The two most misunderstood specs on the Tone Chart are the DC resistance and resonant peak numbers. The DC resistance refers to the resistance of the coil windings. For humbuckers the DC resistance is the sum of both coils. Generally the more wire that is used in a pickup coil the higher its resistance and the higher the output will be**. DC resistance can also be affected by the gauge and type of wire used but in general the DC resistance is still a good indicator of how much output a pickup will have. ** Within a given design configuration, this is true. However, Stacks tend to have very high DC resistance, but low output.
The resonant peak indicates the frequency that the coil is most sympathetic to. The higher the resonant peak, the brighter a pickup will tend to be. This is another good indicator of a pickup's tonal characteristic. At frequencies up to about 7KHz this generally indicated tonal characteristics. But as frequencies approach 10KHz two things happen. 1. There is less energy in the guitar to excite the pickup, and 2. Your ear becomes less sensitive . So, as resonance goes above 7 to 8KHZ , a pickup may actually start to sound less bright and more "flat". Magnets also have an impact on pickups' overall output and tone. Alnico II magnets have the lowest output and warmest tone, ceramic magnets are the highest in output and brightness with alnico V magnets falling somewhere in between. By combining the DC resistance with the magnet type and resonant frequency of a pickup you can get a very good idea of how it will perform and sound, and the Tone Chart makes it very easy to compare one pickup to another. Please keep in mind that these are all generalizations.
WRITTEN ON JUNE 15, 2015, BY