Re: Stacked P-90 for heavy music
Series or parallel are the way of connecting two coils together. Those 2 coils can be in a humbucker or 2 coils stacked or even 2 individual single coils being selected on the 5 way switch.
Parallel means 2 separate coils run individually at the same time, in a stacked or humbucking pickup they are hum canceling. Think of it like having a reverse wound reverse pole strat middle and selecting the neck and middle pickup together. in a humbucker the coils are much closer and in a stack the coils are in the same position.
Series is the standard wiring for a humbucker, it means running one coil through the other one. In a humbucker the coils are reversed and opposite polarity, thus canceling hum. Running the coils end to end like this fattens up both the mid range and the output. Some people put a 4 way switch in the telecaster to get a 4th sound of the pickups in series, makes for a huge sound, Another example is the red special that Brian May used with queen, he had wired for series in some positions.
When a coil is split, it is by itself, this adds a boost over parallel because 2 resistances in parallel halve the overall size resistance, more or less. Putting the coils in series adds the 2 together in resistance thus making it louder than split.
The stacks since they only have one row of poles only see one point on the strings and that point influences how they sound. The second coil in the stack actually faces down away from the strings though and is under the magnet. Being only one spot on the strings you aren't getting a second node or point to fatten up the sound when in series, but you're also not losing as much sparkle with the second coil facing down since it's only getting a weak signal from the strings.
Anytime 2 coils are humbucking, whether series or parallel there is some frequency cancellation between the 2. Some of this can be offset by using 2 different spots under the strings, uneven winding of the coils or even different gauges of wire. That's part of why the 59/custom has such a 3D sound, but it's very hard to get all of the sparkle back and still reject hum or noise. I have seen this complaint with stacks just like I've seen it to a lesser extent with rwrp middle singles. There's are other tricks out there like burying a coil under you pickguard or inside your wiring cavity that cancel the hum without dampening the frequencies, but I haven't tried any.
