Let me explain series and parallel so you understand. Series is the electrons leave the amplifier let's just say out the positive terminal, then flow into the positive side of coil 1, then out the negative side of coil 1. Then the negative side of coil 1 is directly connected to the positive side of coil 2 so the electrons flow through coil 2 and out the negative side which is directly connected to the negative terminal of the amplifier. Since the current had to flow through both coils before returning to the amplifier, they were said to be in series. This is why the impedence is added together. So if they were dual 2 ohm coils the electrons were faced with 2 ohms of electrical impedence twice thus equalling 4 ohms.
With parallel, the electrons flow to each coil independantly. The electrons flow out of the positive terminal of the amp and to the positive coil of both coils simultaneously. It simultaneously passes through both coils and out the negative side to the negative terminal of the amplifier simultaneosly. Since it had two paths at 2 ohms, the impedence was halved in this case. 2 ohms divided by 2 coils = 1 ohm. It doesn't matter how you wire it up in parallel. If all positives are together and all negatives are together, regardless how you got to it, it is in parallel.