Some Pointers For Minimizing The Static In Wireless Rock Speakers

| Monday, November 11, 2013
By Linda Cullmann


Are you searching to get a new a pair of cordless loudspeakers for your home? You may be dazzled by the amount of choices you have. In order to make an informed selection, it is best to familiarize yourself with popular specs. One of these specifications is called "signal-to-noise ratio" and is not frequently understood. I will help clarify the meaning of this expression.

While trying to find a couple of wireless loudspeakers, you firstly are going to check the price, power amid other fundamental criteria. Nonetheless, after this initial selection, you are going to still have numerous products to choose from. Now you are going to focus more on some of the technical specs, like signal-to-noise ratio in addition to harmonic distortion. Each wireless speaker is going to generate a certain amount of hiss and hum. The signal-to-noise ratio will help calculate the level of static produced by the loudspeaker.

You can make a straightforward assessment of the cordless speaker hiss by short circuiting the transmitter input, setting the loudspeaker volume to maximum and listening to the loudspeaker. The hiss that you hear is generated by the wireless loudspeaker itself. Be certain that the volume of each set of cordless speakers is set to the same level. Otherwise you will not be able to objectively compare the amount of hiss between several models. The general rule is: the lower the amount of noise which you hear the better the noise performance.

If you prefer a pair of cordless loudspeakers with a small amount of hissing, you may look at the signal-to-noise ratio number of the specification sheet. Many suppliers are going to display this figure. cordless loudspeakers with a large signal-to-noise ratio are going to output a small level of static. One of the reasons why wireless speakers produce noise is the fact that they utilize elements including transistors and resistors that by nature produce noise. The overall noise depends on how much noise each component produces. Yet, the location of these components is also essential. Elements which are part of the loudspeaker built-in amp input stage are going to usually contribute the majority of the noise.

The wireless broadcast itself also creates static that is most noticable with products that employ FM transmission at 900 MHz. The level of noise is also dependent upon the level of wireless interference from other transmitters. Modern types will normally employ 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 cordless loudspeakers. It is determined by how the music signal is sampled. Furthermore, the quality of parts inside the transmitter are going to affect the signal-to-noise ratio.

Most of latest wireless speakers use power amps which are digital, also referred to as "class-d amplifiers". Class-D amplifiers utilize a switching stage that oscillates at a frequency in the range of 300 kHz to 1 MHz. Consequently, the output signal of wireless speaker switching amps exhibit a rather big level of switching noise. This noise component, however, is generally impossible to hear since it is well above 20 kHz. Though, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. For that reason, a lowpass filter is utilized while measuring cordless loudspeaker amps to remove the switching noise.

The most widespread method for measuring the signal-to-noise ratio is to set the cordless loudspeaker to a gain which allows the maximum output swing. Next a test signal is input into the transmitter. The frequency of this signal is generally 1 kHz. The amplitude of this signal is 60 dB below the full scale signal. Next, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal calculated. The noise signal at other frequencies is eliminated by a bandpass filter throughout this measurement.

Often the signal-to-noise ratio is shown in a more subjective way as "dbA" or "A weighted". In other words, this technique attempts to express how the noise is perceived by a person. Human hearing is most sensitive to signals around 1 kHz while signals below 50 Hz and above 14 kHz are barely noticed. The A-weighted signal-to-noise ratio is frequently higher than the unweighted ratio and is published in most wireless loudspeaker spec sheets.




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