Thursday 12 December 2013

Uncovering The Truth About Recent Wireless Loudspeakers

By Michelle Finger


When buying a new set of cordless speakers, you probably will take a look at the technical features. An often found spec is the frequency response. This parameter while important isn't going to tell the full story regarding how good the speakers will sound. To help you make a more intelligent buying decision, I am going to make clear what this specification means and how to interpret it. This hopefully is going to guarantee you'll get the best cordless speakers for your project.

Wireless loudspeakers are meant to transmit and the reproduce an audio signal to moderate or higher volume level. Manufacturers generally present the frequency range over which the wireless speakers work. If the frequency range is 20 Hz to 20 kHz as an example, the wireless speakers could transmit any signals with a frequency greater than 20 Hz and lower than 20 kHz. You might think the greater the frequency response the higher quality the wireless loudspeakers. That, on the other hand, may not necessarily be the case. You have to check out the specs far more carefully so that you can adequately interpret these.

The truth is, a set of wireless loudspeakers which has a frequency response from 10 Hz to 30 kHz might actually have much worse sound quality than a set that has a frequency response from 20 Hz to 15 kHz. Different suppliers seem to utilize different ways in order to establish frequency response. The most widely used method is to describe the frequency response as the frequency range within which the cordless loudspeakers will have quite constant sound pressure level having a highest decrease of 3 decibel (dB). Generally the drop in sound pressure level is greatest at the lower and upper frequency.

To better understand the frequency response behavior of a certain model, you should attempt to figure out under which conditions the response was determined. You might find this data in the data sheet of the cordless loudspeakers. However, a lot of manufacturers won't show those in which case you might need to get in touch with the manufacturer directly. The fact is that many amplifiers which are incorporated into the wireless speakers will work differently with different loudspeaker loads. This is due to the fact that various speaker loads will cause changes to the behavior of the output power stage of the amplifier.

This change is most obvious with many wireless loudspeakers that use digital amplifiers, generally known as Class-D amplifiers. Class-D amplifiers have a lowpass filter inside their output to reduce the switching components which are produced by the internal power FETs. The lowpass filter characteristic, on the other hand, greatly varies according to the connected speaker load.

A number of amplifiers include feedback in order to compensate for changes in gain because of different connected loads. Another strategy is to provide dedicated outputs for different loudspeaker driver impedances that are connected to the amp power phase by way of audio transformers.




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