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| 1800 Foot cable run [message #321677] |
Sun, 11 May 2008 12:38  |
 Robert Carrell
Messages: 8
Registered: May 2008
Location: Southern California |
Newbie |
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Mac,
Thanks, I agree with you but Zambezi Pyro doesn't want to use the automated firing system. They claim they've had problems in the past.(could just be an ID TEN T error). They are supplying the CD with the music and firing orders premixed by them and specifically asked for the audio this way.
I have walkie talkies and headsets, but they won't use them, I tried. Some clients are more of a challenge than others.
I think the Belden Unreel solution may work fine. I'll check into Ram Electronics, also.
Many thanks to Ivan, Charlie, and yourself.
My apologies for my first posting and the length and simplicity of this one. I have added my real name. Thanks to Hammer, Charlie, Ivan and Mac who replied before the posting was deleted.
Extron's best audio over UTP product is spec'ed to 1000 feet, not 1800. They may work anyway. 20 ga. cable may work also, but at 1800 feet may pickup some unwanted hum and noise. It may be at an acceptable level, but maybe not when amplified to hear the signal over the fireworks in a headset. I do have a 10K ohm input impedance at the far end and can easily supply a low impedance drive source.
I understand the limitations of running an 1800 foot audio signal...high capacitance, requires more power, increased noise, and high freq's degraded, etc.
There is a stage area with sound system for bands and a radio station doing a simulcast. The audience is 1500 people in grandstands, more nearby. The radio station booth plays a CD of music to go with a fireworks display. The music is simultaneously pumped through the sound system. The CD is mono, music on the right channel for the audience and firing orders on the left for the pyrotechnic techs.
Here's the concern: The pyrotechnic gents need a stereo feed to 2 pairs of headphones 1800 feet away, where they launch the fireworks. Again, right channel has the music, left channel has the pyro firing orders so they can manually sync to the music. Pyro guys hear both, the music on the CD's Right side and the firing orders on the left channel. It's "only" 1800 feet away from the sound board and Radio station booth. The audience only hears the music. Pyro hears both.
It doesn't have to be super quality, but decent, intelligible and loud enough for pyro to hear over the fireworks launch and subsequent boom.
The budget is limited, as always, so we're looking for cost effective solutions. Thanks.
[Updated on: Sun, 11 May 2008 14:36]
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| Re: 1800 Foot cable run [message #321686 is a reply to message #321677 ] |
Sun, 11 May 2008 13:07  |
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Mac Kerr
Messages: 5806
Registered: April 2004
Location: Westchester County, NY |
Has No Life |
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If the pyro techs really need to hear the music, pre mix it so you can send just a single line. I have been doing sync'd pyro for close to 30 years with Fireworks by Grucci of Bellport, NY. I believe we were the first to use that system, of multitrack tape with firing cues on one track. while I'm not sure we never did it, I am sure we almost never sent music to the pyro techs. It is counter productive as their fire cues are not in time with any music, it is the opening of the display in the sky that is timed to the music. We have on occasion sent a mix of a timing count off of every second in the show so they could follow a script, but they always had the fire cues. Since most of our shows were fired from barges in rivers or the ocean, running cable was not an option. We used walkie talkies, with a mobile base, like a car mobile as a master, and high noise headsets on the walkies on the barges. With the advent of computer fired shows, we now also send the computer data over radio to laptops on each barge.
If walkie talkies are out of your budget (they are not expensive) I suggest buying a couple of Belden Unreel boxes of rack wire and putting connectors on each end. Just pull the wire out of the box as far as it goes, and start another box. Build the price of the wire into your price.
Mac
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| Re: 1800 Foot cable run [message #321702 is a reply to message #321677 ] |
Sun, 11 May 2008 13:58 |
Charlie Zureki
Messages: 266
Registered: April 2008
Location: Detroit Area |
Has No Life |
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Check with Ram Electronics (New Jersey Area) they may have a solution. I've used a ETS PV 600 System before, but for only a distance of about 1200ft. They may be extendable with drivers in between to give you the distance you need.
Macs advice is probably the best solution by using radios.
The Pyro must be timed to fire preceeding the music.
Good Luck,
Hammer
Be prepared, you'll need it!
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| Re: 1800 Foot cable run [message #321739 is a reply to message #321677 ] |
Sun, 11 May 2008 15:48 |
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Milt Hathaway
Messages: 596
Registered: April 2004 |
Has No Life |
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Milt's obligatory weird solution:
I'd put a 70volt amp at the source, and a 70v to 8 Ohm transformer at the pyro. Run 1800 feet of the cheapest legal cable you can run (plain old zip cable may pass, depending upon your local codes) and you won't lose enough signal to even worry about. (You do lose some low frequencies to the transformers depending upon how hard the system is pushed, but nothing that noticeable in headphones.)
The amp at your end amplifies and converts the low voltage/low current signal you have now to a high voltage/low current signal to send down the line. Low current lets you get away with smaller gauge cable. High voltage lets you directly drive the headphones (after you convert back with a 70v to 8 Ohm transformer) at the other end while virtually eliminating any outside interference from entering the cable. Splices (etc.) are well tolerated, and shielding is completely unnecessary.
Both ends are transformer-isolated from the cable, so you've got some safety factor there also.
BTW, JW Davis (http://www.jwd.com/index2.html) has a nice Excel-based line loss calculator for speaker-level calculations available on their site. As an example: 100 Watts (70.7 volt system) at the source, through 1800 feet of 16g copper, leaves you 60 Watts available at the other end. 18g copper leaves you 47 Watts, 22g copper leaves you 21.5 watts. Still usable, and still at full fidelity.
JW Davis also makes a variable 70v to line level box for the load end, if you need to drive their headphone system.
To me, the biggest expense is that 1800 feet of cable, so anything that can be done to use the cheapest possible helps overall. (Of course, I have 70v amps etc. in my inventory already, so that's a factor.)
--
Milt
FitzCo Sound, Inc.
Midland, TX
http://www.fitzcosound.com
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| Re: 1800 Foot cable run [message #321759 is a reply to message #321742 ] |
Sun, 11 May 2008 16:15 |
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Milt Hathaway
Messages: 596
Registered: April 2004 |
Has No Life |
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| Mac Kerr wrote on Sun, 11 May 2008 15:54 |
| Milt Hathaway wrote on Sun, 11 May 2008 16:48 |
To me, the biggest expense is that 1800 feet of cable, so anything that can be done to use the cheapest possible helps overall. (Of course, I have 70v amps etc. in my inventory already, so that's a factor.)
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A 1000' box of Belden 8451 is cheaper than 1000' of #18 zip cord.
Mac
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My quick Google search gives me a figure of 18 cents/foot on the 8451, and 16 cents/foot for 18 gauge zip (no idea of quality, though)
Really, I was just contributing an alternative method. However, I guarantee my audio signal will get there in better shape (S/N, etc.) than one run at low voltage at that distance.
--
Milt
FitzCo Sound, Inc.
Midland, TX
http://www.fitzcosound.com
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| Re: 1800 Foot cable run [message #321921 is a reply to message #321768 ] |
Mon, 12 May 2008 05:45 |
Charlie Zureki
Messages: 266
Registered: April 2008
Location: Detroit Area |
Has No Life |
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I suppose that they could install a couple of speakers with the 70 volt system and it's volume control, then using the headphones for the firing commands only. Set the speakers directly in front of the operators.
Hammer
Be prepared, you'll need it!
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| Re: 1800 Foot cable run [message #321928 is a reply to message #321776 ] |
Mon, 12 May 2008 07:23 |
Robert Carrell
Messages: 8
Registered: May 2008
Location: Southern California |
Newbie |
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Milt,
Your solution is interesting. I have 70 V amps in my inventory. Using riser rated Cat3 telephone cable at approx $50 / 1000 feet, could work. After all, we're outside, so plenum isn't required. It's only 24 gauge, but using the JW Davis calculator shows 10 watts when using a 100 watt amp. Matching transformers and a headphone amp at the far end provide a level of saftey and volume controls for each headset. I could always double up the pairs to increase effective wire gauge, also.
RDL has some interesting twisted pair audio products, but I can't find a spec for length. They can be piggybacked.
After Doheney Blues Festival (this Sat & Sun,) and a day or two to recuperate, I'll see if I can simulate a few of these ideas in the warehouse. I'll let you all know which seems to work best, but doubt I'll be making measurements other than my ear.
Many thanks to Ivan, Mac and Charlie, too.
Robert
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