Shotgun Speakers

[Schniapereli]

So, I have a question about "Shotgun speakers" (or speaker arrays i've heard them called)
Our school is thinking of buying them as it remodels, and I was wanting to know more about them, and if they would be good or bad in a 1034 seating auditorium. We have a "sound expert guy" who says they are really good. I just wanted to know more about them , and I couldn't find any information on them online (except the weapon), so I was wondering what you guys know about them.

Also, if any of you can explain the RAT (or something like that) system that puts out noise. (the guy said it was pink noise, but described it as what defines white noise), and then it picks it up on the mic, and tells you how to EQ well for the auditorium.

If there is anyone that can explain these both in more depth, that would be cool. (or if anybody knows any other cool sound or lighting thingies that are interesting to know about, and how they work.)

 

[SHARYNF]

HI Here is a good link to get you started, they are typically called line array. The idea at the most simplistic level is a series of speakers with tightly controlled patterns that are arranged in a line so that the speakers are coupled one to another. The result is a sound source that is more "steerable" so that there is better directional control. Usually the array is hung and consists of a series of cabinets which can have their up down angle altered so that they in essence point to the audience area where the sound is desired.

http://www.prosoundweb.com/lsi/tech/la/la.php

You are also talking about RTA Real time analyzer

http://www.prosoundweb.com/studyhall/am_index.php/

Here you are looking at a system that takes a signal source and is able to display the signal that is received typically by a special mic. It has many adavantages in the hands of someone who knows its limitations. It can be a disaster in the hands of someone who simply makes corrections without really understanding exactly what the analysis mic is actually picking up and being analyized

Sharyn

 

[jbeutt]

Line arrays have become a bit of a fad. Don't get me wrong, they are a fantastic tool, but a tool nonetheless that isn't always appropriate. They're an expensive investment and you should be wary of people suggesting them simply as "cutting edge" or universally a good thing. Not to say your guy is wrong because we'd have no way of knowing.
Their usefulness in your space is really dependent on the architecture of the room. Line arrays are a tool that help, as Sharyn said, focus energy to the audience and therefor cut down on unwanted reflections. Generally speaking, they are more useful is longer rooms where energy must be sent farther. A key element to line arrays is their ability to send a fairly even amount of energy a long distance, whereas traditional traps taper their energy off very quickly.

Sharyn covered this, but a good way of describing line arrays is that one array creates a singular wave front, in essence acting like one speaker.

They're gunna cost you though, so that's why I caution against blowing all the coin on them without some good investigation into how appropriate they are for your space. That big price tag brings the benefit, though, that most suppliers and manufacturers will demo different systems for you so you ought to have the chance to hear a couple before buying.

 

[SHARYNF]

Just to expand on Jack's comments

TYPICALLY you are looking at a room with not only depth, but also height, since the line array should be flown in most cases. The industry has moved to these for large concerts, as opposed to stacks. Other than the technical acoustic focus capabilities, the major reason was to get the audio source high up, and beaming down on the audience, instead of out to the audience with a lot of rear and side wall reflections. the use of the multiple boxes allows each box to be directed to where you want the coverage, in a vertical plane.

Because of the complexity of the design of the wave guides etc, the boxes tend to be very expensive it is not unusual to have a cost of several thousands per box, and you typically need 6 boxes or more per side.

Personally I think they found favor with the major touring pa providers due to the abiility to reconfigure and adjust coverage patterns realtively easily, and also the ability to fly the rig and therefore improve visability.

Sharyn

 

[Schniapereli]

Well, the sound guy wants to put the speakers in 2 black boxes on each side of the stage about 10 or 12 feet up from the stage floor. (The one place where they sometimes hang lights for backlight on the apron. Don't know what that place is called.) Sounds kind-of wierd to me...
(...and, that's a really sweet site. Thanks.)

 

[Van]

That area is often refered to as the "Pro-slot" ,Big important factor in placing anything there, make sure it doesn't interfere with the operation of any fire curtain you might have.
On topic, I have a question here. Last year for our production of "Assasins" Our sound designer asked if I would mind building some line array speakers according to the instructions here http://www.partsexpress.com/projectshowcase/Kuze3201/Kuze3201.html

So i ordered all the parts and built the spaekers, Thought I did re-do the math and built 3.75" wide x 7' tall cabinets to mount the speakers in. It was my impression that the reason he wanted to build these was Volume to power consumption ratio and that they were very wide angled and would provide maximum coverage over the entire theatre. They sound fantastic and we're using them in a caberet show right now. But from what I've read here it seems as though you all are saying that Line arrays are not wide angle but rather tightly focused. What gives ?

 

[jbeutt]

Individual line array boxes are very wide in the horizontal coverage pattern and very narrow in the vertical. This narrowing of vertical dispersion (see the linked article above) increases the more boxes you stack on one another.
So your SD was correct in using one to get wide coverage.
Keep in mind though, the directionality that speakers are rated for is really for higher frequencies. Any box will have different patterns at different frequencies and become more omni directional at lower frequencies. Sometimes people get caught up in coverage ratings of speakers which typically (and possibly always, yes?) are talking about the horns.
But still, talking about radiating energy, line arrays are indeed wide horizontally. (edit: can and often are wide horizontally, but can come in varying degrees.)

 

[SHARYNF]

Here is a way to look at Line arrays

A typical single speaker or a point source creates a sound field that is like a balloon vaguely a round sphere of sound energy.

The problem with that is that a lot of the sound goes to areas that you don't want it to for instance above the audience to the ceiling floor etc.

A line array changes this balloon to a cylinder so you keep the same horizontal coverage but get control over the vertical coverage.

In addition with a single point source your sound level drops off as the distance from the speaker increases. In a line array each element is coupled and it increases the distance that the sound can travel keeping the sound level higher. It would be like saying if you mounted a series of lights one above the other instead of getting your illumination at 50 feet, simplistically you could get the same illumination at 75 feet, and adding more lights keep getting further and further distance all at the same level.

It is not that the line array has wide coverage horizontal by design it is that it keeps the horizontal coverage that the speaker has but by mounting the speakers one above the other where the distance from center to center is 1/2 the wave length you can narrow down the vertical coverage and increase the throw distance again creating in essence a cylinder vs a balloon.

So when the design from Parts express was built you get the advantage of the system supporting approx a 14 foot frequency wave and get the additional projection from the drivers.

Way back in the dark ages of early personal pa systems Shure had a system called the vocal master which was in fact a line array. One of the problems that many early designs had was thta they did not understand that you needed to get the drivers as close to each other center to center in the vertical as possible.

So from a practical stand point

If you have sub woofers that are all the same design ie front loading etc you are better stacking all of them one above the other and you will increase the distance that the sound will travel. This is a trick that can be used to improve the performance of the system since low frequencies are non directional. This is the case for instance in a dance club where you want that pounding base to go beyond the first 20 feet. So rather than putting one sub on each side of the stage you will get better performance if you stack them can be in the middle or on one side

If you look at the frequencies and the distances from the center of the driver to driver you will see that most of the line array effect is actually in the under 700-800 range with a typical 9-10 inch driver. The length of the array also has an effect on how low a frequencey you can control.

TYPICALLY you cross your subs at 80-100 and the array covers from that point up to 800 or so and then the highs are controlled via sometimes elaborate designs to attempt to creat more control. It is at the higher frequencies that the design and construction cost comes into play.

We have worked with folks in all sorts of configurations and sometimes a few tricks can really help

One is as I said above stack your subs
Second is make sure your speakers are above the audience pointing down to the audience like a light where the bulk of the coverage is on the audience not the back of the room.

It is possible to take full range cabinets and hang them so that you can get the near and far field coverage there are issues with lobing etc but sometimes you can improve the system inspite of the possible problems

Sharyn

 

[Van]

Thanks I knew y'all would have the answer.