Saturday, July 7, 2012

A Few Practical Guidelines For Purchasing A Pair Of Cordless Loudspeakers

By Lisa Stein


Are you searching to acquire a brand new a set of wireless speakers for your home? You may be dazzled by the number of options you have. In order to make an informed selection, it is best to familiarize yourself with common terms. One of these terms is known as "signal-to-noise ratio" and is not frequently understood. I am going to help clarify the meaning of this expression.

While searching for a pair of cordless loudspeakers, you initially are going to check the cost, power among additional basic criteria. However, after this initial selection, you are going to still have numerous types to choose from. Next you are going to concentrate more on several of the technical specifications, like signal-to-noise ratio in addition to harmonic distortion. An important criterion of wireless loudspeakers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio shows how much hum or hiss the speakers will add to the audio signal. This ratio is generally shown in decibel or "db" for short.

Evaluating the noise level of several sets of cordless speakers can be accomplished fairly simply. Simply gather a couple of versions that you wish to evaluate and short circuit the transmitter audio inputs. After that put the wireless speaker gain to maximum and verify the level of static by listening to the loudspeaker. You will hear some amount of hissing and/or hum coming from the speaker. This noise is produced by the wireless loudspeaker itself. Make sure that the volume of each set of wireless speakers is pair to the same amount. Otherwise you will not be able to objectively evaluate the amount of static between different models. The general rule is: the smaller the level of noise that you hear the higher the noise performance.

If you prefer a set of cordless speakers with a small level of hissing, you may look at the signal-to-noise ratio figure of the specification sheet. Most makers will publish this figure. cordless speakers with a high signal-to-noise ratio are going to output a small level of hiss. There are a number of reasons why wireless loudspeakers are going to add some form of noise or other unwanted signal. Transistors and resistors which are part of every modern wireless speaker by nature create noise. Because the built-in power amplifier overall noise performance is mostly determined by the performance of elements situated at the amplifier input, makers are going to attempt to select low-noise components while designing the amplifier input stage of their cordless loudspeakers.

The wireless broadcast itself also causes noise which is most noticable with products that utilize FM transmission at 900 MHz. The amount of noise is also dependent upon the level of cordless interference from other transmitters. Newer products are going to generally use digital music broadcast at 2.4 GHz or 5.8 GHz. This type of music broadcast provides higher signal-to-noise ratio than analog style transmitters. The amount of static is dependent on the resolution of the analog-to-digital converters in addition to the quality of other parts.

A lot of latest cordless speakers have built-in power amps that include a wattage switching stage that switches at a frequency around 500 kHz. This switching noise may result in a certain level of speaker distortion yet is generally not included in the signal-to-noise ratio which merely considers noise in the range of 20 Hz and 20 kHz.

The signal-to-noise ratio is measured by inputting a 1 kHz test signal 60 dB underneath the full scale and measuring the noise floor of the signal generated by the built-in amplifier. The amplification of the cordless loudspeaker is pair such that the full output wattage of the built-in amp can be realized. Then, the noise floor between 20 Hz and 20 kHz is calculated and the ratio to the full-scale signal computed. The noise signal at other frequencies is eliminated through a bandpass filter throughout this measurement.

Frequently you will find the expression "dBA" or "a-weighted" in your cordless loudspeaker spec sheet. A weighting is a method of expressing the noise floor in a more subjective fashion. In other words, this technique tries to express how the noise is perceived by a human. Human hearing is most sensitive to signals around 1 kHz whereas signals below 50 Hz and above 14 kHz are barely noticed. Thus an A-weighting filter will amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies that are hardly perceived. Many cordless loudspeaker are going to show a higher A-weighted signal-to-noise ratio than the un-weighted ratio.




About the Author:



No comments: