Crossover Core and Assembly  { part 2 }

The crossover core coil must be 4 wires high [8 mm] and 2 wires wide [4 mm].
It's inner diameter is ~ 7 inches.

It must be wound CW and match the cones wind.
The two wires cross at the center.

Build 1

Crossover Core Coil Mold

Plastic Phlanges

Building supply store - Closet Flange Spacer - Diameter is 6 - 15/16 inches. 2 each.


The two are stacked, 2 layers of wax paper go under. Screw them down, then go around with two or three layers of scotch tape.

mold 3

Trim down the scotch tape, and wax the outer edge of the tape with a candle.
Cut the candle so it will reach the bottom corner.

mold 3 1

Steal one of the wifes plastic flower pot underlays. 7.5 inch diameter, cut the outer edge off about 12 mm high.
This ring will be used to seal the outside of the Epoxy pour.

mold 3 2

Wax the inside of the plastic ring, and also the bottom edge.

mold 3 3

Fit the plastic ring around the flanges to check for about 6 mm clearance or more.
Remove the plastic ring, it will be used later.

Coil Winding

mold 4

Two heavy sewing needles used to hold the inner wire. I started using thread to secure the wires together, then later switched to scotch tape.

mold 5

At the end of wrap two, tape all the way around at various points to hold the wires down securely.
The coil must be loose enough to lift up to add this tape around all the wires.

mold 6

Crossover at the completion of the second wrap, then tape just past the crossover point.

mold 7

Lift the coil off the form and now complete the next two turns with the opposite color out using tape on all the same points.
Put the coil back on the form.

mold 8

Waxing the large holes. Fill them both to the top.

mold 9

Waxing is completed.

mold 91

Remove any excess wax from the outside surface of the wires using an alcohol whetted paper towel.
Wax will dissolve in alcohol, be careful not to soak the plastic form or the resin will stick to it if the wax is removed.

mold 92

Now add the plastic ring we prepared earlier, and tape it down to the plywood with an even gap all the way around.
Two wire sized holes are drilled in the plastic, and then wax is melted around them to seal the leaks.
You can hold the board up at about 80 degrees, and drip the wax over the wire holes until a seal is formed all the way around them.

At this point I also added some fiberglass strands and pushed them down on the lower outer hole between the plastic ring and the wires for strength.

mold 93

mold 94

Pouring the Epoxy Resin to the top of the wires, slowly, as it will seep in a bit over time.
Make sure the table is perfectly flat, so the finished ring will have a very even thickness.

mold 95

After about 30 minutes the Epoxy is gelled but very soft, remove the black tape.

mold 96

After about 3 hours, the Epoxy is still pretty flexible. Remove the screws and lift the mold.
Remove the two wax paper layers from the bottom side.
Slowly run a sheet rock knife between the plastic base and the tape layers of the coil being careful not to nick the wires.

mold 97

It may take a bit of pressing around the ring to dislodge the coil from the plastic mold. The wax layer should finally give.
Lift the coil and press out the wax plugs carefully, then crush them, being careful not to damage the wires.
The large plastic outer ring must be cut through in one spot then peeled away using needle nose.
With a little pressure the wires will come out of the holes as the wax seal gives way.

mold 98

If there are thin Epoxy runs along the outer bottom edge, they can be trimmed off using a razor knife before the Epoxy reaches it final hardness the next day.
The final crossover coil core should now be fairly strong and firm.

mold 99

Fitting the coil to the lower cone set.

mold 991

Fitting the top cone set on the coil.

mold 992

Looks a bit better then the last attempt, and this time wound in the correct direction!

mold 993

mold 994

Almost ready to begin testing!

Cosmetic & Wiring


Thin red electrician tape is the perfect size to wrap the Epoxy ring with.
I used  2 - 1/2 turns on the outer edge of the ring.

8 sets of push in connectors will be used to close the circuit.
22 ga connectors also just happen to be red.

I striped 1/4 inch insulation off, tin the end with solder, then crimp on the connectors.
The coil system can be disassembled in three parts.
Upper, center, and lower.


End Wiring

Cones are both treated identically.

End Wiring 1

I chose to leave a little extra wire. Extending both inner to outer rim, and outer to inner tip to cut exactly the same length, to the connector.

Center Wiring

For testing, the core coil is taped inside to the lower cone with normal width red electrician tape.
I believe this will be strong enough for testing purposes.
Wires are cut to length to turn the crossover point, 90 degrees past the lower coupling point.

Splicing Angles

Overall Wiring

This is how it seemed to come out for me, and everything should be relatively symmetrical.

Voltage Nodes

Expected to manifest at resonance.

Dave L    4 - 13 - 2014

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