The following posts are a pictorial of the JBL 3145 crossover network.
Owners of the JBL professional series 4345 monitor may find this information useful should your 4345's require repair, testing or upgrade.
The stock 3145 networks were kindly loaned by Ducatista47 who generously sponsored the opportunity for a detailed examination of these networks.
Ian
Description
This network is the stock crossover network of the JBL professional series 4345 monitor
The assembly consists of a rear mounting plate which supports two stacked PCBs that hold the crossover elements.
The mounting plate is made of a moulded ABS type plastic material. Four terminal posts are located centrally on the mounting plate with a two position multi-pole rotary switch to select either internal passive or external crossover mode for bi amplification. Two iron core chokes are mounted at one end of the rear plate.
A color coded wire loom with crimped spade terminations connects the terminal posts and the biamp switch. Color coded wire links with crimped spade terminations connect the two iron core chokes to the main PCB.
The main PCB is supported by moulded stand-offs on the rear plate with long self tapping screws. The smaller PCB sits atop the main PCB and is attached with clip on PCB stand-offs. Thin rubber washers and a rubber insert pad prevent vibration of the smaller PCB.
The main PCB supports the centrally located rotary switch which is soldered directly to the PCB and the low and the mid frequency filter elements.
A color coded wire link with crimped spade terminations from the main PCB connects to the smaller PCB which supports the high and ultra high frequency filters.
Identification of the crossover filters elements is indicated by component codes on the PCBS.
A series of alpha numeric coded spade terminals on both PCBs connects color coded wire looms and links to the terminal posts, the smaller PCB, the rotary switch, the chokes, the L-pads and loudspeaker drivers.
The wire loom is arranged in three stages for signal from the respective filters to be sent to the L-pads which is then looped back to the PCBs from the L-pads and then to the drivers. Polarity inversion of the signal for mid, high and ultra high frequency drivers is arranged on the PCBs in the final stage of the wire loom to the drivers.
Below spade terminals for the small PCB
HF/UHF PCB filter connections
UHF filter connections
E1 - negative input HF /UHF Pcb
E2 - positive input HF /UHF Pcb
E3 - uhf filter output to L Pad 3 (hot)
E4 - uhf filter Lpads 2 input (hot)
E5 - uhf filter output to L pad 1 (ground)
E6 - negative uhf filter ouput to driver positive input
E7 - positive uhf filer ouput to driver positive input
HF filter connections
E8 - hf filter output to L pad 3 (hot)
E9 - hf filter L pad 2 input (hot)
E10 - hf filter output to Lpad 1 (ground)
E11 - negative Hf filter output to UHF driver negative inout
E12 - positive Hf filter output to UFH driver positive input
Below spade terminals for the large PCB
Mid filter connections
E13 - mid filter output to L pad 3 input (hot)
E14 - mid filter Lpad 2 input (hot)
E15 - mid filter output to L pad 1 (ground)
E16 - negative mid filter output to driver negative input
E17 - positive mid filter output to driver positive input
Woofer filter connections
E7 - woofer positve output to woofer driver positive input
E8 - woofer negative output to woofer driver negative input
Small PCB filter output connections
E9 - negative HF/UHF filter output to HF/UHF to E1 on HF /UHF Pcb
E10 - positive HF/UHF filteroutput to HF/UHF to E2 on HF /UHF Pcb
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