Altec Lansing 9444B - Manual (Page 5)

Operating and Service Instructions for the Altec Lansing 9444B Power Amplifier
SOURCE AMPLIFIER’S INPUTS AUX OUTPUTS
Figure 3 Typical Input Connections
AMPLIFIER’S OUTPUTS LOUDSPEAKER LOADS
Figure 4 Typical Output Connections
Had 18 GA wire been used in the
above excunple, the loss in the
cable would have been 51.9 watts.
This example illustrates the im­ portance of using the proper wire
size.
3.4.2 Calculating Power
Losses with ohm
Loads
To calculate ti:
losses
when using a 4 ohm г.р‘ =акег sys­
tem, multiply the loss 3 ohms
by 8. In the above example, the 10
GA wire would comiuaie 24.3
watts of power while !■ 18 GA
wire would waste 15-‘ watts -
more than half of the amplifier's 4
ohm power rating.
3.5 Damping Fact-.; r
The higher thi diunping
factor rating of air amplifier, the
greater the ability of Üi- amplifier
to control unwanted sp- sker cone
movements. When a signal drives
a woofer, current flow;¡ ’.hrough
the voice coil creates ■ uagnetic
field. This field inters. ^ with the
permanent magnetic field in the
gap and forces the combination
cone and voice coil aiisembly to
move outward. When i he signal is
removed, the assembly moves in­
ward but its momeid.ii causes it
to overshoot its resting point. This
overshoot will damfx n iLself out
eventually but the unwanted mo­
vements can add consirierabie dis­
tortion products to
111 -' .'iound
In the process of movitig inward
through the magnetic field, the
voice coil assembly generates a
current of opposite polarity to the
original
signal. This current
induces a voltage or “1- ick EMF”
which travels through ihe speaker
wore to the ampiiiler's output.
The lower the amplifier’s output
impedance, the faster the over­
shoot of the voice coil vill dampen
out. The output impeilance of an
amplifier can be calculated by
dividing the rated output impe­
dance, typically 8 ohms, by the
damping factor. The U-144B has a
damping factor rating of 200
which correspond^
.■ an output
imp>edance of 0.04 ohms.
S.tS.l C a l c u l a t i n g t h e
Maximun i<‘ngth of
Cable for ü Specified
ALTEC LANSING^ CORPORATION • a Mark IV Company