Wednesday, 4 January 2012

Soundbox — The construction

The Soundbox device I have built uses some construction techniques I want to share with you readers. I'm mainly talking about the enclosure and the texts on controls.

The enclosure itself is built from a simple box bought from a craft store. It was unfinished wooden box with two small hinges and a clasp to hold it closed. The lid and bottom parts were quite nicely suitable size for all the parts, I just needed to build the control panel inside this box.

The control panel is built from 4 mm plywood that I cut to the correct shape with a coping saw (not the best tool for the job, but that was what I happened to have at hand). Then I drilled the holes for the knobs and such. The speaker hole I cut with the coping saw. To keep the control panel in place, I glued some 9 × 9 mm wood bars to the inside of the box, 4 mm from the top of the bottom box so that the control panel will sit flush with the sides of the bottom part.

After constructing the box, I removed the hinges and the clasp and painted the box and control panel with several (maybe four) layers of white spray paint. What surprised me was how much that stuff stinks — I had to keep the parts outdoors for a couple days after painting so that my room would not smell of solvents. The finished box had a distinct solvent smell for like a month after it was done.

The two main knobs — pitch and arpeggio — are of my own design. They're seven-sided knobs with friction fit for the usual 6 mm potentiometer axle. I created the model in Blender and ordered them from a 3D printing company called Shapeways. The design didn't work quite as intended and I had to remove some material from underside of the knob so that the nut that holds the potentiometer in place fits under the knob. I also had to use 6 mm drill bit to widen the centre hole so that the potentiometer axle fits in there.

For the markings on the control panel and the two main knobs I used transfer lettering from Letraset. This is rub-down lettering, that is, you write by finding the required letter from the sheet, placing that to its intended place and rubbing down on the letter sheet so that the letter material is transferred from the sheet to your working piece. These are mainly intended to be used on paper, but they appear to work just fine on wood and plastic.

After writing all the texts I wanted, I coated the control panel, the two red knobs and the box with several (probably three) coats of clear spray lacquer. Before this it would have been possible to rub or scrape the lettering off, though it would have taken some effort. After the lacquer coat the lettering is there to stay. Even though the spray again had quite an amount of solvents, neither the lettering nor the plastic of the two red knobs was adversely affected.

After this, the rest is rather straightforward. I re-attached the hinges and the clasp I had removed before painting the box white. I installed the potentiometers, buttons, switches and the line jack to the control panel with their supplied nuts. The two LEDs and the speaker I attached with hot glue. Eventually I will have to figure out something more sturdy than hot glue for mounting the speaker, for it did come loose at the Alternative Party. The control panel is held in its place by the side walls of the box and the support bars inside the box, but there's nothing stopping you from lifting it upwards to reveal the electronics hidden inside.