The cutout diameter is a measurement of the mounting hole size that was cut out. This is required for the speaker surround and the cone to fit properly. Flip the speaker so that the widest part of the cone is facing down. Use your ruler or tape measure and write down the measurements of the diameter at the widest point

The speaker cutout diameter is the measurement of the outside or outside diameter of a loudspeaker. You can measure it in either inches or millimeters. To measure speaker cutout diameter, use your ruler and measure from the edge to edge of the speaker cone as shown in Figure 1 below.

To measure car speakers cutout diameter, flip the speaker upside down so the magnet is on the top of the speaker. The cutout diameter is the widest part of the cone attached to the back of the speaker basket. The right way to measure it is to use the ruler and look from the top of the magnet down.