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Introduction

In an increasingly wireless world, home audio is one of the last holdouts for physical cabling. A typical

home theater system may require as many as eight speaker cables, each of which has to be run

somehow from the source to the speaker. The practical advantages of replacing the copper rat’s nest with

a wireless solution should be obvious to anyone who has ever had to pull speaker cable through an attic,

under a floor or through walls. However, up until now, wireless home audio has not delivered the HD

audio quality consumers demand. This is about to change.

The WiSA™ (Wireless Speaker and Audio) Association, established in 2011, fosters a new quality and

interoperability standard for the wireless transmission of HD audio in a home entertainment environment.

Created by a group comprised of industry leaders from across the home theater ecosystem, the

association’s main charter is to certify interoperability between WiSA-compliant transmitters, such as

DTVs, set top boxes, and Blu-ray players, with receivers, comprising home theater speakers from many

brands.

WiSA compliance starts with a common wireless speaker technology that provides high-reliability, high-

fidelity surround audio via the U-NII frequency spectrum for an interference-free HD audio experience of

exceptional quality. To ensure that every consumer gets an easy-to-use, high quality experience in their

system regardless of their purchasing decision, WiSA testing makes sure that every conforming piece of

equipment, regardless of brand, interoperates without degrading the quality promised by the underlying

technology. These are the subjects of this white paper.

The WiSA logo on equipment stands for great audio quality, high reliability, ease of setup, scalability, and

global interoperability with no compromises.

WiSA System Standards

With speaker cables, consumers have simple and realistic expectations. They expect the sound to come

out of the speaker with the best quality afforded by the content and the investment in their equipment.

Once connected correctly, speaker cables only cause sound interruptions or noise when they have worn

out – and certainly only once in a lifetime. Except in extreme circumstances, a speaker cable can connect

equipment from any brand to speakers from any number of brands. Brands can even be mixed and

matched. Speaker cable problems can be diagnosed just by looking at them. Wire is conceptually simple.

Introducing wireless connectivity necessarily introduces complexity. Quality now relates to abstract

concepts such as bandwidth, sample rate, and format – terms previously reserved for media distribution.

Reliability depends on ethereal radio concepts – power, frequency bands, interference, and error

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Transmitter

Speaker Receivers

No Wires!

handling. Adding new speakers involves networking concepts such as discovery, addressing, and

protocol. These concepts must all be brought in line with what consumers expect in order to gain adoption

for the wireless approach.

On the other hand, wires cause a major inconvenience.

With wires, the user has to dig around behind

equipment, try to get the wires into those clips or

binding posts without falling out, place the wires into the

correct channels, and set the correct phases.

Furthermore, the speaker wires must be routed to the

speakers. Many times, consumers run the wires across

the floor, under rugs, or over doorways. Those with

more money or energy work the wires through the walls,

in ceilings, or under floors. Once the wires are run, the

possible speaker locations dictated by wire placement

become a significant factor in placing and rearranging

furniture.

With wireless, all of the disadvantages of wires

disappear. The speakers need only be placed in the

room, with each one approximately in the right place.

The speakers assign themselves to the correct channel.

Phase is correct from the factory. When it is time to

rearrange the room, the speakers can simply be moved

with the furniture.

To summarize, consumers demand that wireless audio must sound great, perform without pops, clicks,

hiss or other distracting artifacts, scale to larger (or smaller) systems, and be interoperable across brands.

As a bonus, wireless is easy to set up and reconfigure.

Great Sound

The quality of speaker wire is a matter of diameter based on the power to be delivered over a given

length. Salespeople are generally well trained in helping consumers with this choice. Even if these

parameters aren’t quite met, the resulting sound will have decent fidelity.

Analog wireless is plagued by serious hiss, hum, and squelching artifacts, and has only succeeded in

high-end professional systems. Good wireless speakers systems were only a dream at that point. Digital

systems are able to perform exact error correction for small problems, and with larger problems, can

conceal them so well that it’s very hard if not impossible to notice. All new wireless audio systems are

digital.

Now that the digital decision is made, how the digital data will be used becomes an issue that depends on

power, bandwidth, cost, and complexity. The digital wireless game starts with frequency bands, each of

which has legislated power and bandwidth limits. Furthermore, those bands are generally shared with

other traffic (as is the case with WiFi and Bluetooth bands), further restricting bandwidth availability. There

is little room left for audio data. To ensure some level of robustness, digital wireless audio systems

compromise by reducing the sample rate or performing compression, both of which reduce quality.

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High-quality Stereo MP3

Stereo CD Audio (> 6x)

Stereo HD Audio (> 18x)

WiSA compliance ensures

great sound for home theater

and live performance.

Relative Quality

Reducing the sample rate rolls off high frequencies, making the content sound muffled. Compression

effects the sound two ways: it introduces artifacts such as hissing or ticking and it introduces latency. The

better the compression the more complex it becomes. With increased complexity comes increased

computation (cost) to compress and decompress the signal. This induces latency in the system that can

cause lip sync problems or frustrate game players. Furthermore, if the latency is variable, then related

content playing to multiple speakers could arrive at a different time, ruining the surround experience.

To be sure, audio has different requirements than information networks because of its persistent desire

for constant delivery. Information networks are generally built for the highest possible bandwidth, but not

for constant delivery. Maximum bandwidth is achieved by allowing a content stream to proceed with

minimum interruptions for however long it takes. One of these long bursts could continue for many

milliseconds, causing interruptions in audio data. To cover up these interruptions, audio is delivered in

similar long bursts, but large bursts take a long time to play. The amount of latency introduced depends

on how long the audio must wait for its turn.

To succeed, wireless sound quality should match the content for best

reproduction regardless of media, and this is where WiSA compliance

draws a line:

24-bit uncompressed audio – HD Audio quality, perceptibly 50%

better than CDs

Sample rate that matches the content: 32, 44.1, 48, and 96k

samples/sec – Realistic sound, 2 times better than CDs, HD

Audio quality

Rapid error detection and recovery – smooth, uninterrupted

sound

5 ms fixed latency – perfect lip synch and game response

Under 160ns speaker-to-speaker delay – theatre quality

surround experience

Amplifiers and speakers matched and balanced as a unit –

same quality sound in all directions

An interesting note is that wireless increases fidelity over wired speakers because a wireless speaker

must have an integrated amplifier. This means that the wireless amplifier and speaker drivers are

matched, equalized, and phase-matched by design. With wired speakers, the (pre)amplifier must

compensate for speaker power and frequency response. This also means that less expensive wireless

speakers can have better quality than even superior wired speakers.

That a WiSA-compliant system operates with such high quality makes no difference to how content is

used. Uncompressed audio is a universal format that is independent of the kind of music played. Network

audio, MP3, Dolby Digital™, DTS™, CDs and other formats are played through a WiSA-compliant system

with the best possible fidelity. In fact, uncompressed audio is future-proof because new audio coding

approaches can always be converted seamlessly to the uncompressed format with true fidelity.

Robust Performance

Wired speakers are completely robust; however, wireless audio systems must take special care to meet

this important customer challenge. Wireless has the reputation for adding annoying artifacts such as

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drops, pops, clicks, hisses, and the like. To reverse this trend, WiSA compliance ensures that these

artifacts are eliminated.

When it comes to improving wireless quality, the best defense is a good offence. WiSA audio avoids the

popular digital audio frequencies used by WiFi, Bluetooth, baby monitors, and microwave ovens. A set of

frequencies have been opened up within the international unlicensed (U-NII) 5 GHz radio band that

require Dynamic Frequency Selection (DFS) procedures. These frequencies were historically reserved for

weather and military radar applications, but have recently become available as long as conflicts with

these important functions are avoided. A WiSA compliant transmitter goes one step further and does its

best to find a totally unoccupied channel. Further, it also looks ahead for another unoccupied channel, so

in case of interference, it can jump directly to that channel without losing a single bit of audio information.

The UNII Band

The DFS channels from 52-140 go mostly unused, leaving plenty of quality space for wireless audio

shown on DFS channel 56. 5GHz 802.11nWiFi traffic is shown on channels 40-48 and 153-161.

The transmitter is looking ahead to find the next DFS channel for it to occupy.

Because the nature of 5 GHz radio and strict DFS requirements, DFS frequencies are seldom used, and

the U-NII band has up to 24 available channels, leaving plenty of room for all of the neighbors. By working

in a clean radio band and using it to its fullest, almost all of the reliability problems with wireless

communications are avoided. As a bonus, WiSA-compliant audio will not interfere with existing networks –

no degradation of WiFi performance is experienced.

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Because of wide available bandwidth and fewer errors due to interference, low-latency and economical

approaches to quality can be exercised. In case of inevitable communication errors, the system falls back

on tried-and-true recovery methods, such as those used on CDs:

Forward error correction – extra data is sent to make 100% repairs

Error concealment – missing (uncorrected) data is filled in a way that is unnoticeable.

Play-out buffer – allows longer concealment ability

Silence – avoid noisy artifacts at all cost

All WiSA compliant components are all tested in to ensure clean communications within a 30x30 foot

(10x10m) area even when interference is present. Frequency selection and correction must operate

quickly and free of noise.

Easy Setup and Optimization

WiSA compliant ensures that components are simply easy to set-up. Just position the speakers

conveniently in the room, then plug-in the transmitter unit (TV, disc player, game console, AV Receiver)

and the speakers into mains power. If the speaker positions need to change, then they can simply be

moved. There are no speaker cables, connection, or speaker-amplifier matching to do.

Channels (e.g. Front, surround, rear, right, left, center) are assigned to speakers either automatically or

by selection on a screen. This is the same for letting the system know the locations of the speakers.

In less expensive systems, selection is done visually by using an on-screen display (OSD) or using a

mobile app as shown below:

The speakers are simply dragged to the

correct relative positions in the room to

assign channels and determine the

distance between speakers. From there,

the components correct for volume and

the delay in the room.

The listener position can even be

changed by dragging (e.g. from the left

to right side of the couch) and the

system instantly adapts by again

changing the volume and delay for all of

the speakers.

For more fully-featured speakers, the automatic approach involves the use of ultrasonic transducers

(“pingers”), for which WiSA compliance has a provision for correct interoperability over the entire room

size. Each speaker contains a pinger and from one speaker, the distances are measured to all of the

other speakers, much like the way whales, dolphins, and bats locate things. This serves the purpose of

automatically mapping the locations of the speakers and their channel assignments just by turning on the

system.

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Note that the transmitter never contains a

pinger and can support both manual and

automatic approaches, making WiSA

compliant transmitters universal and low-cost.

Listener location can still be changed

manually, and the OSD or app shows the

automatically derived positions from the

pingers. With the addition of another pinger to

a WiSA compliant remote control, the listener

position is determined automatically with the

touch of a button.

Scalability

WiSA compliance ensures interoperability among transmitter and speaker brands. This is particularly

important when it comes to scaling. When a customer buys their initial system, they may simply get a

sound bar and possibly a subwoofer bundled with a

TV. Later on, as they get comfortable with their

home theatre setup and want more capability, they

buy a set of surround speakers. They may move

the system to another room or house, and can use

front speakers. They then realize that they have

access to 6.1 or 7.1 titles and want to take maximum

advantage and buy rear speakers and possibly a

WiSA compliant AV receiver with a 7.1 decoder.

A child could move out of the house and the basic

system given to them, replaced with higher quality

components for the now-missing pieces.

Consumers’ decisions might be made due to features, quality, cost, or even color. The important point is

that they have choices as they expand their system and are not limited to the decisions made by a single

brand. To achieve this, the WiSA certification and testing programs ensures that all brands interact

correctly.

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Global Interoperation

The WiSA Association’s mission is to ensure that the consumer gets the best possible experience from

their wireless speaker system purchases. This means that the consumer can have choices, return and

improve their system, have a great out-of-the-box experience, and be comforted that their decision to go

wireless was a good one.

To do this, the WiSA Association produces a Certification and Test Suite (CTS) to which all equipment

that bears the WiSA logo complies. The CTS specifically tests interoperation of all of the features

described above for both transmitters and receivers. Simplay® Labs, LLC (the same experienced

company that tests HDMI compliance) has been selected to provide WiSA compliance testing world-wide.

As part of testing, they will also test equipment for compatibility to other equipment already on the market.

To help vendors (ODMs, OEMs, and brands) develop products that can pass the CTS, the WiSA

Association also provides not only the CTS to its members, but also white papers, application notes, and

reference designs. The CTS environment can be reproduced in-house to ensure best success for final

testing.

Conclusion

WiSA compliance offers a compelling value proposition in home audio, home theater, and DTV

applications centered on the consumer experience. It ensures that wireless audio offers performance and

reliability on a par with legacy wired connections. From a usability standpoint, it allows for simple system

set-up and configuration, eliminating a significant barrier to home theater adoption and making 5.1 and

7.1 surround audio easy for consumers to adopt.

Most importantly, when the consumer sees the WiSA Logo, they are ensured that their wireless speakers

are as universal as connecting speakers with speaker wire. Any choice of source equipment – either type

or brand – can be mixed and matched with speakers from any brand. This is done without compromising,

rather improving upon the wired speaker experience.

For more information, please visit www.wisaassociation.org

1140 East Arques Ave, Suite 500 Sunnyvale, CA 94085 1-866-651-1764 www.wisaassociation.org © 2011 WiSA, LLC. All rights reserved. Descriptions and specifications contained in this document are subject to change without notice and may differ from country to country. WiSA and the WiSA logo are a trademark, registered trademark or service mark of WiSA, LLC in the United States and/or other countries. All other trademarks and registered trademarks are the property of their respective owners in the United States and/or other countries. Product specifications are subject to change without notice. 12/2011.