Bass speakers need repair if their cone is ripped or their driver unit is damaged. If the cone is torn, a professional repair shop is needed to recone it. If a driver is defective, you can usually make the repairs yourself be installing a replacement driver. Speaker drivers often fail when they are driven too hard by an amplifier, but a hard drop during a move can jar the driver's internal voice coil and also cause the unit to fail. If a driver fails because it is too weak for the amplifier it is connected to, this is a good time to upgrade to a more powerful driver.
Determine the location of the speaker mounts. Speaker cabinets are either front or rear loaded. If the cabinet has screws along the outside perimeter in the back, it is most likely a rear-loaded cabinet. If no screws are visible, it is probably a front-loaded cabinet.
Lay the cabinet on a padded or carpeted floor or workbench. Place front-load cabinets face up, and rear-loaded cabinets face down.
Access the drivers in rear-loaded cabinets by removing all of the screws on the cabinet back with a screwdriver and removing the back panel. Access front-loaded cabinets by removing the front speaker grill. Speaker grills are mounted either with plastic pins, allowing them to be easily pulled off, or screws. Screws will be visible and are removed with either a slotted or Phillips screwdriver.
Loosen and remove the driver mounting nuts with pliers on rear-loaded cabinet. For front-loaded cabinets, remove the speaker mounting screws with a screwdriver. Place all screws and nuts in a plastic sandwich bag for safekeeping.
Pull front-loaded speaker drivers straight up by grasping the edges with your fingers. When the speaker magnet has cleared the cabinet, lay the driver down, magnet-side down, on the cabinet top, and inspect the wires. Drivers have a positive and negative wire. The positive wire will be indicated by a dot, or "+" sign stamped next to the driver's wire terminal. Wrap a piece of masking tape around the positive wire and label it with a pen. Wiring in rear-loaded cabinets will be visible when the back is removed. Label the positive wire in the same way.
Remove the driver wires from the terminals and remove the speaker from the cabinet. Most wires have clips that slide over the terminals, which are removed by pulling them off. Some drivers are equipped with push-spring terminals with bare wire inserted. The wire is removed by pressing the push button and pulling the wire free. Very few drivers use soldered terminals, but if found, the wire must be unsoldered with a hot soldering iron.
Install a replacement speaker driver by reversing the above removal steps. Soldered connections must be re-soldered using a hot soldering iron and solder.
The replacement driver needs to be at least the same output wattage as the amplifier. If the driver was blown because of excess amp power, a higher wattage driver should be seriously considered.
Be careful with tools around new drivers to avoid puncturing the cone.
If multiple drivers are present in the cabinet, draw a wiring diagram to avoid confusion when reinstalling drivers.
Always replace drivers with the exact ohm rating as the original. Ohm ratings are usually stamped on the driver, or can be found on the manufacturer's website or owner's manual. Installing a driver with a different ohm rating can seriously damage amplifiers.
Never experiment or guess with multiple driver wiring. Wiring multiple units incorrectly with change the overall ohm rating, and may cause serious amplifier damage.