4 or 8 ohm coils...

[gdv]

Hey everyone!  I'm working on a special project where I need to make 2 to 4 coils...  They need to be either 4 or 8 ohm as I will be powering them with a home or "the other" type of system found in vehicles which run at 12V dc...   

I need them to be about 3 to 4 inches in diameter...  Is there something readily available like this?  If not, recommendations on what wire to use, how to "BEST" roll/wrap it into the 3 to 4" diameter & best way to calculate resistance...  I know how to calculate resistance at each end of the wire, so do you keep trial n error it till you get the desired ohms?

I spent a little time researching the issue, but did not find too much good info...  Below is one link I found to make the coils...

http://www.steam-engine.org/coil.asp?r=8

Will greatly appreciate any/all helpful info...


Thanks!!!
George


 

[OldiesButGoodies]

Hmm,   these feels suspiciously like illegal contraband in car audio tips in the forum...

But that is fine - great topic!   Here's a fancy one though there are a bunch of less fancy manual ones on ebay:

http://www.ebay.com/itm/Automatic-Coil-Wire-Winding-Machine-Hand-Coil-Winder-w-Electronic-Counting-/230931917065?hash=item35c49d6909

Feels like we should be able to do this using a drill and some patience,  not worrying so much about counting the turns and relying on the size of the plastic barrel to get it roughly there.

OBG