In this article, I am going to explain the specification “total harmonic distortion”, often also named “THD” which is often used to describe the quality of cordless speakers. It is often tough to choose a suitable set of wireless outdoor speakers manufactured by Amphony due to the huge amount of products. Aside from looks, you will often be confronted with having to study a few of the technical specifications. THD is typically not as easily understood as a few other commonly used terms such as “signal-to-noise ratio” or “frequency response”. In a nutshell, THD shows the difference between the audio that is produced by the loudspeaker versus the audio signal with which the loudspeaker is driven. The most widespread methods to express distortion are percent and decibel. These 2 conventions can be translated into one another. The percentage given as THD shows which amount of energy which is radiated by the speaker are higher harmonics versus the original signal. 10% would mean that one tenth is distortion. 1% would mean one hundredth et cetera. 10% is equal to -20 dB as 1% is equal to -40 dB.
Harmonic distortion in a cordless loudspeaker is really the result of several elements, including the power amp that is built into the loudspeaker in order to drive the loudspeaker element. Amplifier distortion usually is dependent on the amp output power and is now and then shown for several power levels.
Having amp distortion specs for several output power levels offers a better indication of the amplifier distortion performance.Generally distortion is measured with a 1 kHz test tone. Distortion, though, is usually dependent on the signal frequency. Many amplifiers will show rising distortion with rising frequency. Specifically digital class-D amplifiers will have rather large distortion at frequencies higher than 5 kHz. The next contributing factor is the speaker element itself. Most loudspeakers utilize a diaphragm kind driver which is driven by a coil that is suspended in a magnetic field. The coil is going to track the magnetic field that is controlled by the music signal in order to move the diaphragm. However, this movement is not completely linear. As such the result is distortion caused by the loudspeaker element. A lot of vendors will show harmonic distortion based on the power level as typically the higher the loudspeaker is driven the bigger the amount of distortion.
The overall distortion of the loudspeaker thus is the total of the amp distortion in addition to the speaker element distortion. Furthermore, there are different contributing factors. The loudspeaker enclose will vibrate to some extent and consequently contribute to the distortion. Total distortion is best determined via measurement. A signal generator is utilized that offers a highly linear sine tone to the loudspeaker. The sound is picked up by a measurement microphone. The microphone signal is then analyzed by an audio analyzer. The audio analyzer is going to compute the amount of higher harmonics or distortion. Intermodulation distortion analysis is an additional technique that gives a better picture of the loudspeaker distortion performance with real-world signals by using a test signal with two harmonics and measuring how many harmonics at different frequencies are produced by the loudspeaker.
Wireless speakers are going to also have some amount of distortion during the audio transmission. The level of distortion is going to depend on the sort of wireless transmission method and the quality of components. Usually 900 MHz FM transmitters have among the highest amount of distortion. Improved types are going to utilize digital transmission and transmit at 2.4 GHz or 5.8 GHz to minimize audio distortion.
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