This article is about how an electric bass guitar produces sound. If you’d like to learn the bass guitar, view our article here.
Playing the bass is an awesome experience. The bass, along with the drummer, provides the rhythmic and harmonic foundation for the band. Without that low-end support, music sounds a bit empty. If you are considering taking up the bass, it is important to understand how the bass makes sound. This will help you select the appropriate equipment to suit your music-making needs. Let’s take a look at the five basic steps on how the bass guitar makes sound.
How does a bass guitar make sound? The electric bass guitar produces an electrical signal by means of a magnetized string and pickup. Through amplification, the electrical signal is increased and converted into a sound wave, which can then be heard.
Let’s dive in now to the steps a bass guitar goes through to make it’s sound.
Step #1 – Activating the string
The first step in making any sound on an electro-magnetic instrument is that a magnetized object is put in motion over a fixed coil. In the case of a bass guitar, the object that is moved is the magnetized string. It can be moved in a variety of ways, e.g plucking the string, picking the string, or even slapping or tapping the string. Each of these string activations will produce a different type of magnetic flux, which in turn, produces an electrical signal.
Step #2 – Electrical signal converted into a sound wave
In acoustic instruments, the activated string moves the air around it and creates a sound wave. The sound wave is then amplified by the materials of the instrument, e.g. wood, brass, etc. However, in electric-magnetic instruments the process is different. Let’s see how this works. Essentially, there are two parts to this process: 1) a magnet or something magnetized, and 2) a coil of wire. Let’s step back for a minute and briefly explain how electricity is created by using magnets.
If you move a magnet across a conductor, e.g. a coil of wire, the electrons in the conductor move creating an electric current. Returning to the bass guitar, the string is magnetized by magnets in the pickup, also in the pickup is a wire coil, when the magnetized string moves over the coil, an electric current is produced. This is then sent to some type of amplifier that will boost the weak electrical signal and convert it into sound waves by means of a speaker.
Step #3 – Passive and Active Basses
Now that the sound wave has been converted into an electrical signal, the signal can be altered in different ways before it is converted into a sound wave that reaches our ears through the speaker of the amplifier. The simplest way that a signal can be altered is by using resistors in the form of tone and volume potentiometers or “pots”. Pots are wired to the pickups and are between the pickup and the output jack in the signal flow. A bass with passive pickups will only be able to attenuate, i.e. reduce signal flow to shape the tone.
Think of it this way- when the volume and tone pots are turned completely on, the signal flow from the pickup is 100%. That signal can be reduced by the pots but it cannot be increased. Alternatively, there are active basses that either has active pickups or a preamp with E.Q. built into the guitar, or a combination of both. This system requires a separate power supply, usually in the form of a nine-volt battery, located in the back of the bass. An active system will allow the signal to be increased in various ways, e.g. certain frequencies of the original signal can be boosted to create new tone shapes.
Step #4 – Effects
Although effects pedals and multi-effects units are not absolutely necessary, many bass players use them to further shape their tone. After the signal leaves the bass guitar from the output jack and into the instrument cable, it can then be sent through a variety of signal processing effects before it enters the amplification stage. Let’s take a brief look at some of the most common types of effects and what they do.
First, let’s mention the type of effect that overdrives the signal to create a distorted tone. In this category, you have different levels of intensity from which to choose, e.g. overdrive, distortion, fuzz, etc. Secondly, there are effects that modulate the tone, such as chorus, flanger, and phaser. A modulated tone is created when the original signal is mixed with another signal. Delays and compressors are yet another possible tone shaping effect you can use. A delay effect can create a short echo called a “slapback”, or the delay can be lengthened as well as regenerated to create a continuous repetition of the notes you are playing. A compressor is a subtle effect that can be useful in maintaining a consistent output volume so that the extremes of soft and loud are focused in the middle.
Step #5 – Amplification
We have now arrived at the final stage of the signal chain where the electrical signal is boosted, shaped, and changed into sound waves. There are four sound stages in an amplifier: preamp, tone shaping, power stage, and sound. Let’s break each of these down a bit. As the signal enters the amp it is boosted, i.e. signal strength is added to it. This allows the tone of the signal to be further shaped. At this point, amplifiers will have, depending on their design, two-way (low and high), three-way (low-mid-high), or a multiband equalizer. This E.Q. stage allows for individual frequencies to be increased or reduced, e.g. if you need more low frequencies you can increase the low-end E.Q. knob or in the case of a multiband E.Q. you can increase a specific low-end frequency, e.g. 50Hz.
Now that the sound signal has been shaped, the signal will be boosted again and driven through the speaking, becoming a sound wave. The power amp stage and speaker accomplish this. The larger the power amp, which is rated in watts, and the larger the speaker, or amount of speakers, will determine the volume and how well your bass will be heard in the mix with other instruments.
If you are practicing at home, a lower watt single speaker amp will work fine. However, if you are playing with a drummer and guitarist, you will need a larger amp and a large speaker, or multiple speakers, to cut through the mix and be heard. For perspective, a practice amp may have 20-50 watts, whereas a gigging amp can range from 600 – 2000 watts! Amps come in two basic configurations, amplifiers (called the “head”) and speakers (called the “cabinet”) that are separate, or a combo amp that incorporates both in one cabinet.
A combo amp is more portable than a head and cabinet arrangement. It is a great option for a practice amp or a live playing situation with low to moderate volume. However, for playing situations with large volumes, you may need to look into the option of using a head with separate speakers.
