A Brief Introduction Of The Harmonic Distortion Specification Of Wireless Loudspeakers

Are you considering to choose a pair of outdoor speakers? You may be puzzled by all of the technical language used by vendors in order to exhibit the quality of their products. I will explain one commonly used term which, nonetheless, ist frequently misunderstood: "total harmonic distortion" or "THD".It is often tricky to choose a suitable set of wireless surround sound speakers due to the large amount of models. Aside from looks, you will often be faced with having to examine several of the technical specifications. THD is typically not as easily understood as several other frequently used terms including "signal-to-noise ratio" or "frequency response".In brief, THD describes the difference between the sound which is produced by the speaker versus the audio signal with which the speaker is driven. The most widespread methods to state distortion are percent and decibel. These 2 conventions can be converted into one another. The percentage given as THD shows which amount of energy which is radiated by the loudspeaker are higher harmonics versus the original audio. 10% would mean that one tenth is distortion. 1% would mean one hundredth and so forth. 10% is equal to -20 dB while 1% is equal to -40 dB.

On the other hand, be careful as there are in fact several components which cause harmonic distortion. Cordless speakers in addition to any sort of active loudspeaker or active subwoofer all have built-in power amps to drive the loudspeaker element. Customarily the bigger the amp is driven the higher the amount of amp distortion. For this reason, some suppliers will show amplifier distortion based on amp output power.

Distortion ratings for various power levels are generally provided for a few power levels or as a diagram listing distortion versus output power. Both of these methods allow to better evaluate the performance of the amplifier.Customarily distortion is measured with a 1 kHz test tone. Distortion, however, is usually dependent on the audio frequency. Many amplifiers will show increasing distortion with rising frequency. Specifically digital class-D amplifiers will have quite high distortion at frequencies above 5 kHz.Another component causing distortion is the speaker element which usually operates with a diaphragm which carries a voicecoil that is suspended in a magnetic field. The coil is moving in accordance to the change in the magnetic field that is excited by the music signal but does not correspond 100% with the signal due to core losses and other reasons. As such there will be speaker element distortion that furthermore depends on the amount of output power with which the speaker is driven.As such both the amp and also the speaker element itself add to distortion. In addition, there are other factors which also contribute to distortion. The whole amount of distortion is the total of all of these factors. Depending on the material used to manufacture the loudspeaker enclosure, there will be vibrations or box resonances. These typically depend on the sound pressure level, the enclosure shape, the enclosure material as well as audio frequency. Thus additional sound distortion is going to be brought on by the enclosure itself.Total distortion is best determined by measurement. A signal generator is used that provides a highly linear sine tone to the loudspeaker. The sound is recorded by a measurement microphone. The microphone signal is subsequently analyzed by an audio analyzer. The audio analyzer is going to work out the amount of higher harmonics or distortion. Intermodulation distortion analysis is a further technique that provides a better picture of the speaker distortion performance with real-world signals by utilizing a test signal with two harmonics and measuring how many harmonics at other frequencies are generated by the loudspeaker.

Cordless speakers will also have some level of distortion during the audio transmission. The amount of distortion will depend on the sort of cordless transmission technique as well as the quality of components. Generally 900 MHz FM transmitters have among the largest level of distortion. Superior types are going to make use of digital transmission and transmit at 2.4 GHz or 5.8 GHz to reduce signal distortion.