Pickup shapes are usually associated with the instruments that first used them - P-Bass* pickups, J-Bass* pickups, Music Man* pickups, etc - and with the sound of those original instruments. But we make several different structures (coil and magnet arrangements) that we are able to put in many different shapes of pickup shells.
To us, the shape of the pickup is important only because some of our structures fit in some shapes and not in others. If we could, we would make every one of our structures available in every pickup shape we make. This would make every tonality and response that we can create available to every musician regardless of the instrument used. Unfortunately, there are some limitations.
The following diagrams show the different structures available in our pickups. In these diagrams the aperture (A) is the length of string sensed by the pickup. Narrow apertures usually yield brighter, more defined sound. Wide apertures usually yield a fuller, mellower sound. However, the frequency response and Q factor of the coil system will shape the tonal quality and voicing and will affect the tone as strongly as the aperture of the pickup.
In the following diagrams the string sensing coils are shown with a solid line and hum-cancelling coils are shown with a dashed line.
These single coil structures are inherently quieter than the traditional Alnico cylinder structures. We add shielding and cast them in epoxy to prevent microphonics (noise due to mechanical impact such as from picks, fingernails, etc.). The resulting structures are very quiet for single coils but not enough to use with electronics (which will amplify signal and noise equally)
The tone quality is smooth, clear and even. Depending on the coil winding the voicing can range from deep to very bright without becoming harsh.
Viewed from the top the magnetic structure of our single coils looks the same as that of the stacked coil pickups we have made. If you use the EMG® "green paper" to see this keep it in motion over the surface of the pickup moving it back and forth about 1/4 inch and watching the features that remain constant in the display. This very fine idea is a little too sensitive and tends to show much more of the magnetic field than actually interacts with the string. It is a very useful tool, nevertheless. Do not use steel wool shavings unless you are prepared to clean them off the pickup and neighboring areas very, very thoroughly. They can come back and haunt you later.
In the recent past we have started to make what we call "J" and "K" structures. These are similar to split-coil humbuckers. They are the equivalent of a "P-Bass* pair in a box" if you wisht to think of them that way. They have a higher output level and (depending on the winding) can have a much "meatier" tone than the stacked coil structures.
We make these structures for 4, 5, 6 and 7 string basses. They are capable of covering a wide range of string widths. The 59J, for example, covers string widths from 64 to 74mm. For some builders and manufacturers we have put two of these structures in the larger shells (MM, MV, M5, etc.).
The tone of the "J" version of this structure is quite strong in the lows and low mids. The tone of the "K" version is stronger in the treble frequencies.