Multichannel Wireless Headphones

Miscellaneous
1

Hi all,

as a university project we´re developing a small multimedia “adventure park” for next year´s PopKomm fair in Berlin. Visitors should get wireless headphones and will be tracked with a MAX/MSP/Jitter system. for the system to be really interactive we´re searching a way to send each visitor his own dedicated audio signal.

I found out that most In-Ear-Monitoring systems provide up to 16 selectable channels, but the problem is that we have a tight budget, and a system for 10 visitors would be too expensive. Normal consumer headphone systems all have only 3 channels, which is too few.

Does anyone know a system that can transmit at least 6, better 10 independent stereo mixes to different wireless headphones and does cost max. 100 Eur/$ per set? Or is there a place/forum that would be a good place for this question?

Any hint is appreciated :slight_smile:

Seppoman

2

Hi Seppoman

Go for the professional system! Most companies and/or distributors will support such projects, if you place their banner somewhere. Just write them a letter (possibly approved from your university) and explain your needs and ask them, what they could do for you.

Greets, Roger

3

You might look at some of the FM transmitters from Ramsey electronics, you could use 10 transmitters all on different frequencies and use standard consumer throw away priced jogging radios on the headset end.

You want digital tuned transmitters though, otherwise your channels will be walking on each other.

Its also a great way for a church to save thousands compared to the cost of a standard hearing assist system.

Used to work great for the drive in movie theatres here before they all went away, if you had a decent system in your car!   ;D

Best!

Smash

4

Hi Roger, Smash,

today I talked to one of our professors about getting IEM systems. He has quite good industry contacts everywhere through his work in the VDT (german Tonmeister Asociation). He will contact Sennheiser about this issue, but said it will be difficult to get so many systems because of their price and fragility.

The idea about FM transmitters is interesting, but I doubt we´d get permission to use them. The PopKomm is a large fair of the entertainment industry and I suspect some neighbours could get angry if we transmit on non-specialized frequencies. Also, the quality of cheap jogging radio headsets will probably not be sufficient - after all, we´re studying Audio Engineering so the audio quality of our presentation is important.

Thanks a lot for your input :slight_smile:

Seppoman

5

PopKomm is a large fair of the entertainment industry

… that’s exactly why Sennheiser just could be interrested. Imagine how many systems they’re using for musicals and I know that Sennheiser did sponsor such events in the past.

Greets, Roger

6

Hi Roger, Smash,

today I talked to one of our professors about getting IEM systems. He has quite good industry contacts everywhere through his work in the VDT (german Tonmeister Asociation). He will contact Sennheiser about this issue, but said it will be difficult to get so many systems because of their price and fragility.

There is no way you should be handing out commercial IEMs to anyone but performers needing a foldback/monitor system.

To match the midrange consumer technology’s sound quality with a real IEM will cost you at least $1K for the earpieces alone, and they need to be custom fitted for comfort.  

The idea about FM transmitters is interesting, but I doubt we´d get permission to use them. The PopKomm is a large fair of the entertainment industry and I suspect some neighbours could get angry if we transmit on non-specialized frequencies.

That’s up to the laws where you are.  In the US, you can transmit on unused FM up to a certain transmitter power before without breaking the law or FCC rules or needing any license. I don’t know if the laws there are similar.  As long as there are at least a few gaps on your local radio dial you can do this without walking on anyone elses signal.

Also, the quality of cheap jogging radio headsets will probably not be sufficient - after all, we´re studying Audio Engineering so the audio quality of our presentation is important.

Thanks a lot for your input :slight_smile:

Seppoman

IEM’s are way behind consumer technology on sound quality. You could buy quite a few great sounding digital tuning FM radios with headphones for what only one of the cheapest Sennheiser IEM recievers will cost.

It would be very cool if Sennheiser would help you out!

Just food for thought…Seen FM work as well and sound better than way more expensive solutions…

Also you should consult your local nameity about health practice/requirements for allowing people to share headphones.  During your show with a health code officer would be the wrong time to learn these things…

Best!

Smash

Almost forgot to ask, what tracking technology are you using?

7

Hi Smash,

There is no way you should be handing out commercial IEMs to anyone but performers needing a foldback/monitor system.

To match the midrange consumer technology’s sound quality with a real IEM will cost you at least $1K for the earpieces alone, and they need to be custom fitted for comfort.  

I wasn´t thinking of earpieces - I wouldn´t like to put earpieces into my ears that had been worn by dozends of strangers before  :o But the IEM receivers normally have 3.5 mm mini jacks so you can connect a normal headphone.

Quality - if our Prof. can get IEM systems at all, they´ll probably be the ones for $1k+ :slight_smile: until now he often managed talking companies into borrowing us e.g. HDR systems for $20k+ - he´s very talented in these things :wink:

That’s up to the laws where you are.  In the US, you can transmit on unused FM up to a certain transmitter power before without breaking the law or FCC rules or needing any license. I don’t know if the laws there are similar.  As long as there are at least a few gaps on your local radio dial you can do this without walking on anyone elses signal.

I will email the PopKomm fair management about this - they´d have to permit these transmissions in the first place.

Almost forgot to ask, what tracking technology are you using?

We just started working on this. The whole thing will be realized with Max/MSP/Jitter. Yesterday we programmed a rudimentary color space tracking. One problem is latency - even without any other tasks running we had about 300ms using a miniDV with a 1.3 GHz G4 Mac. Another question is how to uniquely identify the visitors.

I thought of using 2 pulsed IR LEDs per headphone. With an IR filter before a DV cam you can have a black image with only the LEDs visible and the pulse frequency could be identified. Problem is: strong IR LEDs need a lot of current (ca 100mA) and are very directional, so if the visitor looks downwards the cam doesn´t get the IR signal. So I´ll try strong normal (colored) LEDs next, perhaps using some diffusor in front of them. Color combinations would be used for identification.

As you can see, we´re still at the beginning :wink:

Cheers,

Seppoman

8

Hi Smash,

I wasn´t thinking of earpieces - I wouldn´t like to put earpieces into my ears that had been worn by dozends of strangers before  :o But the IEM receivers normally have 3.5 mm mini jacks so you can connect a normal headphone.

Quality - if our Prof. can get IEM systems at all, they´ll probably be the ones for $1k+ :slight_smile: until now he often managed talking companies into borrowing us e.g. HDR systems for $20k+ - he´s very talented in these things :wink:

You might also shop around the local production companies, one might have a rental system that is perfect and fits your budget.  Some of the video production rental houses in Dallas have rental wireless IEM setups that match your spec., your looking for the same type of setup they use with the “talent” at a sporting event for TV broadcast.  Might be an easier sell to the PopKomm management also… :wink:

We just started working on this. The whole thing will be realized with Max/MSP/Jitter. Yesterday we programmed a rudimentary color space tracking. One problem is latency - even without any other tasks running we had about 300ms using a miniDV with a 1.3 GHz G4 Mac.

I wonder if any of your latency is related to the DV format?  Not knowing much about Jitter is it reading the frames through quicktime via a standard codec?  Also have you tried sampling a lower frame rate?  Humans have fairly predictable movement speeds… :wink:

Another question is how to uniquely identify the visitors.

I thought of using 2 pulsed IR LEDs per headphone. With an IR filter before a DV cam you can have a black image with only the LEDs visible and the pulse frequency could be identified. Problem is: strong IR LEDs need a lot of current (ca 100mA) and are very directional, so if the visitor looks downwards the cam doesn´t get the IR signal. So I´ll try strong normal (colored) LEDs next, perhaps using some diffusor in front of them. Color combinations would be used for identification.

As you can see, we´re still at the beginning :wink:

Cheers,

Seppoman

I think you are on the right track for this with the different frequencies.  You should look around the net for DIY laser tag sites and info, Some of those guys have surely spent time on engineering around the LED throw angles…

Let me know how it goes, and I’ll help if I can!    :)

Best!

Smash

BTW Here is a motion tracking system that uses RF, Not a suggestion just interesting reading - it does what you need to do using different technology…  http://www.wybron.com/Entertainment/AutopilotII/