Is the Sound Quality of Wireless Speakers Good Enough for High-end Applications?

When setting up speakers, you may not be able to run speaker cables to the space that you want to set up your speaker in. Wireless speakers promise to solve the speaker cable problem. They can be set up virtually anywhere without the hassle of running speaker cable.

Many people hesitate when buying wireless speakers since they may not be able to match the sound quality as corded models. In this article, I will investigate whether modern wireless speakers have improved on the inferior sound quality of classic models. Wireless speakers integrate a number of components.

These components all affect the speaker sound quality. Only if all of these components are designed well will the wireless speaker have optimum sound quality. The sound quality of the speaker can only be as good as the quality of the wireless signal.

Older transmission methods would use FM which causes hissing and popping of the speaker depending on the distance between transmitter and speaker as well as the presence of interference. Today's wireless transmitters use a different approach. Prior to transmission, the audio is sampled and converted to a data stream.

This data stream is then sent via radio signal. Not only does digital wireless audio achieve CD-quality audio fidelity but it also has advanced methods for dealing with radio interference. The audio fidelity of the internal power amplifier also has a large impact on the speaker sound quality.

Linear and switched-mode (Class-D) amplifiers have quite different operating principles. In order to provide a low output impedance, a linear amplifier has a power-transistor stage which typically consists of two complementary power transistors. These transistors are driven by an analog audio voltage.

The amplified signal is proportional to the original audio signal. This operating principle, however, has fairly low power efficiency. The power stage of Class-D amps also has two complementary transistors.

Typically MOSFET transistors are used for this stage. Class-D switch this power stage to both voltage rails and thereby generate a square wave voltage. This square wave output voltage contains several spectral components.

The main energy is located around the switching frequency. This switching component which is usually located between 300 and 800 kHz is filtered by a subsequent low-pass stage. The operating principle of Class-D amplifiers is non-linear.

The pulse-width encoder as well as the switching stage cause harmonic audio distortion. Newer amplifiers, however, continue to minimize the amount of harmonic distortion. Newer types of Class-D amplifiers compare the amplified audio signal with the original audio signal and are able to compensate for offsets and thereby lower the harmonic distortion of the amplified signal.

This feedback mechanism, however, is sometimes overdone. The result is an audio amplifier with ultra-low audio distortion. However, in listening tests this amplifier won't sound as good as another amplifier with regular distortion.

The enclosure of the speaker itself as well as the woofer and tweeter are critical for a good-quality speaker. Poorly designed speaker enclosures are often causing poor sound quality. Similarly, having good-quality transducers is key when it comes to making a good speaker.

Designing a wireless speaker poses some challenges. The speaker needs to integrate a power supply, power amplifier and wireless circuit. All of these components will affect the sound waves inside the speaker.

These parts are usually fairly large. Therefore they will impact the air volume of the speaker. Also, sound waves will bounce off these components and possibly cause rattling which will impact the sound.

Wireless speaker enclosure designers don't just have to worry about maximizing the sound quality. In addition, they need to worry about how to place all of the internal parts and also how to allow access to the electronic controls and indicators. All of these parameters will have an affect on the speaker sound.

While some models of wireless speakers finally are starting to emerge which have a sound quality that comes close to corded speakers, there still is room for improvement.