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[Kevin Conlon]

The post about damping factor covered a few of my questions, but i have some more. The speaker stack at the far end of the amps,distro, etc. is going to to be near 100 feet of wire for an outdoor festival i am doing in April. I know i need large wire to do this right. My plan is to rack up the amps i need for the far side and use shorter # 10 wire to the subs. Seems sending 240 volts to the amps is more cost effective than buying all the speaker cable i would need to run 6 18's at that distance. This seems logical to me, you great people here have more experience than i do, so feel free to offer any advice. If i were to supply the far side stack from the main side how large a cable will i need?   6 18" drivers in three cabs. I did this show last year but i feel it could have been better, all stacks run from stage left supply, only with 12 wire, i perceived a difference in the balance. There will be more time for testing and tuning this year. Am i going in the right direction with amp placement? Thank you all for sharing your knowledge.

[Luke Geis]

100' of 12ga. cable pushing a 4ohm load will have a DF of 12.3 if the amp has a 500 DF. The wattage loss will be significant too. If you are sending 1000 watts out of the amp, the speaker would actually only get 858.5 watts!

To get the DF above 20 and maintain as much wattage as you can with a 100' cable it would need to be unusually large. Even with a 10ga. cable you would only get to a DF of 19.25 and the wattage loss would leave you at 907 watts at the speaker.

Now granted the loss of 140 watts due to cable length isn't that bad really, it could be enough between all of them once added to be noticeable. It is less than 1db ( about .66 of a db ). That is .66db of loss per speaker and if my math is correct you would be down about a 4db deficit from the other side in total output. Now that is enough to notice! I would want to fix it...... since 10ga. cable is the thickest practical cable you could get and would get you essentially close enough to a DF of 20, I think you would be fine. The db loss form the 10ga. cable would be .42 per cab, so about 2.5db in total. Though not great, it's not so bad that you have to stop the presses. The better option would be to move the amps to the other side of the stage of course.

This link has a really helpful calc to figure this stuff out: http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf

[Keith Broughton]

The post about damping factor covered a few of my questions, but i have some more. The speaker stack at the far end of the amps,distro, etc. is going to to be near 100 feet of wire for an outdoor festival i am doing in April. I know i need large wire to do this right. My plan is to rack up the amps i need for the far side and use shorter # 10 wire to the subs. Seems sending 240 volts to the amps is more cost effective than buying all the speaker cable i would need to run 6 18's at that distance. This seems logical to me, you great people here have more experience than i do, so feel free to offer any advice. If i were to supply the far side stack from the main side how large a cable will i need?   6 18" drivers in three cabs. I did this show last year but i feel it could have been better, all stacks run from stage left supply, only with 12 wire, i perceived a difference in the balance. There will be more time for testing and tuning this year. Am i going in the right direction with amp placement? Thank you all for sharing your knowledge.

Having the amps close to the speakers and shorter speaker cable runs is the way to do it.
Your idea to run power over to the other side of the stage is a good one.

[Ivan Beaver]

That is .66db of loss per speaker and if my math is correct you would be down about a 4db deficit from the other side in total output.

You don't add the losses to each cabinet up.

If everything is the same-then the loss to 1 cabinet will be the same as the loss to the total cabinets.

Think of it this way-if you kept adding speakers, then (with your math) the losses would keep adding up. and soon you would have NO sound------------

Sure the losses do add up (kinda) but you ALSO have to ADD IN the GAIN from the extra cabinets.

[Ivan Beaver]

You need to provide more information before a AC wire gauge can be suggested.

Things like-what model amp are you using and how many?

Different amps draw more power than others.

What you are asking is like "How many gallons of fuel will it take to drive from point A to point B?"

It depends on the car used-the driving style-the load you are carrying and so forth.

It is not not a simple answer.  But if you want to be sure of minimal losses- then use #0000 wire.

That is probably way overkill-but it would get the job done.  At a pretty high price though.

You have to help us (by providing USEFUL information) to help narrow things down.

It will ALSO depend on how you are getting your power.  Are you plugging into wall outlets? or are you tieing in power?  How far is the run from the source to the amp rack?

Yes all of these things matter.

[Lyle Williams]

If your system isn't running completely flat out, wire it up with the cable you have from the locations that are convenient.  If you have 2dB of wire loss on one side, turn the amp up 2dB.

[Kevin Conlon]

Thanks to all for responding. I just got home from working on a system for a nashville date next week and need to go to bed. I will respond with more detail another day. For now moving amps and feeding them with #8-4 from a 200 amp tie in is my thinking. Will get back when i have time and am more awake. Thanks again,    Kevin C.

[Kevin Conlon]

You need to provide more information before a AC wire gauge can be suggested.

Things like-what model amp are you using and how many?

Different amps draw more power than others.

What you are asking is like "How many gallons of fuel will it take to drive from point A to point B?"

It depends on the car used-the driving style-the load you are carrying and so forth.

It is not not a simple answer.  But if you want to be sure of minimal losses- then use #0000 wire.

That is probably way overkill-but it would get the job done.  At a pretty high price though.

You have to help us (by providing USEFUL information) to help narrow things down.

It will ALSO depend on how you are getting your power.  Are you plugging into wall outlets? or are you tieing in power?  How far is the run from the source to the amp rack?

Yes all of these things matter.

Did not intend to "bump" this post, but since i am, i am going to run ac to the other side. Ivan, i know you are sort of  joking about wire size as i gave no real details, i only have #2 on hand, and only need #8 or maybe #6 to do the job. The power is 200a to the distro and the whole show can run on a lot less, so we are good in the ac department. Real question was how large a speaker cable was needed to go 100 feet at 1000 watts per cab. I am going with ac power to the far side and #10 wire to the subs. The sound got us this return gig and another last season that we have been asked to do again this year. Just want to make sure it sounds as good as it can. Thanks to all of you for this great forum. KC.

PS, Nashville was a good show, everyone was stuck where they were by the ice/snow. A good time was had by all, it was a great night.

[Ivan Beaver]

Real question was how large a speaker cable was needed to go 100 feet at 1000 watts per cab.

The wattage has nothing to do with the size of the "suggested" speaker wire.  Unless you plan on running 30 ga or something like that--------

It is the IMPEDANCE load that determines the loss across the cable.

The higher the impedance-the smaller wire you can use.

That is why 70/100V systems are so popular in some cases.  Because the impedance is higher, the wire can be smaller and less expensive.

And then you must ask yourself-what IS an acceptable loss over the cable?

0.5dB? 3dB? 

To be totally honest, I have done installs in which the length of the wire vs the impedance is in the "not suggested" range. 

Nobody could tell the difference-it sounded just fine.

And if the extra cost had been incurred for the larger conduit and larger wire-nobody would have noticed-except the wallet would be a bit lighter.

It is all a matter of compromise.

Sometimes we get hung up on things that really don't make a big enough difference in the real world.  But are fun to play with on paper.

[Kevin Conlon]

The wattage has nothing to do with the size of the "suggested" speaker wire.  Unless you plan on running 30 ga or something like that--------

It is the IMPEDANCE load that determines the loss across the cable.

The higher the impedance-the smaller wire you can use.

That is why 70/100V systems are so popular in some cases.  Because the impedance is higher, the wire can be smaller and less expensive.

And then you must ask yourself-what IS an acceptable loss over the cable?

0.5dB? 3dB? 

To be totally honest, I have done installs in which the length of the wire vs the impedance is in the "not suggested" range. 

Nobody could tell the difference-it sounded just fine.

And if the extra cost had been incurred for the larger conduit and larger wire-nobody would have noticed-except the wallet would be a bit lighter.

It is all a matter of compromise.

Sometimes we get hung up on things that really don't make a big enough difference in the real world.  But are fun to play with on paper.

Ivan, I really enjoy all of the posts you respond to, sometimes it's hard to tell if your handing out a "are you that dumb" or if your kidding with us. Thanks for your replies. I thought about the 70 volt thing and have used it before, with matching amps at each end, may be a way to go. I had the idea of running each cab in series, 16 ohms instead of 4, but if one driver acts up you loose both drivers. I, like anyone, over-think things that really don't add up to anything in the end. It worked last year, it will work better this year, even if no one can tell. Thanks again for the advice, and Luke for all the math.  Thanks to all...  KC.

[Ivan Beaver]

I thought about the 70 volt thing and have used it before, with matching amps at each end, may be a way to go. I had the idea of running each cab in series, 16 ohms instead of 4, but if one driver acts up you loose both drivers. I, like anyone, over-think things that really don't add up to anything in the end. It worked last year, it will work better this year, even if no one can tell. Thanks again for the advice, and Luke for all the math.  Thanks to all...  KC.

A 70V system is all in parallel.  So if 1 fails, only that one fails.

What you tap the speakers at determines the impedance and the load "draw" on the amp.

It is a simple impedance issue.

Generally you simply add up all the taps-then add 10% or so and that is the size of 70V amp you need (or larger if desired)

A 1 watt tap is 4900 ohms, 10 watts is 490 ohms and a 100 watt tap is 49 ohms.

So if you used 1 of each of the above taps, you have a load of 111watts.  Or a total load of 44 ohms.

Assuming everything is "perfect"-which it is not.  Hence the reason to add 10% for just in case.  Or 122 watts

An amp that can produce 600 watts@8 ohms will drive a 70V line to full power.

I would not suggest 70V for subs-at least real subs.  The transformers get to be a problem at low freq.

[Kevin Conlon]

A 70V system is all in parallel.  So if 1 fails, only that one fails.

What you tap the speakers at determines the impedance and the load "draw" on the amp.

It is a simple impedance issue.

Generally you simply add up all the taps-then add 10% or so and that is the size of 70V amp you need (or larger if desired)

A 1 watt tap is 4900 ohms, 10 watts is 490 ohms and a 100 watt tap is 49 ohms.

So if you used 1 of each of the above taps, you have a load of 111watts.  Or a total load of 44 ohms.

Assuming everything is "perfect"-which it is not.  Hence the reason to add 10% for just in case.  Or 122 watts

An amp that can produce 600 watts@8 ohms will drive a 70V line to full power.

I would not suggest 70V for subs-at least real subs.  The transformers get to be a problem at low freq.

Right, i only thought about it. The 70 volt stuff i have done was to power the speakers on the utility poles around a town square, worked great but sounded like a transistor am radio, but the ones paying were happy. Never tried it with subs, and now i won't with that info. With all my amps on 240 volts, all logic says put the needed amps and a spare close to the speakers. I have what i need to do that. Volt lines are great for a department store, do they have any real use in quality live sound? Delays maybe, but i like wireless for that. Thanks again..KC

[Ivan Beaver]

Right, i only thought about it. The 70 volt stuff i have done was to power the speakers on the utility poles around a town square, worked great but sounded like a transistor am radio,

Don't blame the 70V distro system for the sound quality.

Blame the speakers hooked up to it.

Yes the deeper lows can suffer in a 70V system, but larger transformers will help that-at the expense of size-cost and weight.

[ProSoundWeb Community]