4
TEST PROCEDURES
Figure 1. Free Space
®
Model 16 Loudspeaker
Test Setup Diagram
1. Phase Test
1.1 Turn the rotary switch to the "8
Ω
"
position and apply a 6-10V DC signal
to the input terminals with the posi-
tive signal applied to the "8
Ω
" terminal
and negative signal applied to the
"COM" terminal.
1.2 The driver should move outward
when the DC voltage is applied.
2. Air Leak, Rub and Tick Test
2.1 Set up the system as shown in
Figure 1.
2.2 For the air leak, rub and tick, and
power sweep tests, all listening will be
done at a distance not to exceed 1
foot if the ambient noise is greater
than 65 db. An air leak is considered
to exist when audible while facing the
baffle of the speaker assembly.
2.3 Apply a 6 Vrms, 20Hz signal to the
8 ohm input with the rotary switch set
at 8 ohm to the terminals of the
loudspeaker.
Reject any speakers with air leaks.
Except for air leaks resulting from
defective driver or gaskets. Replace
any driver that has a rubbing or ticking
noise.
Small (quiet) ticks are acceptable if
they cannot be heard at a distance of
1 foot.
Note: There is a normal suspension
noise. To distinguish between a rub or
tick and suspension noise, displace
the cone slightly with your finger. If
the rubbing can be made to go away
or gets worse, then it is a rub or tick. If
the noise stays the same, it is a
suspension noise.
3. System Sweep Test
3.1 Set the rotary switch to the 8 ohm
position.
3.2 Apply a 6 Vrms, 80Hz signal to the
input terminal of the loudspeaker.
Change the oscillator frequency slowly
from 80Hz to 16kHz. Listen carefully for
buzzes, rattles, or other extraneous
noises from the driver or from the
internal parts. The whooshing noise
from the port around 80 Hz is accept-
able.
4. Transformer Tap Select Check
Apply a 70 Vrms, 100Hz signal to the
input of the loudspeaker under test.
Slowly change the tap selection, on
the unit under test, from the high
position (16W) to the 1W position. A
decrease in level should be heard for
each descending tap.
Power Amplifier
INPUT
OUTPUT
Audio Signal
Generator
