So you’re in the market for some pickups. You pull up Google and start looking. So many options, so many builders. This one says it has AlNiCo III magnets, this other one says AlNiCo V and yet another says it’s loaded with AlNiCo II. What does this mean and what is the difference, really?
Let’s start with what the word AlNiCo even means. AlNiCo is an acronym for a metal blend of aluminum, nickel, cobalt, and iron. The number following AlNiCo represents the proportions of each metal in that blend. For example, AlNiCo V contains 8% aluminum(al), 14% nickel(ni), 24% cobalt(co), 3% copper(not included in AlNiCo acronym), and the balance (51%) is iron. AlNiCo III, and II use different proportions to achieve different magnet strengths and properties.
AlNiCo magnets were invented in the 1920’s as an alternative to weaker Iron magnets. Iron magnets weakened quickly and lost charge easily with shock or temperature changes. Alnico magnets keep a stronger magnetic field over time and are more resilient to shock and heat.
The most popular AlNiCo magnets you will see in guitar and bass pickups are AlNiCo V, AlNiCo II, AlNiCo III, AlNiCo IV, and AlNiCo VIII. Most commonly you will see AlNiCo V and ceramic (which is a different animal and found in many modern, more aggresive pickups).
Leo Fender started using AlNiCo blended magnets in his experimental pickups as early as 1940. In the Blackguard Book, Nacho Baños writes that Leo used AlNiCo III in the early Broadcasters and Teles. Early P.A.F. humbuckers used AlNiCo V or II. Often, builders used what was available at the time and they changed every few years. Fender was notorious for this.
When shopping for vintage style pickups, you will see alnico II referenced often. This blend is used by many pickup makers for vintage reissue pickups. It is similar to AlNiCo III in that it is weaker than the AlNiCo V we hear so often, but the composition and resulting tone is very different.
Alnico V is by far the most used magnet in our shop with 95% of all pickups produced here using that blend. AlNiCo V has a stronger magnetic pull than AlNiCo II or III. This translates into tighter low end response and a more aggressive, edgy tone.
A good way to imagine the difference between Alnico magnets is to compare them to shocks in a car. Alnico II is like a set of worn in shocks, Alnico V is more like a set of stiff shocks, and Neodymium is like a hardtail Harley, translating every bump in the road.
So what do I use?
There are a few considerations here: