Multiple channels of wireless mic and IEM - suggestions?

[Sam Jelfs]

Hi all,

 

I have the need to have 6-channels of bi-directional wireless audio transmission, and one option maybe to use multiple wireless mic and IEM systems, but does anyone have any suggestions over some not-too-expensive systems? not looking for amazing quality, but low latency is a must. Looking around at the Thomann type systems seems to suggest that a maximum of 4 channels is possible? This is only for a prototype to be used in the lab, so we don't want to be spending too much on it if it can be helped.

 

Any pointers gratefully received, be it for IEM / mic systems, or for other possible solutions.

 

Thanks

[bruce]

re latency - how low is "low" ?

 

6 channels - is that 6 bidirectional channels, so 12 in total?

 

If you were to move into the digital domain, there's off the shelf hardware that will do what you want, which can be tweaked to give latencies of around 20ms.

[timtheenchanteruk]

depending on if cross talk is an issue, the IEMs can do 2 channels each.

 

when you say six channels of bi directional, is that 6 send, 6 receive? that would be 9 or 12 channels

you wont be able to do more than 4 channels of RF without buying a licence, (ok, you can get 6 channels with sennheisers kit, its still 3 shots, and not under the "not too expensive" heading)

 

if quality is not an issue, how about PMR radios? this would provide best bang for the buck, or some DECT phones

[Sam Jelfs]

well low latency isn't critical, but constant latency is... so if we have say a constant 30ms latency, then I can correct for it, but if it varies, then it becomes a problem.

 

and we have say a control position, and 6 remote positions, the control position has to be able to both send and receive audio from the 6 remote positions.

 

I need to be able to receive from multiple sources at once, so that would rule out PMRs.

 

Also, as for license, I don't know what the rules are out here (Netherlands), so shall have to check up on what we can and can't use, and what we do and don't already have licenses for.

[timtheenchanteruk]

oops, didnt see where you were based, your rules may differ.

[Paul TC]

and we have say a control position, and 6 remote positions, the control position has to be able to both send and receive audio from the 6 remote positions.

 

I need to be able to receive from multiple sources at once, so that would rule out PMRs.

 

As you have a single control position is there a requirement to send a differrent signal to each position at the same time ? If all remotes can receive the same signal then you can use one sender on 1 frequency and 6 rx on same frequency.

 

Do not know if you have cheap PMR446 PMR in your country. It has 8 rf channels availble in UK.

 

However 1 freq for tx at control for go, each remote has a radio on rx.

 

Remotes each have a second radio on dedicated freq talking back to a second dedicated radio for each remote at control point. (Gives Full Duplex).

 

If you need to partion and assuming that the control needs privacy to only talk to one station at a time, use 6 radios for the go on the same frequency but use CTSS signalling for each pair of radios on the go path to only talk to the required radio.

 

12 cheap PMR446 radios will (can) be cheaper than radio mics and IEM's

[Sam Jelfs]

each remote position has to receive a separate feed, also there is no person involved other than at the control position, so the remotes need to basically constantly receive / send.

[Paul TC]

each remote position has to receive a separate feed,

 

I assume therfore it is simultaneous transmission of 6 differrent signals ?

 

Can I ask why if in a lab, 6 lengths of 4 core will not do the job, are the remotes mobile ?

[Sam Jelfs]

yeah, each remote location is mobile (within a single large space) - currently everything is cabled, but the theory is that the final result will be wireless, unfortunately some people have less ability to imagine things than others... if we say it shall be wireless, it better be wireless ;)

 

edit: and yes, think multi-channel audio, 6 speakers, each replaying different content at once.

[paulears]

I'm confused - Not too expensive is analogue, so there isn't any latency as there's no A/D, then D/A conversion - Have I misunderstood what you're after?

[Sam Jelfs]

I don't care if it is analogue or digital as such, so long as any latency that is introduced is constant. I have a central control position, it needs to be able to feed individual audio feeds to 6 remote locations wirelessly, those same 6 locations need to be able to feed mic signals back to the central location.

 

I wish I could explain in more details, but corporate secrets / patents applications etc make things awkward...

[paulears]

Stick with analogue if you need time aligned signals, if you go digits then the price is going to go up and there will be some latency, not huge amounts and certainly not enough for people to perceive as a delayed signal - but certainly present. The only potential problems will be receiver desense from the local transmitter for the return leg, and the central transmitters having the same effect on the outgoing signals. However, depending on what the rules are on available frequencies in the Netherlands, I'd suggest as much separation of transmit and receive frequencies. here in the UK, I'd be tempted to look at the current ch 69 and/or ch 70 deregulated frequencies for one way and ch 38 for the other. They are far enough apart to make desensitisation much less of a problem. However - if you can't explain for secrecy reasons, we can't really say for certain as you could be planning something that will stop it working.

[Sam Jelfs]

Stick with analogue if you need time aligned signals, if you go digits then the price is going to go up and there will be some latency, not huge amounts and certainly not enough for people to perceive as a delayed signal - but certainly present.

 

as I said, latency isn't an issue, so long as it is consistent, in fact in the current wired set-up there is all sorts of d-a / a-d converters which will incur delays, and thats not a problem.

 

The only potential problems will be receiver desense from the local transmitter for the return leg, and the central transmitters having the same effect on the outgoing signals. However, depending on what the rules are on available frequencies in the Netherlands, I'd suggest as much separation of transmit and receive frequencies. here in the UK, I'd be tempted to look at the current ch 69 and/or ch 70 deregulated frequencies for one way and ch 38 for the other. They are far enough apart to make desensitisation much less of a problem. However - if you can't explain for secrecy reasons, we can't really say for certain as you could be planning something that will stop it working.

 

I shall see what I can find about radio licensing out here... but let me phrase it another way, I have a 6-piece band, each musician needs a radio mic, and each needs a dedicated radio IEM feed, what equipment in that scenario would the board recommend? lets not worry too much about cost currently, just so long as I can have a working set-up without too much interference between channels.

[paulears]

Personally, I have Sennheiser and Trantec IEM kit here. The Sennheisers allow you to take the incoming two channel audio and have both headphones able to balance the two channels, which although absolute separation isn't possible, does give you the ability to send two transmitters 4 different mixes, and by switching one receiver to ch1, and another to channel 2, two people only need one transmitter - making it a bit cheaper. So for 6 musicians each with their own mix, you would needs 6 receivers stage end for their instruments, and 3 IEM transmitters to return the monitor mixes to them from 6 inputs. I'd buy ch70 IEMs I suspect - it's tricky, because at some point channel 70 will become very busy - and have more users in it. Only you will know if the kinds of places you will go to are likely to have other ch 70 users close. The ch 70 transmitters seem to survive better in the IEM mode of operation because the aerials are usually up and in the clear, getting more RF out into the ether - something that a pocket transmitter often fails to do when the aerial is inside clothing or has accidentally been screened behind something metallic. I'd then buy ch 38 kit for the RF systems from musician to receiver rack. Sennheiser G3 for the IEMs, and G3 or the new XS for the conventional systems.