Secure a tweeter and a subwoofer or speakers that produce high- and low-end frequencies, respectively (see Resources). Using separate speakers within your loudspeaker for high- and low-end frequencies produces a better sound quality.
Download a schematic of a frequency crossover from an Internet resource (see Resources). A crossover is a circuit that splits an audio signal into high-frequency and low-frequency and sends discrete signals to your tweeter and woofer. A schematic represents an electronic circuit using symbols for electronic components and solid lines for the wiring of the electronic components.
Collect the electronic components represented in your crossover schematic from an Internet resource, such as Centerpointe Electronics, Parts Express (see Resources) or your local electronics hobby shop. The symbols in the schematic represent electronic components, such as resistors, capacitors, hi-pass and low-pass filters and transistors.
Assemble the electronic components on your blank circuit board by slotting each component into the prefabricated holes. Follow the orientation of your schematic and mark important features like the audio source inputs and the hi-pass and low-pass filter signal paths. After slotting components through your blank circuit board flip the board over and bend the connection pins at a 90-degree angle.
Solder the components directly to the board with a soldering iron. Place a small amount of rosin-core solder against the bent joint and circuit board and melt a bead of solder directly to the board and joint with the heated tip of your 25-watt soldering iron. Following the paths of the solid lines of your schematic melt an identical path of conductive copper directly to your circuit board with a wiring pencil.
Connect the outputs of your crossover circuit to your tweeter and subwoofer. Connect the path from the hi-pass filter to the tweeter by soldering stereo wire from the output of the path to the input of the speaker. Connect the path of the low-pass filter similarly.
Create plans for a loudspeaker enclosure from scratch or download plans provided by manufacturers, like Swan Speakers, on their websites (see Resources). A single enclosure housing a subwoofer and tweeter is large enough for both the speaker components and the crossover circuit. Generally, such an enclosure includes a perforated divider between the subwoofer, which is placed at the bottom, and the tweeter, which is placed at the top. A bass vent, or secondary hole between the woofer and tweeter on the woofer side of the enclosure, is useful, but optional.
Either have a lumber yard cut plywood boards to the specifics of your enclosure plan or use a rotary saw to cut the pieces yourself. For the circular openings that house your tweeter and woofer, drill two small holes in the wood with a power drill, and then use a protractor to draw a circle of appropriate size to your woofer and tweeter from the central point. Use a jigsaw to cut the rest of the circular openings.
Apply wood glue to edges of your plywood and assemble the speaker cabinet leaving the back panel open so you can install the electronic components. Use a clamp to compress the glued joints of the plywood boards until the glue dries. Once the glue is dry use wood screws and a power drill to reinforce the structure.
Mount the woofer and tweeter into their pre-cut holes and use a power drill and wood screws to affix the speakers to the cabinet enclosure. Drill a hole in the enclosure's back panel large enough to accommodated the audio-in port of the crossover circuit. Line up the crossover circuit with the audio-in port and affix the circuit to the board using wood glue or wood screws and a power drill.
Fix the back panel of the speaker enclosure in place with wood glue and clamp down. As the glue dries use wood screws and a power drill to reinforce the structure.