Building a Jack 112 Bass Cab




Introduction: Building a Jack 112 Bass Cab

About: MATE Robotics Competitor Wood and Metal Working Average Struggling College Student Bass Player Tennis Player

I wanted to build a lite weight high quality bass cabinet to use with my band. After doing some research on the web and talking with some folks I chose to build a Bill FitzmauriceJack 112. It was less expensive, less power hungry yet still provides great sound. To purchase a similar speaker at retail was way outside of my budget.

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Step 1: What You Need!

List of Materials: (what I used but can differ)

Bill Fitzmaurice Jack 112 Plans

1/2" 5' x 5' Baltic Birch Plywood

1 1/2" Acoustic Eggcrate Foam 1' x 6'

8 Peizo Tweeters (Model 1016)

Eminence DeltaPro 12a

2 NL4 Speakon Jacks

Crossover Components: (High Pass)- 5.6 uF Capacitor, 5 mH Coil, 30 ohm and 4 ohm resistors, (Low Pass)- .6 mH Coil, 15 uF Capacitor

2 Penn Elcom Flush Folding Handles

8 Penn Elcom Chevron Corners

4 Penn Elcom Rubber Feet

Loctite ProLine Wood Glue

General Finishes Mahogany Gel Stain

West Systems Epoxy

Jig Saw



Table Saw


Various Sized Clamps

Tape Measure

Masking Tape

Wire- Solid Copper Core 16 Gauge

Speaker Wire- 14 and 16 Gauge

Soldering Iron

Adhesive Spray


Foam Brushes

Epoxy Roller

Sanding Block

Various Sand Paper Grits 120-400

Step 2: Cut, Organize and Mark Your Plywood

This was a rather tedious step, simple but hard. Used the table saw to cut the plywood to size. Marked plywood for all glue points and connections. We cut the center of the horn braces out, these are called "lightning holes" to make the cab lighter. The hardest part of this marking the wood, we wanted to get it to match the plans.

Step 3: Build Duct

Using right angle clamps to keep the corners square we clamped and glued the duct together creating a open ended wooden box. We tried to make this as square possible by utilizing clamps rather than screws. The glue we used expands as it cures to create a air tight enclosure. This is very important or else your speaker will not sound as good as it could. After it has all cured you install the duct to the baffle. Once it has cured you then install the side braces for the cab onto the the Baffle/Duct Assembly. T

Step 4: Installing Throat Panels

This process tedious as we wanted to build this without using screws. Having marked right helped a lot. As you see in the images, having lots of various clamps made a huge difference. The reason for the bungee-cord was one side kept slipping and would not stay in place. The bungee cord made it not slip. Using screws would have made this step much easier. All being said it turned out just fine.

Step 5: Installing the Top, Bottom and Sides

This part was rather easy. Glued and clamped the top and bottom to the duct/throat panel assembly. Easy if you have pre-marked all of your lines. Also having 4 long clamps made this easier. Gluing the sides was also about the same. You just have to make sure that you get the cab square by aligning all the corners.

Step 6: Building the Back Panel

This part was also easy. All we really needed was a jig-saw to cut a hole in the center for our jack plate. You also needed to install two braces onto the back. It took some creative clamping but it all came out fine.

Step 7: Phase Plug Extension, Driver Spacer and Rear Box Frame

This step was easy also. Making the phase plug. The instructions say to use wood or high density foam. We decided to make the phase plug out of foam because it would end up being a little lighter. We cut some foam and then painted it black to blend in with the driver once it is installed. For the driver spacer, it was kind of hard. We decided to use a compass to make the correct sized circle and then proceeded to cut it out with the jig-saw. The rear box frame was not very hard. You just had to glue wood stripes together and then mount the glued stripes inside of the cab. This is used to hold the back in.

Step 8: Tweeter Array Braces

This was rather easy except for the clamping because the wood kept slipping. We put them in at 45 degrees. This was to hold the tweeter array in place. The tweeter array produces much better highs then what the driver can deliver. This enhances your sound a lot.

Step 9: Adding the Handle Mounts and Staining!

We decided to put the handles in the hard way, Yaaay! We used a router to bore out the handle cavities rather then cutting all the way through with the Jig-Saw. This had some Advantages and Disadvantages. Advantage: Creates a more air tight enclosure. Disadvantage: The router was spinning at 23,000 rpms. The vibration emanating from the cab created a ear piercing sounds at about 140 db. USE EAR PROTECTION! After that was done we proceeded to stain the cab. We use General Finishes Gel Stain.

Step 10: Mounting Acoustic Foam

This was very easy, except when the foam stuck where you didn't want it. We did this using 3M Super 77 Adhesive Spray and 1-1/2" Acoustic Foam. We pre-cut the foam to size and then we sprayed the foam and cab and pressed the foam into place.

Step 11: Coating With Epoxy!

We wanted to make the cab look like wood and keep the stain. We then decided to coat the whole cab in epoxy. This would provide more strength and also make a durable,repairable long lasting finish. It also makes the cab look really glossy and shiny. This was easy because we already knew how to lay epoxy. We ended up doing two coats because the first ended up having some thick and then spots on it.

Step 12: Installing Your Hardware and Components.

This step was fun and easy, the end is in sight. Having pre-drilled all of the holes made this easy. We put on the corners, handles, feet, tweeter array and the driver. It all came out well and was easy to install.

Step 13: Soldering Crossovers and Wiring the Cab

The soldering was kind of easy. The soldering points on the crossover I had made fell apart slipped some so I had to use more solder then I wanted put it was fine. I think they came out fine. I used 14 gauge wire. Wiring the cab was harder the I thought. We had very little clearance between the back of the cab and the driver because the jack plate was a inlay. Then the Speakon Jacks them selves went down even more. I ended up bending the connections on the Speakon Jacks to make it all fit. It worked out fine. I used enough wire to make so when i pulled the back off nothing was pulled with it. (Crossovers are mounted on the back panel) Overall it came well!

Step 14: Finished!

This was a very educational process. Researching different cabinet designs and selecting the right one for my equipment and style of playing. I have a four string bass and 375 watts of power to work with. The Jack 112 seemed like a great fit. The build was challenging and took much more time in the sense we decided to clamp and not use screws to go for a finished product maintaining a natural wood look. I am happy with the end result and look forward to many years out of my new cabinet. Have my first gig with it this weekend! Hope this inspires others to learn more about their music and be creative.

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6 Discussions


6 years ago

Feel free to comment and ask any questions!


5 years ago on Introduction

since you are using birch ply I wouldnt bother with screw on corners - just more to catch on doorframes etc and rip the screws out . When it gets dinged up just bondo the holes and repaint


5 years ago on Introduction

Nice going ! Spent years designing ,building , gigging speakers up to a 20k rig in the past so I appreciate the work that goes in ,plus Im a big fan of manifolding drivers (peavey HDH , renkus heinz etc) . Piezos dont really need a crossover per se though ,just a ceramic wirewound resistor to tame them a bit , but hey !Each to their own ! Nice to see a phase plug too....wrestled with them a lot in the past , GRP torpedoes and all that , good to see a simple one . A lot of people run eminence down as a driver but we found they had the same Q factors as the top of the range stuff , were easier to re cone yourself and of course....cheaper ! Also , they actually manufacture and re badge a lot of the big names drivers for them .Or did in my day .


Reply 5 years ago

Hey. Thanks! I'll keep that in mind for my next build.


6 years ago on Step 14

Nice to see that the folded horn is not extinct. These systems used to be common in the days before transistors made high-power audio cheap. Probably the most famous case was Paul Klipsch's Klipschorn, which used a corner of the room for the final fold. Rated at 100 watts, it could deliver 90dB on-axis with ONE watt.


Reply 6 years ago on Introduction

Ya, the array really provides good highs. Glad that I ended up doing it. The horn you told be about sounds really cool.