easy, clip one of the wires, at the terminal.....now you have two separate coils. touch the + and - leads of your ohmmeter together tightly and hold for 10 seconds. then tell us what your ohmmeter reads. write that number down. then touch your leads to the + and - terminal on one side of the sub only, does not matter that one of them has a wire soldered to it. tell us what that number is. for your own knowledge, take the first number you wrote down and subtract it from the second number and that gives you the DCR at rest or Znom number. (impedance of one coil) now repeat the same task for the other side of the speaker, measuring the other + and - terminals. they should be identical after you subtract the first number from it. Do the same thing for the other sub. all four coils should read the same if nothing is wrong with any single coil. If the coil is between 3 and 4ohms, you have a W4. If it reads between 5 and 6 ohms, you have a W6. it's been too damned long for me to remember what made the W5 different from the W4, i think it was single voice coil only. used to do some STUUUUUPID blowthru bandpasses back then using 12W4's' but that's another post another time.