Speakers are prized by many car audio aficionados at the 15 by 22.5 cm (6 by 9 inch) size for their excellent full-range reproduction of the highs and lows in music. Installing a pair in your vehicle is a good way to improve the audio performance of the system. But even if your car's speaker locations won't accommodate speakers of this size, you can still add them to your system by building 15 by 22.5 cm (6 by 9 inch) speaker boxes.
Cut front and back panels for your boxes with a circular saw, each measuring 27.5 cm by 20 cm (11 by 8 inches).
Cut top and bottom panels, measuring 27.5 by 25 cm (11 by 10 inches).
Cut side panels, each measuring 25 by 17.5 cm (10 by 7 inches).
Assemble the side, top and bottom panels to form a hollow square that measures 27.5 by 20 cm (11 by 8 inches) around the outside edges. Screw the panels together with 2.5 cm (1 inch) wood screws spaced every 7.5 cm (3 inches).
Cut an opening in the front panel for your speaker. Use the template that came with the speaker as a guide and make the cut with a jigsaw.
Screw the front and back panels onto the box with 2.5 cm (1 inch) wood screws, spaced every 7.5 cm (3 inche)s.
Drill a 6 mm (1/4 inch) hole in the back of the box and slide the end of your speaker wire into the box.
Grasp the speaker wire and pull it out of the front opening, then connect it to the speaker. Place the speaker into the opening and screw it in place with the screws supplied with the speaker.