Friday, 27 July 2012

Unique Content Article on speakers,internet,computers,hardware,music,tv set,radio,technology,shopping

A Couple Of Technical Suggestions For Buying A Couple Of Cordless Speakers


by Lisa Stein


To help you select a pair of wireless speakers, I am going to describe the term "signal-to-noise ratio" which is usually used to depict the performance of cordless speakers.

While trying to find a couple of wireless loudspeakers, you firstly are going to check the cost, wattage among other essential criteria. However, after this initial choice, you will still have several products to choose from. Now you are going to focus more on several of the technical specifications, including signal-to-noise ratio as well as harmonic distortion. One important criterion of cordless loudspeakers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio explains how much hum or hiss the loudspeakers will add to the music signal. This ratio is usually described in decibel or "db" for short.

Comparing the noise level of several sets of wireless loudspeakers may be accomplished quite easily. Simply get together a couple of products which you wish to evaluate and short circuit the transmitter audio inputs. After that set the cordless loudspeaker gain to maximum and verify the level of hiss by listening to the speaker. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This noise is generated by the wireless loudspeaker itself. Make certain that the gain of each couple of cordless loudspeakers is pair 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 level of hiss which you hear the better the noise performance.

If you prefer a pair of cordless speakers with a small level of hissing, you can look at the signal-to-noise ratio figure of the spec sheet. Most producers will publish this figure. cordless loudspeakers with a large signal-to-noise ratio are going to output a low amount of static. Noise is created due to several reasons. One reason is that modern cordless loudspeakers all utilize components including transistors plus resistors. These elements will produce some amount of noise. Because the built-in power amplifier overall noise performance is mostly determined by the performance of components situated at the amp input, makers are going to try to choose low-noise components whilst developing the amp input stage of their cordless speakers.

A different cause of hiss is the cordless music broadcast itself. Normally models which use FM style transmission at 900 MHz will have a fairly large amount of hiss. FM transmitters are extremely prone to wireless interference which is why newer models commonly make use of digital music transmission. The signal-to-noise ratio of digital transmitters is independent from the distance of the cordless loudspeakers. It is determined by how the audio signal is sampled. In addition, the quality of parts inside the transmitter will influence the signal-to-noise ratio.

A lot of latest wireless speakers have built-in power amplifiers that incorporate a power switching stage which switches at a frequency around 500 kHz. This switching noise may cause a certain level of loudspeaker distortion yet is generally not included in the signal-to-noise ratio which merely considers noise between 20 Hz and 20 kHz.

The signal-to-noise ratio is measured by inputting a 1 kHz test tone 60 dB underneath the full scale and measuring the noise floor of the signal generated by the built-in amp. The volume of the wireless speaker is couple such that the full output power of the built-in amplifier can be realized. Next the noise-floor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.

Frequently you will find the expression "dBA" or "a-weighted" in your wireless loudspeaker specification sheet. A weighting is a technique of expressing the noise floor in a more subjective way. In other words, this method tries to express how the noise is perceived by a person. Human hearing is most sensitive to signals around 1 kHz while signals under 50 Hz and higher than 14 kHz are hardly heard. The A-weighted signal-to-noise ratio is usually larger than the unweighted ratio and is published in most cordless loudspeaker spec sheets.




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