A question I get almost on a daily basis either through a phone call or one on one interactions with customers is, what type of coil does my tweeter drive have and which drive should I buy?.tweeter drives come in various sizes and types and knowing which coil you should use could be the difference between clear sound vs distorted /rough sound. this article is meant to address that issue.
Mass production tweeter drives come in about 10 different sizes, there is 25.5mm(spoon coil),34.5mm,35.5mm,38.5mm 44.4mm,51.0mm,51.5mm.also, 74.5mm and 99.2mm are available although not that common.
prefer different coil arrangements for their own reasons, a company like an eminence prefers coils with the together terminals in their tweeter drives for 44.4 and 51.5 https://phelectronics.co.ke/product/tweeter-coil-51-5/ same as Wharfedale and Neureton. Peavey and Jbl have the apart terminals
As a side note when buying a tweeter drive choose one whose coil is readily available and affordable to you. a drive that uses the 35.5mm coil has difficulties in finding the coils at least in my country Kenya.44.4 is the most easily available.