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Full Board Set for JBL 4300 Series 4-way Models

Full Board Set for JBL 4300 Series 4-way Models

Regular price $329.99 USD
Regular price Sale price $329.99 USD
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Set of four high-quality printed circuit boards that allow owners of the legendary JBL 4300 Series 4-way Studio Monitors (or those who are building their own DIY clones) to upgrade their existing passive crossovers to modern standards using polypropylene film capacitors, air-core inductors, and the charge-coupling technique used by JBL in their ultra-high-end studio monitors such as the DD67000.

The Full Board Set comes with 2 main boards and 2 auxiliary boards, supporting both full passive (single-amp) and bi-amp configurations.  Detailed PDF documentation is provided with purchase of the boards, which contains full parts lists for each of the supported systems, as well as instructions on how to assemble the boards and integrate them into your system.

Please check the list of supported speaker models below to ensure that your system is compatible with these boards.

Supported Models



2mm thickness for extra rigidity under the weight of the heavy crossover components

2oz copper plating for high ampacity and low trace resistance

Leaded HASL finish

Clearance holes for zip ties to hold inductors in place


12.75" x 9.25"

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Customer Reviews

Based on 2 reviews
Andrew Ryan
Incredible Upgrade to 4345's

I ordered these boards from Matt after having great success with a similar board upgrade on a pair of L200’s converted to L300’s. The boards came in a few days and were REALLY well-built / heavy. They have some mass to them for sure. Everything was clearly marked on the boards and the instructions were fantastic. I got confused on the l-pad wiring a bit and then looked at the diagram included and it made total sense. When I told Matt this, he immediately updated the instructions to help folks in the future - incredible care and service put into this product. So, the build was easy enough if you know how to use a soldering iron (and if you don’t, you can learn on YouTube like I did).

The real question is how do they sound. I mean, I don’t really even know where to start. The speakers sound like different speakers than they were before. The transparency is just incredible. I am hearing things I’ve never heard before on records I have spun many, many times. It took me a few minutes to adjust my l-pads to get it just right, but once I did, I was transported to another dimension. I spent 4 hours digging out records and putting them on when I only intended to spend 15-20 minutes. I have several sets of speakers over $10k and a few over $20k. These 4345’s are now, by far, the best sounding pair I own. Buy this product if you have 43xx speakers. You haven’t heard what they can do yet.

Now, Matt, we need boards for the 4435’s of L220’s! ;) Thanks for everything!

Bill Pedersen
High recommendation

June 13th, 2023

Received the ordered sets today.

The first thing I noticed was the weight of the package, I had ordered several sets of circuit boards, for the 4345 and 4355. The package was really well packed and the different circuit board sets were each in their own safety position, so they didn't get bumped or scratched. Matt had even secured the circuit boards with tape, which meant that they did not slide against each other during transport.

I have to admit that when I first got the circuit boards in hand, the high quality becomes apparent. The small details and sense of quality jump out at you. Which reflects the weight.

These are by far the best-looking and best-thought-out circuit boards I have experienced so far. I have worked with electronics for many years, so I have experienced bad and good Quality, and the boards from Matt is on the high end. Well done Matt.

Before sending off my order, I had a bunch of questions that I sent to Echo-mountain-audio and got a quick response back from Matt.

Matt is a really nice person and helps in all areas with your questions.

Thank you very much for the transaction Matt.

I will need printed circuit boards for future projects, so I really hope that you will make printed circuit boards for many more of the old vintage JBL models, there is a real need for them.

Kind Regards Bill/ From Denmark