Changing your car speakers is usually a fairly straight-forward task. Speaker manufacturers and many retailers have extensive databases showing what size speakers fit into the speaker locations of specific vehicles. In some cases, however, there is no information available. Perhaps the car is too old, or it may be an unusual or obscure model. If this is the case, you'll need to measure the existing speakers to see what will fit into your vehicle.
Remove the existing speaker. Given the vast range of models of vehicles, it's beyond the scope of this article to detail that step.
Measure the mounting depth of the speaker. This is the distance measured from below the speaker's mounting flange to the base of the magnet. This ensures that your new speaker won't be too deep, and bump against obstructions below it.
Measure the mounting height of the speaker. This is the distance measured from the bottom of the speaker's mounting flange to the highest point of speaker. This ensures that your new speaker won't be too high, and bump against a door panel or factory grill.
Measure the cutout diameter of the speaker. This is the size of the opening necessary to accommodate the speaker, measured from where the basket drops down below the speaker flange.
Measure the mounting screw width. This is the distance between the screw holes on the flange of the speaker, measuring across the speaker. This is perhaps not as critical as the other measurements, because new holes can often be drilled to hold a new speaker.
Check your specs against those of speakers you're considering for purchase, to be sure you're buying a speaker that can fit into your car.