Photo courtesy of singlecoil.com
First, let’s discuss polarity. In short, we can define the polarity of a pickup as the direction—north or south—of the magnetic field.
It’s important to consider polarity when attempting to combine pickups and achieve a hum-canceling effect. You’ve probably seen RWRP—reverse wind, reverse polarity—in a pickup description, especially when looking for Strat middle pickups. Hum canceling is only achieved when both pickups have opposite phase and opposite polarity—so, one pickup needs to have north and the other south polarity.
Humbucker pickups also work on this principle. Both coils have opposite phase and polarity, so when you combine them in series or in parallel, it will be free of hum. (The fun really starts when you start considering coil-splitting options, but that’s for another time.)
What happens if you combine mismatched pickups? You’ll receive hum or out-of-phase tones, and, in the worst possible scenario, both at once. As a guideline: If you want two pickups to be in phase, both the polarity and the wind direction have to be either identical or opposite. In other words, two pickups with the same wind and polarity will be in phase, and so will two pickups that have opposite polarity and wind. If the two pickups have the same wind but different polarity, or the same polarity but different wind, they will be out of phase with each other.
“What happens if you combine mismatched pickups? You’ll receive hum or out-of-phase tones, and, in the worst possible scenario, both at once.”
Since many pickup manufacturers do not mention the polarity in their pickup descriptions, here are some simple ways to figure it out on your own. (This can be a real problem because you need the pickups on your table to test them. If you need to know about polarity before ordering a new pickup, there is no way around contacting the manufacturer and asking for it.)
Use a pickup polarity tester. There are several polarity testing devices on the market that are specifically made for pickups. They are usually not very expensive and are a must-have tool for every guitar tinkerer. The most common one is made by Schatten Design Canada, which is very easy to use. It’s a see-through tube with a magnet inside, you simply move it on the magnet you want to test and receive a clear reading if it is north or south.
Photo courtesy of singlecoil.com
Using a compass. If you have an analog compass, you can use it as a polarity tester for pickups. When using a compass, the needle will always point toward the north magnetic pole. So, if your pickup has a polarity of north, it will point toward the pickup, and if it’s south, it will point away.
Photo courtesy of singlecoil.com
Using an analog meter. In the ’60s, it was common that analog meters had a built-in polarity test. Most of these vintage meters are sought-after items today and fetch high prices. We have a Philips meter from the late ’60s in the shop. If you have one, here is how to use it to determine polarity: Connect the pickup wires to the meter: connect the white one as the + and the black one as the –. Use a heavy screwdriver or a piece of steel and move a piece of steel quickly towards the magnets of the pickup without touching them. (A regular string doesn’t have enough mass for this.) When the polarity meter (the small rectangular display on the right bottom of the main display marked in red) shows +, this is defined as north, while – means south.
Now, let’s take a look at phase. We can define the electrical phase of a pickup as the direction of its winding, which can be clockwise or counter-clockwise. But it’s not all that easy.
You can determine the direction of a pickup’s winding by how it is wound when looking at it from above, with the pickup facing up toward you. I think this definition comes from the early Fender years, and the factory never changed this terminology, winding all pickups for several decades in a clockwise way. For a long time, reverse-wound middle pickups had a clockwise winding, and to change the phase they simply interchanged the two pickup leads. From an electrical point of view, this is all okay. But there are two good reasons to make reverse-wound pickups in a counter-clockwise direction:
Many players believe that a counter-clockwise wound pickup sounds different or better than a clockwise-wound one with reversed leads. And if a string contacts the pickup’s magnet, a clockwise-wound pickup with reversed leads will short out when the hot gets connected to ground and will go silent. If you touch the magnets of such a pickup with your finger, you will be rewarded with a loud humming noise.
Besides the clockwise/counter-clockwise terms, some pickup makers will use the following descriptions, which explain how the pickup is attached to the winding machine and the direction it moves in the machine:
• top right, top going (counter-clockwise)
• top right, top coming (clockwise)
• top left, top going (clockwise)
• top left, top coming (counter-clockwise)
So, if you have to determine the phase of a pickup, here’s how you can do that.
Build yourself a phase-testing unit. This was covered back in our July and August 2017 issues (and can be found here and here), and is probably the easiest way to measure phase.
Use an analog meter with a polarity test option as mentioned above. Connect the pickup wires to the meter, the white (hot) one as the + and the black (ground) one as the –. If the wires of your pickup have different colors, you will have to use the ones that are defined as hot and ground according to the manufacturer. Now, use a heavy screwdriver or a piece of steel or iron and move it quickly toward the pole pieces of the pickup without touching them. When the polarity meter shows +, it means that the wire that is connected to the + input jack is really the hot connection of the pickup. If it shows –, it means that the pickup wire connected to the + input jack is ground. You will be surprised how many times the white wire is not really the hot connection!
Using a standard analog meter without a polarity test is not recommended, and you’ll risk breaking your meter. There are ways to tweak a standard analog meter for this measurement, e.g. using the zero and scale setting or a resistor in series with the pickup to get the needle somewhere off zero, near the middle of the scale. It’s also possible to use a standard digital multimeter by connecting the pickup to it, using the DC/ohms setting, but you have to look quick to note what happens. These MacGyver procedures are only recommended for experienced techies.
This phase/polarity table shows what you can expect from every possible combination:
I hope this will help you avoid possible trouble when you want to combine pickups from different companies. We’ve only scratched the surface of phase and polarity, so ask a pickup pro sometime and they can tell you all about it.
That’s it! Next month, we will take a deep dive into the G&L Passive Treble and Bass control (PTB), so stay tuned!
Until then ... keep on modding!
As a musician, you want to be heard when you play. How loud you need to be to “be heard” depends on your style of music, the size of your audience, and venue.We buy amplifiers by the number of available watts, and expect that to translate to loudness. And it does, but in unexpected ways.
Our ears and brains perceive sound on a logarithmic scale. Here’s a table of examples adapted from Wikipedia (“Sound power”*) The middle column is the power of the actual air moving against your eardrums.We sense a doubling of power, which is a 3dB change, as a just-perceptible change in loudness. A sound that seems “twice as loud” has to be ten times the power, a 10db increase. That’s why the middle column of the SPLs is in powers of ten. Humans perceive a jackhammer as about twice as loud as a chain saw and a machine gun as about twice as loud as a jackhammer. A full-blown rock concert might only seem twice as loud as a machine gun. 
The sound power is not the amplifier power you’d need to be that loud. Most amplifier power is wasted as heat in moving the speaker cone around; little of that gets radiated away as sound. The following table shows some speaker sensitivities as quoted by the makers, in sound pressure level (SPL) at 1W of amplifier power as heard one meter away from the center of the speaker, as well as the maximum amplifier power before they burn out. I computed the estimated maximum SPL column. 
[N.B. - These are not necessarily representative of all the speakers from the manufacturer. For instance, all Jensens are not always the quietest and all Fanes are not the loudest speakers. Due to overloading and other factors, these speakers may not sound exactly as loud as this projection shows.]
Remember that 3dB is just noticeable and it takes 10dB to be a factor of twice as loud. So at 1W, the most efficient Fane is not quite twice as loud as the lowest efficiency Jensen P12R, differing by +8dB SPL. If we wanted to make the Jensen sound as loud as the Fane is at 1W, we would need to drive the Jensen with +8db of power, which is 6.3 times the power, or 6.3W (trust me, that’s the way the math works out). The Jensen is loudest at its max of 25W: 109dB SPL. The Fane produces 109dB when driven with 4W. So if you replace a Jensen P12R in a cabinet with a Fane AX.12.150, the amp now sounds like it is now six times the power as it was before.
And that gets us down to watts and loudness.Watts don’t make loudness alone; the amplifier power and the speaker efficiency together make loudness. You can make an amplifier sound like it has more watts by using a more efficient speaker; or like it has fewer watts by using a less efficient speaker.
If you simply must have the tone of an inefficient speaker, be prepared to buy a bigger amp to keep your loudness the same, or to use multiple speakers and amps to get the loudness back. If you must have more loudness and don’t want to change your amp, consider more-efficient speakers. Greater efficiency doesn’t always mean better tone; it just gives you more volume.
Keep speaker efficiency in mind when you’re wondering about watts – you might make that 50W amp sound like it has 100W … or 25W.
*article found at: https://en.wikipedia.org/w/index.php?title=Sound_power&oldid=82695953
R.G. Keen
Cheif Engineer
Visual Sound
www.visualsound.net