Mechanics Hate Us

Multi-channel audio has become mainstream and manufacturers have come up with many types of basic and more advanced technologies like wireless surround speakers, virtual surround sound to simplify the installation of home theater products. I will review the latest trends to understand which devices really work. I will also give some guidance for choosing the best components.

Historically, setting up a TV would be speedy since they would already provide built-in stereo speakers. This, though, has all changed with multi-channel sound. These days external speakers are used to create a surround sound effect. The most commonly used 5.1 surround sound format requires installing a total of 6 loudspeakers. These are one center speaker, two front side speakers, two rear speakers and a subwoofer. The more recent 7.1 standard increases this number to 8 by adding two extra side speakers.

As a result, home theater setups have turn out to be fairly complicated. Running cables to remote loudspeakers also is often undesirable because of aesthetic reasons. A number of technologies have emerged to simplify this procedure.

The first approach is building so-called virtual speakers by applying signal-processing to the audio and introducing phase shifts and special cues to those audio components that would ordinarily be broadcast by the remote loudspeakers. The signal processing is engineered based on how the human hearing determines the location of a sound. The audio signal is then broadcast by the front loudspeakers. Due to the signal processing, the viewer is deceived into thinking the sound is originating from virtual remote surround speakers.

Virtual surround eliminates the remote speakers and simplifies the setup and also avoids long speaker cord runs. On the other hand, it also has a drawback. The form of each human’s ear is slightly dissimilar. For that reason everybody processes sound in a different way. The signal processing is based on measurements which are done using a standard human ear model. If the shape of the ear changes, sound will travel differently. For that reason virtual surround will not function equally well for every person.

One more method for simplifying home theater setups and avoiding long speaker cord runs is to employ wireless surround sound devices or wireless speakers. A wireless solution will normally incorporate a transmitter module that connects to the TV or source and wireless amplifiers that will be connected to the remote loudspeakers. The transmitter will normally have amplified speaker inputs as well as line-level inputs and come with a volume control to adjust it to the source audio level.

Some wireless speaker products are designed to connect 2 loudspeakers per wireless amplifier. A better solution would provide a wireless amplifier for each remote speaker to avoid the cord runs between each of the 2 remote loudspeakers. The most basic wireless systems utilize FM transmission. FM transmission is susceptible to noise and audio distortion. More sophisticated devices make use of digital audio transmission to completely preserve the original audio. To make certain that all speakers are in sync in a multi-channel application, make certain that you pick a wireless system that has an audio latency of just a few milliseconds at most. If the latency is higher than 10 ms then there will be an echo effect which will deteriorate the surround sound. Wireless kits frequently use the 900 MHz or 2.4 GHz frequency band. Some products also use the 5.8 GHz band. These products have less competition from other wireless gadgets than products utilizing the crowded 900 MHz or 2.4 GHz bands.

Another solution are side-reflecting speakers. These kits are also known as sound bars. There are additional loudspeakers positioned at the front which broadcast the sound for the remote loudspeakers from the front at an angle. The audio is then reflected by walls and seems to be coming from besides or behind the viewer. The effect by and large depends on the shape of the room and interior design and not work well in a lot of real-world scenarios due to different room shapes and obstacles in the room.

Latest wireless audio gadgets such as iPods, wireless headphones and cell phones support latest wireless protocols. These protocols are supposed to cut the cord and deliver perfect high-fidelity audio. We will look at some of the newest devices to discover which applications they work for.

These devices fall into 2 categories. The first category of products already has wireless built in. Second-category products, including a few streaming audio products, have optional wireless capability. Normally they have a slot to add a wireless LAN card. Latest generation iPods and cell phones already come with built-in WiFi and Bluetooth support.

The Bluetooth protocol is a relatively low-cost solution. Yet, its limitations have an influence on high-quality audio applications and are often overlooked.

1) Inadequate operating range

Bluetooth devices typically merely have a 30-foot range which confines Bluetooth to single-room applications.

2) Audio compression because of restricted data rate

Bluetooth offers a maximum reliable data rate of roughly 1 Mbps only. This rate is not large enough to send uncompressed CD-quality audio. Consequently Bluetooth wireless devices use audio compression. This is less critical though for compressed audio such as MP3 audio but excludes Bluetooth from use in high-quality audio applications.

3) Signal latency

As a consequence of audio compression, Bluetooth will introduce a signal delay of no less than 10 ms which will cause the audio to be somewhat out of sync in case of video and real-time applications. This is again less of a dilemma for MP3 players.

4) No multiple headphone support

Bluetooth cannot stream to numerous headphones at the same time. This may be a problem in cases where a number of people like to listen to the same Bluetooth transmitter.

Uncompressed audio streaming is supported by WiFi. WiFi is a very common protocol. Yet, WiFi also has limitations in regard to simultaneous transmission to a number of receivers. Because of the fairly high power consumption it is rarely used in wireless headphones though. WiFi is suitable for streaming audio from a PC however because nearly all PCs have WiFi access.

Wireless speakers and wireless amplifier products for home theater speakers typically utilize their own proprietary protocol. Entry-level wireless headphones and speakers generally still utilize FM transmission which offers low cost but is prone to noise and audio degradation.

More recent wireless audio protocols are based on digital transmission. This avoids audio degradation. A number of protocols also incorporate error correction to cope with interference from other wireless products.

Newest-generation wireless amplifiers permit streaming to an infinite number of receivers and support uncompressed audio transmission.

The audio latency ranges from below 1 ms to up to 20 ms. A small latency is vital for wireless surround sound applications. These wireless audio transmitters typically work at 2.4 GHz. There are also some devices such as Amphony’s line of wireless audio devices which work at 5.8 GHz. Products that work at 5.8 GHz have less competition from other wireless devices than those using the crowded 2.4 GHz frequency band.

Wireless amplifiers are available with different levels of audio quality, power consumption and standby power. Getting a high-quality low-distortion amplifier is vital for good sound quality. Wireless Class-D amplifiers typically have standby power of 5 Watts or less and a power efficiency of larger than 80% but sometimes high audio distortion. It is vital to select a wireless amplifier with low audio distortion. This will guarantee good sound quality. High-quality amplifiers have audio distortion of 0.05% or less.

Multi-channel audio has become mainstream and manufacturers have come up with many types of basic and more advanced technologies like wireless surround speakers, virtual surround sound to simplify the installation of home theater products. I will review the latest trends to understand which devices really work. I will also give some guidance for choosing the best components.

Historically, setting up a TV would be speedy since they would already provide built-in stereo speakers. This, though, has all changed with multi-channel sound. These days external speakers are used to create a surround sound effect. The most commonly used 5.1 surround sound format requires installing a total of 6 loudspeakers. These are one center speaker, two front side speakers, two rear speakers and a subwoofer. The more recent 7.1 standard increases this number to 8 by adding two extra side speakers.

As a result, home theater setups have turn out to be fairly complicated. Running cables to remote loudspeakers also is often undesirable because of aesthetic reasons. A number of technologies have emerged to simplify this procedure.

The first approach is building so-called virtual speakers by applying signal-processing to the audio and introducing phase shifts and special cues to those audio components that would ordinarily be broadcast by the remote loudspeakers. The signal processing is engineered based on how the human hearing determines the location of a sound. The audio signal is then broadcast by the front loudspeakers. Due to the signal processing, the viewer is deceived into thinking the sound is originating from virtual remote surround speakers.

Virtual surround eliminates the remote speakers and simplifies the setup and also avoids long speaker cord runs. On the other hand, it also has a drawback. The form of each human’s ear is slightly dissimilar. For that reason everybody processes sound in a different way. The signal processing is based on measurements which are done using a standard human ear model. If the shape of the ear changes, sound will travel differently. For that reason virtual surround will not function equally well for every person.

One more method for simplifying home theater setups and avoiding long speaker cord runs is to employ wireless surround sound devices or wireless speakers. A wireless solution will normally incorporate a transmitter module that connects to the TV or source and wireless amplifiers that will be connected to the remote loudspeakers. The transmitter will normally have amplified speaker inputs as well as line-level inputs and come with a volume control to adjust it to the source audio level.

Some wireless speaker products are designed to connect 2 loudspeakers per wireless amplifier. A better solution would provide a wireless amplifier for each remote speaker to avoid the cord runs between each of the 2 remote loudspeakers. The most basic wireless systems utilize FM transmission. FM transmission is susceptible to noise and audio distortion. More sophisticated devices make use of digital audio transmission to completely preserve the original audio. To make certain that all speakers are in sync in a multi-channel application, make certain that you pick a wireless system that has an audio latency of just a few milliseconds at most. If the latency is higher than 10 ms then there will be an echo effect which will deteriorate the surround sound. Wireless kits frequently use the 900 MHz or 2.4 GHz frequency band. Some products also use the 5.8 GHz band. These products have less competition from other wireless gadgets than products utilizing the crowded 900 MHz or 2.4 GHz bands.

Another solution are side-reflecting speakers. These kits are also known as sound bars. There are additional loudspeakers positioned at the front which broadcast the sound for the remote loudspeakers from the front at an angle. The audio is then reflected by walls and seems to be coming from besides or behind the viewer. The effect by and large depends on the shape of the room and interior design and not work well in a lot of real-world scenarios due to different room shapes and obstacles in the room.

Latest wireless audio gadgets such as iPods, wireless headphones and cell phones support latest wireless protocols. These protocols are supposed to cut the cord and deliver perfect high-fidelity audio. We will look at some of the newest devices to discover which applications they work for.

These devices fall into 2 categories. The first category of products already has wireless built in. Second-category products, including a few streaming audio products, have optional wireless capability. Normally they have a slot to add a wireless LAN card. Latest generation iPods and cell phones already come with built-in WiFi and Bluetooth support.

The Bluetooth protocol is a relatively low-cost solution. Yet, its limitations have an influence on high-quality audio applications and are often overlooked.

1) Inadequate operating range

Bluetooth devices typically merely have a 30-foot range which confines Bluetooth to single-room applications.

2) Audio compression because of restricted data rate

Bluetooth offers a maximum reliable data rate of roughly 1 Mbps only. This rate is not large enough to send uncompressed CD-quality audio. Consequently Bluetooth wireless devices use audio compression. This is less critical though for compressed audio such as MP3 audio but excludes Bluetooth from use in high-quality audio applications.

3) Signal latency

As a consequence of audio compression, Bluetooth will introduce a signal delay of no less than 10 ms which will cause the audio to be somewhat out of sync in case of video and real-time applications. This is again less of a dilemma for MP3 players.

4) No multiple headphone support

Bluetooth cannot stream to numerous headphones at the same time. This may be a problem in cases where a number of people like to listen to the same Bluetooth transmitter.

Uncompressed audio streaming is supported by WiFi. WiFi is a very common protocol. Yet, WiFi also has limitations in regard to simultaneous transmission to a number of receivers. Because of the fairly high power consumption it is rarely used in wireless headphones though. WiFi is suitable for streaming audio from a PC however because nearly all PCs have WiFi access.

Wireless speakers and wireless amplifier products for home theater speakers typically utilize their own proprietary protocol. Entry-level wireless headphones and speakers generally still utilize FM transmission which offers low cost but is prone to noise and audio degradation.

More recent wireless audio protocols are based on digital transmission. This avoids audio degradation. A number of protocols also incorporate error correction to cope with interference from other wireless products.

Newest-generation wireless amplifiers permit streaming to an infinite number of receivers and support uncompressed audio transmission.

The audio latency ranges from below 1 ms to up to 20 ms. A small latency is vital for wireless surround sound applications. These wireless audio transmitters typically work at 2.4 GHz. There are also some devices such as Amphony’s line of wireless audio devices which work at 5.8 GHz. Products that work at 5.8 GHz have less competition from other wireless devices than those using the crowded 2.4 GHz frequency band.

Wireless amplifiers are available with different levels of audio quality, power consumption and standby power. Getting a high-quality low-distortion amplifier is vital for good sound quality. Wireless Class-D amplifiers typically have standby power of 5 Watts or less and a power efficiency of larger than 80% but sometimes high audio distortion. It is vital to select a wireless amplifier with low audio distortion. This will guarantee good sound quality. High-quality amplifiers have audio distortion of 0.05% or less.