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Pickup Bobbin Size Humbuckers

 

Picking the right-sized bobbins/pickups will ensure an excellent fit and reliable sound. Generally, a 49.2 MM-sized pickup will fit in most cases, but if the guitar has a floyd rose or a tremolo system, a larger-sized pickup will have better alignment with the strings regarding pole and screw pieces. Because of this, pickups with 50 MM bobbins have been called “trembuckers” by Seymour Duncan. A sure way of telling if a guitar needs humbuckers or trembuckers is to measure the distance from the E string to the E string. If the measurement is 2″, humbuckers are the way to go. If it measures larger than 2″, then trembuckers will fit the strings more accurately. The bobbin size and the string spacing only matter when you can see the pole/screw pieces. If the humbucker/trembucker has a cover over the pole/screw pieces, then the difference in sizes of the bobbin doesn’t matter unless you have more than six strings. There might be a concern that you might not get the right tone if the pole/screw pieces are not aligning under each string. Worry not because if the pickup is magnetized with a bar magnet, the screw/pole pieces are purely aesthetic. However, some humbuckers, such as CuNiFe wide-range pickup, have magnetic pole pieces.   

 

Frame base plate leg length for humbuckers

 

Two factors differentiate between standard humbucker pickups when it comes to dimension- the bobbin size described in another section and the leg length of the baseplate. There are long legs, ½”, and short legs, ¼.” Short-legged pickups will fit in many more guitars than long-legged, but there are a few instances in which the longer legs will be needed- when the pickup must be raised a considerable amount higher for sound amplification of the strings. An example of a guitar that needs long-legged pickups is the Gibson SG standard, in which you need the extra height for the pickup to be raised satisfactorily over the pickguard. The short-legged pickup is more versatile than a long-legged one because with a deeper pickup cavity, either one can work, while with a shorter pickup cavity, the long-legged pickup would not fit in because the height would be too much. Another baseplate leg-length consideration is the springs that secure the pickup inside the cavity via the mounting rings. If replacing long-legged pickups with short legs, the springs used for the longer leg will not fit for the shorter and vice versa.      

Magnet wire (the coil of the pickup) for general pickups

A few factors go into the magnet wire used to build the coil for a pickup, and the variability in these factors determines how the pickup will sound. Magnet wire is copper wire that is coated with various insulators. This coat of insulation allows the copper to be wrapped around the bobbin without shorting out with copper touching copper. Many different insulators are used in magnet wire, but the three most commonly used in Frontier’s shop for making pickups are plain enamel, poly, and heavy formvar. There are many different views on how these materials may affect tone- some believe these insulators make a nominal difference that can’t be heard. Others believe there is a substantial difference. It is my view, as someone who hand winds many pickups with each type of magnet wire, that each of them has a different feel and malleability. These changes in consistency will inevitably differentiate how each pickup is wound. Regardless of opinions, it is factual that plain enamel and formvar magnet wire have been used since the first electric guitars were made, so they are considered vintage. It is also true that poly has been used to wind most modern pickups. How these insulators are applied to the copper wire is also different. For instance, plain enamel may have slight inconsistencies with the coating, while poly is more uniform. Because of this, it would be easier to get the same sound out of multiple poly pickups versus plain enamel. When dealing with hand-wound pickups, each will sound different regardless because of the human factor going into the winding, but this is positive. This brings me to specific measurements that let you imagine what an individual pickup will sound like before you even plug it in. These are resistance, inductance, and capacitance.  

  • Resistance, the pickup ohm reading (Ω), will tell you if the pickup is functioning as it should. This reading of output is beneficial in making sure the coil has no shorts- a standard humbucker may read 8.2k ohms which is fine, but if it reads 50k ohms, you have a problem. This is also an excellent way to check variability in pickups. If you have two humbuckers, one overwound and the other with the standard winds, the overwound one should read a higher output. This metric can change due to the temperature, so it isn’t the same reading year-round. The colder the coil is, the lower the output will read. After potting the pickup (submerging it in melted wax), the ohm reading will be significantly higher; the ohm reading can be even 1k higher than before/after it cools down from the potting. 

Henries (H) and capacitance (C) are both metrics related to each other regarding pickups. Capacitance is the ability to store energy in an electric field, while inductance is the ability to store energy in a magnetic field. Think of the guitar strings’ vibration as a large spectrum of sound, while the pickup is a flashlight illuminating specific areas of the range. Changing the coil size and magnet will change the illumination, and capacitance/inductance will inform you what is in the spotlight. This is a very abbreviated analogy, but it will be even more simplified in the following few bullet points, in which I will describe how these metrics provide insight into what tone you will be getting.

  • Henries (L) will tell you if the pickup will amplify higher or lower frequencies. The lower the inductance, the higher frequencies will be amplified. Vice versa is true: the higher the inductance, the lower frequencies will be amplified. Guitar pickups usually measure anywhere from 1.8-10 henries. Like anything else, this may have exemptions, such as a tele hot rod pickup measuring up to 15 Henrie. Low inductance pickups may be referred to as “bright and twangy,” while higher inductance may be seen to favor the midrange, be “darker and fatter.”  
  • Capacitance (C) is measured in farads and will tell you how much treble is being cut off because of what the pickups highlight in the sonic footprint. In general, the higher the capacitance measures, the more treble will be audible. To oversimplify this already simplistic explanation, think of a tone potentiometer- a dial with a capacitor on it for you to tweak the tone. With this in mind, think about the farads of a pickup compared to the position of the tone knob. A pickup measuring higher capacitance will be like a pickup measuring lower but set to a higher value on the tone knob. The standard pickup’s self-resonance (internal capacitor measurement) can be between 50-300pF. This is usually measured in 200nF, as on the back of frontier pickups. This conversion will be seen as anywhere between 10-35 200nF.  

 

Magnet type

 

As a testament from this synopsis of pickups, many variables go into the design that affects what it will sound like. Still, the magnet is the most critical part. You can make a pickup if you have a coil of wire, anything with magnetic properties, and an input jack. That magnet interacts with the vibrations of metallic strings for the coil to translate an electronic signal. Different magnets have different properties, which, in turn, interact with strings differently. In the 1930s, the discovery of combining aluminum, nickel, and cobalt to iron to create a magnet that is 3,000x stronger than the earth’s magnetic field, does not corrode easily and maintains its magnetic properties. This was perfect timing for the pioneers of the electric guitar. These magnets are named Alnico, AL-NI-CO, for iron alloys that are used to make them. Alnico 2,3,4,5 & 8 are the most common magnets for pickups, with Alnico 5 being the most common. It is important to note that the numbers do not relate to the magnet’s power but rather the percentage of alloys being used. Alnico 3 has the weakest magnetic properties (in bar form, not rod form), while Alnico 8 has the strongest. 

 

Magnet Aluminum  Nickel Cobalt 
Alnico 2 10% 19% 13%
Alnico 3 12% 25% 0%
Alnico 5 8% 14% 24%
Alnico 8 7% 15% 35%

 

The tone associated with these magnets is as follows:

  • Alnico 2: Focuses on the mids and highs with less emphasis on the lows. It provides a vintage tone with lower output.
  • Alnico 3: the lowest output of all commonly used magnets, Alnico three has no cobalt and illuminates the mids and highs more than the lows. The tone is referred to as “bright and glassy.” 
  • Alnico 4: this is the most equalized magnet for lows, mids, and highs. The output is lower than Alnico 5 & 8 but is higher than 2&3. 
  • Alnico 5: when you think modern pickup, think Alnico 5. While Alnico 4 has an equal balance of the highs, mids, and lows, the Alnico 5 suits the standard guitar playing the most (not to say the best, and while a default, people going after certain sounds will find other magnets more appealing) with its punchy and bright tone.  
  • Alnico 8: Distortion and lows are what Alnico 8 is best utilized for. If you want high output and aggressive tone, this magnet will achieve that better than the other Alnico’s. 

It is also noteworthy that ceramic magnets are commonplace in electric guitars. Frontier primarily uses Alnico, so that is the focus of this synopsis. While Alnico was the strongest magnet at the conception of the electric guitar, rare earth metal metals that drive ceramic magnets were discovered in the 1980s. It is also important to note that the magnet’s placement will significantly impact the sound. With neck pickup being closer to the center of the string, more vibration will be picked up than the bridge. If you have two humbuckers, one Alnico 5 and the other Alnico 2, it might be worth experimenting with which sounds better in which position. My go-to is Alnico 5 in the neck and Alnico 2 on the bridge for a lot of punch on the neck and soft harmonic chords on the bridge.