There are bluetooth speakers. You may have heard Sonos. You may know Alexa and Google Home does multi-room music. How about Airplay 2 or Chromecast? All these are related to multi-room wireless music technology. These are not just special speakers rather these are ecosystem of its own analogous to Apple vs. Google vs. Amazon.
In order to understand wireless multi-room speaker(s), let’s take a look at what makes speaker a wireless and Multiroom, one at a time.
Wireless
Wireless part of these speaker means they connect to music source wirelessly via bluetooth, Wifi, Airplay, or chrome-cast i.e. wireless technology. The speaker itself usually have power code but other than that all other input/output are optional.
This is not a new category of speaker. For example, Airplay technology was introduced almost 10 years ago, which allowed Airplay compatible speakers to connect to Apple devices wirelessly and stream music from one’s iPhone/iPad or Mac computer.
In a big picture, local consumer eletronic wireless connection technology divides into two major protocols: bluetooth or Wifi.
*Cellular network for your cellphone is not applicable here because its not a local network/wireless connection technology.
Bluetooth
Bluetooth is a short distant wireless connection technology with relatively limited bandwidth (data transfer capacity). Older but more prevalent version of Bluetooth technology has bandwidth limitation that does not even allow CD quality music data transfer rate.
However, newer protocols like AptX HD allows Hi-Res audio transfer up to 24-bit/48kHz.
Wi-Fi
WiFi connection is prevalent as it is the technology that we use for home wireless network. This technology have much higher bandwidth. This is the technology allowing us to stream multiple 4K movies simultaneously. With this technology, Hi-Res music can be transferred without any loss of data.
Another advantage of Wi-Fi is much longer range of signal so your device such as phone does not need to be too close to the target speaker.
Apple has own Wi-Fi connection protocol, Airplay. Chromecast is Google’s Wifi connection protocol. In the world of wireless multiroom audio, each brand have their own Wi-Fi connection protocols.
Can speaker directly connect to musics source?
Another important concept is how is the speaker connecting to musics source when the source is not on your controlling device e.g. smart phone.
Device stream play vs. Direct speaker play
Wireless audio play can be divided into two major categories either your device act as direct audio streaming source to speaker (device stream) vs. device is just a remote and once you tell the speaker to play a music, the speaker directly plays audio from actual source such as streaming website (direct speaker play). The direct speaker play have several advantages over device stream play.
- Higher bandwidth: For example, if Airplay is used, which has CD quality stream limitation, it becomes a bottleneck and Hi-Res music such as Amazon HD will not be played at its highest quality (Airplay part will downsample music down to CD quality).
- Device independence: Once musics are added to playlist on the speaker, you can listen to other music, watch YouTube on the phone you just controlled the speaker and it won’t stop the currently playing/queued music on the speaker.
- You can even take the phone outside of the Wifi network and music will still continue to play.
- Other phone/tablet/computer can edit playlist of the speaker.
Multi-room
The multi-room portion of speaker ecosystem allows following two scenarios:
- Play same music on multiple speakers in house simultaneously e.g. a music playing in your kitchen is also playing in your bedroom, living room and bathroom in synch.
- As sub-set of this, many brands often offers stereo paring of two speakers so one act as right and the other act as left source.
- Play different musics in different speaker. This sounds nothing special but it means one can play different musics stored on your phone on different speakers simultaneously. Usually, this is not possible with regular bluetooth technology
If above just doesn’t sound special, then think two pairs of headphones with a single phone as a source. Can you play different musics to each headphones or listen same song at once on both headphones? The latter may be possible with headphone jack splitter but you know it’s not simple/routine things you can do.
Airplay and Chromecast
These are not separate wireless connection technology but rather proprietary way of utilizing either Wi-Fi or Bluetooth. In fact, one can think these as an ecosystem that allows to have different brand devices work together. Airplay is for Apple ecosystem people and Chromecast is for those on Android ecosystem.
Chromecast
Chromecast is speaker-centric device and Google used to sell Audio specific version where one can plug in this device to 3.5 mm line-in and make any speakers wireless, multi-room speaker even with Hi-Res support; however, this was discontinued in January 2019. As of today, there is no replacement.
The technology itself; however, is not died yet. For example, premium wireless speaker, NAIM Mu-So second generation has built in chromecast support.
Airplay
For Apple users, Airplay technology use Wi-Fi connection, specifically Wi-Fi direct i.e. Wi-Fi connection without having actual Wi-Fi network. It has 2 second buffering/delay before play back begin as part of protocol. Although technologically it is capable of transferring Hi-Res audio data without an issue, original Airplay supported only up to CD quality audio (16 bits/44.1kHz).
Airplay 2 appears to be limited to 24 bits/44.1kHz, which technically meets the Hi-Res audio definition but most Hi-Res audio have higher sample rates (96kHz or 192kHz).
Apple’s AirPlay 2 protocol downsamples audio files to 24-bit 44.1 kHz
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However, one of major feature update for Airplay 2 from audio play stand point of view is indeed multi-room support. As a source pretty much any recent iOS devices and Apple computers support them. For target speaker, it needs certain hardware. There are increasing numbers of speakers from various brand starting to support AirPlay 2 including Sonos, Bose, Denon, aforementioned Naim, and even reputable audiophile speaker brands such as Bowers & Wilkins. However, one must make sure that individual speaker support the standards if one is interested in this feature. For instance, Denon’s HEOS speaker series or Sonos speakers have various products but only handful of them currently support Airplay 2.
Alexa
Most of us consider Alexa as smart home navigation platform. However, it can be a multi-room speaker platform. Obvious is ability to connect Echo speaker series as wireless multi-room speakers; however, Alexa app allows one to set default speaker for the given room. By using this feature, one can connect different brand of speakers as long as the speaker works with Amazon Alexa.
Technology Comparison
Now that we have fundamental concepts down, what are actual difference of each technology?
| CD Quality | Hi-Res Quality | Direct speaker play | Multi-room | Stereo Pair** | |
| Bluetooth | |||||
| Bluetooth | No | No | No | Yes | No |
| Bluetooth AptX HD | Yes | 24 bits/48kHz | No | No | No |
| WiFi | |||||
| Airplay | Yes | No | No* | No | No |
| Airplay 2 | Yes | 24-bit/44 kHz | No* | Yes | Yes |
| Chromecast | Yes | 24-bit/96 kHz | Yes | Yes | No |
| Proprietary | |||||
| Sonos Net | Yes | No | Yes | Yes | Yes |
| HEOS | Yes | 24-bit/192 kHz | Yes | Yes | Yes |
| BlueOS | Yes | 24-bit/192 kHz | Yes | Yes | Yes |
| Naim Mu-So | Yes | 24-bit/88 kHz | Yes | Yes | No |
| B&W formation | Yes | 24-bit/96 kHz | Yes | Yes | Yes |
*Apple Music stream may be exception on and direct speaker play may be performed on special speaker like Homepod.
**Stereo pairing are restricted within the brand and need same speaker from the same brand.
Limitation of Airplay 2 is lack of Hi-Res audio and direct speaker play. Bluetooth AptX HD limitation is it is not for multi-room. Even though it supports Hi-Res file, it is technically lossy Hi-Res.
Chromecast sounds almost perfect with checking all boxes; however, just like Airplay and bluetooth, itself is not a speaker so one still need speaker and this is just a plug in for it. If one has multiple speakers in home and you just want to add capability of wireless multi-room speaker, this was indeed a great way. However, with discontinuation of the product, it is now sold at overprice on Ebay.
WiFi Network are proprietary to each brand. They do not talk to each other. However, as you can see if you pick one and go with the ecosystem, you get the best out of all. Comparison of these different multi-room wireless system are totally separate and in fact harder topic. Stay tuned for the future articles.