setting up an amp

[sound_nerd]

well, see, you're trying to run power from an amplifier down what is at the most, 18awg wire, maybe 22awg. That is BAD NOW. Bad in theory, bad in practice. If you already set it up, unplug it asap. In a pinch, you can run 14awg extension cord with speakon ends from the booth to the speakers. That would be cheaper than 100 feet of professional speaker cable.

 

[tjbaudio]

You will damage the snake by using the returns with speaker level. The wire in most snakes is closer to 22 or 24 awg (think phone line) That is unless the returns are built to take speaker level. If it is ment to do that the wire for the returns will be thicker. However you still need to check the specks on the snake. Even if it is rated for speaker level you are still better off running the amps at the stage by a long shot. Keep in mind though that if by chance the snake is ment to run speaker level through then the speaker lines are not good for line level.

 

[zac850]

Well, I talked to some people, so we are not going to use it until we get some 12 gauge 1/4 inch TS cable... a bit over $100, but it will be done.

Thank you so much for catching that mistake everyone. It will be dealt with, and until that happens, we won't be using sound in that room.

Thanks again!

 

[m4g1cky]

Thank you so much for catching that mistake everyone. It will be dealt with, and until that happens, we won't be using sound in that room.

Thanks for catching his mistake, I didn't either, but of course, I was just testing him.

Now, time for one of my questions: Since you all are saying to have the amp at the other end of the snake, I was wondering if it would be feasible to have a sort of wooden road case to house the amp, as it has rack mounts? To illustrate, I have included a happy mspaint:
[mspaint]

[/mspaint]
Now, one of my motivations for suggesting this is that I believe it would save us some time and money as we would just roll the amp out, plug it into the returns, and the speakers, and have the cables stored in the road case. Is it feasible for us, or would it just be easier to have it run from the booth.

zac850 disagrees, and will be responding with a rebuttal soon (Heh, butt.)


ps. I'm the sound guy he is always referring to. .

 

[zac850]

My rebuttal--see, its only a little funny...

Anyway, my point of view is that it will not save us more time. If we are running the amp from the booth with a 12 gauge cable, we have about 97% efficencty. Since we have a 500 watt amp and a 400 watt speaker, so the 19 watt's that are lost in the cable arn't all that important.

If we do it the way m4g1cky sugests, we would have to run a 100 foot power cable next to the snake, down the counduit so that the amp and the rest of the sound system are on the same circuct.

To set up we would have to wheel out the amp (which would be kept in the back closet with the all of the cleaning equptment and chairs and stuff) plug it into the power, plug in the returns from the snake and the speaker output.

If we have it run from the booth, we just have to purchase 2 100 foot 1/4' 12 gauge speaker cable and run it down the conduit. The cost of this is just over $100 (about $50 somad each from PSSL). The ends would sit right next to the breakout of the snake, and when needed we would just use 2 adaptors that we already have to plug another 1/4" TS cable in and run it to the speakers

One thing that m4g1cky reminded me: the booth is sitting right infront of a hot air vent from the heating system. While I am trying to get some wood to block this off, it is fairly hot (i don't know the tempature, but it would be about 90' up there). As I said, I am trying to get this off, but this could be a factor.

Anyway, we leave it to you CB, which do you sugest we do, and why?

 

[tjbaudio]

I personaly like the idea of having a cart with all of the cabling in it. As has said having the amp closer to the speakers is better. However I do understand having the amp in the booth where it is safer. I will admit that in the system I just installed I put the amps in the booth, but I used heavy wire to the main cluster (1 12 awg run for each of 3 speakers) and I used better ends than 1/4" (hard wired to the amp and NL4's at the cluster) Using the 1/4" ends and the cheep adaptors is asking for problems. They tend to short the amp as they are conected and the 1/4" to 1/4" adapters tend to just short out all on there own. The 1/4" ends are called "PHONE" plugs because that is what they were ment to do, hook up phones at a switch board. Get some heavy Nuitric NL4panel mounts and run some 12-4 or 2 runs of 12-2. for your speakers run NL4 to 1/4" cables from the wall.

Also as for havign a 500 watt amp on 400 watt speakers, stop worieing about it! At 500 watts of beringer power you are probably still under powering the speakers if you want maximum performance. The extra power in the amp is headroom. And using long cables to "reduce" the power the speakers see is just a bad idea. With longer cables you reduce the dampaning factor of the system. The dampining factor is the amps ability to controle the speaker movement. With poor dampining the speaker driver can flop and bottom out easyer than with a good short cable. The speaker will also sound better with shorted (or thicker) cables.

TJB

 

[zac850]

Well, if I buy the cable it will be 12 awg.

Someone here (i forget who) made a power-loss calculator

When putting in all the information I get 96.15% efficiency, a loss of 19.23 watts. That still gives me 480 watts getting to the speakers, so we still have some headroom for that.

The thing is, I am really worried about the amp getting damaged if it is placed in a movable cabinet in the back closet. Things could get dropped on it, someone could not know what it is and put it out in the rain, etc.

Any other opinions?

 

[tjbaudio]

Running a 12 awg cable for each speaker is fine. BUT please make it NL4 for as many conections as posible. I thing a 1/4" jack is only rated for 50 watts. The contact area is tiney and like I said before, they short the out put of the amp if they are pluged/ unpluged. THe worst is if it is 1/2 unpluged and no one notices. The amp is then just sitting there driving a dead short.
TJB

 

[The_Guest]

You'll eventually fryout your snake returns, that's not good. Leave your long runs to your balanced siginals, leave your short runs to your inbalanced. In just about every portable applacation (Even though this in your facility, you still have to strike your amp and speakers. Therefore, it's portable) the amps belong at the stage. You're washing your signal down the drain with such long runs like that. It's okay to put amps in the booth just as long as it's an install, you're using top notch wires, it's hardwired, and the wires will be wired away from nasty things in the walls that will cause buzzing ahd hums. I have found more interferance problems in systems with longer amp runs than shorter ones. Those high powered inbalanced lines are just asking for interferrance. If you can consider converting your speakers input jacks to speakon (neutrik NL-4), you really have no idea how much it will improve your system.

Poor connections and cabling often are responsible for the largest problems and lag on computer networks. Thousands each day are spent fixing these problems, and in reality good cables cost so little.

 

[zac850]

Well, the way it is run now keeps the cables away from power, so I'm not worried about hum that way. What my mind keeps coming back to is that I do not trust my school to keep the amp's safe. things get thrown around, little kids run around, and people throw things around without knowing what there doing (the speaker's are constantly used as a table for water, soda, chips, etc.)

OK, so, what if I got 2 100 foot speakon cables, and then when I got to where the snake ends used an adaptor of some sort to get to 1/4 inch? or... I believe that the speakers also have an XLR input. If I used an adaptor at the amps and got the speakon over to XLR (3 pin, so balanced, right?) and then ran the XLR down to the back of the gym where the normal snake ends, would that work? What gauge is normal XLR cable? I remember seeing speakon to XLR adaptors somewhere for like 5 or 10 bucks, so that would be easy....

I'm just really scared about keeping the amps where anyone could touch them and spill soda on and break....

 

[The_Guest]

Well, the way it is run now keeps the cables away from power, so I'm not worried about hum that way. What my mind keeps coming back to is that I do not trust my school to keep the amp's safe. things get thrown around, little kids run around, and people throw things around without knowing what there doing (the speaker's are constantly used as a table for water, soda, chips, etc.)

OK, so, what if I got 2 100 foot speakon cables, and then when I got to where the snake ends used an adaptor of some sort to get to 1/4 inch? or... I believe that the speakers also have an XLR input. If I used an adaptor at the amps and got the speakon over to XLR (3 pin, so balanced, right?) and then ran the XLR down to the back of the gym where the normal snake ends, would that work? What gauge is normal XLR cable? I remember seeing speakon to XLR adaptors somewhere for like 5 or 10 bucks, so that would be easy....

I'm just really scared about keeping the amps where anyone could touch them and spill soda on and break....

First of all you'll need a quick cable lesson...

XLR-3 pins, low z, balanced. Great for microphones and interconnects between audio components (ie: mixer to processor, processor to amp, or mixer to powered (active) speakers, etc). Not to be used with passive speakers.

TRS-3 contacts (pins), low z, balanced. Stands for Tip, Ring, Sleeve. It's basically XLR but in a 1/4" form. Great for audio interconnects (CD players, auxilaries, mainouts, snake returns, effects units, balanced compressors, etc) It is a balanced signal it can be ran long distances. Because of it's 3 pins I can also run an unbalanced stereo signal, which many headphones use. Even though TRS is balanced it can be ran unbalanced by bypassing the "Ring", thus functioning like a TS cable.

TS-2 contacts (pins), hi z, unbalanced. Stands for Tip, Sleeve. It's just basically guitar/bass cable, often used for unbalanced inserts for compression. This is not something you'd want to run down a snake because of it's unbalanced siginal. In theory these cables can be used for speakers, but regular TS is not insulated or strong enough to handle heavy power loads from an amp.

1/4"-2 contacts (pins), hi z, unbalanced. Even though 1/4" often refers to TRS, TS, 1/4" loudspeaker, etc. We'll refer to 1/4" as a hi z, unbalanced, loudspeaker cable. Even though they're unbalanced they should not be used with guitars, compressors, or other unbalanced audio devices. This cables have more insulation and a tougher guage wire. As with all loudspeaker cables, try to cut down on length to generate a cleaner signal.

Speakon-the poles (pins) vary from connector to connector. I've seen everything from 2 poles, to all the way up to 8 poles. Often reffered to as (neutrik) speakon NL-2, NL-4, NL-8, BSR-WR, etc. Speakon is much more robust cable/connector than 1/4" loudspeaker. Speakon cables lock when mating to prevent any disconnections, which definitely can prevent some nasty noises and even protect your loudspeakers. Another reason to go speakon is it's just simply a different cable, it avoids the 1/4", TRS, TS confusion. Which you can really benefit in your high school environment you speak of, it will definitely avoid mistakes. Things will get done the right way, the first time, definitely an educational plus.

Now that you've learned a thing or two about cables you now know it's impossible for a speaker to have both 1/4" loudspeaker and XLR. XLR is an balanced lo z signal that could not handle the force of an amplifier. 1/4" loudspeaker is suited for linking a power amp and a passive (non- powered) loudspeaker together. However powered speakers (in which the amp is built into the speaker) can accept an XLR cable.

Personally I would ditch the 1/4" loudspeaker jacks on your speakers and install speakon jacks. This is not hard to do at all, the connectors are cheap too. It's just basic soldering skills, if you can't do it I'm sure someone around could do it for you if you showed them which wires go to which. Just by doing this your already running a cleaner signal, is definitely smart thing to do if you plan on running the amp from the booth.

Now I have a quick question...where do you store all of your other equipment? If your worried about losing an amp, I'd be losing sleep wondering if your express 125 was safe and sound. If you have to run a snake and setup everytime (since your in a gym), why not just run the amp on stage and lock it up with rest of your gear when your done. I personally really like the idea of getting a rack with a bunch of storage and putting your amp in there. Think about it, when it's time to setup and start working you just take the rack from the booth and roll it to the stage. You'll have all your stage cables/supplies with you, no need to make trips back to the booth. And you won't have to tape down two extra cables ALONG with your snake.

This reminds me of the last system I designed. I put the mixer/processing all in one main rack. I had this rack put on a seperate dollyrack where the amp and drawer would go. This allowed me to roll in only one rack, but I could split the FOH rack and amp rack up. So if I needed to mix a longer distance from the stage I could split it up. Or if it was not necessary to mix far away I could still have the amp and FOH racks together.

Hope this helps.

 

[Mayhem]

Jeff - you raise some pretty valid points here but I think there is some confusion between the connectors and the cable.

For example, some of the older amps and speakers left the factory with 3pin XLR connectors on them. Only one of my 3 main amps has Speakon connectors. The important thing is the cable that is used in between the connectors.

As you correctly point out, speaker cable is different to signal cable. Not only in the conductor gauge, but in the fact that speaker cable should not be sheilded. When you think speaker cable think of power cable.

The main difference between say a mic lead and a speaker lead (appart form the cable) is that the speaker cable will have two female xlr connectors on it and the mic cable will have one male and one female.

I agree that where ever possible you should use speakon connectors for the visibility factor but it is the application not the connector in my view that makes the difference.

Again - I agree with Jeff and everyone else that has recommended keeping the amp as close to the speakers as possible and I certainly run my amps on stage. As for the power thing, the important factor is reducing noise and one way around this is not to have lights on the same circuit or even use a line filter. Many amps now have an ground lift switch on the back that will disconnect the signal ground from the chasis ground, and in most cases this will remove the hum.

Many good points raised in the posts on this topic and when running an amp on stage I still prefer to run it flat out and control the volume from the desk. I know a few people have commented on the inability to know what setting to use if other people use the desk. My response is that who ever uses the desk should do a sound check and besides, if you decide that you need to turn the amp up, do you really want to have to run to the stage to do it??

Just my thoughts after a long hot day!

 

[zac850]

Well, the snake is permanently run in a conduit under the gym, and that is where any additional cables will be run as well. It is permeant, and it is never leaving.

The express 125 is safe, because it is in the booth, where I want to keep the amp.

So.... what if we ran speakon under the gym through the conduit and once we're there, switched it to 1/4' for the speakers? The speakers are 1/4 inch, and I would like not to spend the however much to change them over.

I understand what everyone is saying, and at every theater (excecpt 1) that I worked at, the amp is back stage. However, I just can't get over my fear of the amp getting broken/destroyed.

 

[m4g1cky]

Just a clarification for my own state of mind, if we keep the amp backstage, we would use the returns on the snake to go from Amp to Soundboard correct? I'm just a little confused about this.

Also, would it be easier to make a roadcase or buy one($$$?) and if so, would it be safe in it? Since that is Zac's main concern, and mine as well (Though not as much), it would probably be the deciding factor in using a road case.

If we were to run it back stage, it would be off a different circuit than the lighting.

edit: On another note, does anyone know of any sound system design software. Similar to Lightwright for lighting? I'm interested to do this in my spare time, to save time actually working with the equipment.

 

[sound_nerd]

here is a simple solution, that is very cost effective. Also, its a method that I used when wiring the portable student council sound system at our school. Go to your nearest pro audio dealer. Buy 4 Speakon NL-4 connectors, or whatever connectors you need. Go to Home Depot (or lowes, or wherever) and buy 200 or more feet of 12/2 power cable or 12/3 might be easier to find. Make sure it has thick insulation, its much cheaper than standard speaker cable, and for an application like yours, it will do just fine.

 

[Mayhem]

Just a clarification for my own state of mind, if we keep the amp backstage, we would use the returns on the snake to go from Amp to Soundboard correct? I'm just a little confused about this.

Yes - the returns from the snake would join the output from your sound board to the inputs of your amp. That is what they are designed to do.

Also, would it be easier to make a roadcase or buy one($$$?) and if so, would it be safe in it? Since that is Zac's main concern, and mine as well (Though not as much), it would probably be the deciding factor in using a road case.

Depends upon your application and for security you might see if your manual arts teacher can make up a steel frame to which the amp can be bolted in to and then locked in place.

Or you could get a conventional rack and leave one of the top bolt holes empty and place a padlock through this hole and the rack frame. The rack can them be chained into position if needed.

Although, as long as the amp/rack are stored in a secure position before and after each show I fail to see a problem.

If the sound goes out during the show, just look for the guy with your amp in his hands and head him off before he gets to the door!!

 

[len]

I was always one of the "open it up all the way" type people. However, the people at QSC say it's not a good idea. According to them you should run an amp at about 70% as a baseline, and then make minor adjustments from there.

 

[mr_sound]

I well built roadcase will protect it from the abuse you're worried about. The amp itself is probably tough enough to take the occasional bottle of windex falling on it....but not IN it...that's another story. If you pack it up in a decent quality rack (like SKB, or even make your own flight case..hell check ebay), it'll be fine for most abuse. What exactly do you think is going to be done to it? This can take being moved around and bumped into and such....but it's not going to take a fall down a flight of stairs well (though if it weren't a behringer, it just might live).

Now you've been warned by everyone else about behringer....but take it from me...I bought a lot of behringer stuff for my sound rig and over the years most of it has decided to stop working in some ways. I got the digital board with the mic pre's screwed up. I got the 32 chan analog board with noise problems, and half the auxs are dead. I've got feedback destroyers where a connector goes bad....and these are things that haven't seen much road abuse either. I've got a behringer compressor/limiter that is just not causing me problems. Here's what hasn't stopped working though: My QSC amps, and even my Mackie board and speakers. Behringer is crap...they fall apart much too easily, and the cheap cost in my opinion doesn't make up for all the time you'd spend fixing their stuff. If you're on a tight budget go with makie or peavey. They're not top of the line either....but for the money it's good. I've had my mackie board for 5+ years now, and it still keeps ticking...whereas the behringer digital board lasted almost a year.

 

[mr_sound]

I well built roadcase will protect it from the abuse you're worried about. The amp itself is probably tough enough to take the occasional bottle of windex falling on it....but not IN it...that's another story. If you pack it up in a decent quality rack (like SKB, or even make your own flight case..hell check ebay), it'll be fine for most abuse. What exactly do you think is going to be done to it? This can take being moved around and bumped into and such....but it's not going to take a fall down a flight of stairs well (though if it weren't a behringer, it just might live).

Now you've been warned by everyone else about behringer....but take it from me...I bought a lot of behringer stuff for my sound rig and over the years most of it has decided to stop working in some ways. I got the digital board with the mic pre's screwed up. I got the 32 chan analog board with noise problems, and half the auxs are dead. I've got feedback destroyers where a connector goes bad....and these are things that haven't seen much road abuse either. I've got a behringer compressor/limiter that is just not causing me problems. Here's what hasn't stopped working though: My QSC amps, and even my Mackie board and speakers. Behringer is crap...they fall apart much too easily, and the cheap cost in my opinion doesn't make up for all the time you'd spend fixing their stuff. If you're on a tight budget go with makie or peavey. They're not top of the line either....but for the money it's good. I've had my mackie board for 5+ years now, and it still keeps ticking...whereas the behringer digital board lasted almost a year.

 

[zac850]

I'm not worried about things getting bumped, what I'm worried about is someone setting an open soda on it, goes off to play basketball, the soda falls over and gets all over the amp.

Yes, yes, I know, behringer is crap, I know. However, we had a very small price range to choose from and it was between behringer and american DJ, and I have personally have a horrible time with some American DJ lighting gear, so I choose the Behringer. We just really need to make this last for about 3 or 4 years, and then we will hopefully getting a theater space that is not a gymacafatoriam and the sound can get a well deserved face lift.