Tell it how many subs you have, whether they are single or dual voice coil, and what impedance they are — it works out every possible wiring, draws the circuit, and spells out which wire goes where.
What are you wiring?
use the nominal coil impedance, not the measured one
How many speakers
Voice coils
Two terminals on the back of the sub means one coil (SVC), four terminals means two coils (DVC).
Impedance per coil
This is what the label says: "DVC 2 Ω" means 2 Ω per coil.
What the amp can handle
The lowest impedance the manufacturer rates as stable. Do not go below it.
The result
Wire it like this
positive side negative side internal link
Series
impedances add up · 4 Ω + 4 Ω = 8 Ω
They sit in one chain: amp positive to the first coil's positive, the first coil's negative to the next coil's positive, and the last coil's negative back to the amp's negative. The same current flows through all of them.
Higher impedance: the amp delivers less current and less power — in exchange it stays cooler and will not drop into protection.
Parallel
impedance divides · 4 Ω ∥ 4 Ω = 2 Ω
Every coil's positive goes to the amp's positive, every negative to the amp's negative. With identical coils the result is the coil impedance divided by the number of coils.
Lower impedance: the amp delivers more current and more power — but it runs hotter, and at some point you drop below what it can take.
Which coil is which?
the back of the sub
Single voice coil — SVC
2 terminals: one positive, one negative
Nothing to get wrong here: one coil, one pair of terminals. With several subs you wire these to each other in series or parallel.
Dual voice coil — DVC
4 terminals: two separate coils, A and B
Two separate coils on one cone. Always wire both of them, equally — drive only one and the sub will not do what the spec sheet promises.