I've been playing my Splawn QR through a Marshall JCM800 412 for almost a year now at my cover band's practice space. It's the bassists cab and he told me it was wired for 16ohms with Greenbacks. A few weeks ago we took it apart to install these speaker baffle rings that angle the speakers up more towards the player. After putting it back together (wiring was untouched except at the jack) I measured and not only are they GT75's (surprisingly because they sound really good and I hate those speakers) but they are wired for 8 ohms, so I have been running it mismatched for quite a long time. Luckily no damage to the amp but it does sound better now that it's running matched. Always a good idea to have a DMM on hand and confirm what the actual impedance is on a speaker cab you will running into.