P90 and Humbucker volume
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freefrog
Well-known member
In a humbucker, coils are wired in series but with reverse polarity and out of phase. So, with the same number of turns (and despite the phenomenon of "mutual inductance"), a humbucker has a lower overall inductance* than a P90 (like 3.7H to 4.8H for the humbucker vs 5.9 to 7.5H for a P90). This parameter alone makes the humbucker slightly weaker electrically, albeit it compensates this loss thx to a more efficient "magnetic window".
The two magnets of a P90 also make it a wee bit stronger magnetically just above the pole pieces - and a P90 sounds weaker / thinner with one magnet only, although it doesn't loose much inductance (because the repelling magnets limit it when there are two bars under the coil).
IOW, guitar pickups are falsely simple - and I'm not even sure that my explanation is optimal, therefore. ;-)
*Indifferent note: in a stacked humbucker with symetrical coils, the overall inductance is even lower... TWICE lower than if the same stacked humbucker was converted in a noisy giant "dual single coil" by wiring it in series and in phase. That's why first generation stacks tended to have a very high DCR: much more wire was necessary to obtain an overall inductance in the ballpark of a real single coil...
The two magnets of a P90 also make it a wee bit stronger magnetically just above the pole pieces - and a P90 sounds weaker / thinner with one magnet only, although it doesn't loose much inductance (because the repelling magnets limit it when there are two bars under the coil).
IOW, guitar pickups are falsely simple - and I'm not even sure that my explanation is optimal, therefore. ;-)
*Indifferent note: in a stacked humbucker with symetrical coils, the overall inductance is even lower... TWICE lower than if the same stacked humbucker was converted in a noisy giant "dual single coil" by wiring it in series and in phase. That's why first generation stacks tended to have a very high DCR: much more wire was necessary to obtain an overall inductance in the ballpark of a real single coil...
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Interesting! What is a magnetic window?
freefrog
Well-known member
A metaphor for the "aperture" of the pickup: the width/lenght along which it magnetizes the strings and therefore reacts to their vibrations...
The following page hosts visual simulations that I often share when such things are evoked. These pics are roughly on par with what has been measured here by various magnetometers.
https://skguitar.com/SKGS/sk/Images/pickups/Pickup stuff/Magnetics.htm
freefrog
Well-known member
The higher inductance of a P90 is also due to the area of its coil, BTW, while the coils of the humbucker are less inductive because narrower: even if they were in series with a same polarity, their overall inductance would remain lower than in a P90...
This precision making my contribution even more complex, I've wondered how to give a clearer idea of the functional difference between P90 and humbucker without oversimplifying the explanation... Let's try by sharing a few things.
Below is the raw electrically induced response of a P90 vs a Gibson HB. Both were in guitars with typical pots, measured through a typical cable in a 1M input. The "resonant peak" (the frequency at which the coil is electrically stronger) is lower pitched for the P90. So we can consider that it makes louder the frequencies under 2.5khz while the humbucker does the contrary...
freefrog
Well-known member
... but the humbucker captures the vibrations of the strings through two adjacent coils so it comb filters the notes differently. This difference will appear if one types "1.28" (width of a P90) then "1.43" (width of an uncovered humbucker) in the "Width (inches)" column of the following applet:
https://till.com/articles/PickupResponseDemo/index.html
TBH, the difference of response can't totally be reduced to a question of physical width of the coils: a P90 has in fact a larger overall magnetic field, shaped like a 4 leafs flower, as shown in the skguitars FEMM simulations. This oddly shaped magnetic field being more diffuse, it contributes to promote the low mids with P90's, albeit it is not directly as efficient volume wise as with a single magnet parallel to the strings, like in humbuckers...
What does it gives once all these factors took in account? Maybe it will help to share the following pic, which shows how Roland guitar modeling simulates the response of a bridge P90 vs a bridge Les Paul Humbucker (note: it's NOT the response of real pickups, so. It translates the correction added by Roland processors to the flat signal of GK3 transducers to make them sound like passive pickups)...
What it might make clearer is that one kind of pickup is not louder than the other: they promote different frequencies (each being louder or weaker depending on the frequency range considered)...
https://till.com/articles/PickupResponseDemo/index.html
TBH, the difference of response can't totally be reduced to a question of physical width of the coils: a P90 has in fact a larger overall magnetic field, shaped like a 4 leafs flower, as shown in the skguitars FEMM simulations. This oddly shaped magnetic field being more diffuse, it contributes to promote the low mids with P90's, albeit it is not directly as efficient volume wise as with a single magnet parallel to the strings, like in humbuckers...
What does it gives once all these factors took in account? Maybe it will help to share the following pic, which shows how Roland guitar modeling simulates the response of a bridge P90 vs a bridge Les Paul Humbucker (note: it's NOT the response of real pickups, so. It translates the correction added by Roland processors to the flat signal of GK3 transducers to make them sound like passive pickups)...
What it might make clearer is that one kind of pickup is not louder than the other: they promote different frequencies (each being louder or weaker depending on the frequency range considered)...
freefrog
Well-known member
... but the humbucker is still a wee bit more efficient magnetically... so what is the final result?
Below is the response of a neck P90 vs a neck Gibson HB, both played in chords from unfretted strings to 12th fret, direct to the board, through a 1M input...
These spectra look like a mix between the various sims and measurements previously shared... but they don't translate a SO different overall response and volume finally.
All this fuss for so little progress!
And don't start me on "transients" or my contribution will get worse... <:0)
FWIW : Useless rambling from an old geek. Still not sure it's an optimal explanation. Hope it will bring something to other geeks, nevertheless... ;-)
Below is the response of a neck P90 vs a neck Gibson HB, both played in chords from unfretted strings to 12th fret, direct to the board, through a 1M input...
These spectra look like a mix between the various sims and measurements previously shared... but they don't translate a SO different overall response and volume finally.
All this fuss for so little progress!
And don't start me on "transients" or my contribution will get worse... <:0)
FWIW : Useless rambling from an old geek. Still not sure it's an optimal explanation. Hope it will bring something to other geeks, nevertheless... ;-)
beaubrummels
Well-known member
Number of winds isn't the only factor in the output of a pickup. Strength of the magnet factors in also. And everything freefrog posted.
... but the humbucker is still a wee bit more efficient magnetically... so what is the final result?
Below is the response of a neck P90 vs a neck Gibson HB, both played in chords from unfretted strings to 12th fret, direct to the board, through a 1M input...
These spectra look like a mix between the various sims and measurements previously shared... but they don't translate a SO different overall response and volume finally.
All this fuss for so little progress!
And don't start me on "transients" or my contribution will get worse... <:0)
FWIW : Useless rambling from an old geek. Still not sure it's an optimal explanation. Hope it will bring something to other geeks, nevertheless... ;-)
Excellent explanation! It wasn't useless, it help alot! Thank you very much
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freefrog
Well-known member
Yeah, I've left magnet alloys (and height settings) out of the equation in order to avoid an added layer of complexity. :-D
