Voice coil depth

sweaty v

2013-04-30 9:25 pm
Hi all,
First post, not sure if my question belongs here or not.My first project is some speaker reconing. This will be my first dumb question of many but here goes: Is there a science or formula to determine voice coil depth on an old 10" celestion? 7442 frame.
Thanks and be gentle.
No image... you want to use the Manage Attachment function in the "Go Advanced" or Post Reply button thingies...

You don't have the original cone & VC??

the VC length will (for an over hung VC) depend entirely upon the Xmax figure for the suspension. The VC windings need to be in the gap to maintain control.

Some drivers have the windings leave the gap, bad designs though.

Also the length of the VC former has to be such that it doesn't slap the back pole piece on return...


Paid Member
2010-12-11 12:39 am
Hi sweaty v,Your picture did not download,however if you mean Xmax which is an indication of the voice coil movement in one direction,then subtract the magnet front plate thickness from the height of the voice coil winding and divide the result by two.This is for the usual case of overhung voice coils.If you need to measure the front plate you can bend the end of a thin piece of copper wire at right angles to form a small hook,insert this into the magnet gap,twist it to hold against the hidden side of the front plate and then fold back the upper section of the wire against the outer face of the same plate.Carefully manoeuvre the wire out of the gap and the profile of the wire should give you the plate thickness.