Last week I found myself in the hands an audio amplifier that I had ordered some time ago. So I thought I'd start building my new DIY hi-fi sound system! I decided to build two passive bookshelf speakers connected to an active subwoofer. For some parts I used 3d printing. Just follow these steps to build it ! Here we go!

Supplies

(2x) 6,5” woofers
(2x) 2” tweeters
(2x) bass reflex tube (internal diameter 2”)
(1x) tpa3116 150w amplifier (2 channels for bookshelf speaker and the other one for the sub)
(2x) 2 way crossovers
(4x) speakers terminal connectors
wood vinyl wrap (45cm x 150cm)
white vinyl wrap (45cm x 250cm)
18 awg cable
some screws
MDF wood (thickness 1,5cm)

Step 1: Design and Measurements

As a first step I decided to get an idea of how to build it. Thanks to the use of fusion 360 I made a sketch of the enclosure of the speakers

Measurements (Laterals speakers):

front panel 20cm x 30cm
right and left panels 20cm x 30cm
top and bottom panels 20cm x 17cm
back panel 20cm x 30 cm

Measurements (subwoofer speaker):

front panel 25cm x 25cm
right and left panel 20cm x 25
top and bottom panels 20 x 22 back panel 20cm x 25 cm

Step 2: Choice of Wood

You can improve the performance of an excellent speaker by taking care of the precision of the cabinet construction.

The classic multilayer, type of birch, is good, but only of high thicknesses (above 2.5 cm) and a possible combination of multilayer-MDF is still excellent.

A good solid wood is also good, always pleasing to the eye, to be chosen, however, rigid, muted and seasoned. Excellent for example beech, cherry, very bad rose wood instead fir.

To discard the chipboard, difficult to work and to finish.

The solution that I consider best is the use of 1.5 cm MDF. The panels constructed in this way are rigid and very damped and the few vibrations can then be further dampened by a sound-absorbing material. The assembly is not particularly difficult and the processing rather precise, allowing then a pleasant finish and the cost is not high.

Step 3: Cut the Wood

To cut the wood I used a bench saw and I followed these measures

Measurements (Laterals speakers):

front panel 20cm x 30cm
right and left panels 20cm x 30cm
top and bottom panels 20cm x 17cm
back panel 20cm x 30 cm

Step 4: 3d Print Bass Reflex Tubes

I decided to print the tubes of the bass reflex to make them the size I prefer 5 cm internal diameter. After printing them I sanded and black painted them to make them more aesthetically pleasing.

This is the link of the bass reflex tube https://www.thingiverse.com/thing:199464

Subwoofer bass reflex tube https://www.thingiverse.com/thing:2122055

Step 5: Making the Hole and Milling

To position the woofer I decided to make a milling about 0.5 cm deep with a dremel (diameter 17cm milled) then with an alternative hacksaw I created a hole with a diameter of 16cm. For the hole of the bass reflex I followed the same procedure with the hole with a diameter of 4cm and the milling 5cm. The hole of the tweeter is also 4cm in diameter and 5cm milled.

Step 6: Glue the Side Panels

To glue the panels of the speakers I used a vinyl glue and on the parts to be glued , I also placed weights to ensure perfect adherence.

Step 7: Cover With Vinyls and Woofer Positioning

After having perforated the panels I covered all the wooden parts with the vinyls (on the front I attached a fake wood, on the sides and behind I attached the white vinyl), then I positioned and screwed the woofers, tweeters and bass reflex tubes , on the back I screwed the connectors.

Step 8: Wiring the Parts

Cut 6 pieces of 18awg cable about 40 cm long and solder according to the wiring diagram

Step 9: Cut the Panels of the Active Subwoofer

To cut the subwoofer panels I used the bench saw following these measures :

subwoofer speaker measure

front panel 25cm x 25cm
right and left panel 20cm x 25
top and bottom panels 20cm x 22cm
back panel 20cm x 25 cm

Step 10: Drilling and Milling the Front Panel

To drill the front panel I designed the shape of the subwoofer, first I milled and then the hole with the jigsaw.

Step 11: Drill and Mill the Side Panel

For the bass reflex I performed a milling (diameter 9cm) and the hole (diameter 8cm). On the inside I screwed the 3D printed support, I made 4 holes and a milling (1.2cm deep) for the amplifier knobs.

Step 12: Glue the Speaker Panels

To glue the subwoofer I used vinyl glue and put weights on the parts to be glued.

Step 13: Wiring

To solder the various cables and carry out the wiring, I followed the diagram. On the dc connector I soldered two wires and I soldered another connector and I inserted it on the back side because it is in a more comfortable position, finally I screwed the amplifier on the support and I closed the speakers.