There is a BIG difference between a Single-coil and Twin coil Side-winders and Humbuckers.
The purist Kinman P-90 Hx is the only true Zero-Hum single-coil ... and it has two Alnico-5 bar magnets.
There is only one way to tell the truth, tell it like it is. We can't sugar coat deception and mis-representation. This is a plain talking article that does not wince from blunt honesty, it is not our intention to offend anyone but if it happens then so be it.
Stacks have 2 coils, both sense noise and string signal almost equally. The pickup produces almost equal string signal in each coil, and equal hum level in each coil. The coils are wired out of phase to cancel signals in common. Hum is a signal in common but so is the string signal. Both hum and signal get cancelled, but the signal gets cancelled a little bit less because the strings are positioned on one end of the magnet so there is a little less signal sensed in the lower coil. The sonic output of the pickup is the difference between the level of string signal between the two coils.
Since the output level difference between the two coils is small, manufacturers attempt to magnify the level of that difference by winding the coil with finer wire and many more turns. This increases Parasitic Coil Capacitance within the coil. Excessive capacitance is the arch enemy of good sound. Resistance of stacks is double and three times that of noisy single coils. This indicates a lot of turns of very fine wire.
The Mutual Inductance factor will shock you: One Stack we measured 2.3 Henrys inductance in each coil, but the combined inductance was just 3.3 Henrys. A case of 1 + 1 = 0.6
AKA "Middle Point Humbucker". We were very curious about Side-Winders since Fralin and Mojotone released their Quiet Coil. To learn about this weird design we made our own Side-Winder and although we made a number of improvements we found the design is flawed, it is extremely in-efficient because it lacks Mutual Inductance. Mutual Inductance is a case of 1 + 1 =3 as in the case of side-by-side humbuckers. But with Sidewinders 1 + 1 = 1.8.
Examples: two coils of a side-by-side humbucker each have inductance of 2.3 Henrys but total combined inductance multiplys to 5.7 Henrys (significantly more than the sum of each coil, positive +25% to be precise). This is Mutual Inductance.
Now 2 coils of a Sidewinder, each having 2.3 Henrys have a total combined inductance of 3.9 Henrys which is significantly less than the sum of the two coils (Negative 15%) and way less than the humbucker.
This is what's wrong with Sidewinders, it's the electrical flaw we talk about with the result that the second coil doesn't contribute to output, it's sole function is to cancel hum, but it does contribute Parasitic Coil Capacitance and it equalizes the output signal and robs the pickup of high frequency presence and those are bad things if it's tone and feel you want. Consequently an inordinate number or coil turns is required to attain acceptable output level. As with Stacks, coils with very fine wire and lot of turns are necessary to magnify the string signal to an acceptable level. The big trouble with doing that is the massive amount of Parasitic Coil Capacitance in all of those coil turns which impact on transparency and dynamic response and that's the reason Stacks and Sidewinders have a dry sound as distinct to a lush, juicy sound of a genuine single coil such as the Kinman P-90 Hx. There is no solution to the Sidewinder flaw, it's just the Laws of Electrical Physics having their way with inventions created by those who know nothing about Electrical Engineering.
Mojo Tone's Quiet Coil is a Sidewinder wound with 42g wire and weak Alnico magnets, it produces very weak output level compared side-by-side to a real P-90. Fralin noiseless P-90 is also a Sidewinder and both have about 14 parts. Fralins coils are crammed with excessive turns of fine, high resistance wire (18k Ohms), the result is excessive coil capacitance which destroys dynamics and the lush feel of a genuine single-coil P-90. It should be remembered there are all kinds of trickery than can be used to hide the sonic negatives of Sidewinders in YouTube demos. Kinman will NEVER resort to trickery and we don't need to, our P-90 Hx is an honest to goodness pickup designed the right way with a singular main coil and a dedicated hum sensor and there is no conflict beween them.
Fralin Sidewinder mis-represented as a P-90, should be called a Soapbar
Kinman's P-90 Hx: is a true single coil with two Alnico-5 bar magnets and our Gen-3 v2 [600 Ohm] hum sensor with it’s very low Parasitic Coil Capacitance means there are no compromises in sound quality. It does not interfere with or produce string signal so our high-output, absolute Zero-Hum Nasty 90 sounds near identical to a conventional lush n juicy non-noiseless Gibson P-90. Kinman's DC resistance is lower than noisy single coils because our coils are highly efficient and with that comes great benefits.
Kinman's have a dedicated hum sensor, and unlike crude Stacks have a much different dedicated string sensor. There is negligible cross-talk (magnetic coupling) between the two coils thanks to our patented Magnetic Shield and minimized Hum Sensor. The 600 Ohm hum sensing coil, with it's high transparency factor, does only one job, the one it was designed to do, which is to sense hum. It produces 1,000 millivolts of hum signal but it does not interfere with or produce string signal. This is the proper way to make a Zero-Hum P-90, it is not simple and it uses technically advanced materials and construction technology but that's what it takes to silence a high quality P-90.
The beautifully made exquisite Kinman P-90 Hx (Hx = Hum Canceling)
Below is a 1960's Gibson sidewinder which was used only in their EB type basses because it sounded too horrible in guitar and bass doesn't need a strong treble response. Note the strong resemblance of Fralins noiseless P-90.
Resistance of Sidewinders is about three times that of noisy single coils. This indicates a lot of additional turns of very fine wire. In other words Sidewinders sound awful to anyone who appreciates fine sound character. Sidewinder P-90"s are look-alike pickups, and definitely not sound-alike. Anyone who loves genuine P-90 sound will know they sound nothing like a real P-90 what-so-ever.
BTW Kinman's DC resistance is often lower than noisy single coils, not more like Side-Winders and Stacks are. Eg our Bright Nasty 90 measures 3.5K on the top coil while an original noisy P-90 measures 8k Ohms. Big difference wouldn't you say?