Magnetic Fields

[Woodinblack]

Not refering to the Jean Michelle Jarre album!

 

At the bass bash I brought some magnetic field paper to see what was under the pickups of various devices. Most are pretty obvious what you are going to see, but here are some notable ones. I found it interesting anyway

 

 

 

As a reference, this is a standard bart soapbar, twin coil humbucker, looks like you would expect

 

This is a high gain rickenbacker 4004 pickup, obviously originally designed to go over 4 strings, but covers 5 nicely

 

A dingwall twin pickup - goes with the line of the pickups, with the high notes further out

 

Here is a normal single coil and what I assume is a GK3B (although obviously could be a GK2-b

 

This is a mudbucker on a homemade Gibson Les Paul bass clone - huge area covered and probably explains the name!

 

This is a sandberg pickup in a soapbar case - looks similar to the dingwall pickups mostly - this pickup was lined horizontally, so the pattern is just how it is in the case

 

A fender (actually squier) metal covered split bass pickup - I looked at two of these, and the pattern is the same, the D string has most of the magnets!

 

On the same table - two single coils and a P pickup - no surprises but very well balanced

 

Finally a G&L MDF pickup in a L2000 - as you can see the magnetic field is so high its bending reality around it. And maybe even gravity.

 

Interestingly I wanted to put the Rickenbacker 4003 pickup here, but pressing hard against the pickup I can just make out the dots on the pole pieces, but it is so weak it is very hard to see.

 

 

[Inga]

Wow that's really interesting.. I'll have to try some on a few of my basses.

[BigRedX]

What do the different colours mean?

[Woodinblack]

The magnetic Gauss level and the direction of the magnetic field to the polorisation of the film. Although I didn't notice turning the paper to have any noticable effect.

So effectively it just shows the shape of the magnetic field, there are some charts on the net that seem to say what the field strength is but they don't seem reliable and it seems very much that yellow and red are the opposite of dark green and blue.

[Richard R]

That is interesting.  Had I realised what you were doing I would have been interested to know what was under the covers of my Brawley and how balanced they are.

Where can I find this magnetic paper? 

[Woodinblack]

A few places on the net, some on ebay, there is a magnetic paper shop, I got mine on aliexpress some time ago. If first saw it on a thread about the spector dimension and how the pickup didn't cover the whole 5 strings

[itu]

EMG sold similar magnetic paper. I saw a magnetic window for 1" video tape in the early 90's at a broadcasting company. They used it to find the place for cutting the tape. 

 

Here's my Passion II with Benedetti single coils. 

 

[ikay]

On 20/10/2025 at 21:50, itu said:

Here's my Passion II with Benedetti single coils. 

 

This is curious. Here's a flux pic of the Benedetti SCs in my Excess and the mag field (blue) shows through the centreline of the pickup where the poles are. On the pic above the flux seems to be showing as a halo rather than through the centreline. Having said that, I don't know why mine are showing a white halo!

 

 

[itu]

@ikay : There's most likely a frame of some kind made of metal. That could explain the halo. 

[ikay]

16 minutes ago, itu said:

@ikay : There's most likely a frame of some kind made of metal. That could explain the halo. 

I was thinking the halo outlined the shape of the coil. The curious thing with your pic is that it doesn't seem to show any mag flux along the centreline where the poles are.

[ped]

3 hours ago, ikay said:

This is curious. Here's a flux pic of the Benedetti SCs in my Excess and the mag field (blue) shows through the centreline of the pickup where the poles are. On the pic above the flux seems to be showing as a halo rather than through the centreline. Having said that, I don't know why mine are showing a white halo!

 

 

 

It's because I used to own it, so it's become holy

[ikay]

5 minutes ago, ped said:

 

It's because I used to own it, so it's become holy

😅 haha, the holy grail of bass provenance!