Long distance audio feed - Graduation

[CalabasasTD]

Hey gang,

I just got told by our Asst. Principal that I'll be expected to send an audio feed from the football field to our lecture hall, which is 500 to 1000 feet away, for graduation. This is so the old people have a place out of the sun to go and watch the graduation. The video guy is taking care of his own video feed, but I'm going to be expected to send audio.

The physical challenges of this run notwithstanding, I'm concerned that that's too far. Is there some kind of a signal amplifier that I can put inline to have it make it all the way there and not sound awful?

Also, unless we send the audio and video together somehow, I'm guessing we may have sync. problems. Any thoughts.

Thanks in advance for your input.

Eric

[mnfreelancer]

500' and 1000' feet are two very different situations. I'd say you should be able to drive line level with decent quality for 500' on balanced cable but 1000' is pushing it. Same for doing it wirelessly...given the proper antennae a decent wireless mic with an XLR adapter should do 500' but 1000' is getting beyond design limitations. So which is it, 500 or 1000? or 750?

[CalabasasTD]

Well now I'll have to go measure!! I meet with them tomorrow. Once I know the layout, where we can set up and the distance we'll have to travel, I'll get back on. Thanks!

[rwhealey]

I've heard that you should be able to do 1000' feet with a line level signal- never done it myself.

Are they willing to spend anything to get the sound where it needs to go?

[Derrick]

How is the video guy doing his video? Coax, wireless, IP?

1000' line level is no problem. However running the wire may be a chore.

Where is the school located? Do you have a local radio station there? If so, Check and see if they have a RPU sometimes known as a Marti. If they do, see if you can borrow the tranmitter and receiver and use it to send your audio.

If cellphone quality is acceptable, then you could use an coupler to connect the mixer to the cellphone, call the number at the remote location and use another coupler to connect the received audio to the in house PA.

As far as sync issues, if the video is an IP protocol it will have a fair amount of delay due to the codec processing the video. you might have to apply some delay on your audio lines to match.

What time frame are you under to make this happen?

[BillESC]

Audio Technica's ATW 3110 wireless system can typically transmit 1000' line of sight. To add some confidence the addition of a high gain antenna will make your system 'good to go.'

[mbenonis]

I think a line level send would work just fine. With such a long run, the chance of RFI goes up, and you may need to terminate the send with a good transformer if you are using lower-end sound gear in your auditorium (something along these lines: Radial Twin-Iso two channel Jensen transformer equipped balanced isolator).

See my post about balanced v. unbalanced lines for some good information on transformer isolation and why you might need it.

[epimetheus]

I've did an approx. 1000' line level press feed for an Air Force Thunderbirds performance at Texas A&M a couple years ago. Used a Mackie 1402 mixer on each end to condition the signal. Worked pretty well.

Edit: Come to think of it, I believe it was a balanced line.

[museav]

I'll second Derrick's comments, how is the video being transmitted? There may be some ways to effectively address both and avoid latency issues, such as using a CAT/UTP solution. However, sync may also be a concern if they are doing any digital switching or processing, you might want to find out if the video equipment being used does add any latency.

1000' of balanced audio could probably be worked around but not if it is twenty 50' cables hooked together, you would probably just want to get a 1000' reel of good quality twisted pair audio cable and make it all one continuous run.

[epimetheus]

Originally Posted by museav

I'll second Derrick's comments, how is the video being transmitted? There may be some ways to effectively address both and avoid latency issues, such as using a CAT/UTP solution. However, sync may also be a concern if they are doing any digital switching or processing, you might want to find out if the video equipment being used does add any latency.

1000' of balanced audio could probably be worked around but not if it is twenty 50' cables hooked together, you would probably just want to get a 1000' reel of good quality twisted pair audio cable and make it all one continuous run.

I agree. I'd see if you can keep the audio on the same link with the video.

When we did our 1000' run at A&M we got a 1000' reel of twisted pair audio cable, tied one end to a post near the source and put the reel on a stand in the bed of a Gator and took off.