I want to buy new oval speakers for the rear side of my car.But I'm having trouble figuring out which one to buy.The car came with the holes and ready cables for the speakers but without them. The hole for the speakers is 11.5cm X 9cm(4.5" x 3.5"). Since oval speakers are usually advertised in inches, I'm kinda confused which one to choose because there aren't any oval speakers in that size.
The measurement is the distance between the mounting holes. I suspect you have 6x4 which is the size used across many older Volkswagen and Porsche cars.
You can confirm this by measuring the distance between the mounting holes, not the diameter of the speaker aperture.
There are a range of 6x4 speakers available from a number of manufacturers so you should have no problem finding a set.