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trumpettrousers 1st September 2012 12:45 PM

Real-time wireless audio to multiple devices?

I have a question about real-time (i.e., as lag-free as possible) wireless audio transmission to multiple devices.

I'm involved in a research project examining the effect of physical separation on music ensemble interaction and timing. Basically, I'm investigating how physically separating musicians from each other affects how they play 'together'.

I'm looking for a wireless audio solution which can connect a single audio playback source to a large number (anywhere from 5 to 50+) of devices (e.g., headphones). Minimizing lag is more important than sound quality.

Does anybody know of any technologies, products, kits, or other solutions with which I could wirelessly connect a single source to such a large number of simultaneous playback devices? I'm not necessarily looking for a commercially available solution, so, if the technology exists, I'm happy to build it from scratch.

Thanks in advance for any suggestions!

PS. I'm not sure if this is the best forum in which to post this thread, but since it deals with live audio, I thought I'd try here first. If you think this post would be better dealt with elsewhere, do let me know.

Enzo 1st September 2012 04:28 PM

Commercially available wireless gear has no latency - at least not in audio terms. No one has to adjust to playing through wireless. It is as immediate as wires.

Just what do you want to transmit to what? In live music we routinely have instruments transmitting wireless back to amplifiers. On the other hand we also use wireless in-ear monitors where a mix from the PA is sent to individuals to listen to on stage.

A transmitter is a transmitter - it sends out a signal, it is nothing more than a radio station. You can have one receiver or 100 receivers, the transmitter will not know the difference. So a wireless system doesn't change just because it has multiple receivers.

That changes if you want EACH receiver to get a unique signal. You can't transmit a music signal to receiver A and have receiver B get the same signal but 100ms later. The only way to do that would be to have separate transmitters, or have a delay unit on the receiving end for B.

CHurches haver some sound system options that are not often used elsewhere, among them is wireless headphones for people with hearing problems. One transmitter in the haall will serve any number of wireless headphones. A lecture hall where other language translationjs are used might also use such systems. These are off the shelf ready to go commerial products.

There is a classic demonstration I always liked - you have someone recite the alphabet while his voicce is played back into earphones but delayed one second. It takes tremendous concentration to do it, and most people can;t.

You have not described why it needs to be wireless. Wireless is not the same as portable - for example you may want to spread a quartet across a stage and have each player listening to his own headphones signal. But must his receiver be battery powered? Or can each man have a mains powered receiving system sitting next to him on the floor?

If you want the orchestra to all have headphones, but send them all the same signal, then one wireless phones system covers it. There are commercial systems for this, but there are also consumer versions for home use. Look up "wireless headphones." A quick look at Best Buy and I see wireless phones from $15 up to $600.

Pano 1st September 2012 04:35 PM

Yep, Enzo is right. Most wireless systems use FM and the latency is tiny - usually less than acoustic delay. Some assisted hearing systems use I.R., but latency there is also tiny.

Wireless headphones or assisted hearing systems are off the shelf and easy to use. If you need multiple channels, that can be done, but costs more.

Taking this to the extreme, I remember the group Urban Sax (France) having about 200 sax players start at the outskirts of a village and walk, while playing, into the center of the village were they converged into a huge mass ensemble. They were all sent a radio signal to keep them together during the walk in. That was in the 1980s.

DF96 1st September 2012 05:20 PM

You can either use wireless headphones domestic technology, or wireless microphone stage technology. Both widely available. In most countries you can't legally build the transmitters yourself, as they have to be type-approved. You could build the receivers - typically wideband FM, sometimes with tone squelch and diversity reception.

trumpettrousers 2nd September 2012 06:41 AM

Thanks for all the suggestions!

As for why it should be wireless, Enzo, it doesn't have to be, but binning the cables would be much more convenient, less messy, and allow more freedom of positioning.

The wireless headphone systems (not stage wireless stage monitors) I've checked are all limited in terms of either number of receivers per transmitter, or delay. I couldn't find any systems that feature a single transmitter to multiple (as I say, up to 50+) headphones. Enzo, perhaps you have a specific system in mind?

Wireless stage monitors might, therefore, be the best route to take.

I'm curious about the assisted hearing systems, though, Pano. Do they require line of sight between the transmitter and receiver?

pinkmouse 2nd September 2012 08:53 AM

I can see several flaws with this experiment. Here's a couple. Firstly, most musicians take timing cues from the conductor rather than other players, and latency is very important here, to the extent that most remote systems have to use CRT monitors and analogue wiring to relay the conductor rather than LCD due to the delays innate in digital.

Secondly, the soundfield that the player is used to. Front row fiddles really don't hear much of the basses when they're playing, and brass is equally unlikely to take much timing info from the cellos. To duplicate this effect you would really need to mic up each instrument separately and do an individual headphone mix for each player. Sending a single mix to each player may well invalidate your results before you start.

However, I do think this is a very good project, and could produce some valid results, you just need to think in depth a little more and isolate all your variables. And as a suggestion, you may want to contact someone like AKG or AudioTechnica. They may well be able to suggest systems and even possibly loan you the equipment as this sort of thing is growing importance in event production, (Olympic opening ceremony anyone?).

Good luck!

al/did some very strange things with musicians when he worked at the Royal Albert Hall. :D

:edited for content and appalling spelling.

chrispenycate 3rd September 2012 02:24 PM

Most assisted hearing systems are inductive loop. to keep the signal restrained to a relatively limited area.

I don't know about elsewhere, but in this linguistic hotbed I inhabit translation systems (one transmitter, multiple (up to several hundred) receivers, generally each one multiple (switched) frequencies for the different languages you might require, are easily hired from conference arranging companies. If you go to your local Sennheiser importer and ask for contacts of people who've bought systems like this, you should be able to find prices relatively painlessly. That way you won't finish the experiment with masses of extra gear that you'll never need again (I use Sennheiser as an example, because they've got a good hunk of the local market)

Museums and art galleries use similar systems, but are generally adapted for shorter range.

trumpettrousers 6th September 2012 08:18 AM

Thanks for your thoughts and suggestions regarding the project, pinkmouse! As you say, there are many variables which need controlling, or at least taking under consideration. Interesting to know that analog systems are the industry standard for remote monitoring..

And chrispenycate, thanks for the info concerning translation systems. Could be an interesting avenue to explore..

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