Sending to two bluetooth speakers at once

Question

Is it possible to send the same audio signal to two different Bluetooth speakers at once from a single source?

I remember reading somewhere that it's possible to send audio to two different sinks using PulseAudio, but I'm not sure if that applies to Bluetooth speakers or if Bluetooth has a built in limitation on something like this.

I want to be sure that I can actually accomplish what I'm setting out to do before I purchase Bluetooth speakers and a dongle.

Solution

Bluetooth chips are each capable of connecting to a single device at a time for media streaming. If you want to connect to more than one device, you'll need to get a device made to do this. This is called multi-streaming (that keyword alone should get you far in your search) and there are a few vendors who sell dongles which do this.

You can also use multiple BT transmitters. This is only going to be possible from something like a PC; this isn't going to be an option if you're tx from something like a home theater amp or phone or basically anything else. If you go this route you'll need to use software, like pulseaudio, to route each audio channel to the appropriate device.

Either of these type of setup will also allow you to listen to two sets of headphones at once, BTW.

Multi-streaming devices can be a relatively expensive option both in terms of cost and system overhead. You can save a lot if you can get by with a setup that streams once and uses wires between the remote speakers rather than streaming to each speaker individually.

EDIT: In the time since I've answered this question (late '13) a new BT standard has emerged. The new standard is supposed to be capable of multi-streaming. Soon, most BT devices should have this built in.

https://thenextweb.com/plugged/2020/01/07/bluetooths-new-standard-will-support-streaming-to-multiple-devices/

Comments

[IBr]

Are these speakers are in set as one device (left right stereo for example) or are they 2 completely independent speakers (for example you are going to buy 2 sets of similar speakers)?

[Razzlero]

It is not possible unless the dongle supports it, bluetooth uses several mechanisms to make the signal harder to eavesdrop on, that requires it to send the signal twice and not the same signal. The best bet in my opinion would be to use two (preferably identical, to minimize lag differences) dongles and connect each one to one speaker.

[Scott M]

Alright, so it's tough to do in Bluetooth, but some dongles are capable of it. Should I look for dongles that can support up to 7 devices (for up to 7.1 surround sound) or does supporting 7 devices not mean it will be able to connect to 7 of the same kind of bluetooth device?

[Razzlero]

I've never heard of a dongle capable of connecting to 7 devices in parallel, but YMMV.

[mikeserv]

I have seen these devices. In my experience there was one Bluetooth stream from source to sink, but the sink then split it out and served it to its constituent channels via proprietary RF config.

[phemmer]

This has to do with linux because pulseaudio is very good at working with multiple audio sources/streams/destinations. You can use it to split and redirect audio streams.

[Richard]

@Patrick: But how?

[krowe]

@Richard The answer is that you cannot. The BT standard allows for only a single connected device of each device type per BT chip at a time. There is no software solution to this despite the nice routing capabilities of pulseaudio. You'll still need a second BT chip to connect to the second audio device. Once you have that, you can use pulseaudio to direct different audio streams to each of your BT devices independently but it doesn't add the ability to multi-cast RF signals. Even if it did, that wouldn't make a single BT chip capable of maintaining a connection to two separate audio devices.

[Richard]

It turns out that pavucontrol, accessible on Lubuntu through the context menu for the volume control button (bottom right of task bar), allows you to easily select where each stream should be sent. Fortunately: I have a number of bluetooth cards :-)