Yes the wire wound on the oil is flat or square shaped instead of round.
pros: flatwound usually yields higher thermal handling and slightly higher bL.
cons: flatwound usually cost more. Heavier. I have heard in the past that roundwire coils are better for sq but haven't seen any facts to actually back that up.
For daily and/or spl woofers flatwound is the way to go IMO.
cutaway of a flatwound coil. with roundwire coil u get small gaps in between the windings due to them being round, with flat wire the winding all lay perfectly on top of each other leaving no voids. wish no gaps and more metal/windings, you get more magnetic flux strength in the gap aka higher bL
