SUB 550P - JBL Audio Service Manual (repair manual). Page 9

 

x  Function/signal generator/sweep generator 
x Integrated 

Amplifier 

x Multimeter 
x Speaker 

cables 

1)  From the signal generator, connect line level (RCA) cables to the Subwoofer Line Level Input jacks L/R on 

the UUT. Use a Y-cable from a mono source if necessary to connect to both inputs.  

2)  Turn the CROSSOVER control to maximum (150). 
3)  Turn the LEVEL control on the UUT to completely counterclockwise (MIN). 
4)  LFE/NORMAL switch should be in NORMAL position. 
5)  PHASE switch position does not matter. 
6)  Turn on generator; adjust to 

.

7)  Plug in UUT; turn the power switch ON. LED should switch from Red to Green.  
8)  Turn LEVEL control clockwise 

until vigorous bass response is heard and felt 

from port tube opening on the bottom. 

9)  Turn off generator, turn LEVEL control full counterclockwise (MIN), and disconnect RCA cable. 

1)  Follow steps 1-8 above, using a sweep generator as a signal source. 
2)  Sweep generator from 20Hz to 300Hz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or 

any other noises. If any unusual noises are heard, remove woofer and test. 

1)  Remove woofer from cabinet; detach + and - wire clips. 
2)  Check DC resistance of woofer; it should be 3.4 ohms ±10%
3)  Connect a pair of speaker cables to driver terminals. Cables should be connected to an integrated amplifier 

fed by a signal generator. Turn on generator and adjust so that speaker level output is 5.0V.

4)  Sweep generator from 20Hz to 1kHz. Listen to driver for any rubbing, buzzing, or other unusual noises. 

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