2. WIND A NEW COIL
If your speaker coil is deep enough to let you mount an extension and has wire beefy enough to handle
some high-voltage driving, you can skip this step and add the riser (Step 3) to the existing coil. Otherwise
it’s a better bet to wind your own.
2a. Create a new former by wrapping
a tight loop of packing tape around
the old former with the sticky side
out, so you can slip it off later. It
may take several tries to get a clean,
smooth cylinder.
2b. Wind a new voice coil onto the
tape. Start by taping the end of your
magnet wire securely to the spider
on both sides, leaving some extra
length. Then wind a tight, single-layer
coil around the former with 50 to 100
loops. Don’t make multiple layers
of wire, or the coil will jam in the
magnet or overheat.
TIP: When winding a coil, the first loop is the most important, because it sets the standard for the rest. To make
winding easier, pull the wire off of its spool tangentially, so it doesn’t kink. To help with this, I used a large Allen
wrench in a vise as a spool holder. Spin the former in your hand as you pull the wire and lay it down firmly.
2c. After you’re done winding, spiral
the outer end of the wire down the
former and tape it to the spider. Cut
the wire and strip both ends.
2d. Use squares of aluminum tape to
cover the coil and at least ¼" of the
packing tape that sticks out under-
neath, but leave a small gap down
1 side so that the aluminum doesn’t
create a conductive ring. Make sure no
tape is sticking to the original former.
2e. Slide your new coil off the former.
TIP: Use several small
squares of tape rather
than 1 piece, because
aluminum tape is tricky
to manipulate, and a single
cylinder of tape would
fit poorly on the conical-
shaped cup later.
TIP: Calculate your coil’s resistance by multiplying its length by the
wire’s resistance. For example, my coil had a 2" diameter, 60 windings,
and 30-gauge wire whose resistance is about 0.1Ω per foot.
This gives ( 2×π× 60) × 0.1/12 = about 3Ω.
Make: 127
