(Magnet type, variety, and information)
Magnet strength is measured in a unit known as Gauss. Tonal descriptions are being made assuming the pickup has moderate output; between 6 and 8k. These descriptions can be applied to rod style magnets too, though rod magnets are unique in that the magnet is the pole piece, and not just a pole piece touching a magnet that is located at the bottom side of the coil(s). Let us also note that max charge specs are taken from magnets that are all the same sizes. All magnets are being charged with 24,000 amps @112 Volts.
I mention this because two magnets charged with the same charging setup, to the same strength, will measure different from one another. Whichever magnet possesses a greater mass will yield a greater magnetic strength after the charging occurs.
All alnico magnets can possess their maximum strength. These same magnets can too be degaussed, giving you a lower Gauss rating and in effect, having a smaller magnetic field and sounding not too much different. Degaussing a pickup is a technique used to balance the pickup. This could be done to mellow out a pickup or super charge the magnetic field to add that extra presence and focus. Tighten up lows, focus highs and add Mids. The magnets grade will have a large effect on how the overall sound can be sculpted by way of degaussing.
All Gauss measurements will be listed in (mT). Measurements are taken with the wand touching the center most area of magnet being measured. Converting millitesla to gauss is quite simple; move the decimal point to the right one place:
E.G. (150.50 mT = 1505.00 G)
Concerning rod magnets; it is important to note that there are three standard diameters used in the SAE pickup world: (.187″, .195″ and .250″) This does not speak to the pickups made using the metric system. The point I am trying to illustrate is this; the greater the mass of a magnet, the greater its full charge will be. This is because there will be more Alnico there by weight, and thus, you will have more mass that will hold a charge. This is important when considering a stagger pole pickup design or when selecting your rod magnets height.
Unless otherwise noted.
All bars measured are: (2.444” long x 0.500” wide x 0.125” thick)
All rods measured are: (.187” X .710”)
Listed in order of strength:
Max bar charge: (40 to 49 mT)
Max rod charge: (75 to 79 mT)
The lowest output, soft and well defined. The treble never even threatens to harsh your tone, while still sounding full in depth. Very warm bass, non-intrusive mids, smooth and articulate response. Wonderful magnet for the player who likes the sound of neck pickup leads and is trying to avoid causing breakup in their small to moderate size amp. It should be mentioned that this is a great magnet to have in your guitar with large and powerful amplifier. Anyone who could do without the mid-range focus. Think early rock and roll, warm jazzy tones.
Max bar charge: (50 to 59 mT)
Max rod charge: (96 to 100 mT)
A little higher output than alnico 3, more developed overall sound, a bigger sound, rounded treble. I feel it has a more assertive bass response and more mid-range. The higher strings seem to have less depth or bass when compared to other strings. This helps to creates a smooth breakup. The highs are more subdued when compared to A3, I would say not quite as strong or deep.
Max bar charge: (60 to 69 mT)
Max rod charge: (have never measured an A4 rod)
The happy medium. Halfway between the famed alnico 2 and 5. It tends to remind me of alnico five, but without the authority complex in the way of bass and treble. Alnico 4 has more mids and color than any of the other magnets listed so far. An alnico 4 magnet in the neck position pickup is one of my personal favorites for PAF humbuckers. Its EQ is flat and with its power, you can capture this depth in the higher strings. When you bring the charge down to a lower level, you can enter a clean, colorful, and full sound. This is great because you can have the A4 EQ without the power.
Max bar charge: (70 to 75 mT)
Max rod charge: (137 to 141 mT)
Powerful in delivery, big sounding bass, sparkling treble, scooped mids, wonderful definition great for really moving some air or having serious body behind your leads. This is the magnet of choice for a lot of production humbuckers. With an ability to not only have treble and presence at low strength, but also an ability to retain body, and bass at higher strength charges.
Max bar charge: (145 to 150 mT)
Max rod charge: (never measured an A8 rod)
Very Powerful, has a lot in common with A4 when fully charged. When degaussed, it reminds me of a strong A2 without the first- and second-string weakness. Having a much bigger personality than its alnico counterparts, basically, it is a sculptable ceramic magnet. I see this magnet used a lot in lap and pedal steel type instruments. Unbelievably strong for the Alnico family. This I feel is what helps A8 make little pickups sound huge!
Ceramic magnets are unique in that they are much better at retaining their charge. Charge will not fluctuate even if introduced to a weaker or stronger field, unless it is a magnet charging unit’s field. A ceramic magnet can have its charge manipulated if used in a magnet charger.
(60.0mm x 14mm x 8mm)
Max bar charge: (140-145 mT)
Max rod charge: (never measured a ceramic rod)
Has a variety of overtones, makes me think of a flattened out A5 with more of an accent towards treble. A great magnet choice for a higher output sounding pickup. These magnets are much bigger than a standard bar measuring (2.444” long x 0.500” wide x 0.125” thick) and possessing a charge much greater than what one usually finds in the Alnico family. These are often cut short in length due to the increased magnetic field strength pulling on strings. You can see how much larger it is compared to the C8 marked in white.
(2.35″ Long x 0.250″ Wide x 0.120″ Thick)
Max bar charge: (128 to 136 mT)
Max rod charge: (never measured a ceramic rod)
Because of its power and strength, it will usually be a smaller sized magnet. This is the variety of magnet used in the Lil Trees Dope Troll and TechBro models.
The trick, to me, is playing the game of balancing the two controllable variables. Coil Strength to Magnetic field strength. Coil strength and the characteristics of a wire’s insulation type will have a small role. The gauge of wire will also govern the amount of coil one can physically turn onto a bobbin. This will need to be taken into consideration along with wind cleanliness and shape. Another factor is the tension online. It is important to maintain a set tension on the line during winding. This will keep wraps tidy while eliminating any loose or wandering lengths of wire. A coil wound too loose will be microphonic and be more prone to feeding back. When all the variables mentioned are considered, one can begin to form a very reasonable expectation as for the type of sounds the pickup you are making will have.