I am trying to figure out my SP4 15's when it comes to how many different wiring options i have. My subs are dual 2 ohm subs and right now i am wired to 1.4 ohms at the amp. Seems i cant wire any lower without the amp going into protect. Was just curious about nominal vs. reactive when it relates to my setup.

There is a difference between dc and ac resistance. Impedance is rated over a usable frequency range.

so that means depending on the frequency the impedance changes. If they are d2 they are d2 not 1.4

^^^ Exactly.  Impedance and "reactive" resistance is basically the same thing.  Regular resistance, like a resistor in a circuit, doesn't change with a given frequency, voltage, current, etc.  Any coil wound resistor/resistance has an impedance that changes with the AC frequency that goes through it.  DC current sees a constant resistance value though and is typically lower than AC impedance.  As Julian mentioned the impedance value that is listed is basically like an average for a given range of frequencies.

 

 

1.4 ohms would be about 2 ohms nominal impedance.  You are measuring that resistance with the subs disconnected from the amp, correct?  Three dual 2 ohm subs could be wired to .33 ohms (all parallel), 1.33 ohms (series coils/parallel subs), 3 ohms (parallel coils/series subs), and 12 ohms (all series).  Can be viewed here.

Yeah I just don't know how my amp would take sitting at .33 ohms?

Most amps won't do it daily. My 9s Would play at .25 but required me to play above 50hz or they'd protect instantly

Yeah I feel you....I am going to re-cone them to dual 1's and total out to 4. Them run 2 Crossfire 8k's to all 4 and see how she wangs....