Many times people ask if we can replace a rotted out roll on a woofer.  Usually, rolls are available, but also usually, roll suppliers do not specify rolls by the model and brand name on the woofer:  Rolls and other parts are usually specified by the dimensions and materials used in the part.  We database replacements we do, but there are so many thousands of woofer models “out there”, that sometimes the question “Can you replace the roll on my woofer” requires a question from us:  “Can you tell us what the dimensions of the roll on your woofer are?”  Unfortunately, few consumers know how to describe or measure a woofer roll.  So, going by the old adage “a picture is worth a thousand words”, we present the following drawing and picture.

Below is a cross-sectional drawing showing some basic cone / roll dimensions.  Note that many “cone” people refer to the hole in the bottom of the cone as the “VCID” (Voice Coil Inside Diameter), although this is more properly assigned to the actual inside diameter of the voice coil itself, not the hole in the cone that the voice coil fits into.  A more proper designation is “Body Trim I.D.”, which perhaps would get the acronym “BTID”, though we have not seen this abbreviation in common usage. 

(Click on image for full size image).

The above is sort of a “two in one” drawing, showing, on the left, a “flat attachment” of the roll to the cone body, and on the right, an “angle attachment”.  These two different designs are sometimes called (in reference to the roll design used), a “flat attach roll” and an “angle attach roll”.  (Obviously the roll and body dimensions and styles must match up closely.)

The drawing shows the roll attached to the front, or “face” of the cone body, which is more common.  However, sometimes rolls are attached to the rear surface of the cone body, and that is known as a “rear attachment”.

Below is a view looking at the diameter dimensions of the roll from the front of a typical woofer:

(Click to enlarge image)

When measuring roll diameter dimensions, be sure to measure exactly 180 degrees across the cone.  The best way to do this is to use basket mounting holes, or gasket segment mating points (if present) to line up your ruler, caliper, etc., as done in the above example.  It is also a good idea to take an average in 4 locations if possible, for each dimension, as rolls are not always glued onto cones with perfect concentricity or roundness.