There are three types of acoustic guitar pickup. Magnetic pickups, like those found on electric guitars that rely on electromagnetism. Piezo pickups, that 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 under-saddle pickups.
Interested in amplifying your acoustic guitar? If so you will need an acoustic guitar pickup. Many acoustic guitars now come with 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 the 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.
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 transducer:
- 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 utilises 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)
- Piezo 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 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 protrude out from the soundhole and hang below the guitar, which is convenient with regard to 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 utilise pole pieces that sit directly beneath each guitar string. The pole pieces are either magnets themselves (magnetic Alnico) or steel and sit on top 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 as in 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 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
|Simple to install by fitting across the soundhole. (No drilling into the guitar required). Simple to remove and use on multiple guitars.||Sound is generated only by the strings. Other characteristics of the guitar that are important to the tonal quality of the instrument when played acoustically do not influence the tone produced.|
|Reasonably feedback resistant as the pickup is only detecting vibrations from the strings and not the soundboard.||Some models wont fit smaller acoustic guitars e.g. ½ and ¾ models with smaller than standard soundholes.|
|Good bass response. Magnetic pickups generally sound warmer than Piezo pickups.||Unlike other acoustic guitar pickups, they are visually prominent due to spanning the soundhole of the guitar.|
|In some cases the individual pole pieces are height adjustable. This can be useful if you want to increase the bass response from the guitar for example.||Only suitable for steel string guitars.|
Piezo pickups (Undersaddle and Contact Pickups)
Piezo pickups (pronounced “pee-ay-zo”) while also a transducer, work differently to magnetic pickups. Piezos utilise 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.
Piezo pickups generate a very small electrical current, and in most cases require a preamp to boost the signal. This also allows for equalisation 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, 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 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
|Very responsive.||Can be difficult to install and may require some additional routing beneath the saddle and a small hole drilled into the bridge of the guitar. If the pickup utilises a preamp, you may need a section cut from the top side of your acoustic guitar, which may need to be handled by a professional.|
|More feedback resistant than other types of pickups.||Can sound too bright and percussive and require EQ to achieve a desirable tone.|
|Good note articulation and clarity.||Low signal strength and wide dynamic range e.g. doesn’t respond well to a heavy attack and generally benefits from a preamp to boost and compress the signal.|
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 the pickup to the top of the soundboard first and test in a variety of positions before settling on the ‘sweetspot’.
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
|Due to detecting changes in pressure to the soundboard, the tone produced represents the natural acoustic properties of the guitar more effectively than undersaddle or magnetic pickups.||Placement is important and can make a significant difference to the tonality of the guitar.|
|More feedback resistant than magnetic or microphone pickups.||Low signal strength and wide dynamic range e.g. doesn’t respond well to a heavy attack and generally benefits from a preamp to boost and compress the signal.|
|Simple to install and relatively inexpensive.|
Microphone pickups, are regarded as the most faithful in terms of reproducing the natural tone of the acoustic guitar, however they also present a number of potential issues with regard to 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 goose neck 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 a magnetic pickup functions 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 incorporate more percussive techniques.
Pros and Cons of Microphone Pickups
|More representative of the natural tone of the acoustic guitar.||More prone to feedback issues, not ideal when performing with a band.|
|Picks up more percussive elements of the guitarists playing.||Are more expensive than piezo and magnetic pickups.|
|Can be tricky to install and may require a professional.||Mid range tone can be a little dominant, resulting in a ‘boxy’ sound. Placement of microphone plays a large role.|
|Typically requires a preamp and eq to really get the best out of them.|
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 utilising one preamplifier allowing the signal to be mixed or blended. But 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 a number of options available from reputable manufacturers such as Fishman and L.R. Baggs. The LR Baggs Anthem Tru-Mic is particularly impressive.
Seymour Duncan also produce 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 a number of 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 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
|Allow greater control over the tonal quality of the guitar.||Can be more difficult to install and may require a professional.|
|Adjustments can be made to reduce feedback.||Can be quite expensive compared to the other types of acoustic guitar pickup mentioned above.|
Acoustic guitar pickup comparison
Each type of pickup has its own 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.
- 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 day to day, a blended or hybrid system will be a better option provided 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 ‘sweetspot’ 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 wont detect the strings as they are not magnetised.
Summary – Setting Realistic Expectations
I hope the information above is useful in helping you decide the best acoustic guitar pickup for your requirements. Bear in mind, 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’s a bunch of reasons for this, but mainly it comes down to the fact that an acoustic guitar’s tone is derived from a number of 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 under saddle 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.