I'm connecting a small 3" 8 ohm speaker to a low power, battery operated
amplifier that was originally connected to a 4 ohm speaker. I want to match the
impedances by making my own small audio transformer using just a torroid ring
and some very thin wire from an old AC transformer.

Question...

What are the mechanics involved. I know I'll need two windings, a primary and
then a secondary. Can I just wind some of the wire on one side of the torroid
as the primary and then wind 2 times as much (because of 2 times the ohm value)
around the other half of the torroid?

Is there a minimum number of winds or is it a case of the more winds the better?

I'm trying to keep this bedrock simple.

Any advice will be appreciated.

thanks

elfa