It is easy to be perplexed by the language which cordless speaker manufacturers employ to explain the performance of their products. I will explain the meaning of one usually utilized specification: “signal-to-noise ratio” in order to help you make an informed choice whilst purchasing a brand new a couple of cordless speakers.
While looking for a couple of cordless speakers, you initially are going to check the cost, power amid additional fundamental criteria. Yet, after this initial choice, you are going to still have a number of models to choose from. Next you are going to concentrate more on some of the technical specs, like signal-to-noise ratio in addition to harmonic distortion. The signal-to-noise ratio is a rather essential parameter and shows how much noise or hiss the cordless speaker creates.
One technique in order to perform a straightforward assessment of the noise performance of a couple of wireless outdoor speakers reviewed at amphony.com/products/wireless-speaker.htm is to short circuit the transmitter audio input and then to crank up the cordless loudspeaker to its utmost. Next listen to the speaker. The hiss which you hear is generated by the cordless loudspeaker itself. Next compare different sets of cordless speakers according to the next rule: the smaller the level of noise, the higher the noise performance of the cordless speaker. Though, keep in mind that you should set all sets of wireless loudspeakers to amplify by the same level in order to compare different models. To help you compare the noise performance, cordless loudspeaker makers publish the signal-to-noise ratio in their wireless speaker specification sheets. Simply put, the higher the signal-to-noise ratio, the smaller the amount of noise the wireless speaker generates. There are several reasons why wireless loudspeakers are going to add some form of hiss or other unwanted signal. Transistors and resistors that are part of each modern cordless loudspeaker by nature produce noise. Typically the elements that are situated at the input stage of the built-in power amplifier are going to contribute most to the overall hiss. Therefore makers typically are going to choose low-noise components whilst developing the cordless loudspeaker amplifier input stage.
The cordless broadcast itself also causes hiss which is most noticable with types that use FM transmission at 900 MHz. Other cordless transmitters will interfer with FM type transmitters and bring about additional hiss. Therefore the signal-to-noise ratio of FM type cordless speakers varies depending on the distance of the speakers from the transmitter in addition to the level of interference. To avoid these problems, newer transmitters employ digital audio broadcast and typically transmit at 2.4 GHz or 5.8 GHz. This kind of audio broadcast provides better signal-to-noise ratio than analog style transmitters. The level of noise is dependent on the resolution of the analog-to-digital converters as well as the quality of other components. Many latest wireless speakers have built-in power amps that incorporate a wattage switching stage that switches at a frequency around 500 kHz. This switching frequency is also hiss that is part of the amplified signal. On the other hand, recent wireless speakerspecifications normally only consider the noise between 20 Hz and 20 kHz. The most common technique for measuring the signal-to-noise ratio is to pair the wireless speaker to a gain which permits the maximum output swing. Next a test tone is input into the transmitter. The frequency of this tone is generally 1 kHz. The amplitude of this signal is 60 dB below the full scale signal. Then, only the noise in the range of 20 Hz and 20 kHz is considered. The noise at different frequencies is eliminated via a filter. Next the amount of the noise energy in relation to the full-scale output power is computed and shown in decibel. Time and again the signal-to-noise ratio is expressed in a more subjective method as “dbA” or “A weighted”. This method was developed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most perceptive to signals around 1 kHz. However, signals below 50 Hz and higher than 13 kHz are hardly noticed. The A-weighted signal-to-noise ratio is usually higher than the unweighted ratio and is shown in the majority of wireless speaker spec sheets.
Mobile devices have evolved quite a bit. A lot of cellular phones sold these days are usually smart phones. Most of these mobile phones provide you with loads of functions not found in old mobile phones like the means to store plus play tunes. Ordinarily you’d probably listen to the music kept in your smartphone through the use of some earbuds. Yet, the sound quality of headphones enclosed with mobile phones is generally rather bad. Then again, you may get significantly greater sound quality by sending the tracks to a set of stereo speakers. Here, I will describe a few choices for wirelessly streaming your songs from your mobile phone to a set of loudspeakers. There are actually various options on the market intended for linking loudspeakers to a mobile phone. Bluetooth amplifiers are generally on the list of preferred options with regard to streaming songs from your cell phone. Many of modern cell phones can transmit to these music receivers. That’s because Bluetooth is compatible with many cell phones. The songs that is embedded in the Bluetooth signal is restored by the receiver and output to the stereo speakers. The majority of today’s receivers understand the common standards A2DP as well as AptX. A2DP is certainly the most popular standard to send music by using Bluetooth while AptX is just understood by the most recent generation of mobile phones. An important deliberation over making use of Bluetooth music receivers is the fact that these may just attach to active loudspeakers. Then again you can easily use an audio amplifier. There are also some integrated receivers/amps available on the market. Most of these models do not need a separate audio amplifier plus can easily attach straight to any kind of passive loudspeakers. Bluetooth, though, offers a pretty limited cordless range of around 30 feet and as a result can’t be used for the purpose of transmitting tracks to different areas within the residence. The true range is dependent upon the environment and also on your phone. You may also transmit audio from many other gadgets which support Bluetooth by employing the exact same setup. Airplay may provide improved sound quality as compared with Bluetooth considering that it can send uncompressed music. Then again, usually the music saved on your smartphone is compressed in some fashion. Lots of people keep MP3 compressed audio. If that’s so Airplay will not improve the audio quality over Bluetooth. AptX is a rather recent protocol for the purpose of sending audio via Bluetooth. Several older mobile devices, though, usually do not yet understand AptX.
Bluetooth wireless stereo speakers can be a further alternative designed for playing songs located on a cellular phone. One can find hundreds of designs available. Because Bluetooth loudspeakers frequently do not have similar audio quality as other loudspeakers, it is always a great idea to give them a try prior to your investment. On top of that you really should be certain that any specific type of Bluetooth wireless stereo speakers works with your cellular phone just before your investment.
Music amplifiers are at the very center of each home theater product. As the quality and output power demands of today’s speakers increase, so do the demands of mini audio amplifiers. It is challenging to pick an amplifier given the large range of types and concepts. I will explain some of the most popular amp designs such as “tube amplifiers”, “linear amplifiers”, “class-AB” and “class-D” and also “class-T amplifiers” to help you comprehend some of the terms frequently utilized by amp manufacturers. This article should also help you figure out which topology is best for your precise application. Simply put, the use of an audio amp is to translate a low-power audio signal into a high-power music signal. The high-power signal is large enough to drive a speaker adequately loud. As a way to do that, an amp uses one or several elements that are controlled by the low-power signal to create a large-power signal. These elements range from tubes, bipolar transistors to FET transistors. Tube amplifiers were commonly used a number of decades ago and utilize a vacuum tube that controls a high-voltage signal in accordance to a low-voltage control signal. Regrettably, tube amplifiers have a somewhat high amount of distortion. Technically speaking, tube amplifiers will introduce higher harmonics into the signal. However, this characteristic of tube amps still makes these popular. A lot of people describe tube amplifiers as having a warm sound versus the cold sound of solid state amps.
One disadvantage of tube amps is their low power efficiency. In other words, most of the power consumed by the amplifier is wasted as heat rather than being converted into music. For that reason tube amps will run hot and require adequate cooling. Yet another drawback is the big price tag of tubes. This has put tube amps out of the ballpark for the majority of consumer devices. Consequently, the bulk of audio products today employs solid state amplifiers. I will explain solid state amps in the subsequent paragraphs.
Solid-state amplifiers utilize a semiconductor element, like a bipolar transistor or FET instead of the tube and the earliest type is known as “class-A” amps. In a class-A amplifier, the signal is being amplified by a transistor which is controlled by the low-level audio signal. If you need an ultra-low distortion amplifier then you might wish to investigate class-A amplifiers as they offer amongst the lowest distortion of any audio amplifiers. The major disadvantage is that similar to tube amps class A amps have quite small efficiency. Consequently these amps need big heat sinks to dissipate the wasted energy and are frequently quite heavy.
Class-AB amplifiers improve on the efficiency of class-A amplifiers. They employ a number of transistors to break up the large-level signals into two distinct regions, each of which can be amplified more efficiently. Because of the larger efficiency, class-AB amps do not need the same amount of heat sinks as class-A amps. Therefore they can be made lighter and less expensive. Nonetheless, this topology adds some non-linearity or distortion in the region where the signal switches between those areas. As such class-AB amps normally have larger distortion than class-A amplifiers. Class-D amps improve on the efficiency of class-AB amplifiers even further by employing a switching transistor that is always being switched on or off. Thereby this switching stage hardly dissipates any power and therefore the power efficiency of class-D amps generally surpasses 90%. The switching transistor is being controlled by a pulse-width modulator. The switched large-level signal has to be lowpass filtered to remove the switching signal and recover the audio signal. Due to non-linearities of the pulse-width modulator and the switching transistor itself, class-D amps by nature have amongst the largest audio distortion of any audio amp. More recent audio amps incorporate some kind of means to minimize distortion. One method is to feed back the amplified audio signal to the input of the amp to compare with the original signal. The difference signal is then used in order to correct the switching stage and compensate for the nonlinearity. “Class-T” amps (also called “t-amplifier”) utilize this kind of feedback method and for that reason can be manufactured very small while attaining low audio distortion.
I’ll look at the word “power efficiency” which lets you know just how much wireless loudspeakers waste so that you can select a pair of loudspeakers which are cordless.
A relatively high amount of power is radiated as heat when you get a pair of low-efficiency cordless loudspeakers. This can cause several issues: Low-efficiency wireless loudspeakers are going to squander some power as heat and are more expensive to use when compared with high-efficiency types because of their greater power consumption. To shield the circuit components, low-efficiency cordless loudspeakers need to find methods to remove the heat which is created. Usually extra components must be added in order to radiate adequate power and maintain the ideal working temperature. These components are typically heat sinks and also fans. Heat sinks as well as fans are heavy, consume space and also produce noise. Cordless loudspeakers with low efficiency cannot be put into small spaces or inside sealed enclosures since they demand a great deal of circulation.
Wireless speakers with low efficiency require a bigger power source in order to output the same amount of audio power as high-efficiency types. Further more, the thermal stress on the circuit board elements as well as amplifier materials is more serious and could lessen the dependability.
While shopping for a pair of wireless speakers, you can find the efficiency in the data sheet. This figure is normally shown as a percentage. Class-A amps are amongst the least efficient and provide a efficiency close to 25% only. In contrast, switching amplifiers, often known as “Class-D” amplifiers deliver efficiencies of up to 98%. The larger the efficiency value, the less the level of power wasted as heat. A 100-Watt amplifier having 50% efficiency would have a power usage of 200 W. Yet, there are a few things to note about power efficiency. Firstly, this value is dependent on the level of power that the amp is providing. Every music amplifier is going to use up a specific level of energy irrespective of whether or not it supplies any power to the loudspeaker. That is why the smaller the energy the amplifier provides, the smaller the efficiency. Because of this audio producers usually specify the efficiency for the greatest audio power that the amp can provide. To be able to measure the efficiency, typically a test tone of 1 kHz is fed into the amp and a power resistor attached to the amp output to imitate the speaker load. Next the amplifier output signal is measured and the wattage determined which the amp provides to the load which is subsequently divided by the overall energy the amp consumes. Given that the efficiency will depend on the audio power, generally the output power is varied and an efficiency curve created which is able to display the amplifier efficiency for each level of output power. Cordless loudspeakers that employ switching-mode amps contain a switching stage that will cause some amount of non-linear behavior. Thus wireless loudspeakers that use Class-D amps typically have smaller music fidelity than products utilizing analog Class-A amplifiers. Due to this fact you will need to base your buying decision on whether you require small dimensions and minimal power consumption or highest music fidelity. A number of newer cordless loudspeakers, for example products which have Class-T amplifiers, can reduce music distortion to amounts near to the ones from products using analog music amplifiers and also are able to achieve great signal-to-noise ratio. Selecting one of these kinds of wireless loudspeakers will offer great efficiency and at the same time large music fidelity.
It is easy to be puzzled by the language which cordless speaker manufacturers employ to explain the performance of their products. I am going to clarify the meaning of one commonly used specification: “signal-to-noise ratio” in order to help you make an informed decision while purchasing a new a pair of wireless loudspeakers. As soon as you have chosen a number of wireless loudspeakers, it’s time to explore several of the specifications in more detail in order to help you narrow down your search to one product. Each cordless loudspeaker will make a certain level of hiss and hum. The signal-to-noise ratio will help calculate the level of noise created by the loudspeaker.
You can perform a simple comparison of the cordless loudspeaker hiss by short circuiting the transmitter input, setting the loudspeaker volume to maximum and listening to the loudspeaker. You will hear some amount of hissing and/or hum coming from the loudspeaker. This noise is produced by the wireless speaker itself. Then compare several sets of wireless loudspeakers according to the next rule: the lower the amount of hiss, the higher the noise performance of the wireless loudspeaker. Yet, bear in mind that you have to set all sets of cordless speakers to amplify by the same amount to compare several models. Whilst glancing at the wireless loudspeaker spec sheet, you want to look for a set of wireless loudspeaker with a large signal-to-noise ratio number which suggests that the cordless loudspeakers (Learn regarding wireless outdoor speaker systems) output a small amount of noise. Noise is generated due to a number of factors. One factor is that today’s cordless loudspeakers all utilize elements like transistors as well as resistors. Those elements are going to produce some amount of hiss. Typically the components that are located at the input stage of the built-in power amplifier are going to contribute most to the overall noise. Thus suppliers usually will choose low-noise components whilst developing the cordless speaker amplifier input stage. Noise is also created by the wireless broadcast. Different types of transmitters are available which work at different frequencies. The least expensive sort of transmitters makes use of FM transmission and usually broadcasts at 900 MHz. Other wireless transmitters will interfer with FM type transmitters and result in further static. For that reason the signal-to-noise ratio of FM style cordless loudspeakers varies depending on the distance of the speakers from the transmitter in addition to the level of interference. To steer clear of these problems, modern transmitters make use of digital audio broadcast and generally transmit at 2.4 GHz or 5.8 GHz. The signal-to-noise ratio of digital transmitters is dependent by and large on the kind of analog-to-digital converters and other components that are utilized as well as the resolution of the wireless protocol. The majority of of today’s cordless speaker use amplifiers which are based on a digital switching architecture. These amplifiers are referred to as “class-D” or “class-T” amplifiers. Switching amplifiers incorporate a power stage which is constantly switched at a frequency of around 400 kHz. This switching frequency is also hiss that is part of the amplified signal. Yet, today’s cordless loudspeakerspecifications generally only consider the noise between 20 Hz and 20 kHz. Manufacturers measure the signal-to-noise ratio by means of setting the built-in amplifier such that the full output swing may be realized and by inputting a test signal to the transmitter which is normally 60 dB below the full scale of the loudspeaker amplifier. Next the noise-floor energy is calculated in the frequency range between 20 Hz and 20 kHz and compared with the full scale signal energy.
Often you will find the expression “dBA” or “a-weighted” in your wireless speaker spec sheet. A weighting is a method of showing the noise floor in a more subjective fashion. In other words, this technique attempts to state how the noise is perceived by a human being. Human hearing is most sensitive to signals around 1 kHz while signals under 50 Hz and above 14 kHz are hardly heard. Therefore an A-weighting filter is going to amplify the noise floor for frequencies which are easily perceived and suppress the noise floor at frequencies that are hardly perceived. Most wireless speaker are going to show a larger A-weighted signal-to-noise ratio than the un-weighted ratio. Find even more reading at http://www.necn.com/08/27/13/Sending-a-new-generation-of-kids-off-to-/landing_features.html?blockID=850717.
I’ll take a look at how present day sound transmission systems which are employed in current wireless speakers work in real-world conditions having a great deal of interference from other cordless systems.
The most popular frequency bands which can be used by wireless gadgets include the 900 MHz, 2.4 GHz and 5.8 GHz frequency band. Primarily the 900 MHz and also 2.4 Gigahertz frequency bands have begun to become clogged by the ever increasing amount of devices like wireless speakers, wireless phones and so on.
FM type sound transmitters usually are the least robust when it comes to tolerating interference because the transmission doesn’t have any procedure to deal with competing transmitters. On the other hand, those transmitters use a fairly limited bandwidth and changing channels may often eliminate interference. The 2.4 GHz and 5.8 GHz frequency bands are utilized by digital transmitters and also have become rather congested recently given that digital signals occupy far more bandwidth than analogue transmitters. Simply switching channels, however, is no dependable solution for staying away from certain transmitters that use frequency hopping. Frequency hoppers such as Bluetooth gadgets as well as quite a few cordless telephones will hop throughout the full frequency spectrum. As a result transmission on channels will be disrupted for short bursts of time. For this reason modern audio transmitters incorporate special mechanisms to cope with interfering transmitters to ensure consistent interruption-free audio transmission.
One of these strategies is referred to as forward error correction or FEC in short. The transmitter is going to broadcast additional information besides the sound data. Using this additional data, the receiver may restore the original information even when the signal was corrupted to some extent. FEC is unidirectional. The receiver won’t send back any kind of information to the transmitter. Thus it is frequently employed for products such as radio receivers in which the quantity of receivers is large.
Yet another method utilizes bidirectional transmission, i.e. every receiver transmits information to the transmitter. This approach is only helpful if the number of receivers is small. Additionally, it requires a back channel to the transmitter. The data which is broadcast includes a checksum. Using this checksum the receiver may decide if any specific packet was received correctly and acknowledge. If a packet was corrupted, the receiver will notify the transmitter and request retransmission of the packet. As such, the transmitter needs to store a great amount of packets in a buffer. Likewise, the receiver must have a data buffer. Using buffers will cause a delay or latency in the transmission. The amount of the delay is directly related to the buffer size. A larger buffer size increases the stability of the transmission. A large latency can be a problem for certain applications nonetheless. Particularly if video is present, the sound must be synchronized with the video. Also, in multichannel audio applications where a few speakers are cordless, the speakers for outdoors should be in sync with the corded speakers. Systems which integrate this mechanism, however, are limited to transmitting to a small number of receivers and the receivers consume more power. Often a frequency channel can get occupied by a different transmitter. Preferably the transmitter can understand this fact and change to yet another channel. To accomplish this, a number of wireless speakers continuously monitor which channels are available so that they can instantly switch to a clean channel. Considering that the transmitter lists clean channels, there’s no delay in looking for a clean channel. It’s simply picked from the list. This approach is usually called adaptive frequency hopping spread spectrum.