(EN) DIY 1x8 guitar cabinet - How to build one

The 3D render of the cabinet made in Sketchup

What you see above is the 3D model of the guitar case I made. Its characteristics are:

• 8" speaker

• 20W of rated power

• 8Ω inpedence

• "open back" construction

• dimension of 31(H)x31(L)x20(P) centimeters

It is a small box with modest performance that has served me both as a

first approach to this type of construction, and to use it with the Little Amp and with the various guitar pedals that I build (but that's another story ...). If you want to build one too, below I will explain how to do it.

I initially created a 3D render of the case in Sketchup; this operation allowed me to check the measurements and assembly of the various parts and to correct any errors. Once the correctness of the measurements has been verified, the first step is to get the wood and the electronic components. I chose to use 15mm plywood and I had the pieces cut to size by a home improvement store.

To build the cabinet you'll need:

• two boards 31x20 cm (top and bottom)
• two boards 28x20 cm (laterals)
• two tablets 28x8 cm (rear)
• four 2x3x28 cm strips and four 2x3x24 cm strips (the two frames)
• a 28x28 cm table for the "baffle" (the septum where the cone is mounted)

For the speaker I chose a Jensen Mod 8-20 model in an 8 ohm configuration; having small dimensions and weight and a nominal power of 20 watts, this cone is perfect for this project.

For the two frames I made a simple joint by overlapping two ends of the strips and gluing; when the glue was dry I inserted a couple of reinforcing screws.

Gluing of the first frame

While the frame is drying I made the hole for the speaker in the baffle. For this operation I used the drill on which I mounted a particular drill bit called "adjustable circle cutter"

Adjustable circle cutter

The result is excellent. My drill, however, has too low a speed or insufficient torque, so the operation was not easy. I recommend using a professional drill to use this bit; I also recommend paying close attention when using this tool, it is a potentially lethal weapon.

The baffle with the hole for the speaker

After creating both the frames I realized that they are quite inaccurate, since the strips have the real sections different from the nominal ones; building the cabinet around them would result in a dimensionally wrong and aesthetically unattractive work. I decided, therefore, to proceed with the construction of the main structure of the box and to "build" the frames directly inside it.

The frames inside the main box

When positioning the two frames, it is necessary to remember to move them back from the edge a distance at least equal to the thickness of the baffle and the rear panels, so that these go flush with the cabinet. I positioned the rear frame 1,5 centimeters from the edge, while the front one 2,5 centimeters so that the baffle is set back about one centimeter from the edge.

The structure of the cabinet

The next step is to color the baffle and the inside of the case black. This is necessary for two reasons: the baffle, if left wood-colored, is visible through the protective net (called "grill cloth") and is unsightly; even the inside of the case, as this is an "open back", is unsightly if left wood-colored.

I used a brush and an elastomeric paint for its elasticity and durability characteristics; the latter can be found at all paint stores.

Black painted baffle

Black paint inside the cabinet

While I wait for the paint to dry I dedicate myself to the high rear panel which, when the cabinet is finished, will be the one on which the jack input will be mounted.

Since the 15 mm panel is too thick, it is necessary to make a pocket that allows the correct assembly of the jack.

I discovered that this operation can be carried out easily and with an excellent result by using a forstner bit or a bit called "three points flat". I used a 24 mm wide one (see image) with which I reduced the thickness of the rear panel to three millimeters on a circular area; in the center of this area, using the pilot hole created by the bit, I created the 8 mm hole for mounting the jack using a normal wood drill bit.

Jack mounting pocket and the three points flat bit

Detail of the pocket for the jack

External side of the high panel

For the finishing I used a P180 grit abrasive paper; it is coarse enough for quick and easy roughing but fine enough to give a pleasant finish without having to go over with a finer grain paper.

The finished cabinet

Detail of the rounded edges

To round the edges of the cabinet I used a corner of hard cardboard, which is usually used as a protective packaging, in whose concave part I glued the abrasive paper. To make it more practical I glued a leftover strip in the convex part to create a handle.

diy edge-rounding tool

After the finishing phase, I moved on to the black leatherette vinyl covering. I bought the material in a home improvement store.

I cut a piece of vinyl slightly longer than the perimeter of the cabinet, while the width of the covering I calculated it so that the material covers the case, the edge and the recess that I created by pulling back the frames (1.5 cm rear and 2.5 cm front). As you can see in the photo, I drew a guide line with a pencil on the inside of the coating so as to carry out a straight and crease-free application.

 Guide lines on the leather cover

The first coating attempt was unsuccessful. I used a spray glue that I applied both on the coating and on the cabinet. Unfortunately the glue did not set and therefore the coating moved from its position while covering the various sides of the case.

Note on the coating: it is slightly elastic, not rigid like real tolex is, therefore once applied in position it tends to "deform" slightly; nothing that cannot be managed, but for sure this is the price that must be paid using inexpensive material.

 Cabinet coating

In the end I glued the imitation leather with wood glue (for example a vinyl glue); the skin stays in place immediately and the perimeter coating did not take more than an hour away. For the more difficult points where an instantaneous grip was necessary I used the good old cyanoacrylate.

A separate discussion is the operation of bending the leather on the edges. I spare you the details on the methods that I have followed also because, being my first attempt, I would risk recommending wrong techniques. What I recommend, if you want to try your hand at a building like this, is to proceed by trial and error; mistakes are easily remedied.

In the end I also covered the two tables which act as a rear closure.

I moved on to mounting the speaker on the baffle and coating it with a grill-cloth made from recycled material. I fixed the cone with M4 bolts and nuts directly to the wood.

The speaker mounted - internal

The speaker mounted - external

Il grill cloth montato sulla cassa

The baffle is fixed to the frame by means of screws; the same goes for the rear panels.

To connect the speaker to the input jack I used a piece of power cable from an old computer that I had around the house. On one hand I soldered the wires directly to the jack poles, on the other I installed female Faston connectors for connection to the speaker blades.

Reverse crimping of the faston connector 

Final tear-proof crimp

To make the Faston terminals resistant to tearing, I suggest crimping them in reverse, as I show you in the photos.

Once the cables are connected, the case assembled and the handle and feet are mounted, the final result is as follows.

The finished cabinet - front

The finished cabinet - rear

The "open back" type structure

The solution of the jack screwed directly into the wood I did not like very much both from an aesthetic and durability point of view. I went to a home improvement store and bought a metal plate to which I fixed the input jack. I completely drilled the pocket created previously obtaining a 24 mm through hole and screwed the plate to the rear panel. The result is much better in every respect.

The modified jack input

I chose the metal feet because they give a vintage touch to the case.

Metal feets

The final touch is the metal corners which, although they make up almost 20% of the cost of the case, improve not only the durability, but also the appearance of the cabinet.

Metal corner

Mounted metal corners

Cost summary:

Material	Cost
Wood	14,12 €
Screws	3,00 €
Glue	8,00 €
Jensen MOD 8-20 speaker	20,17 €
Paint (recycled)	0,00 €
Coating	7,25 €
Grill cloth (recycled)	0,00 €
Handle	2,40 €
Feet	2,50 €
Jack plate	1,50 €
Jack and cables	3,00 €
Metal corners	12,00 €
Total	73,94 €

As you can see, the realization of this guitar cabinet was relatively simple and fast, as well as very cheap. If you have decided to make one, then have fun with your new cabinet; if, on the other hand, you have questions to ask me, write them in the comments to this post and I will answer you as soon as possible.

Thanks for reading my blog.