You do not decide firsthand how many meters to use, even less 100 meters which is an absurd number.

To use somewhat realistic numbers (fwiw I commercially design and build speakers, wind own coils, etc.) , a "buildable" subwoofer might have a 2" voice coil, winding (track) length 20mm which with an 8 mm plate will give you quite good 6mm X-Max

With a standard 2 layer VC, you can fit 80 turns total (40 turns per layer) if using 0.50mm wire, average turn length will be 16cm=0.16 meters so total wire length will be 80*0.16=12.8 meters (actually somewhat less because we are ignoring enamel thickness but hey, this is a basic example) so we are getting 8.7*0.128=1.11 ohms DCR, call it a 1.5 ohm speaker.

Not sure you want that,so clearly

**0.5mm diameter enamelled wire is already way too thick**.

So won´t waste time calculating for 0.7mm wire which will give you around 0.4 ohm DCR .... unusable.

Actual design goes the other way: you

__start__ with geometric conditions (VC diameter and track length), then

__solve__ for what wire fits there giving reasonable DCR, then

__find__ how many meters you got.

Small variations of wire diameter have huge impact on final DCR, since it is inversely proportional to the

*cube* of diameter.

Quite counterintuitive until you do the full Math.