When you are chasing after getting the perfect sound quality, it is important to pay attention to the numbers behind the sound as well. Total Harmonic Distortion (THD) is one such figure that shows up time and time again when you look at HiFi specs. So, what is THD? And how does it affect the way that you hear your music? In this article, we will go through what total harmonic distortion means in the real world and why it matters in respect to HiFi audio. We will also take a look at low-THD equipment that is available to achieve the cleanest, most accurate sound.
What is Total Harmonic Distortion (THD) in Audio?
THD harmonic distortion is used to measure the amount of signal that is distorted through the addition of harmonics in the audio that were not present in the original recording. These harmonics are essentially a multiplication of fundamental audio frequencies that appear when the audio signals pass through a speaker, amplifier, or other components.
What Causes Harmonic Distortion?
With 'what is THD in audio' being explored, let us now look into its major causes. THD harmonic distortion is usually caused by imperfections that are present in the audio components, especially when these components are pushed close to their limits in performance, like through dB boost and improper sound layering. Some of the common causes of these include:
- Non-linear behaviour of amplifier
- Poor speaker design
- Mismatched impedance between components
- Overdriven audio signals
The Role of Harmonic Factor in THD
The ratio of the power of all harmonic frequencies above the fundamental tone when compared with the total power output that is provided to the device is called the harmonic factor. In the measurement of THD, often referred to as harmonics THD, the harmonic factor lets you know how “coloured” or altered the signals have become. You can achieve a playback that is closer to the original recording through lowering the harmonic factor.
THD in HiFi Audio Systems: Why It Matters
In the case of HiFi audio, the goal is to get a sound reproduction that is as accurate and transparent as possible. Playback at higher levels of total harmonic distortion (THD) can introduce unwanted noise or warmth that can bring muddiness to your tracks or mask the subtle details. While some equipment, notably vintage ones, intentionally introduce harmonic distortion to get warmer sound, most of the modern HiFi systems aim to get the cleanest signal possible.
THD in Different Audio Components
As mentioned, THD can be caused by all parts of your audio chain; here’s how:
Amplifiers: These are often the main culprit for THD in a HiFi system. The job of an amplifier is to increase the audio strength without making any changes to its character. However, if the system is poorly designed, pushed above its capabilities or uses subpar components, it can introduce distortion to the output.
- Look for amplifiers with THD figures below 0.1% — this ensures minimal distortion and maintains the purity of your sound.
- High-end models, such as the Quad Vena II Integrated Amplifier, often offer THD ratings as low as 0.005%, resulting in cleaner, more accurate playback.
Speakers: Speakers are responsible for converting electrical signals into audible mechanical movements; this process is inherently prone to distortion. The factors that affect the sound quality in speakers are their design, build quality and the materials used.
- Low-quality cones may flex unpredictably, introducing unwanted harmonics.
- Poor enclosure design can cause internal reflections or resonance, increasing THD.
- Better-engineered speakers, like the Edifier P12 Passive Bookshelf Speakers, are designed to minimise distortion through precise driver alignment and damping.
Sources: The source of playback, such as CD players, DACs, and streamers, is also a crucial aspect in determining the THD. While digital sources can seem like they are immune to distortion, digital-to-analogue conversion (DAC) is a crucial point where THD can enter.
- Inaccurate digital signal processing or jitter during conversion can cause harmonic distortion.
- Low-quality or outdated DAC chips may colour the sound, especially at higher volumes or complex passages.
- Using high-resolution, lossless audio files and a quality DAC ensures distortion stays low and details stay crisp.
Cables: Easy to miss and often overlooked, interconnect and speaker cables can also bring about a slight influence on THD, especially in high-end setups.
- Poorly shielded cables may pick up electromagnetic interference (EMI), introducing subtle distortion.
- Long, unbalanced runs of cable can cause signal degradation, especially in analogue connections.
Low-THD Hi-Fi Audio Equipment Picks in the UK
While choosing HiFi equipment, opting to go for models that have a lower THD and minimal harmonic distortion can make sure that you get the cleanest and the most accurate sound reproduction. Here are two standout products that are currently available at Nottingham HiFi that can help to deliver audio that is truly exceptional.
Quad Vena II Integrated Amplifier Mahogany
The Quad Vena II offers ultra-low THD to get a clean and present audio prediction without unwanted colouration. It is made with audiophile-grade internal components that are engineered for transparency and for tonal balance. It also includes:
- Built-in high performance DAC offers premium digital-to-analogue conversion for crisp digital playback.
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Multiple input options, including Bluetooth aptX, USB, and optical for versatile connectivity
- Elegant mahogany finish blends seamlessly into both traditional and modern listening spaces.
- Perfect for users seeking a powerful all-in-one amplifier that prioritises sonic purity.
Edifier P12 Passive Bookshelf Speakers
The Edifier P12 will help you achieve the lowest amounts of THD with the help of their low harmonic distortion drivers, making sure that the midrange and the bass are clear and tight. The speakers come with a neutral and balanced sound profile that is ideal for music lovers who value the accuracy of sound reproduction over artificial enhancements. The product also includes:
- Wall-mountable design offers placement flexibility for tighter spaces or custom audio setups.
- Passive speaker design allows pairing with your choice of low-THD amplifier to optimise system performance.
- Well-suited for HiFi audio and stereo listening, home theatre setups, or nearfield use in desktop environments.
- A great entry point into audiophile-grade sound for budget-conscious listeners.
How to Measure Total Harmonic Distortion in Audio
Measuring the total harmonic distortion requires the usage of precision tools such as a THD meter or an audio analyser. These can generate a known test tone and measure the added harmonics THD after playback.
Are all types of distortion bad for audio quality? Not necessarily; some amount of distortion, for example, in the vintage systems, can be pleasing to the ears. But for accurate reproduction, generally lower THD is better.
Acceptable THD Levels in HiFi Equipment
- Below 0.1% THD is considered excellent and typically inaudible.
- 0.1%–0.5% THD is acceptable in budget gear and often hard to notice.
- 1% THD or higher is usually noticeable and undesirable for HiFi.
Does a lower THD always mean better sound quality? Not always. You are not guaranteed better sounds with very low THD by itself; other factors, such as the frequency response or the speaker's design, are lacklustre, and it might not be great sounding.
Reducing THD for Better Sound Quality
Lowering distortion THD involves both choosing the right gear and using it correctly:
- Use matched components that work well together electrically.
- Avoid pushing amplifiers or speakers to their limits.
- Keep cabling clean, short, and well-shielded.
- Use high-quality DACs and digital sources.
Keep in mind that a proper speaker placement and treating your room properly can also help to reduce the audial perception of distortion, even if there are no changes to the hardware specs.
To Wrap Up
Total harmonic distortion is not something that should just stay in the spec sheets; it is a real measure of how great your sound system is compared to the original recording. By understanding THD and getting a low distortion gear and setting it properly, you will be able to hear music the way it was meant to be heard.
Frequently Asked Questions
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What is a good THD for an amplifier?
Usually, an amplifier with THD that is below 0.1% is ideal for HiFi. There are many high-end amps that go as low as 0.005%.
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Can the human ear detect THD?
Most listeners will be unable to hear distortion that is below 1%, though trained ears might be able to notice issues above 0.3% in terms of high-fidelity systems.
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How much total harmonic distortion is acceptable in HiFi audio?
Anything below 0.5% is considered to be acceptable, and getting it under 0.1% is excellent.
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How do I measure the total harmonic distortion of my audio system?
Using an audio interface that has analysis software such as Room EQ Wizard or Audio Precision tools can help you run tests for THD.
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Is 1% THD audible?
Yes, especially with content that has high frequency or if you are listening in sensitive environments. Higher levels of THD can introduce muddiness or harshness to the sound.