Terminology doesn't make it non existent. Most people know it as box rise for those not being technical. And electrical system plays a LARGE role in it's effects to. For those who compete, it's easily measurable. That's why in some classes in competition, it's better to remove some batteries in the install to prevent the amplifiers from running at such a low impedance. Your impedance "curve" alters what each frequency in the playable spectrum will be but if a user measures that, that information can greatly be changed\altered by upgrading\downgrading your electrical system... Whatever the purpose is.