Speaker Flat Pack Assembly tips

So, you bought a flat pack speaker box and want to know the best way to assemble it, or maybe it has gaps at the seams and you want to know why.

Since these parts are all cut on a CNC machine there is a possibility they may have tabs on the edges of some of the pieces. These tabs can sometime interfere with the joints of the enclosure making it appear as if the parts are not cut square. First thing you should do when you unpack the kit is brush all parts with a stiff brush paying careful attention to the inside corners of the dado cutout. Sawdust build up in this area can prevent the enclosure from fitting tightly and squarely.

Second is to check the inside ends of all rabbets. When the machine cuts it sometimes leaves tiny bits of uncut material at the inside of the corners. These, being on the assembly edge of the box, can also prevent a tight, square fit when assembling the box. I use a box cutter or razor knife to trim any excess material that might be left over on the inside of the dado cuts. Third, thoroughly clean all parts again with a stiff brush. I found a dry dish brush works very well for this. You want to remove any and all loose material but you don’t want to change the shape of the parts at all. The machine is very accurate at cutting the part out but sometimes it pack dust tightly into corners making square assembly difficult.Begin by laying out and identifying the parts.

  • Front and Back are 11 ½” x 7 ½.
  • Sides have rabbets cut around the outside edges
  • Top and bottom are different sizes with Top being the smaller nearly square piece.

First order is to carefully clean all parts. I use a stiff bristle brush like a dish brush or a hard toothbrush. Carefully inspect each piece to remove any sawdust that might be packed up against the edges or inside the rabbet cutout. Carefully brush any loose material away and inspect for any protrusions. Some of these are cut with “tabs” in place to hold the part from flying off the table during the last and final cutout. Tabs are usually sanded off but in order to prevent sanding too much material sometimes there are small protrusions left behind. Carefully sand or cut these protrusions. I use a piece of 80 grit sand paper set on a flat surface. Carefully drag the edge of the part across the sandpaper until the protrusion is gone. Do not keep sanding the edge once the protrusion is gone or the box may not seal properly.

After a thorough cleaning it’s important to dry fit all the parts before applying any glue. Start with the bottom. Set it on a flat area making sure there is nothing rough beneath it t
Initial Assemblyo keep it from sitting flat. Next assemble the sides with the flat edge facing you.

Add back and check for fit






Check back for gapNow add the back and note whether there is a protrusion at the top. The back and top are cut slightly longer to make up for any inconsistency in thickness of materials. Assembling the box so this protrusion is on top allows them to be easily sanded flat before finishing the enclosure.


Note also that the front might also be a few hundredths of an inch long. If it is the front too must be assembled such that the protrusion is out the front so the rear joints will fit properly. To assemble the front it may be necessary to sand the top edge flat with the sides and bottom for a perfect fit. This extra length is done on purpose so a perfectly tight joint and box can be assembled with only wood glue and sandpaper, even if the MDF is from a different supplier or slightly thinner. The front and/or back edge can be sanded flat with either a sanding block or an electric sander using 80 grit paper.

Once you are ready to assemble the box and after a thorough cleaning and dry fit, start as pictured above. Place a newspaper or paper towel under the box to catch any glue drips. Apply glue to the sides and back and assemble. Lightly clamp across the sides and flip the box on it’s back. Apply glue and fit the top in place allowing any protrusion to extend out the front. Double check all seams and clamp as desired for a tight fit. Once again,  any protrusions from material thickness difference should be extending past the top and front for an airtight box.

Once the glue has dried and any front edge protrusion has been sanded flat, the baffle can be glued in place. I do offer a custom baffle with speaker holes, recess cuts and a 1/4″ rabbet around the edges so the front fits slightly inside the enclosure. Just ask…

Lastly, if you discover a part is not cut square, have any questions that aren’t answered here or in any other way dissatisfied be sure to let me know ASAP. You can send email to cnc@trbailey.net.

Thanks for your purchase and I hope your project goes well.

Leave a Reply