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Author Topic: Long distance audio transmission  (Read 5319 times)

Stephen Noffke

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Long distance audio transmission
« on: July 31, 2018, 04:43:24 PM »

Hi all,

I have an event that requires that audio to be transmitted 2000-3000 ft. It spans the entire campus of the small college I work for. I think I can get the audio fairly well spread with speakers in 6-8 locations. (some on top of buildings.) The audio does not need to be loud, just easily audible.

I have been looking at Xirium pro, but I am concerned about line of sight. If I truly need line of sight then I will need almost double the units. (trees would be the obstructions here)

Cabling seems to be problematic given the distance as well as a number of roads that would need to be traversed.

I'm tempted to run the audio through a voice-chat application like discord and just do it over the campus network. I can't seem to think of a reason that won't work, but I might be missing something.

I seem to be a bit lost on how to do this without shelling out 30k on speakers, and a way to get the audio there. The audio there doesn't need delay or super-high fidelity, but it does need to be reliable.

Thanks,
Stephen
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Scott Holtzman

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Re: Long distance audio transmission
« Reply #1 on: July 31, 2018, 04:51:30 PM »

Hi all,

I have an event that requires that audio to be transmitted 2000-3000 ft. It spans the entire campus of the small college I work for. I think I can get the audio fairly well spread with speakers in 6-8 locations. (some on top of buildings.) The audio does not need to be loud, just easily audible.

I have been looking at Xirium pro, but I am concerned about line of sight. If I truly need line of sight then I will need almost double the units. (trees would be the obstructions here)

Cabling seems to be problematic given the distance as well as a number of roads that would need to be traversed.

I'm tempted to run the audio through a voice-chat application like discord and just do it over the campus network. I can't seem to think of a reason that won't work, but I might be missing something.

I seem to be a bit lost on how to do this without shelling out 30k on speakers, and a way to get the audio there. The audio there doesn't need delay or super-high fidelity, but it does need to be reliable.

Thanks,
Stephen

If you use a packet system and have any overlap in the audio the out of sync streams will make a mess.  At one gas station I frequent they have streaming TV's in the pumps and they are always about a second apart.  The effect is maddening.
\
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Scott AKA "Skyking" Holtzman

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David Buckley

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Re: Long distance audio transmission
« Reply #2 on: July 31, 2018, 08:19:29 PM »

You mentioned a "campus network" - is that a wired campus network?  If so, and with some networking magic (a L2 VLAN to all sites), you could use Dante.

Another option is to rent (with a licence) a FM transmitter and several receivers, try the local broadcast rental houses, these sorts of things are often used in that context.
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Luke Geis

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Re: Long distance audio transmission
« Reply #3 on: July 31, 2018, 08:25:00 PM »

While I haven't had to do quite a large network of dispersed audio, I can see two major issues. There really isn't a network based system meant for portable use that is affordable. The Toa NX-100 / 300 series is one that does exactly this, but at $1k - $2k per unit ( oh you need at least 2 btw ) it is a rather pricey setup and it is not exactly meant to be portable. There is a free version of a similar type of system that can only  be done VIA MAC, made by a guy named Zach Poff. As with anything free and low cost, there is some downsides. Problem two is still the remote nature of getting audio from a networked source out to the speaker.

The only reliable way to transport audio over distance right now is XLR. Anything else that is affordable is not quite as reliable, but works, you could say. With the now common network audio systems, 200' - 300' is about the max you can run and generally you can only link up to 2 devices. This makes cascading a little more difficult in your case. There are some proprietary units such as Q-sys by QSC and the TOA NX-100 / 300 series stuff, but these are single units that cost between $1k & $2k each and of course you need one at each location. There is AoE protocols that exist, but its the software and reliability of it at the price they demand that makes it challenging. Better systems cost lots and the free ones are caveat emptor.
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Jordan Wolf

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Re: Long distance audio transmission
« Reply #4 on: July 31, 2018, 10:27:30 PM »

I’d be inclined to use the physical layer of Ethernet connections/patchbays to handle line-level signal distribution.

No worrying about packet loss, latency, network config aside from bypassing switches.

Break-in/break-out adapters are fairly easy and cheap to find and/or build, and you can distribute 4ch. on each cable if you want to.

You’ll need a solid line driver for each output, and some DSP for alignment, etc.
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Mark Cadwallader

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Re: Long distance audio transmission
« Reply #5 on: August 01, 2018, 12:42:18 AM »

When you say "audio", what do you mean?  Speaking voice only, recorded music, live music, or what?  Does the audio need to be sync'ed to images that are being shown on screens?  A little more detail would help us examine options.

Is this a one-off event, or something that will occur regularly?  What is your budget?
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Luke Geis

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Re: Long distance audio transmission
« Reply #6 on: August 01, 2018, 02:03:39 AM »

I don't believe that the recently popular cat 5 audio boxes will work in his case. Getting a direct connection between multiple buildings is not going to be very likely. I think it will have to be a wireless or simple physical connection that gets used.
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Scott Holtzman

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Re: Long distance audio transmission
« Reply #7 on: August 01, 2018, 02:50:58 AM »

I think Jordan is spot on.  Use the Cat 5 as 600 ohm balanced twisyed pair.

If you are handy there are boatloads of Telabs or Westel 600 cards that were used to send program material over the phone network. They are just matching transformers and eq circuits to compensate for the cabling impedance.  They are available on eBay and many telecom surplus sites.





Sent from my VS996 using Tapatalk

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Scott AKA "Skyking" Holtzman

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Jordan Wolf

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Re: Long distance audio transmission
« Reply #8 on: August 01, 2018, 09:35:24 AM »

To the OP: if there IS network connectivity close by to each location, have you looked into DANTE-capable audio devices?

Other than simply using the copper, that may be the only other way I can think of to reliably get audio over distance and use the network in its entirety.
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Stephen Noffke

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Re: Long distance audio transmission
« Reply #9 on: August 01, 2018, 11:11:20 AM »

Thank you all for your responses!
If you use a packet system and have any overlap in the audio the out of sync streams will make a mess.  At one gas station I frequent they have streaming TV's in the pumps and they are always about a second apart.  The effect is maddening.
\
I thought of that, and for that reason I was considering the chat application. My thought was that if the application was designed for two-way communication, that they would design it to minimize that.

The FM transmitter seems easy, but what are the FCC restrictions? Is there a wattage or signal strength limit? Do I need to reserve the bandwidth. (We are pretty rural)

When you say "audio", what do you mean?  Speaking voice only, recorded music, live music, or what?  Does the audio need to be sync'ed to images that are being shown on screens?  A little more detail would help us examine options.

Is this a one-off event, or something that will occur regularly?  What is your budget?

This event would be speaking voice only. There is no need to sync with images. (it is a 20 minute long collective prayer that they want people surrounding the campus for) This is a one-off event. There is not a specific budget. If the system or pieces of it could be used later, I'm sure that the budget could be bigger. If not I think I could get them to spend about 8-10k. I already have 8 - 10 speakers of the 16 I think I need.

I’d be inclined to use the physical layer of Ethernet connections/patchbays to handle line-level signal distribution.

No worrying about packet loss, latency, network config aside from bypassing switches.

Break-in/break-out adapters are fairly easy and cheap to find and/or build, and you can distribute 4ch. on each cable if you want to.

You’ll need a solid line driver for each output, and some DSP for alignment, etc.
I'm afraid that I am not familiar with what you are referring to. Would I need to disconnect switches from our network to make this run? I'm sorry, I'm still a bit confused on this one.

To the OP: if there IS network connectivity close by to each location, have you looked into DANTE-capable audio devices?

Other than simply using the copper, that may be the only other way I can think of to reliably get audio over distance and use the network in its entirety.
You mentioned a "campus network" - is that a wired campus network?  If so, and with some networking magic (a L2 VLAN to all sites), you could use Dante.

Another option is to rent (with a licence) a FM transmitter and several receivers, try the local broadcast rental houses, these sorts of things are often used in that context.
I haven't looked at Dante, but I will check it out.

Thanks,
Stephen
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David Buckley

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Re: Long distance audio transmission
« Reply #10 on: August 01, 2018, 09:14:04 PM »

I’d be inclined to use the physical layer of Ethernet connections/patchbays to handle line-level signal distribution.

This works perfectly in-building, but the networking between buildings on a campus is universally fibre.

However, OP may find that there is copper around the campus for phones, and balanced audio travels just fine through phone copper, even over miles.  All it takes is that the sending and receiving devices have transformers, keeps the grounds out of the audio link.

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ProSoundWeb Community

Re: Long distance audio transmission
« Reply #10 on: August 01, 2018, 09:14:04 PM »


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