Please give me a reference to an article showing the amount of distortion that is audible for loudspeakers in the bass range.
The audibility of low-order Total Harmonic Distortion (THD) on loudspeakers playing music is complex and depends on several factors, including the type of distortion, the listener's sensitivity, the nature of the music, and the listening environment. However, we can make some general observations.
Understanding THD
Total Harmonic Distortion (THD) is a measure of the distortion introduced by a system, such as a loudspeaker, when it produces harmonics of the input signal that were not present in the original signal. Low-order harmonics (2nd, 3rd, 4th, etc.) are typically more audible than high-order harmonics.
Audibility Thresholds
- Low-Order Harmonics: The 2nd and 3rd harmonics are generally more audible and can be perceived at levels as low as -40 dB below the fundamental signal, depending on the listening conditions and the music content. These harmonics are closer to the original signal frequency and can sometimes blend with the music, making them less objectionable.
- Higher-Order Harmonics: Harmonics higher than the 4th are less audible because they are further away from the fundamental frequency and can be masked by the music. These higher-order harmonics usually need to be at a higher level to be audible, typically above -30 dB below the fundamental.
Practical Audibility in Music
- Music Content: Complex music with a lot of overlapping frequencies and rich harmonic content can mask distortion, making even relatively high levels of THD less noticeable. Simple, pure tones or music with sparse instrumentation can make distortion more noticeable.
- Listening Environment: Quiet listening environments can reveal lower levels of THD compared to noisy environments.
- Listener Sensitivity: Some individuals are more sensitive to distortion and can detect lower levels of THD.
Typical Thresholds
Studies and empirical data suggest that:
- THD levels below 1% (-40 dB) are generally inaudible to most listeners when listening to music in a typical environment.
- For critical listening or highly sensitive listeners, THD should ideally be below 0.3% (-50 dB) to ensure that it is inaudible.
Summary
In summary, low-order THD on loudspeakers playing music is typically inaudible if it is kept below -40 dB relative to the signal. For the most sensitive listeners or in critical listening scenarios, aiming for THD levels below -50 dB ensures minimal audibility. The exact threshold can vary depending on the factors mentioned above.