abnormal impedence or not, they don't care about whole numbers... as long as the impedence connected is within manufacturer recommended tolerance then you're golden... an example, if the manu. says 1 ohm minimum, as long as its 1 ohm or higher then you won't have any issue no matter how many woofers you have... 1.3, 1.7, 2.6, 3.2 ohms, it could be 100 woofers it just doesn't matter... some amps are ok below 1 but it's not recommended if you don't know what you're doing...