P Bass Pickup Design questions

[Davidjlo]

So I have been working on a MIJ Fender P Bass for a friend and we refinished it etc but now I'm moving on to electronics. I found some damage to one of the original pickups' coil so I ordered a cheap set of wilkinson replacements. I'm sure that they might be considered sub-par but I put them in anyways. I decided to repair the originals so I unwound the damaged one until i passed the damage and now they're ok. I noticed however that the wilkinsons and the originals are made differently and was hoping someone could shed some light on this.

The originals have 2 magnets sandwiching the pole pieces on the bottom,
the wilkinsons have just one magnet directly under the pole pieces
and yet when i search around i find that you can also just magnetize the pole pieces themselves and not use a magnet underneath?

What are the differences here?

Obviously the ones with magnets beneath have steel slugs and the ones without magnets are actually made with magnet material.

I guess what I mean is how does the placement of the magnets change the EM field and sound etc.

[David Schwab]

The original Fender P bass pickups use alnico V rod magnets, and no magnets on the bottom.

This is the bottom of a 1974 P bass pickup:



So the poles you see there are the magnets.

The cheaper Fender pickups use steel rods for poles with ceramic magnets on the bottom. Some other pickups like the DiMarzio Model P also use steel poles with ceramic magnets on the bottom.

With the pickup that use ceramic magnets, the ones with two magnets have the magnets facing the pole pieces with the same polarity, so that polarity is presented to the top of the poles. A cheaper version will have one magnet on the bottom. The two magnet version is usually stronger.

As far as tone, both ways can sound good depending on how you wind the pickup.