| Public Address System
: Good quality public
address system |
| (Amplifier, loudspeaker,
microphone, cable connector
) amplifies |
| low level sound to high
level sound. Right & correct combination / |
| connection of the
system gives quality sound and long life. |
|
|
|
| Impedance
: Specification & combination of loud speaker |
| is very
important to know for matching & connection to get |
| quality sound.
Check specification of unit before connection. |
| Driver
unit 16 ohms |
Horn
Speaker 8 ohms |
Box
speaker 8 Ohms |
|
|
|
|
|
|
|
Example
Connection
|
|
|
|
Back Plate of the
AMPLIFIER |
| |
|
|
EARTH the AMPLIFIER
|
|
|
|
Use earth terminal / water
pipe to connect amplifier earth.
|
|
| Connection of Horns & Column Speaker
: These Connections |
| require correct impedance matching
& total power of driver unit |
| and column
speakers is more than rated power of the amplifier. |
| Driver Unit AU35 |
| 35 x
1=35 watt |
| |
| Column. MC15 |
| 15 x 2 =
30 watt |
| |
| Total Power |
| = 35+30 =65 watt |
|
 |
|
|
OUTPUT Power
Distribution to combination of Speakers
|
| Series : Power
to Spkr. 1= 1/2 P / Power to Spkr. 2= 1/2 P |
| Parallel :
Power to Spkr. 1= 1/2 P / Power
to Spkr. 2 = 1/2 P |
| Series-
Parallel : Power to Spkr. 1=
1/2 P / Power to Spkr. 2= 1/4 P |
| / Power
to Spkr. 3= 1/4 P |
|
Ri = Resultant Impedance |
| |
|
|
|
| Series : L1(+) is connected |
Parallel:
L1(+) is connected to |
| to L2(-) of other unit. |
L2 (+) of other unit &
in same way |
 |
all L2(-) are connected. |
 |
|
| Series-Parallel Connection : Two
/ more driver
unit / loud speaker |
| first connected in series then series
group connected in parallel. |
| |
| |
|
|
|
| Impedance Matching :
If Ri is more than impedance tap of amplifier, |
| speaker group will
draw less current & give less sound output. If Ri |
| is less than impedance
tap of amplifier, speaker group will draw |
| more current resulting
in overheat of the amplifier & transistor. |
| |
|
|
|
|
Resultant / Total
Impedance ( Ri )
|
| Series Impedance
: Group A= RA= R1+ R2= 16 + 16= 32 Ohms |
|
Group B= RB= R3 + R4 = 16 +16 = 32 Ohms |
| Parallel
Impedance :RAxRB/RA+RB=32x32/32+32=1024/64=16ohms |
|
|
|
|
Point to
Remember |
| 1. PA amplifier,
equipment, microphone, loud speaker, cables, driver
units, connectors must be of good
quality. |
| 2. Resultant impedance
of the group must be correct & equal or
more than the amplifier |
| 3. Low Impedance
speaker wattage should be 30% more than
amplifier wattage. |
| 4. Many long distance
speaker should be with 100 V LMT &
connected in parallel. |
| 5. total wattage of
100V LMT speaker should be equal or less to
amplifier watts. |
| 6. Bass control of the
amplifier should be in cut position when driver
unit / horn speaker are used. |
| 7. Check phasing of
the driver units & earth connections of the
amplifier before operation. |
|
| How Many Unit Can
be Connect To Amplifier : To
avoid damage |
| to the speaker, total wattage of the driver
units should be 30% high |
| than the rated power of
amplifier. As some high signal during the |
| programme, than amplifier
are unsafe & damage the driver units. |
| Example :
2 Nos driver unit ADU40 / total Wattage= 40x2 =80 watt |
| 60 watt amplifier = 60
watt |
| |
| |
|
|
|
