I have 2 Kustom 50 amps (model K50-2). Each contain a single 12" speaker. One of the amps has a Jensen speaker with the following numbers written on the rim of it: 30410 C8774-4R C12N 220033. Can anybody tell me what the impedence of this speaker is? Also, do all K50-2 amps require the same impedance speaker? Thanks for your comments!