A perfect coil is like a fine tuned engine. I hold the tip near my ear(don't stick it in the ear LOL) & listen. If the coil is 'just right', it will sound like a well tuned engine with no 'misses'. The more the coil 'crackles' & 'pops' (misses)the more 'out of tune' the coil is. Sometime the coil (like a engine) just needs to be run through the paces to settle in(seat properly)........& sometimes it needs a 'complete rebuild'. So,next time you think that coil is just right, Lay the coil along side your ear & listen. Nothing like the sound of a 'fine tuned' coil. The sound of the coil will 'expose' any short comings of the builder HaHa. You can also hear through the mouth,but the ear is more telling. How's your coil sound?
