<s>
Constant-voltage	B-Device
speaker	I-Device
systems	I-Device
refer	O
to	O
networks	O
of	O
loudspeakers	O
which	O
are	O
connected	O
to	O
an	O
audio	O
amplifier	O
using	O
step-up	O
and	O
step-down	O
transformers	B-Algorithm
to	O
simplify	O
impedance	O
calculations	O
and	O
to	O
minimize	O
power	O
loss	O
over	O
the	O
speaker	B-Device
cables	I-Device
.	O
</s>
<s>
Constant-voltage	B-Device
speaker	I-Device
systems	I-Device
are	O
also	O
commonly	O
referred	O
to	O
as	O
25-	O
,	O
70-	O
,	O
70.7-	O
,	O
or	O
100-volt	O
speaker	O
systems	O
;	O
distributed	B-Device
speaker	I-Device
systems	I-Device
;	O
or	O
high-impedance	O
speaker	O
systems	O
.	O
</s>
<s>
Constant-voltage	B-Device
speaker	I-Device
systems	I-Device
are	O
analogous	O
to	O
electrical	O
power	O
transmission	O
methods	O
employed	O
by	O
electric	O
utility	O
companies	O
to	O
transmit	O
electric	O
power	O
over	O
long	O
distances	O
.	O
</s>
<s>
Similarly	O
,	O
in	O
a	O
constant-voltage	B-Device
speaker	I-Device
system	I-Device
,	O
the	O
amplifier	O
uses	O
a	O
transformer	B-Algorithm
to	O
step	O
up	O
the	O
voltage	O
of	O
the	O
audio	O
signal	O
to	O
reduce	O
power	O
loss	O
over	O
the	O
speaker	B-Device
cable	I-Device
,	O
allowing	O
more	O
power	O
to	O
be	O
transmitted	O
over	O
a	O
given	O
wire	O
diameter	O
.	O
</s>
<s>
Each	O
speaker	O
in	O
the	O
system	O
has	O
a	O
step-down	O
transformer	B-Algorithm
to	O
reduce	O
the	O
voltage	O
to	O
a	O
usable	O
level	O
.	O
</s>
<s>
Each	O
loudspeaker	O
's	O
step-down	O
transformer	B-Algorithm
can	O
be	O
designed	O
for	O
a	O
single	O
power	O
level	O
or	O
it	O
can	O
have	O
multiple	O
taps	O
,	O
one	O
of	O
which	O
is	O
selected	O
to	O
match	O
the	O
desired	O
power	O
level	O
to	O
be	O
applied	O
to	O
the	O
loudspeaker	O
.	O
</s>
<s>
Transformers	B-Algorithm
with	O
various	O
taps	O
allow	O
the	O
installer	O
to	O
adjust	O
the	O
sound	O
pressure	O
level	O
up	O
or	O
down	O
at	O
an	O
individual	O
loudspeaker	O
.	O
</s>
<s>
Purpose-built	O
models	O
are	O
available	O
that	O
have	O
the	O
transformer	B-Algorithm
contained	O
within	O
the	O
loudspeaker	B-Device
enclosure	I-Device
.	O
</s>
<s>
The	O
loudspeaker	O
step-down	O
transformer	B-Algorithm
primary	O
is	O
connected	O
in	O
parallel	O
to	O
the	O
constant-voltage	O
line	O
.	O
</s>
<s>
Constant-voltage	O
lines	O
can	O
be	O
driven	O
by	O
a	O
conventional	O
amplifier	O
with	O
external	O
step-up	O
transformer	B-Algorithm
,	O
an	O
amplifier	O
with	O
an	O
internal	O
step-up	O
transformer	B-Algorithm
or	O
a	O
high-voltage	O
amplifier	O
with	O
transformerless	O
output	O
.	O
</s>
<s>
Its	O
output	O
is	O
connected	O
to	O
the	O
primary	O
of	O
an	O
external	O
step-up	O
transformer	B-Algorithm
.	O
</s>
<s>
Special-purpose	O
transformers	B-Algorithm
can	O
tailor	O
the	O
system	O
design	O
to	O
the	O
project	O
's	O
target	O
power	O
levels	O
.	O
</s>
<s>
Multiple	O
amplifiers	O
can	O
be	O
combined	O
together	O
via	O
transformers	B-Algorithm
to	O
yield	O
higher	O
voltage	O
and	O
higher	O
current	O
capacity	O
lines	O
.	O
</s>
<s>
For	O
instance	O
,	O
three	O
70-volt	O
amplifiers	O
have	O
been	O
used	O
to	O
make	O
a	O
210-volt	O
line	O
by	O
connecting	O
them	O
to	O
a	O
special-purpose	O
external	O
output	O
transformer	B-Algorithm
that	O
has	O
three	O
primaries	O
and	O
a	O
single	O
secondary	O
.	O
</s>
<s>
Amplifiers	O
with	O
built-in	O
70-volt	O
output	O
transformers	B-Algorithm
are	O
available	O
with	O
low	O
impedance	O
and	O
high	O
impedance	O
output	O
connections	O
,	O
the	O
latter	O
typically	O
labeled	O
"	O
25	O
V	O
"	O
and	O
"	O
70	O
V	O
"	O
.	O
</s>
<s>
High-voltage	O
constant-voltage	O
systems	O
can	O
be	O
designed	O
to	O
use	O
140-	O
,	O
200	O
-	O
and	O
210-volt	O
lines	O
,	O
depending	O
on	O
the	O
transformers	B-Algorithm
selected	O
and	O
the	O
amplifier	O
connection	O
topology	O
.	O
</s>
<s>
600	O
watt	O
transformers	B-Algorithm
are	O
widely	O
available	O
for	O
contractors	O
needing	O
high	O
power	O
loudspeakers	O
in	O
constant-voltage	O
installations	O
.	O
</s>
<s>
Special-purpose	O
transformers	B-Algorithm
capable	O
of	O
handling	O
1250	O
watts	O
down	O
as	O
low	O
as	O
50	O
Hz	O
are	O
available	O
.	O
</s>
<s>
One	O
problem	O
with	O
high	O
power	O
,	O
high	O
current	O
transformers	B-Algorithm
is	O
that	O
fewer	O
can	O
be	O
used	O
on	O
a	O
single	O
constant-voltage	O
line	O
.	O
</s>
<s>
Larger	O
diameter	O
speaker	B-Device
wire	I-Device
is	O
recommended	O
.	O
</s>
<s>
Larger	O
transformers	B-Algorithm
needed	O
for	O
high	O
power	O
handling	O
have	O
reduced	O
high-frequency	O
response	O
.	O
</s>
<s>
The	O
traditional	O
alternative	O
to	O
constant-voltage	B-Device
speaker	I-Device
systems	I-Device
are	O
low	O
impedance	O
speaker	O
systems	O
(	O
commonly	O
referred	O
to	O
as	O
"	O
8-ohm	O
speaker	O
systems	O
"	O
in	O
spite	O
of	O
the	O
fact	O
that	O
their	O
impedance	O
may	O
not	O
be	O
8	O
ohms	O
)	O
,	O
in	O
which	O
the	O
amplifier	O
and	O
speaker	O
are	O
directly	O
coupled	O
without	O
the	O
use	O
of	O
transformers	B-Algorithm
.	O
</s>
<s>
The	O
disadvantages	O
relative	O
to	O
constant-voltage	O
systems	O
are	O
that	O
speaker	B-Device
cables	I-Device
need	O
to	O
be	O
shorter	O
or	O
larger	O
in	O
diameter	O
and	O
that	O
more	O
amplifiers	O
are	O
needed	O
if	O
different	O
listening	O
levels	O
are	O
desired	O
at	O
different	O
locations	O
.	O
</s>
<s>
Another	O
alternative	O
are	O
powered	B-Device
speakers	I-Device
with	O
an	O
amplifier	O
built	O
into	O
the	O
speaker	B-Device
enclosure	I-Device
.	O
</s>
<s>
The	O
main	O
disadvantage	O
of	O
powered	B-Device
loudspeakers	I-Device
is	O
that	O
they	O
have	O
the	O
additional	O
requirement	O
of	O
requiring	O
AC	O
power	O
,	O
whereas	O
passive	O
speakers	O
have	O
no	O
such	O
requirement	O
.	O
</s>
<s>
The	O
main	O
advantages	O
of	O
using	O
a	O
constant-voltage	B-Device
speaker	I-Device
system	I-Device
over	O
a	O
conventional	O
low	O
impedance	O
speaker	O
system	O
are	O
:	O
</s>
<s>
Frequency	O
Response	O
:	O
Inexpensive	O
transformers	B-Algorithm
may	O
have	O
poor	O
reproduction	O
of	O
low	O
and	O
high	O
frequencies	O
.	O
</s>
<s>
Distortion	O
:	O
Overdriven	O
transformers	B-Algorithm
can	O
add	O
ringing	O
distortion	O
to	O
the	O
audio	O
signal	O
.	O
</s>
<s>
Low	O
cost	O
transformers	B-Algorithm
are	O
prone	O
to	O
distortion	O
at	O
higher	O
power	O
levels	O
,	O
especially	O
with	O
regard	O
to	O
low	O
frequency	O
response	O
.	O
</s>
<s>
Low	O
level	O
signals	O
can	O
fail	O
to	O
energize	O
a	O
poorly	O
designed	O
transformer	B-Algorithm
core	O
enough	O
to	O
prevent	O
higher	O
than	O
normal	O
amounts	O
of	O
harmonic	O
distortion	O
.	O
</s>
<s>
Variation	O
:	O
Unit-to-unit	O
variation	O
can	O
be	O
observed	O
in	O
poorly	O
made	O
transformers	B-Algorithm
.	O
</s>
<s>
Insertion	O
loss	O
:	O
The	O
transformers	B-Algorithm
themselves	O
commonly	O
reduce	O
total	O
power	O
applied	O
to	O
the	O
loudspeakers	O
,	O
requiring	O
the	O
amplifier	O
to	O
be	O
some	O
10%	O
to	O
20%	O
more	O
powerful	O
than	O
the	O
total	O
power	O
that	O
is	O
intended	O
to	O
be	O
applied	O
to	O
the	O
loudspeakers	O
.	O
</s>
<s>
Typical	O
transformer	B-Algorithm
insertion	O
loss	O
measurements	O
are	O
taken	O
at	O
1,000	O
Hz	O
to	O
optimize	O
the	O
transformer	B-Algorithm
's	O
specifications	O
.	O
</s>
<s>
The	O
best	O
transformers	B-Algorithm
reduce	O
mid-band	O
frequencies	O
by	O
0.5	O
dB	O
(	O
approximately	O
10%	O
power	O
loss	O
)	O
or	O
less	O
,	O
resulting	O
in	O
a	O
ten	O
watt	O
loudspeaker	O
drawing	O
11.1	O
watts	O
from	O
the	O
amplifier	O
.	O
</s>
<s>
Capacitance	O
:	O
To	O
achieve	O
higher	O
power	O
levels	O
,	O
transformers	B-Algorithm
must	O
be	O
physically	O
larger	O
.	O
</s>
<s>
Large	O
transformers	B-Algorithm
(	O
above	O
200	O
watts	O
)	O
begin	O
to	O
suffer	O
from	O
high	O
frequency	O
attenuation	O
due	O
to	O
self-capacitance	O
.	O
</s>
<s>
More	O
expensive	O
:	O
If	O
high-power	O
loudspeakers	O
are	O
used	O
with	O
an	O
emphasis	O
on	O
low	O
frequency	O
response	O
,	O
the	O
required	O
transformers	B-Algorithm
will	O
be	O
much	O
larger	O
and	O
will	O
add	O
significant	O
cost	O
to	O
the	O
project	O
.	O
</s>
