Acoustic Guitar Pickups

There are three types of acoustic guitar pickup. Magnetic pickups, like those found on electric guitars, rely on electromagnetism. Piezo pickups, detect changes in pressure caused by the vibration of the strings, bridge, or soundboard and microphone pickups, located either internally or externally to the guitar body.

Blended or hybrid systems also exist that utilize a combination of pickups, mostly microphones, and undersaddle pickups.

Interested in amplifying your acoustic guitar? If so you will need an acoustic guitar pickup. Many acoustic guitars now come with accessories such as pickups included.

If not preinstalled, depending on the type of pickup you choose, it’s relatively simple to install one yourself or have one installed without breaking the bank. But what types of acoustic guitar pickups are best and what are the fundamental differences between them?

Even if you are familiar with electric guitar pickups, acoustic guitar amplification is a different beast altogether. Unlike electric guitars, where electronics play a major role in the overall tone of the instrument, acoustic guitar pickups are designed to reproduce the natural characteristics of the acoustic guitar as accurately as possible.

In the following article, we will investigate acoustic guitar pickups, explain what a pickup is and how they work, the differences between the four main types of acoustic guitar pickups available, and list the pros and cons of each, so you can make a more informed choice if considering amplifying your acoustic guitar.

What is a pickup?

Before we differentiate between the different types of acoustic guitar pickups available it’s helpful to understand what a pickup is, how they work, and what benefits they offer to acoustic guitarists.

Transducer Pickups

In simple terms, a pickup is a transducer. A transducer is simply a name for a device that converts a signal from one form of energy into another. A home solar system is a good example of a transducer. It converts the sun’s energy into electrical energy that can then be used to power lights and electrical appliances within the home.

There are two main types of transducers:

• Mechanical transducers convert electrical power into mechanical energy. An example of this is an electric motor. The electrical signal is converted into mechanical energy that creates motion.
• If converting a signal from a physical property, such as the vibrations from guitar strings, soundboard, or bridge of a stringed instrument to an electrical signal the type of transducer is known as an electrical transducer.

Active and Passive Transducers

Transducers can be either active or passive. If a transducer is active it utilizes an external power source to boost the strength of the signal. This also allows some control over the signal in the form of equalization.

Unsure if your pickup is passive or active?

If your acoustic guitar features an on-board preamplifier e.g. you have controls that allow you to increase volume, bass, and treble, it will require the use of a battery and is, therefore, an active transducer.

If on the other hand, your guitar does not use a battery as an external power source, it is a passive transducer.

Acoustic Guitar Pickup Types

Acoustic guitar pickups are available in four specific categories.

• Magnetic pickups (soundhole pickups)
• Piezoelectric pickups (undersaddle and contact pickups)
• Microphone pickups (internal or external microphone)
• Blended systems (a combination of pickup types)

In the following section, I’ll explain the differences in how each pickup works and the pros and cons of each.

Magnetic Pickups (Soundhole Pickups)

Magnetic pickups are most associated with electric guitars. When used on an acoustic guitar they are typically fitted across the soundhole and as a result, are referred to as soundhole pickups.

This style of pickup can be fitted permanently, in which case the input jack replaces the rear strap button, and the wiring is threaded through the internal cavity of the guitar or fitted temporarily.

When fitted temporarily,  the cable and input jack protrudes out from the soundhole and hang below the guitar, which is convenient for swapping the pickup out but can be inconvenient due to the cable getting in the way.

How do Magnetic Pickups Work?

Magnetic pickups rely on electromagnetism. To achieve this, magnetic pickups utilize pole pieces that sit directly beneath each guitar string. The pole pieces are either magnets themselves (magnetic Alnico) or steel and sit on top of a larger magnet that is positioned on the base plate of the pickup. The entire unit is then wound, between 5000 to 9000 times in copper wire, creating a coil and ultimately a magnetic field.

Faraday’s law of induction explains the concept of electromagnetism. In simple terms a changing magnetic field e.g. when a guitar string (acoustic guitar strings have steel cores and are therefore magnetic) is vibrated over a magnetic pickup, there is a change to the magnetic field and an electrical signal is created equal to the frequency, or pitch of the string.

The diagram below shows the components of a single-coil magnetic pickup.

Single coil and humbucking magnetic pickups

Magnetic pickups come as either single-coil pickups or humbuckers. If unfamiliar with the two terms, you can usually spot the difference in terms of the size of the pickup.

Humbuckers are wider than single-coil pickups because they are essentially a combination of two single-coil pickups.

The advantage of a humbucker is the pickup’s ability to prevent the electrical hum often associated with single-coil pickups. The hum is caused by electrical interference (electromagnetic interference or EMI) from mains electricity such as fluorescent lights, computer monitors, and even power lines, hence the name ‘hum-bucker’.

Humbuckers, while still subject to a small amount of interference are far less affected by EMI. They do this by reversing the electrical current (the copper wire is wound in the opposite direction to the first coil) and the polarity of the magnets is reversed.

Without getting too scientific, the two magnetic coils are then connected out of phase which cancels the hum associated with outside electrical interference without affecting the strength of the signal created by the pickup.

Pros and Cons of Magnetic Pickups

piezoelectric pickups (Undersaddle and Contact Pickups)

Piezo pickups (pronounced “pee-ay-zo”) while also a transducer, work differently from magnetic pickups. Piezos utilize a compressed quartz crystal material (other materials such as zinc oxide and aluminium nitride can also be piezoelectric) that detects changes in pressure as a result of vibrations (the term Piezo is taken from the Greek word ‘piezein‘ meaning to apply pressure e.g. to compress) as opposed to detecting a disturbance to a magnetic field.

In a practical sense, this means they are equally at home steel string and nylon string guitars. They are also resistant to feedback, which is a fairly common issue for acoustic guitarists when using microphones, either internally as a pickup or as an external microphone.

While magnetic soundhole pickups are hard to miss on an acoustic or electric guitar, piezos are usually located beneath the bridge (undersaddle pickups) of the guitar or on the underside of the soundboard (contact pickups) and the only way of telling the guitar has a pickup is the input jack.

Signal Strength

Piezo pickups generate a very small electrical current, and in most cases require a preamp to boost the signal. This also allows for equalization and compression. Compression is often required with piezo pickups as the dynamic range is much greater than a magnetic pickup. For those unaware, dynamic range simply means the difference between the largest and smallest value something is capable of producing. In the case of piezo pickups, dynamic range refers to volume.

In simple terms, this means, that if your attack on the strings is harder e.g. you pluck the strings with more attack the dynamic range (volume) increases exponentially. For example, when playing a magnetic pickup the volume increases by 50% if you hit the strings 50% harder.

If playing a Piezo pickup, however, the volume may increase by 100% when hitting the strings 50% harder and this continues to increase depending on how much intensity you play with. Compression can be used to reduce the highs and boost the lows, balancing the dynamic range.

Undersaddle Piezo Pickups

Undersaddle pickups are the most common acoustic guitar pickup type and are often seen in new acoustic guitars. They are typically more articulate, percussive, and brighter sounding than magnetic pickups due to the placement of the pickup which is located directly beneath the end of the strings. They are highly responsive, making them a good option for fingerstyle, classical, and smaller-bodied guitars.

When installing an undersaddle pickup, the entire unit is placed beneath the bridge saddle. The piezo material is housed within a channel that serves as a negative conductor, while the top of the unit is covered with a section of copper that serves as a positive conductor.

Each string has a matching piezo element that sits within the channel and detects changes in pressure caused by vibrations of the strings which are transferred to the bridge of the guitar via the saddle.

Pros and Cons of Undersaddle Pickups

Piezo Contact Pickups (Soundboard Transducers)

Contact pickups, are also piezo pickups and work the same way as undersaddle transducers except they are placed on, or beneath the soundboard and detect vibrations that have been transferred from the strings, through to the bridge and ultimately the soundboard.

I recently installed one on my son’s guitar and discovered how important it is to locate the ‘sweet spot’ of the guitar’s soundboard. e.g. some sections of the soundboard are more resonant, and richer sounding than others. This is often to the rear of the bridge, on either the underside or top surface of the soundboard. To get the very best from a contact pickup, it is recommended that you connect the pickup to the top of the soundboard first and test in a variety of positions before settling on the ‘sweet spot’.

Contact pickups typically have an adhesive applied to the underside of the pickup allowing the pickup to be easily removed as the need arises.

When installed internally, the guitar’s rear strap button is removed and the cable is threaded through the internal cavity of the guitar. This generally does require some drilling of the guitar body.

Contact pickups come in a variety of options, both internal and external, and include either one sensor (most common on external types) or up to three in the case of a bridge plate transducer, which is another type of contact pickup. The Schaller Oyster contact pickup is a reliable and affordable option if considering an internal contact pickup.

Pros and Cons of Contact Pickups

Microphone Pickups

Microphone pickups are regarded as the most faithful in terms of reproducing the natural tone of the acoustic guitar, however, they also present several potential issues concerning feedback, particularly at high volume due to their higher sensitivity.

Available in both internal and external models, the most common is typically the internal microphone which is a small condenser microphone positioned within the internal cavity of the guitar and placed on a flexible arm to allow the guitarist to adjust the position of the microphone. External microphones are usually positioned on a gooseneck adjustable arm allowing the guitarist to position the microphone so it doesn’t hinder the picking hand.

Depending on the placement, microphone pickups tend to capture more of the internal resonance of the guitar resulting in a far more authentic and natural sound, compared to an undersaddle pickup for example. This is the reason artists such as Tommy Emmanuel prefer this style of pickup.

What’s the difference between a microphone and a magnetic pickup?
You may be aware that microphones also work on the concept of electromagnetism, however, there is a difference in how magnetic pickups function compared to a microphone. 

Microphones detect soundwaves, magnetic pickups detect vibrations caused by the guitar’s strings. While both are transducers, microphones will project a more natural sound as they will also pick up on percussive noises such as modern fingerstyle playing that incorporates more percussive techniques.

Pros and Cons of Microphone Pickups

Blended Systems

Blended or hybrid pickup systems offer the best of both worlds in terms of controlling the tone of the guitar using two separate pickups and utilizing one preamplifier allowing the signal to be mixed or blended. However due to the added complexity and manufacturing costs, this style of pickup is a more expensive option in general.

In the majority of cases, blended pickup systems combine the authentic natural character of a microphone pickup with the articulation and clarity of an undersaddle or contact pickup. There are several options available from reputable manufacturers such as Fishman and L.R. Baggs. The LR Baggs Anthem Tru-Mic is particularly impressive.

Seymour Duncan also produces a blended or hybrid pickup (Seymour Duncan SA-6 Mag Mic) that features an undersaddle pickup combined with a magnetic pickup that is also well-reviewed.

Having the ability to blend two different types of acoustic guitar pickup can be useful for guitarists who perform in several different venues. For instance, in a more feedback-prone environment reducing the input from the internal microphone can help reduce feedback. Alternatively, if you are playing in a more intimate setting you will likely prefer the natural warmth of a microphone pickup while adjusting the piezo pickup to provide just enough clarity without making the tone of the guitar sound overly bright. Blended systems afford the guitarist more control over their sound.

Pros and Cons of Blended Pickup Systems

Acoustic guitar pickup comparison

Each type of pickup has its unique pros and cons, meaning it’s difficult to pinpoint which is ultimately the best in each situation. Pickups are also difficult to ‘try before you buy’ unlike guitars themselves. Therefore it’s a good idea to do your research, kudos to you for reading this article.

The acoustic pickup that will best suit your needs will come down to individual preference. And, while the guitar itself is an important consideration, in most cases the choice should be more influenced by the style of music you play, the amount you can afford to outlay, and the environment you are playing in.

e.g.

• Are you performing as a solo artist or part of a group?
• Do you flat-pick or play with your fingers?
• Is feedback a concern?
• Are you limited by budget?
• Do you need to remove the pickup without too much hassle?

In most cases, if you are playing in an environment where you don’t need to play with a high amount of volume internal microphone pickups are generally a superior option. However, if you are not in control of the environment and therefore have different volume requirements, a blended or hybrid system will be a better option provided the cost is not a factor.

If on a budget, contact pickups are a great option as they are relatively inexpensive, don’t require professional installation, and provided you position the sensor in the ‘sweet spot’ of your soundboard can sound very authentic.

Finally, if you are looking for an option that is easily removed, or you tend to play with effects, magnetic pickups will be your best option, but remember if you play a nylon string guitar a magnetic pickup won’t detect the strings as they are not magnetized.

Summary – Setting Realistic Expectations

I hope the information above is useful in helping you decide on the best acoustic guitar pickup for your requirements. Bear in mind, that it is important to set realistic expectations when it comes to amplifying acoustic guitars. The truth is while many types of acoustic guitar pickups work well, it’s unlikely you will reproduce the tone of your acoustic completely accurately.

There are a bunch of reasons for this, but mainly it comes down to the fact that an acoustic guitar’s tone is derived from several characteristics of the instrument e.g. the tonewoods used, the build quality, the size of the guitar, and the internal resonance produced.

For instance, a contact pickup is only detecting vibrations in one very specific spot on the guitar, this is much the same with undersaddle transducers, which personally tend to sound awful when used for recording. Magnetic pickups on the other hand are only influenced by the vibration of the strings. The tone of an acoustic guitar is more holistic than this. Pickups, regardless of how good they are generally can’t reproduce this accurately.