Sunday, October 25, 2015

JBL ES250P POWERED SUB WOOFER FUNCTION TEST AND CIRCUIT DIAGRAM

JBL ES250

POWERED SUB WOOFER 

FUNCTION TEST AND CIRCUIT DIAGRAM 

ES250P Test Set Up and Procedure

Equipment needed:
# Function/signal generator/sweep generator

# Integrated Amplifier
# Multimeter
# Speaker cables

General Unit Function (UUT = Unit Under Test)
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 50mV, 50 Hz.
7) Plug in UUT; turn the power switch ON. LED should switch from Red to Green.
8) Turn LEVEL control full clockwise (MAX); immediate and vigorous bass response should be heard and felt from port tube opening on the bottom.
9) Turn off generator, turn LEVEL control full counterclockwise (MIN), and disconnect RCA cable.

Sweep Function
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.

Driver Function
1) Remove woofer from cabinet; detach + and - wire clips.
2) Check DC resistance of woofer; it should be 3.6 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.
ES250P SPECIFICATIONS
Amplifier Power (RMS): 400 Watts
Peak Dynamic Power *: 700 Watts
Driver: 12" (305mm) PolyPlas
Inputs: Line Level (switchable to LFE)
Low-Pass Frequency: Variable from 50Hz to 150Hz (24dB/octave, continuously variable)
Frequency Response: 25Hz – Low-pass crossover setting
Adjust Gain
Turn your Subwoofer-Level Control  up to the halfway position. If no sound emanates from the subwoofer, check the AC-line cord and input cables. Are the connectors on the cables making proper contact? Is the AC plug connected to a “live” receptacle? Has the Power Switch § been pressed to the “On” position? Once you have confirmed that the subwoofer is active, proceed by playing a CD, record or cassette. Use a selection that has ample bass information. Set the overall volume control of the preamplifier or stereo to a comfortable level. Adjust the Subwoofer-Level Control until you obtain a pleasing blend of bass. Bass response should not overpower the room but rather be adjusted so there is a harmonious blend across the entire musical range. Many users have a tendency to set the subwoofer volume too loud, adhering to the belief that a subwoofer is there to produce lots of bass. This is not entirely true. A subwoofer is there to enhance bass, extending the response of the entire system so the bass can be felt as well as heard. However, overall balance must be maintained or the music will not sound natural. An experienced listener will set the volume of the subwoofer so its impact on bass response is always there but never obtrusive.
Phase Control
The Phase Switch  determines whether the subwoofer speaker’s pistonlike action moves in and out with the main speakers, 0 degree , or opposite the main speakers, 180 degree . Proper phase adjustment depends on several variables such as room size, subwoofer placement and listener position. Adjust the phase switch to maximize bass output at the listening position.
Crossover Adjustment
The Crossover Adjustment Control determines the highest frequency at which the subwoofer reproduces sounds. If your main speakers can comfortably reproduce some low-frequency sounds, set this control to a lower frequency setting, between 50Hz and 100Hz. This will concentrate the subwoofer’s efforts on the ultradeep bass sounds required by today’s films and music. If you are using smaller bookshelf speakers that do not extend to the lower bass frequencies, set the Crossover Adjustment control to a higher setting, between 120Hz and 150Hz.
NOTE: This control will have no effect if the LFE/Normal Selector  is set to LFE. If you have a Dolby Digital or DTS processor/receiver, the Low-Pass Frequency is set by the processor/receiver. Consult your owner’s manual to learn how to view or change this setting
CIRCUIT DIAGRAM 
INPUT AND PRE AMP 
FILTER 
AUTO ON OFF CIRCUIT 
EQUALIZATION CIRCUIT  
LIMITER 
POWER AMPLIFIER