Re: what makes a neck pickup a neck pickup?
It's kind of a long story (he said in his best wheezy grandfathery voice) but pull up a chair, sonny boy, and I'll try to keep it longer.
Back in the day, there was no such thing as a bridge or neck pickup -- or middle pickup either for that matter. All were identical and interchangeable. Or really, they were SUPPOSED to be identical.
The winders in those days were just trying to fill up the bobbin with wire and really had no idea if they put the same amount of wire on bobbin #3 or bobbin #65 that day. In most cases, you looked at the bobbin and if it looked full, you soldered the lead on, taped it up, you're done, next bobbin please, how long til lunch break?
At least in the case of the PAF's, this naturally led to pickups that varied pretty widely in DCR and coil mismatches. Though the overwhelming majority were somewhere between 7.5 and 8.5k, some were as low as the high 6's and some almost 11k. So because the pickups were installed interchangeably, you could get a Gibson with a neck pu hotter than the bridge.
In the 50's no-one really thought about the differences between pickups because the electric guitar itself was so new, so all electric guitars sounded like...electric guitars. It's sort of like if you moved to Korea or India, everyone would look alike to you for a while before you got used to the basic appearance of the locals and started to notice how different each person's face really is.
But somewhere in the 60's folks -- like Seymour -- finally did start noticing that "Hey, your guitar is just like mine but it sounds different. Why?" Prior to this, you could sometimes order a pickup from as a replacement but you did this only when a pickup stopped working. But when Seymour and others started investigating these sound differences, the aftermarket replacement pickup -- the kind you bought to change the SOUND, not just replace a busted pickup -- was born.
NOW WITH THE BORING HISTORY LESSON BEHIND US, what really does make a neck pu a neck pu and a bridge a bridge? The line between the two is kind of blurry, but at its most basic, the difference is typically that the bridge pu has more turns of wire to make up for the relatively weak vibration of the strings close to the bridge vs. the much wider/stronger vibrations toward the neck.
You might well use to two identical vintage-voiced pickups as they did back inthe day. But a typical vintage pu will be a bit jangly and thin in the bridge -- fine for some but most want more punch. To get more punch, you either raise it closer to the strings than the neck pu, or you replace it with a pickup that has significantly more turns of wire and/or a hotter magnet.
My own rule of thumb for humbuckers and P90's is neck pickups tend to get muddy once you get much past 7.7-7.8k and bridges don't get that growl most crave 'til at least 8.5k. This line will vary depending on the other factors, like magnet, coil geometry, the guitar it’s going in, individual playing technique, etc. The line is blurry also for reasons of personal taste -- some folks might want a hotter neck pu well above 8k because they play primarily single note lines with a lot of gain, so they don’t worry about muddy chords. Other folks want both neck AND bridge under 8k because they want a vintage bluesy tone, a touch of Tele sting and attitude in their humbucker guitar. (Another complication is that 24-fret guitars can handle a hotter neck pickup before they start to sound muddy, because the position of a neck pu on a 24-fret guitar is closer to the bridge.)
Also keep in mind, that the above numbers are for buckers and P90’s. The numbers are a bit different for Strat and Tele pu’s, but the concept is the same.
The above is pretty much hard science, getting the right relative output for each position. Where it gets really "artsy" is making a pickup for each position that not only gets the right relative output to the other pickup, but GETS THE RIGHT EQ RESPONSE for each position. This is where the magic is – getting the right combination of wind pattern, coil tension, wire gauge, magnet type, magnet aging, baseplate and cover materials, coil mismatches if any, etc., and arranging them in such a way that they take full advantage of the harmonic node of the string each pickup and coil sits under, de-emphasizing the frequencies you don’t want and emphasizing the ones you do want but are kind of weak in that position.
To my mind that’s what makes the difference between a true neck or true bridge pickup, one built from the baseplate up to get the best possible sound out of each position for what the player has in mind. The downside is that the more specially calibrated a pickup is for neck, bridge or middle, the more likely it will sound like crap if it's installed in another position.
Hope that helps you more than it hurt my fingers to type all this...
