Speaker size measurement

Measure the size of the speaker (speaker, jargon "unit") according to the effective vibration radius. That is, the diameter of the outer edge of the paper cone is not pressed into the fixed rubber ring. It is customary to use inches for the diameter of the speaker.
Most people use metric rulers. After measuring the diameter of the paper cone, divide it by 2.54 (2.54 cm equals one inch) to get inches.
4-inch speaker: The diagonal distance between the screw holes is 11.5 cm, the distance between adjacent holes is 8 cm, and the diameter of the speaker is 10 cm;
5-inch speaker: The diagonal distance between the screw holes is 13.5 cm, the distance between adjacent holes is 9.5 cm, and the diameter is 13 cm;
6.5-inch speaker: The diagonal distance between the screw holes is 15.5 cm, the distance between adjacent holes is 11 cm, and the diameter is 16.5 cm;
The distance between adjacent screw holes of 4X6 inches is 12.3 cm and 7.3 cm;
The distance between adjacent screw holes of 6X9 inches is 16.5 cm and 11 cm respectively.