,	O
such	O
lateral	O
wave	O
energy	O
bounces	O
off	O
of	O
the	O
obstruction	O
and	O
is	O
reflected	O
outward	O
toward	O
the	O
listener	O
.	O
</s>
<s>
Phase	B-Architecture
plugs	I-Architecture
for	O
woofer	B-Device
cones	O
are	O
typically	O
solid	O
plugs	O
positioned	O
over	O
the	O
woofer	B-Device
's	O
central	O
dust	O
cap	O
,	O
or	O
in	O
the	O
center	O
of	O
the	O
woofer	B-Device
,	O
replacing	O
the	O
dust	O
cap	O
.	O
</s>
