New Charge Coupled Crossovers in the house

[Lynn Allen]

What started out to be a fairly strait forward charged coupled crossover project, turned out to be much more than I ever expected. I reviewed several designs from LHS and Audiokarma members looking for a solution that would allow for an external crossover which could be used with my custom built 4344’s. My main criteria was to end up with a good looking, great sounding design which could be displayed on top of my 4344’s and retain the period correct look of my listening room. I reviewed the following design and liked the look, however, was not quite sure this was exactly what I was looking for.
Very nicely built crossovers by Dave at Katzass audio

[Lynn Allen]

Bottom View of Crossovers

[Lynn Allen]

Further research found this version on from Dave that seemed a potential candidate for the project, but I was still not sure if this was really what I was looking for.

Another variation of crossovers by Dave at Katzass Audio

[Lynn Allen]

With the basic criteria set I still was looking for something that was unique in design and allowed for the crossovers to be installed separately with one crossover on top of each speaker. Since the speakers are bi-amped I wanted a design to provide the best sound possible. More research found this charged coupled design by Giskard for the 4345. Even more research revealed that this was not only a great design, but was an upgrade for the 4343’s, 4344’s and the 4345’s. All my research kept directing me to Giskard and his charged coupled designs. With the experience and expertise he brings to the LHS forum and crossover designs, it didn’t take much coaching to realize that his design would be the best choice from my custom built 4344 crossover build. Thanks again Giskard for all your posts and help to everyone on the LHS forum!! This would not be possible without your help.

Giskards charge coupled 4 way crossover design

[hjames]

Interesting. The schematic you posted shows a 4 leg circuit, but it appears your CC systems only have 3 legs and yet there are 3 trim-pots.
How are you running your bi-Amp design - wondering how you are doing the hi-low split and what amps are involved?

Thanks for the time and the detailed information!

With the basic criteria set I still was looking for something that was unique in design and allowed for the crossovers to be installed separately with one crossover on top of each speaker. Since the speakers are bi-amped I wanted a design to provide the best sound possible. More research found this charged coupled design by Giskard for the 4345. Even more research revealed that this was not only a great design, but was an upgrade for the 4343’s, 4344’s and the 4345’s. All my research kept directing me to Giskard and his charged coupled designs. With the experience and expertise he brings to the LHS forum and crossover designs, it didn’t take much coaching to realize that his design would be the best choice from my custom built 4344 crossover build. Thanks again Giskard for all your posts and help to everyone on the LHS forum!! This would not be possible without your help.

Giskards charge coupled 4 way crossover design

[mbottz]

Interesting. The schematic you posted shows a 4 leg circuit, but it appears your CC systems only have 3 legs and yet there are 3 trim-pots.
How are you running your bi-Amp design - wondering how you are doing the hi-low split and what amps are involved?

Thanks for the time and the detailed information!

For Bi-Amp purposes the components within the dashed lines of the schematic are deleted from the circuit. The LF amp is connected directly to the Woofer. On the original JBL crossovers, changing the switch to Bi-amp mode did the same thing.

mb

[opimax]

Is there any HF attenuation on the woofer? active or passive?

Mark

[mbottz]

Not at this point. We will be experimenting with a passive LF bandpass filter to see what difference that makes. Any suggestions?

[CosmicS]

For Bi-Amp purposes the components within the dashed lines of the schematic are deleted from the circuit. The LF amp is connected directly to the Woofer. On the original JBL crossovers, changing the switch to Bi-amp mode did the same thing. mb

Hey Mike! I bought these 4344's and the custom charged crossovers from the fellow that bought them from Lynn years ago. He let me know that Lynn passed and that I should look into threads here to learn more about the original build. I have these currently set up as my house speakers running from a modern Yamaha AS2100 integrated amp (no biamp.. yet). They sound great but I feel they could do more. I am looking to biamp in the future and have started looking into a Mc 225 for the high end and something else for the lows.. also looking at going with something like an Audio Research Classic 120 (both are somewhat local).. Do you know what Lynn ran or have any suggestions for the setup? The previous owner (after Lynn) powered them non biamped with an old Spec 1 & 2 set up which I could get my hands on as well.. Anyways any thoughts from anyone is greatly appreciated.

[mbottz]

Feel free to pm me for any questions!

[Lynn Allen]

After finalizing the electrical design I called upon another LHS member Mbottz, a fellow LHS forum member. Mbottz is a JBL resource in the Dallas area that has rebuilt and restored JBL cabinets and grills for me to better than new condition over the years. He can also repair and build electronics for vintage equipment as well as anyone I have found.Working with him was a pleasure. He was able to take my ideas, refine them, and create a design that met all my expectations.
In our lunchtime brainstorming sessions at Hooters and Twin Peaks we discussed designs and options. (Sure we did!!) It was there I decided that the finished product must have a cabinet that would contain the l-pads on the front and the speaker connections on the back. While never straying from the task at hand, we relentlessly brainstormed on how to best design and build my “ultimate crossover” without compromising looks and sound. (An occasional look at the scenery helped keep the project from getting boring), a few beers later our design was complete. Knowing the quality of work Mbottz produces and with Giskards charged coupled design there was no doubt it would look and sound great.
With the concept clearly in our minds, (as well as the Flannel wrapped Twin Peaks memory) the first thing was to lay out was the components in a neat and orderly fashion. The layout had to be functional as well as pleasing to look at. (Again memories of Hooters waitresses did not cloud our thinking at all) I think our design is spot on. Further research and a couple more beers, determined our build warranted a walnut mounting case which would show off the components. All wiring was concealed to further promote the professional and neat appearance of the design. Here are pictures of the build from start to finish.

Neat Component Layout shown off with a walnut base.

[Lynn Allen]

A shot of the ugly but necessary wiring which is concealed below.

[Lynn Allen]

After finishing the component placement and wiring, an enclosure was built which would complement the 4344’s and retain the style of a JBL product from the same era. After a few more discussions, it was decided that larger rear binding posts would be installed to support a large gauge wire. (Up to 6 AWG if required) Separate terminals for input and outputs mere a must. The faceplate would be removable to provide for the installation of the l-pads. Mbottz came up with the design which used rare earth magnets to hold the front plates securely on the cabinet. These unique magnets are glued with epoxy into holes drilled in the cabinet and faceplate. When finished they hold with the strength of nails while allowing for the removal of the faceplate. The L-pads while part of the crossover are hidden to provide the cleanest look possible for the finished project. A removable top trim cover was designed, which sets on top of the crossovers, hiding the l-pads, yet allows the main components to still be visible.
The front trim around the l-pads was styled to closely resemble the front trim of my custom 4344’s. To achieve that factory JBL look I wanted a logo and control graphics panel to resemble the original used on the 4345’s.
RJ Timmerman of the sign shop (another LHS member) was called upon to make the front labels for the controls. For those not familiar with RJ’s work you simply cannot find a better quality graphic for restoring your JBL projects. He also sells grill pegs, knobs, and screws which are exact replacements for JBL restoration projects. (Shameless plug) Thanks RJ for a quality product to finish this build. The next pictures are the results of the combined efforts of Mbottz, Giskard, and RJ Timmerman. I am extremely pleased with the outcome.
Components shown installed in the finished case.

[aktivkampi]

Congratiolations Wonderful work

[JuniorJBL]

Very Nice!!