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Wednesday, July 4, 2012

A Number Of Practical Guidelines For Purchasing A Couple Of Wireless Speakers

By Lisa Stein


Are you searching to buy a brand new a pair of cordless loudspeakers for your home? You might be dazzled by the amount of alternatives you have. To make an informed selection, it is best to familiarize yourself with frequent specs. One of these terms is referred to as "signal-to-noise ratio" and is not often understood. I will help clarify the meaning of this expression.

Whilst searching for a pair of wireless speakers, you firstly are going to check the price, wattage amid additional basic criteria. Nonetheless, after this initial selection, you are going to still have several types to choose from. Now you are going to concentrate more on a few of the technical specs, including signal-to-noise ratio and harmonic distortion. Each wireless speaker is going to produce a certain amount of hiss and hum. The signal-to-noise ratio is going to help calculate the level of static created by the loudspeaker.

Evaluating the noise level of several sets of wireless speakers may be accomplished fairly easily. Just collect a couple of products which you wish to evaluate and short circuit the transmitter audio inputs. Afterward set the cordless speaker volume to maximum and check the amount of static by listening to the loudspeaker. You will hear some amount of hissing and/or hum coming from the speaker. This noise is created by the wireless speaker itself. Make certain that the gain of each pair of wireless loudspeakers is set to the same amount. Otherwise you will not be able to objectively compare the amount of noise between several models. The general rule is: the lower the level of hiss which you hear the higher the noise performance.

In order to help you evaluate the noise performance, cordless speaker manufacturers publish the signal-to-noise ratio in their wireless loudspeaker specification sheets. Simply put, the larger the signal-to-noise ratio, the lower the amount of noise the wireless speaker creates. One of the reasons why wireless speakers produce noise is the fact that they use components like transistors as well as resistors that by nature produce noise. Mostly the components that are located at the input stage of the built-in power amp will contribute most to the overall hiss. Therefore makers normally are going to choose low-noise elements while developing the cordless loudspeaker amplifier input stage.

Noise is also created by the cordless transmission. Different styles of transmitters are available which operate at different frequencies. The cheapest type of transmitters uses FM transmission and generally broadcasts at 900 MHz. The amount of noise is also dependent upon the amount of wireless interference from other transmitters. Modern types are going to normally use digital audio transmission at 2.4 GHz or 5.8 GHz. The signal-to-noise ratio of digital transmitters is independent from the distance of the wireless speakers. It is determined by how the audio signal is sampled. In addition, the quality of parts inside the transmitter are going to affect the signal-to-noise ratio.

The majority of recent wireless speakers use power amps which are digital, also referred to as "class-d amps". Class-D amps utilize a switching stage that oscillates at a frequency in the range of 300 kHz to 1 MHz. This switching noise can cause a certain level of speaker distortion but is usually not included in the signal-to-noise ratio which only considers noise between 20 Hz and 20 kHz.

The most common method for measuring the signal-to-noise ratio is to couple the wireless loudspeaker to a gain that allows the maximum output swing. After that a test tone is fed into the transmitter. The frequency of this tone is typically 1 kHz. The amplitude of this tone is 60 dB underneath the full scale signal. Then the noise-floor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.

Often the signal-to-noise ratio is shown in a more subjective way as "dbA" or "A weighted". This technique attempts to evaluate in how far the wireless loudspeaker noise is perceived by human hearing which is most sensitive to signals at frequencies at 1 kHz. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is typically larger than the unweighted signal-to-noise ratio.




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