Have you ever asked what some of the technical jargon means which manufacturers use in order to show the performance of wireless speakers sold by Amphony? In this expose, I am going to highlight one frequently used specification: THD or “total harmonic distortion”.
Cordless speakers are available in all different shapes and sizes. Picking the correct model can frequently be tough. I will shed some light on a commonly utilized term that is used in order to show the technical performance of the speaker: “total harmonic distortion” or “THD”. Total harmonic distortion is usually not very well understood. Nevertheless, this term is still important in terms of determining the performance of a specific type. Other specs, for instance “output power” or “frequency response” are generally easier understood. In a nutshell, THD describes the difference between the sound which is produced by the loudspeaker versus the audio signal with which the speaker is driven. The most common methods to state distortion are percent along with decibel. These two conventions can be translated into one another. If a speaker specifies a distortion of 10% to provide an example then one 10th of the energy radiated by the loudspeaker is distortion. A distortion of 10% may also be shown as -20 dB. 1% distortion is equal to -40dB.
Harmonic distortion in a cordless speaker is actually the result of several components, such as the power amp which is built into the speaker to drive the speaker element. Amplifier distortion normally depends on the amplifier output power and is sometimes specified for several power levels.
Distortion ratings for different output power levels are generally specified for several power levels or as a diagram listing distortion versus output power. Both of these techniques allow to better evaluate the quality of the amplifier.Typically distortion is measured with a 1 kHz test tone. This enables comparing equipment from various manufacturers. Though, distortion usually varies with different frequencies. Many digital amplifiers will show growing distortion amid higher frequency which cannot easily be uncovered by glancing at the specification sheet. The next contributing factor is the loudspeaker element itself. The majority of loudspeakers use a diaphragm kind driver that is driven by a voicecoil which is suspended in a magnetic field. The coil is moving according to the change in the magnetic field which is excited by the audio signal but does not correlate 100% with the signal as a result of core losses along with other factors. As such the result is distortion caused by the speaker element. Many manufacturers will display harmonic distortion based on the power level since usually the higher the speaker is driven the higher the level of distortion.
The total distortion of the speaker thus is the sum total of the amplifier distortion in addition to the loudspeaker element distortion. Furthermore, there are other contributing factors. Depending on the material used to manufacture the loudspeaker enclosure, there will be vibrations or enclosure resonances. Those normally depend on the sound pressure level, the box shape, the housing fabric in addition to audio frequency. For that reason extra audio distortion will be caused by the enclosure itself.
The total distortion of the speaker is usually determined by a measurement which involves a low-distortion audio generator plus a microphone which is connected to an audio analyzer. The audio analyzer is going to calculate the amount of higher harmonics and compare these with the main signal in order to calculate the distortion. Then again, pure sine signals hardly give an accurate indication of the distortion of the wireless speaker with real-world signals. A better distortion analysis is the so-called intermodulation distortion analysis in which a test tone which includes a number of sine waves is used. Then the level of harmonics at other frequencies is measured.
Cordless loudspeakers are going to also have some level of distortion during the audio transmission. The amount of distortion will depend on the sort of cordless transmission method and the quality of components. Generally 900 MHz FM transmitters have among the highest level of distortion. Superior models are going to utilize digital transmission and transmit at 2.4 GHz or 5.8 GHz to reduce signal distortion.
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