The “Shark Fin” Cabinet Construction

I have finished building the first cabinet prototype of the Shark Fin Portable PA. I used 1/2″ plywood for the shell of the cabinet and 2x stock wood ripped into specific shapes and angles for the frame of the cabinet. Elmer’s Carpenter’s glue was the main glue for the construction. I used GE Silicone II 100% Silicone Window & Door Caulking to seal the cabinet.

This the bottom panel or base of the cabinet. The wood frame was ripped from scrap 2×10’s that I had lying around the basement. I used the Google Sketchup tools to determine the proper angles to cut all of the bracing pieces. All of the bracing was glued to the base and not screwed so there would be no screw heads on the bottom of the shell to cause the cabinet to be off-balance or wobbly.

Each bracing piece was glued and clamped separately. Elmer’s sets quickly (30 mins), so it didn’t take very long to get all the base pieces attached.

I used 90 degree angle clamps to hold the sides of the cabinet in place to make sure that I cut all of the angles correctly. The angle clamps are essential in getting the pieces together plumb and square. The two side pieces are being glued in place and front panel is locked in to make sure that the side pieces are in the right place.

This is the front view of the panels’ alignment being verified.

Now that the side panels have been glued in place, I am gluing in the bracing pieces for the bottom front panel. Notice that the cross bracing has already been installed to hold the side panels apart. After the side panels were glued in I used self drilling pan-head screws to screw the panels onto the frame for additional strength.

This is the view of the previous photo from the inside of the cabinet.

The front panel has been glued and screwed down. The extension clamps were used to pull the sides of the cabinet into square before the panel was screwed down.

The view from the front after the front top panel has been added to the cab.

Another of the same.

Clamping and gluing the top panel to the frame. No screws will be used here so that there will be no screw heads to interfere with the PA’s controls.

This is the caulking I used to seal the inside of the cabinet. This small tube is much easier to work with inside the box. I never would have been able to get a full-size caulk gun in there.

Detail of the sealed seams inside the cabinet.

Detail of the + and – leads attached to one of the Galaxy Audio full-range speakers. Note that I used colored tape to clearly show the polarity of the speaker leads. I used a battery to determine the polarity of the actual speaker because they weren’t clearly marked.

The two audience facing speakers. The bottom larger speaker is the Selenium woofer.

A full view of the cabinet with the leads and the speakers installed.

This is a detail of the panel where the speaker jacks are installed. The top jack feeds the “monitor” speaker and the bottom jack feeds the bottom two “audience” speakers. The top jack is 8 Ω and the bottom with two speakers is 4 Ω. I used on outdoor blank switch cover plate for the jack panel. These cost about a dollar, are very easy to drill and come with a foam rubber gasket.

Full length view from the back before the cabinet is closed.

Front view of the closed cabinet ready for frequency response testing.

The next steps after testing are determining if a tuned port will be needed to extend the low frequency response of the cabinet, adding the amplifier and battery power to the cabinet, and adding mixer inputs and controls.

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