Thursday, November 21, 2013

A Peek At The Wireless Overall Performance Of Tv Wireless Speakers

By Linda Cullmann


To help you select a set of cordless speakers, I will describe the expression "signal-to-noise ratio" which is usually utilized in order to depict the performance of cordless loudspeakers.

Whilst searching for a pair of wireless loudspeakers, you first are going to check the cost, power amid additional essential criteria. Yet, after this initial choice, you will still have a number of products to choose from. Next you will focus more on a number of of the technical specifications, including signal-to-noise ratio and harmonic distortion. An important criterion of cordless loudspeakers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio describes how much hum or hiss the loudspeakers are going to add to the audio signal. This ratio is generally described in decibel or "db" for short.

Evaluating the noise level of different sets of wireless speakers may be done fairly easily. Just collect a few types which you wish to evaluate and short circuit the transmitter audio inputs. Next put the wireless loudspeaker gain to maximum and verify the level of static by listening to the loudspeaker. The static which you hear is generated by the cordless speaker itself. Make certain that the gain of each set of cordless loudspeakers is set to the same amount. Otherwise you will not be able to objectively compare the amount of hiss between different models. The general rule is: the smaller the level of hiss that you hear the higher the noise performance.

To help you compare the noise performance, cordless speaker makers show the signal-to-noise ratio in their wireless loudspeaker specification sheets. Simply put, the higher the signal-to-noise ratio, the lower the amount of noise the cordless loudspeaker generates. Noise is produced due to several reasons. One factor is that modern wireless speakers all use components such as transistors in addition to resistors. These elements are going to create some amount of noise. The overall noise depends on how much hiss every component creates. Yet, the location of these elements is also vital. Elements which are part of the speaker built-in amp input stage are going to in general contribute the majority of the noise.

A further cause of static is the cordless audio transmission itself. Generally models that use FM type broadcast at 900 MHz are going to have a comparatively high level of static. Other wireless transmitters will interfer with FM type transmitters and create further noise. As a result the signal-to-noise ratio of FM type cordless speakers varies depending on the distance of the loudspeakers from the transmitter and the level of interference. To steer clear of these problems, newer transmitters employ digital music transmission and usually transmit 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 audio signal is sampled. Also, the quality of parts inside the transmitter will influence the signal-to-noise ratio.

Most of today's wireless speakers use power amps which are digital, also known as "class-d amps". Class-D amplifiers use a switching stage that oscillates at a frequency in the range of 300 kHz to 1 MHz. In consequence, the output signal of wireless speaker switching amps exhibit a fairly big amount of switching noise. This noise component, though, is typically impossible to hear because it is well above 20 kHz. On the other hand, it may still contribute to loudspeaker distortion. Signal-to-noise ratio is typically only shown within the range of 20 Hz to 20 kHz. Thus, a lowpass filter is utilized while measuring cordless speaker amplifiers in order to eliminate the switching noise.

Makers measure the signal-to-noise ratio by setting the built-in amp such that the full output swing may be achieved and by feeding a test signal to the transmitter which is usually 60 dB underneath the full scale of the loudspeaker amp. Next, only the hiss between 20 Hz and 20 kHz is considered. The noise at different frequencies is removed by a filter. Then the level of the noise energy in relation to the full-scale output wattage is calculated and expressed in db.

Often you are going to discover the expression "dBA" or "a-weighted" in your cordless loudspeaker spec sheet. A weighting is a technique of expressing the noise floor in a more subjective fashion. In other words, this method attempts to state how the noise is perceived by a person. Human hearing is most perceptive to signals around 1 kHz whereas signals below 50 Hz and higher than 14 kHz are hardly noticed. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is usually larger than the unweighted signal-to-noise ratio.




About the Author:



No comments:

Post a Comment