Hi,
I have query regarding selection of cable gauge over long distance to drive number of speakers.
Setup:
Amplifier - VP-2421 CF(420W)
Speakers - Horn Type (SC-615M) - 15W Taping
No, of Speakers - 20(300W) connected in parallel taping
Total Distance Containing speakers on line - 1.5KM
First speaker starts over distance - 1.2KM
I want to connect 20 horn speakers in parallel taping of 15W on a line amplifier line over distance of 1.5km. I'm using above mentioned amplifier for line driving.
Please can use suggest me the Cable gauge to use for this setup to work effectivity. Also can you provide me the formula for the calculation of mentioned above setup.
Thanks.
I have query regarding selection of cable gauge over long distance to drive number of speakers.
Setup:
Amplifier - VP-2421 CF(420W)
Speakers - Horn Type (SC-615M) - 15W Taping
No, of Speakers - 20(300W) connected in parallel taping
Total Distance Containing speakers on line - 1.5KM
First speaker starts over distance - 1.2KM
I want to connect 20 horn speakers in parallel taping of 15W on a line amplifier line over distance of 1.5km. I'm using above mentioned amplifier for line driving.
Please can use suggest me the Cable gauge to use for this setup to work effectivity. Also can you provide me the formula for the calculation of mentioned above setup.
Thanks.
The loading is a standard 100volt line regardless of transformer fed speakers until the 300Watt power level is exceeded.
So, 300Watts maximum power at 100volts.
Using Ohms Law, P = 300, V = 100 therefore I = 3Amps.
1.0mm copper cable is good for up to 10Amps, so aim for that or at least 0.5mm for 5 Amps.
I would and have done successfully in the past at large shows, used RF transmission over the first 1.2 km and that saved a lot of expensive cabling runs.
So, 300Watts maximum power at 100volts.
Using Ohms Law, P = 300, V = 100 therefore I = 3Amps.
1.0mm copper cable is good for up to 10Amps, so aim for that or at least 0.5mm for 5 Amps.
I would and have done successfully in the past at large shows, used RF transmission over the first 1.2 km and that saved a lot of expensive cabling runs.
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There is loss of course but 100volt line is primarilly for speach and low fi music, so not noticeable as a rule.
There are lots of confusing theorum on the intranet, most of which does not apply.
The bandwidth is greatly reduced on a 100 and 70volt line due to the transformers and medium quality speakers or horns. Typical 3dB frequency response is 100HZ to around 8kHZ depending on speaker quality.
There are lots of confusing theorum on the intranet, most of which does not apply.
The bandwidth is greatly reduced on a 100 and 70volt line due to the transformers and medium quality speakers or horns. Typical 3dB frequency response is 100HZ to around 8kHZ depending on speaker quality.
Quite true, a wireless mic setup may cost less than 4000 feet of even the cheapest twisted pair running at line level with the amp located with the first speaker. OTOH, if there is no power at the first speaker, you also have to factor in generator rental.
You can't just go by amperage capacity of the cable, at that distance you would need to up-size by at least two wire gauges because of voltage drop. I don't know off the top of my head, but if you went by the book you might even need a #10 or even an 8 (for 3% drop on a typical 120V, 3 amp load). You could live with a lot more, but you don't want to lose half your power either. You would probably end up with a 14, which would be crazy expensive.
You can't just go by amperage capacity of the cable, at that distance you would need to up-size by at least two wire gauges because of voltage drop. I don't know off the top of my head, but if you went by the book you might even need a #10 or even an 8 (for 3% drop on a typical 120V, 3 amp load). You could live with a lot more, but you don't want to lose half your power either. You would probably end up with a 14, which would be crazy expensive.
Pieces of copper wire aren't always the same.
I did a job using long wires for a CCTV system and did some research into wires.
I was quite surprised at the differences in resistance per metre of the wires.
Clearly the wire should be as low resistance per metre as possible to prevent too much loss.
I did a job using long wires for a CCTV system and did some research into wires.
I was quite surprised at the differences in resistance per metre of the wires.
Clearly the wire should be as low resistance per metre as possible to prevent too much loss.
The lowest resistance wire (assuming only copper) would be magnet wire. There is no way you would use that for a number of reasons. If you ran the signal at line (+4 dBu) level the cheapest way would be cat5 Ethernet cable. If you absolutely had to do it at speaker (100 volt line) level, #14 Romex. But either one adds up quick. When the wire costs as much as the amplifier, you start to re think things.
This table would seem to recommend heavier wire than .5mm, something more like 1.5mm (14 ga US) for 1dB loss. However, the chart considers 1 speaker, not 20. So the chart is just a tad misleading, but stay with this a bit.
When specifying wire size, it is meaningless to say something like "1.0mm copper cable is good for up to 10Amps" because those ratings have to do with heating and maximum safe current carrying capacity. In this application we're concerned with total voltage drop, not maximum current. In this application, every wire that provides adequate voltage drop performance will be operated far below it's maximum current.
It turns out, with 20 speakers at 1.2km of 1.5mm diameter wire, you'll loose about 4.5dB in the wire. That means total power available to all of the speakers will be more like 150W, not 420, and the actual maximum power won't hit 15W, even if tapped that way. If you've calculated the number and location of speakers based on SPL at 15W, you'll be off a bit because of the cable loss.
However, there seems to be a few odd things about this design.
Questions:
1. Is there no way to power an amp closer to the speakers? That 1.2km of wire is a killer.
2. Why are you running those speakers on the 15W tap? That will be quite loud (112dB/w/m, you end up at about 124dB at 1m) Do you really need that much?
3. What is the purpose of the system(sounds like paging, perhaps?)
4. It's almost impossible to get wire in more than 300m put ups. Are you planning to splice?
Wireless microphones may not work over 1.5km well at all, that would require a different kind of RF link. Cable is almost always better, but line level wire is way less expensive than speaker wire. Cat3 for example is quite cheap, and will work just fine.
The bandwidth of 70V or 100V transformers is no where near as bad as most make it out. The FR of the horns is by far the limiting factor in response. Definitely use a constant voltage distributed system, either 70V or 100V. Local codes often dictate which to use.
When specifying wire size, it is meaningless to say something like "1.0mm copper cable is good for up to 10Amps" because those ratings have to do with heating and maximum safe current carrying capacity. In this application we're concerned with total voltage drop, not maximum current. In this application, every wire that provides adequate voltage drop performance will be operated far below it's maximum current.
It turns out, with 20 speakers at 1.2km of 1.5mm diameter wire, you'll loose about 4.5dB in the wire. That means total power available to all of the speakers will be more like 150W, not 420, and the actual maximum power won't hit 15W, even if tapped that way. If you've calculated the number and location of speakers based on SPL at 15W, you'll be off a bit because of the cable loss.
However, there seems to be a few odd things about this design.
Questions:
1. Is there no way to power an amp closer to the speakers? That 1.2km of wire is a killer.
2. Why are you running those speakers on the 15W tap? That will be quite loud (112dB/w/m, you end up at about 124dB at 1m) Do you really need that much?
3. What is the purpose of the system(sounds like paging, perhaps?)
4. It's almost impossible to get wire in more than 300m put ups. Are you planning to splice?
Wireless microphones may not work over 1.5km well at all, that would require a different kind of RF link. Cable is almost always better, but line level wire is way less expensive than speaker wire. Cat3 for example is quite cheap, and will work just fine.
The bandwidth of 70V or 100V transformers is no where near as bad as most make it out. The FR of the horns is by far the limiting factor in response. Definitely use a constant voltage distributed system, either 70V or 100V. Local codes often dictate which to use.
1) I suggest you put an amp close to the center of the speaker cluster.
So if they stretch from 1200 meters to 1500 meters away, put amplifier 1350 meters from you.
Then interconnect them with a 100V line BUT you have 2 advantages:
a) longest run is now 150 meters
b) each branch needs to carry half the power, so we are talking half the current.
2) if you have local mains power, use it
If not, sending 220V AC over 1.35 km is easier/cheaper than sending the straight Audio power.
As of signal, consider the RF option or, if impossible, use a microphone type balanced shielded cable.
Absoute worst case maybe you can use telephone type balanced twisted cable.
Usable if you drive it hard, so signal is well above noise/hum/interference floor.
So if they stretch from 1200 meters to 1500 meters away, put amplifier 1350 meters from you.
Then interconnect them with a 100V line BUT you have 2 advantages:
a) longest run is now 150 meters
b) each branch needs to carry half the power, so we are talking half the current.
2) if you have local mains power, use it
If not, sending 220V AC over 1.35 km is easier/cheaper than sending the straight Audio power.
As of signal, consider the RF option or, if impossible, use a microphone type balanced shielded cable.
Absoute worst case maybe you can use telephone type balanced twisted cable.
Usable if you drive it hard, so signal is well above noise/hum/interference floor.
Well, that can't be true. The wire size would be at least that of a 100V speaker circuit, and the type may be seriously more expensive, that's assuming local codes even permit a circuit of that voltage to be that physically long.2) if you have local mains power, use it
If not, sending 220V AC over 1.35 km is easier/cheaper than sending the straight Audio power.
Neither of those is cheaper that speaker wire.
Hardly the worst case! Actually, more along the lines of the correct solution. Telephone cable is fine, and you don't have to drive it hard. Common-mode Hum and noise is cancelled by virtue of it being a balanced line. It's actually the preferred solution, provided there's power available at the other end to plug the amp into.
Can u please share me any formula with which i can calculate.
Regarding Questions:
Q1. Is there no way to power an amp closer to the speakers? That 1.2km of wire is a killer?
A. There is not any place near where i can place my equipments and also there is desgin releated problems i am using system manager and suvelanceframe which making it impossible.
Q2. Why are you running those speakers on the 15W tap? That will be quite loud (112dB/w/m, you end up at about 124dB at 1m) Do you really need that much?
A. I want to achive 90db and the area is hander type.
Q3. What is the purpose of the system(sounds like paging, perhaps?)
A. For purpose of public addressing system with live and perrecorded message playback in metro depot.
Q4. It's almost impossible to get wire in more than 300m put ups. Are you planning to splice?
A. Tring to install cable in one row. if require we are using wago.
This spreadsheet is fairly complete. It's missing an SPL calculation.
You need to calculate required SPL first based on measured background noise and required signal to noise ratio. Then calculate required speaker power based on distance from speaker to ear. Then calculate number of required speakers based on coverage area and dispersion angles.
OK, but you're going to have to splice. There's a practical limit to installation of wire based on pulling, maximum cable tension, and distance. Codes usually require pull boxes at intervals for this, and other reasons.
I'm getting that you aren't a professional sound contractor?
I figured that much - and it sounded like it was for some one-off gig. In this type permanent install you consult the code book and be prepared to throw multiple thousands of dollars at it. Or pay a contractor about 3X and let him worry about code compliance. The speaker wire itself becomes a fraction of the overall expense.
So, then I get to vent for a second...
[vent mode on]
You'll hire a carpenter to build it, or a steel-worker to build it, a dry-waller to finish it, an electrician to wire it, a plumber to pipe it, and an HVAC guy to heat and cool it. But when it comes to a sound system, THAT's the DIY gig.
Some of us have spent lifetimes learning our trade. Just because it doesn't involve air, water, or high voltage, or won't fall down and crush you if it's done wrong, does that mean it's not worth doing right?
And the budget gets cut right there.
You know what? That's just fine. I get a lot of my work from jobs that were initially DIY. I fix them, and charge them for what could have been done cheaper, and better the first time.
In fact, 75% of my work comes from fouled up jobs of one kind or another.
So keep it up! You think you're saving money...or something...but I, or someone like me, will eventually get that money anyway.
[vent mode off]
Can't tell you how many times one different forums I've answered questions about distributed systems, only to be ignored, or worse yet, argued with. In fact, one of the last times I even bothered to get involved, the guy eventually told me distributed systems were unnecessary, and he was going to cover his entire facility with two hifi speakers. Wonder how that's working out.
To the OP...read these posts carefully, you're on the bleeding edge of the learning curve. Plan to learn, and bleed.
[vent mode on]
You'll hire a carpenter to build it, or a steel-worker to build it, a dry-waller to finish it, an electrician to wire it, a plumber to pipe it, and an HVAC guy to heat and cool it. But when it comes to a sound system, THAT's the DIY gig.
Some of us have spent lifetimes learning our trade. Just because it doesn't involve air, water, or high voltage, or won't fall down and crush you if it's done wrong, does that mean it's not worth doing right?
And the budget gets cut right there.
You know what? That's just fine. I get a lot of my work from jobs that were initially DIY. I fix them, and charge them for what could have been done cheaper, and better the first time.
In fact, 75% of my work comes from fouled up jobs of one kind or another.
So keep it up! You think you're saving money...or something...but I, or someone like me, will eventually get that money anyway.
[vent mode off]
Can't tell you how many times one different forums I've answered questions about distributed systems, only to be ignored, or worse yet, argued with. In fact, one of the last times I even bothered to get involved, the guy eventually told me distributed systems were unnecessary, and he was going to cover his entire facility with two hifi speakers. Wonder how that's working out.
To the OP...read these posts carefully, you're on the bleeding edge of the learning curve. Plan to learn, and bleed.
I can't count the number of times someone has posted up on DIYAudio only to be told "hire someone", "only buy name brand speakers, don't try to build anything"' "just take the amp to a shop"', "don't you DARE replace those unobtainium TO-3's with MJ21194's", or something along those lines. Sometimes it's the right answer, sometimes it's not.
Stringing up something temporary and installing in a municipality are two totally different things, and give different answers as to whether to DIY. Running 4000 feet of conduit is no simple or cheap task, and would be required just to pull telephone or Ethernet cable driven by an LM3886 chip amp (to drive line-ins). Shorter branch circuits from nearby power would be cheaper and easier than one long run - and if code says you can't run 4000 feet above 30 volts you have your answer as to whether to run speaker or line level. If you can't pass for an electrician you have your answer as to whether or not to DIY.
I've done plenty of diy electrical and construction projects, and hired out just as many. I pick my battles, with time being the number one determining factor. What I have found, almost universally, is the 3X difference in cost between what it would take to buy everything at Home Depot and hiring it start to finish. Worth it if it needs to be done *now* or if I just don't have the tools. What I absolutely cannot justify is a 3X adder to any of my sound-related projects, since they are not essential. If I can't DIY, I just DI-without. $3-4K subwoofer cabs are just not an option, and neither are Behringer Eurolives.
Stringing up something temporary and installing in a municipality are two totally different things, and give different answers as to whether to DIY. Running 4000 feet of conduit is no simple or cheap task, and would be required just to pull telephone or Ethernet cable driven by an LM3886 chip amp (to drive line-ins). Shorter branch circuits from nearby power would be cheaper and easier than one long run - and if code says you can't run 4000 feet above 30 volts you have your answer as to whether to run speaker or line level. If you can't pass for an electrician you have your answer as to whether or not to DIY.
I've done plenty of diy electrical and construction projects, and hired out just as many. I pick my battles, with time being the number one determining factor. What I have found, almost universally, is the 3X difference in cost between what it would take to buy everything at Home Depot and hiring it start to finish. Worth it if it needs to be done *now* or if I just don't have the tools. What I absolutely cannot justify is a 3X adder to any of my sound-related projects, since they are not essential. If I can't DIY, I just DI-without. $3-4K subwoofer cabs are just not an option, and neither are Behringer Eurolives.
Well, those are all different answers to very different questions, so yeah...
Understood on the cost. But you, apparently, have a pretty good perspective. Some, not so much.
The other little matters are accountability and liability. I have to be accountable for my work when charging for it, and that's a whole different world than DIY, regardless of for whom. Liability...well, if you wreak havoc, and you are not a pro with pro-level liability insurance, your life could be over as you know it, no matter who asked you to just get it done.
It could be a simple job, just drop a couple of speakers into a ceiling, wire them up and turn on the receiver. But while you're up there mucking around with ceiling tiles, you nudge a sprinkler head, and whoosh, you soak the office and bring in the fire department. Who's gonna pay for that one? Sure, a pro could nick a sprinkler too, but we've been around them enough to know the consequences and treat them with great respect, so the chances are minimized.
Just one example of things going wrong quickly because someone's never done it before.
Thanks everyone for their replies.
I looked into this found out that these type of system called "constant voltage speaker systems". So, Basically the 100V is used on the line to drive multiple speakers. At the speakers end step down transformer is used to get voltage to speaker withstandable level.
My question is if i use wire which gives me drop of 30 % to 40 % of voltage at the last connected speakers what will happen?
1. Is current on speaker increases?
2. Is the speaker volume decreases?
3. Or any other thing?
I looked into this found out that these type of system called "constant voltage speaker systems". So, Basically the 100V is used on the line to drive multiple speakers. At the speakers end step down transformer is used to get voltage to speaker withstandable level.
My question is if i use wire which gives me drop of 30 % to 40 % of voltage at the last connected speakers what will happen?
1. Is current on speaker increases?
2. Is the speaker volume decreases?
3. Or any other thing?
Constant voltage systems are intended to power "long" runs - but not *that* long. 300 feet is more typical. 30% voltage drop is half the power lost in the wire. You would get 70 volts at the last speaker. The impedance goes up, and you actually get a drop in current and power from the amplifier. You could theoretically cheat and use the 70 volt tap on the transformer to try to compensate, but you would still have power loss (as in less power at the speaker's) and it would increase the load on the amplifier back to what it would have been. It might also fly in the face of code to be running equipment outside the range of what was intended. If you have to run it over that long run and have 30 % drop, you would need to keep the run at 100 volts, oversize the amp by 3dB, and use the next higher wattage tap on the low impedance side of the transformers at the speaker (typically 3 dB steps). That would get the loading correct on the amp, and the right (maximum) power at the speakers.
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