Transmitting audio via UHF

[johndenim]

Hi all.

 

I have several disco events at a hotel this month.

 

Guests are dining in two separate suites, each with a built in p.a (ceiling speakers and amp ) and XLR inputs in the wall.

Main disco area is in a large lounge, approx 20-25 metres from the two suites.

 

 

I have been asked to provide the same music ( that I am playing in the lounge ) to each of the suites, during dinner.

Long XLR cables are out as there are too many trips hazards and to be frank, too much effort.

 

During the summer, I had tried our Sennheiser G2 i.e.M transmitter, and Radio mic receiver in one of the suites.

It worked ok, but I only have one of each.

 

Would this work with two receivers?

I don't want to hire in and it won't.

I.e, with my transmitter in the lounge, and with a receiver in each of the suites, is this possible?

Is there any issues with two receivers receiving one signal?

There are a few walls and no direct line of sight, but the distance is short.

Sorry if I don't make sense! :)

[MarkPAman]

I seem to be able to listen to Radio 4 at the same time as other people without any problem!

 

You should be fine, if there's enough power from you transmitter to reach the rooms where your receivers are, you could have 1000s of them!

[ramdram]

It may be a wise notion to have a dummy run first, well before the first date, so you can tweak the rx aerials for optimum signal in both rooms. There may be AC ducts or lift shafts(?) to avoid.

 

The range is not that great and perhaps there is a position where the tx can be placed so as to be as close to the both rooms ref the lounge, so as to optimise the rf for both rx.

 

Be advised tho' that the set up may need a slight tweak when rooms are full of guests. Aerials should be placed high as opposed to low.

 

HTH

[cedd]

You also don't have to use the stock aerials supplied with the receivers.

 

this situation is a real gift for antenna selection - you have a known, fixed source that isn't going to walk around the stage! I'd be looking for some nice tight pattern Yagi's and I'd be pointing them directly at the source. Also spend some time making sure the polarisation is correct (work out which way up your transmitter aerial is and make sure the receivers are the same way). This is something you can't guarantee in radio mic work, but can in this instance.

 

Don't be tempted to do too much in terms fo aerial tweaking with the transmitter. The chances are you'll be treading on the wrong side of the licensing for your channel - any directional antenna will most likely have gain, increasing your effective radiated power to above the allowed limit. Plus if your two rooms are in opposite directions, you want an omni directional radiation pattern.

 

Where possible, move your receiver or transmitter and extend with audio cabling, rather than moving your aerial away from the device using aerial cabling - the losses experianced over aerial cabling are not exactly negligible.

[henny]

Is the hotel wired with cat5 most are nowadays, you could use something like LINK

 

I have done this many times to get audio around buildings

[ramdram]

Ref #5.

 

Henny, that looks to be quite interesting stuff. There was precious little gen about the kit on that site and the only other gen was on Octoparts, quoting the MCM site itself presumably, which has only a partial description.

 

If it uses the cat5e (or whatever is actually installed) I presume it uses two of the possible four twisted pairs?

 

I'm keen to know more. If you have a moment any chance of a bit more info please...or anyone else perhaps?

[timtheenchanteruk]

those baluns just send the audio over cat 5, its unlikely in this situation that there is going to be cat5 going from one room to another without gong through a switch or two, these just wouldn't work in this situation, they don't convert the signal to ip.

 

There is a slim chance that you would be able to create a direct link between the rooms in the patch bay, but again, IMO unlikely, as even if they have a network engineer onsite, unless you are lucky, they wont understand what you are trying to achieve, and it will get a blunt "no".

[ramdram]

Ref #7.

 

I appreciate this is a bit OT but still on the audio" distro'" subject but thanks for the gen on those XLR-RJ45 boxes.

 

Quite apart from the switching thing, it was how the signal is "applied" to the cat5e which was carrying a digital circuit as well as. I had wondered about filters etc.

 

I understood too that you could graft the audio onto the domestic mains (assuming phase was same):

 

http://www.russandrews.com/article-Your-ma...k-powerline.htm

 

although this was not considered ideal. Or there's this:

 

http://www.reghardware.com/2008/01/29/devo...ros_dlan_audio/

 

None of these systems are new but might be worth a few moments consideration???

[timtheenchanteruk]

the ones you link to convert the audio to ip (network data) this would pass through switches etc, the baluns posted to originally just convert the XLR to RJ45, with a bit of passive circuitry to take care of the difference in impedance. This is fine for sending audio down a single bit of cat5, but as it is not network traffic, it would do nothing if presented to a network switch.

 

there are solutions for sending audio and video over networks, but its not that simple...

[ramdram]

Ref #9.

 

I have used the internet via the mains in a domestic situation with the plug in units. I found the system worked quite well and even across another ring circuit through the consumer unit, so the "audio plugs" might work for the OP at a pinch, even if the two rooms he has to wire up are on separate ring mains. Would not want to predict how the system worked across the phases tho'.

 

(The internet system could be PW protected and you could set up networks within networks across the mains. This is again OT but the gen might suit anyone who found their theatre in-house wifi was upset by a Line 6 ISM band radio mic system, say...)

 

The stuff I was interested in was how the audio was transported on the cat5e itself, there being 4 twisted pairs to choose from. Does this imply a maximum of two separate "stereo" sound circuits? The item was not very well documented on the web page.

 

I am going to presume further that the term "balanced" meant exactly that and one twisted pair equated to a balanced mono circuit, hence the two XLR sockets.

 

Perhaps the send unit could be regarded as a DI box but not in its familiar form? And the receive unit as a "DI box in reverse"...but you could have more than one rx unit.

 

Perhaps Henny could find some more gen?

[johndenim]

Thanks for the input guys.

 

I don't really want to lay out this king of expense, plus it's getting a bit technical for me!

I think the only option would be to hire another receiver and try to place in line of sight with long XLR's, as mentioned by cedd.

 

Transmitter is a G1 unit, will this be fine with G2 receivers?

[cedd]

from memory, I don't think G1 did pilot tone, which your receivers will be looking for to lift their mutes. I'm pretty sure there's an option on the receiver to disable pilot tone. Other than that, I think it should be pretty ok! There'll be some compression as the audio passes through the compander, but I'm afraid that's the way it is with wireless.

[AdrianW]

Ref #9.

 

The stuff I was interested in was how the audio was transported on the cat5e itself, there being 4 twisted pairs to choose from. Does this imply a maximum of two separate "stereo" sound circuits? The item was not very well documented on the web page.

Yes - you only need one twisted pair for each balanced circuit, so CAT5 = 4 pairs = 4 balanced circuits.

 

I am going to presume further that the term "balanced" meant exactly that and one twisted pair equated to a balanced mono circuit, hence the two XLR sockets.

A balanced mono circuit is ONE XLR socket (the pair being the hot & cold legs)

Perhaps the send unit could be regarded as a DI box but not in its familiar form? And the receive unit as a "DI box in reverse"...but you could have more than one rx unit.

Its like a DI box, converting an unbalanced source to a balanced one. I use exactly this method to transport audio around the CAT5 cabling in my home - two stereo sources are sent (TV sound & media PC audio - using 4 balancing transfomers in a box, 4 x FMXLR in 1 x CAT5 out) at each receiving point I have a small box with a CAT5 input socket, two balancing transformers, a 4 pole switch & 2 x MXLR sockets, the switch selected which two pairs of the CAT5 are routed to the transformers.

 

Perhaps Henny could find some more gen?

[ramdram]

Ref #13.

 

Thanks for that AW. Just to clarify for me that is, it is two XLRs = one stereo feed. Which is why I presumed they built it like so, ie one XLR circuit for L and t'other for right.

 

I wondered also how Henny achieved this, what with the comment regarding the data switchers.

 

I had not considered using this way at all if you wanted to build tie lines around your theatre, and other buildings, for things like a show relay to powered spkrs (or signalling possibly)...inexpensively that is.

[henny]

It's just a matter of talking to the correct person to gain access to the data cab and just cross patch .