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Understanding the frequency response “curve” of speakers can help visualize what happens when audio distortion begins emanating from your loudspeaker. While not uncommon, it is essential to know that the quality and design of the speaker may help minimize the potential for this deviation.
So, what is the frequency response “curve”, and how does it pertain to sound quality?
The “curve” represents the SPL (sound pressure level or loudness) at each frequency, from the lowest audible bass (around 20 Hz) to the highest trebles (around 20 kHz). Above and below these frequencies, most humans cannot hear the sound produced, although, as we know, many animals can. 20 Hz to 20 kHz is often called the audio frequency spectrum, or audio band.
The perfect speaker system design would have a flat frequency response with minimal dips and peaks within the audio band. This speaker system would provide equal loudness to all frequencies, meaning it would follow the dynamics of the sound recording.
Most speaker systems, though, do not have a flat frequency response across the entire audio band. When there are deviations from a flat frequency response, the speaker system is imparting its own tonal characteristics onto the sound recording.
That is one type of distortion, other types of distortion also exist and are caused by other factors.
Why Loudspeaker Sound Gets Distorted
Sound distortion in loudspeakers can occur when the component drivers begin to behave erratically, reproducing the sound in a non-linear pattern, creating harmonics of the original frequency. Among other causes, the speakers might have been pushed beyond their design parameters through excessive demand, or the system may have overheated.
Possible causes of audio distortion problems may be:
- Wrong input level to the amplifier
- Amplifier gain is set too low or high
- Not enough amplifier power
Although the sound problem might stem from the quality of the loudspeaker, some quick-fix, everyday solutions might be to:
- Determine the quality of the audio source
- Lower the volume of the audio source, such as a PC, to about three-quarters of the maximum
- Adjust the volume setting on the amplifier until the sound quality improves
Audio distortion could also be related to speaker location. If the speaker is near a wall or other reflecting surface, the sound waves that bounce off the surface can change the imaging that speakers create. Imaging is the spatial placement of instruments or singers that is captured during a recording. Moving the speaker could be a solution and improve imaging.
Choosing a Loudspeaker that Minimizes Audio Distortion
To minimize or eliminate the risk of audio distortion, choose a speaker that can achieve your Sound Pressure Level (SPL) goal and match with an amplifier that can supply the necessary power while remaining below 1% THD. These statistics are generally shown in the equipment specifications.
In simple terms, the SPL is a numerical measure of how loud any sound happens to be. Measured in decibels (dB), the rating represents the ratio of the absolute sound pressure against a set reference level of sound in the air. This level can be measured by a device known as a sound pressure level meter.
THD represents Total Harmonic Distortion. This metric determines by percentage the degree to which the sound deviates or is distorted from the recording. An amplifier that delivers power with less than 1% THD produces sound with very little audible distortion.
High-Quality Design Solutions Prevent Audio Distortion
Everyday solutions like the ones listed above are needed to correct distortion in certain speakers. However, seeking speaker drivers that incorporate design parameters to prevent audio distortion in the first place should be your objective.
Designing speaker drivers that will achieve the highest level of performance requires in-depth knowledge of physics and engineering and extensive testing processes to achieve the highest levels of sound quality.
From the start, top-quality speaker designs define each performance parameter like frequency response, sensitivity, power handling, impedance, and more. Mechanical elements like the intended location, size, and appropriate materials must be specified for their intended use.
As mentioned, environmental factors can play a significant role in a loudspeaker’s performance. Anticipating indoor or outdoor placement, temperatures, chemical resistance, and other potential interfering elements in the initial design is also essential to reduce the possibility of environment-related distortion.
Extensive performance testing should be the ultimate process before releasing the speaker to the customer.
Importance of Speaker Performance Testing
Engineering and design are critical elements of a loudspeaker. But a design is only as good as the quality of the output.
Superior speaker driver manufacturers test extensively to ensure their designs maintain the target performance and durability levels. Extensive acoustic testing, designed to meet the client’s SPL goal, assures the levels of sound quality are met while also duplicating the client’s power demands.
Assessing longer-term reliability while reproducing applicable environmental exposure will ensure the speakers will withstand the anticipated conditions.
Large signal analyses determine how much power a speaker can withstand and how far a speaker may move before it begins to distort.
