Some Pointers For Decreasing The Static In Outdoor Cordless Speakers

| Monday, December 9, 2013
By Linda Cullmann


It is easy to be bewildered by the terminology that cordless speaker manufacturers utilize in order to describe the performance of their models. I am going to explain the meaning of a regularly used parameter: "signal-to-noise ratio" in order to help you make an informed choice while buying a brand new a set of wireless speakers.

Once you have chosen a range of cordless speakers, it's time to explore some of the specifications in more detail in order to help you narrow down your search to one product. The signal-to-noise ratio is a fairly vital parameter and shows how much noise or hiss the cordless loudspeaker produces.

You can do a straightforward comparison of the cordless speaker noise by short circuiting the transmitter input, setting the loudspeaker volume to maximum and listening to the loudspeaker. The noise that you hear is generated by the cordless loudspeaker itself. Make sure that the gain of each couple of wireless speakers is pair to the same level. Otherwise you will not be able to objectively compare the amount of static between different models. The general rule is: the smaller the amount of hiss that you hear the better the noise performance.

In order to help you evaluate the noise performance, cordless loudspeaker manufacturers publish the signal-to-noise ratio in their cordless speaker specification sheets. Simply put, the higher the signal-to-noise ratio, the smaller the amount of noise the wireless speaker generates. Noise is created due to a number of factors. One factor is that today's cordless loudspeakers all employ components such as transistors as well as resistors. Those components will create some amount of hiss. As the built-in power amp overall noise performance is mostly determined by the performance of components situated at the amplifier input, makers are going to try to pick low-noise parts while developing the amp input stage of their wireless speakers.

One more cause of hiss is the wireless audio transmission itself. Typically products that make use of FM type broadcast at 900 MHz are going to have a comparatively large amount of hiss. FM transmitters are very prone to wireless interference which is why newer types commonly utilize digital music transmission. The signal-to-noise ratio of digital transmitters is dependent by and large on the type of analog-to-digital converters and other components which are utilized and also the resolution of the cordless protocol.

A lot of recent cordless loudspeakers have built-in power amplifiers that include a power switching stage that switches at a frequency around 500 kHz. As a result, the output signal of wireless speaker switching amps have a fairly big amount of switching noise. This noise component, though, is typically impossible to hear because it is well above 20 kHz. Nonetheless, it can still contribute to speaker distortion. Signal-to-noise ratio is generally only shown within the range of 20 Hz to 20 kHz. Therefore, a lowpass filter is used while measuring cordless speaker amps to eliminate the switching noise.

The most common technique for measuring the signal-to-noise ratio is to couple the wireless loudspeaker to a gain that enables the maximum output swing. After that a test signal is fed into the transmitter. The frequency of this tone is generally 1 kHz. The amplitude of this signal is 60 dB underneath the full scale signal. Subsequently, only the noise in the range of 20 Hz and 20 kHz is considered. The noise at other frequencies is removed by a filter. Next the level of the noise energy in relation to the full-scale output wattage is calculated and expressed in db.

A different convention to express the signal-to-noise ratio employs more subjective terms. These terms are "dBA" or "A weighted". You are going to find these terms in most cordless speaker spec sheets. This method tries to examine in how far the cordless speaker noise is perceived by human hearing which is most responsive to signals at frequencies at 1 kHz. Therefore an A-weighting filter will amplify the noise floor for frequencies which are easily heard and suppress the noise floor at frequencies which are hardly noticed. Many cordless loudspeaker are going to show a higher A-weighted signal-to-noise ratio than the un-weighted ratio.




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Shopping Hints For Stereo Amplifier Products

| Tuesday, December 3, 2013
By Mike Heller


I will look at a number of audio amplifiers and explain some basic vocabulary to help you choose the best amp for your speakers

It is tricky to pick the perfect audio amplifier as a consequence of the large amount of types. All of these models have different specs. They are based on different technologies and come in all kinds of shapes and sizes. However, you don't have to be a specialist to pick the perfect type. By following some fundamental rules you won't regret your purchasing decision.

The huge majority of today's audio amplifiers are solid state amplifiers versus more traditional tube amplifiers. Tube amps have been dominant a decade or so ago. Tube amplifiers, however, have a relatively high amount of harmonic distortion. Harmonic distortion refers to how much the audio signal is degraded whilst being amplified. This term is frequently used while comparing the audio quality of amps.

Tube amplifiers will have audio distortion of up to 10%. Solid state amplifiers will have less audio distortion depending on the amplifier technology that is employed. The most conventional amplifiers utilize a "Class-A" and "Class-AB" technology. These amps are also called "analog amplifiers". Whereas amplifiers utilizing these technologies generally have low audio distortion, power efficiency is merely 10% to 30%. Power efficiency describes how much of the electrical power is utilized to amplify the audio as opposed to being wasted as heat. Amps with low power efficiency will require quite big heat sinks since the majority of the power is radiated.

"Class-D" amplifiers, however, which are also referred to as "digital amplifiers" have a power efficiency of at the least 80% and are smaller and have a smaller power supply than comparable analog amplifiers. The tradeoff is that digital amps regularly have higher audio distortion than analog amplifiers. This is for the most part a consequence of the switching distortion of the output power stage. Most recent digital audio amplifiers, on the other hand, employ a feedback mechanism and can reduce the audio distortion to below 0.05%.

In contrast, "Class-D" amplifiers which are also named "digital amplifiers" have a power efficiency of normally 80 to 90%. This allows the amplifier and power supply to be made a great deal smaller than analog amplifiers. The downside is that digital amps often have larger audio distortion than analog amplifiers. This is mostly a consequence of the switching distortion of the output power stage. Newest digital audio amplifiers, on the other hand, make use of a feedback mechanism and can minimize the audio distortion to below 0.05%. When choosing an amp, ensure that the output power is adequate to drive your speakers. The required power will be determined by how much power your loudspeakers can tolerate as well as the size of your room where you will be listening. Speaker power handling capability is specified as peak power and average power. The peak power value refers to how much power the speaker can handle for a short period of time whereas the average power handling value denotes how much power you can drive the speaker at continuously without damage.

If you have a fairly small listening environment then 20 to 50 Watts of power should be sufficient while your loudspeaker might be rated for 100 Watts or more. Low-impedance loudspeakers generally offer high sensitivity and are easier to drive to high volume than high-impedance speakers. Not all amplifiers can drive every speaker impedance. Find out the impedance of your speaker which is given in Ohms. Then look at your amplifier manual to guarantee that your amp can drive this impedance.

Last but not least, make sure that your amp introduces little noise and has a broad enough frequency response. High-quality amps will have a signal-to-noise ratio of at least 100 dB and a frequency response of at least 20 Hz to 20 kHz.




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