Fabricating Coil Bobbins

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I've decided to upgrade my old discotheque loudspeaker crossovers from a 12db/octave to a 18db/octave and this involves making new coils as well as replacing the capacitators. The designs I first made them too, were publish in ETI-Circuits No.2 magazine back in 1978 **LINK** pages 75-80 . However, one of the coils needs to be on a larger bobbin than those that I used before. When I first did them, I was able to use the plastic bobbins that PTFE tape is supplied on, but one of the coils in each of the new crossovers will not fit on them without introducing significate insertion loss.

Starting with cutting out some blanks with a holesaw from a 20mm thick worn offcut of a composite plastic sheet, which I saved from the bin during my old job over 12 years ago now.

With a bit of machining, two of these will form part of the core and one side of the bobbin. Firstly the worn side was faced off and the edge trued up, then using a 28mm holesaw, half of the core was cut into the face and the outer section was parted off.

This was then trued up and the half core part was turn to fit into the connecting tube. The connecting tube is just a piece of 32mm ABS waste pipe, which will become the full core, which the wire will be wound onto and this was superglued onto the half of the core formed on the bobbin side.

The connecting tube was then faced to length, which will dictate the width of the bobbin. Two on these have been made and are ready for the other side and half core.

 

Regards Nick.

Edited By Nicholas Farr on 18/09/2018 00:25:18

[Nicholas FarrParticipant @nicholasfarr14254]

Bobbins for loudspeaker crossover coils

[Neil WyattModerator @neilwyatt]

Core!

Sorry Nick….

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, yesterday I found time to finish making my bobbins. Although these other two sides have a larger diameter, they were made in the same way and were superglued in. The larger diameter sides are for drilling fixing holes. Just have to wind 150 turns of 1.25 mm of enamelled copper wire on to each of them.

Regards Nick.

[Ian S CParticipant @iansc]

I made some coils lately for a little magnetic motor, and used bits salvage from old circuit boards with the copper removed for the cheeks of the bobbins.

Ian S C

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