JBL 3145 stock crossover.- A pictorial

[Ian Mackenzie]

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

[Ian Mackenzie]

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.

[Ian Mackenzie]

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.

[Ian Mackenzie]

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.

[Ian Mackenzie]

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

[Ian Mackenzie]

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

[Ian Mackenzie]

Large PCB connections

Switch connector wiring:
E1 - positive passive input
E2 - positive external input
E3 - negative external input
E4 - negative passive input
E5 - 5.4 Mh choke output
E6 - 5.4 Mh choke input
E11 - 4.8 Mh choke input
E12 - 4.8 Mh choke ground

[Ian Mackenzie]

Internal passive / external biamp two postion multi pole rotary switch.

The two postion rotary switch can be set for internal or external biamp mode. The switch functions to route positive and negative polarity of the woofer input via the passive or external loudspeaker input terminal. In the external postion the woofer filter elements are bypassed.

In addition the rotary switch functions to byass the high pass midrange filter elements in the external position.

[Ian Mackenzie]

To be continued.

When available an image of with the appropriate camera angle will indicate the color coded wires from the wiring loom and the designated alpha numeric codes of the spade terminals.

[Ian Mackenzie]

I nearly forgot about this thread..oops...

To finalise this particular thread I post here the color coded wire looms and the designated alpha numeric codes of the spade terminals for the 3145 network.

No doubt anyone considering changing out the stock network or any particular reason will find these a useful reference if not now at a later date.

A special thanks to Clark (Ducatista47) the trustee of this thread who graciously sponsored the shipping of the networks and many of the images seen in this thread.

Ian

[jbl4ever]

Excellent work as always Ian
Great system too and beautiful dog:applaud:

[Ian Mackenzie]

Thanks.

Clark made it happen so all the credit belongs to Clark.

I am so way way off the main drag and out of the action down here I rarely get to see anything like this much.

We both had a lot a fun. There were lots of laugh's and it was quite insightful.

The whole thing about it of course is it here out in the open for everyone to check out and hopefully will answer a lot of questions.

Be sure to keep an eye out for Clark's own diy project which I had a small hand in:

Two Approaches - Loaded and Cocked.


Ian

[Ian Mackenzie]

Clark's project here:

http://www.audioheritage.org/vbulletin/showthread.php?p=178769#post178769

[butlern]

hi
sorry to but in here, but anyone able to help with supplying a set of 4344MK11 networks, along with pots and foilcals?
regards
nigel



Large PCB connections

Switch connector wiring:
E1 - positive passive input
E2 - positive external input
E3 - negative external input
E4 - negative passive input
E5 - 5.4 Mh choke output
E6 - 5.4 Mh choke input
E11 - 4.8 Mh choke input
E12 - 4.8 Mh choke ground

[Ian Mackenzie]

I doubt it.

Suggest you search for 4344mk11 schematic and consider the diy route