Bass bench: Mysterious magnetism – Premier Guitar


Wouldn’t it be great if we could actually see these lines of magnetic flux? Image courtesy of Gregg Stock and Strymon

There are a myriad of little helpers, gadgets, and parts that claim to improve bass sound, and all of them cost money. And then there are the free ones that will only cost you a little of your time, but nobody really uses them. Hands up, low end: Have you adjusted your pickups yet? Just as I suspected. And typically for those who have tuned pickups, the thought goes like this: “Okay, the pickup doesn’t quite hit the strings, so it’s as loud as possible.” Adjustment made!”

If this “setup” sounds unconvincing, many of us are tempted to replace our existing pickups with new ones we ultimately found after spending nights on a forum. These new pickups are getting excited about by people we’ve never spoken to, let alone heard play. But we all love buying new toys, right?

I offer you an alternative: before spending the money, why not spend some time on an easy DIY? Let’s find out what your ax is capable of as it is currently configured.

Michael Faraday discovered electromagnetic induction in 1831, trying to reverse the electromagnetic principle then known – an electric current creates a magnetic field. He realized that a magnet could create an electric current, and that’s the principle behind all magnetic pickups. Thank you, Mr. Faraday.

Yet, as with all those things we can’t see or have no sensors for, it’s hard to imagine what magnetism is. Even electricity isn’t quite as murky, as anyone who’s ever strayed too close to a power outlet can attest. It’s a kind of sensor.

But back to the pickups and the applied magnetism: the magnetic forces – and therefore the resulting signal – strongly depend on the distance between the string and the magnet, in particular one of its poles.

As with all those things we can’t see or have no sensor for, it’s hard to imagine what magnetism is.

Case 1: We like loud sound, so we try to get the pickups as close to the strings as possible without touching them. The first side effect? The increased magnetic attraction eats the hold of our strings. (It should be noted that the pull is always there whether you use this pickup or not.) And the second side effect: this higher pull influences how the string vibrates. The vibration—composed of the fundamental and its higher harmonics—becomes less ideal, moving the higher harmonics away from being discrete multiples of the fundamental. If that sounds too mathematical, try this: it sounds out of tune and out of tune, like a broken chorus. Ask your guitarist friends, they experience it more often. Of course, very close configurations can work without the above effects if the mic has weak magnets, such as are often used in active mics.

Case 2: If there is a “too close” scenario, there will surely be a “too far” counterpart! Let’s forget about the extreme case where we get no signal and see what we can expect at real distances. Along with increased sustain and more natural upper harmonics, there is also the inevitable loss of output. This is usually not a big deal, as we can compensate for it by increasing the input gain of our amp. Unfortunately, we also decrease the signal to noise ratio. In other words, there is a constant amount of noise that gets amplified more and more as we compensate for the decrease in output volume. This can be a problem with non-humbucker systems, as well as currently popular bass distortion effects that focus on the loud edge of our tonal spectrum.

Ultimately, the final adjustment must be, again, a compromise. And so far we’ve only touched on the unavoidable magnetic effects, not the role that different setups can have in our search for tone. And once we start looking for sound, there are also things like string-to-string and mic-to-mic balance that we need to keep in mind.

With thousands of slightly different pickups available, there won’t be a simple answer to which is best. There’s a lot to explore and experiment with, but it’ll only cost you time to make the most of what you already have. Strategies for this differ, but let’s see if there are any basic principles to help you achieve this goal. Stay tuned.


About Author

Comments are closed.