I think it's important to give accurate information to our friends here. Some are just beginners and it is not always easy to distinguish the difference between fact and opinion.
Agree, accurate information is important. I regularly run events wit screen ranging in size from the small 16' to 40' plus and I've walked the crowds with not only a db meter but a spectrum analyzers to assess our sound reinforcement. I've spoken to professional in the sound reinforcement and live audio fields about this subject and others in an attempt to learn so my company could and would stand out against the competition. I didn't just make up what I said in my earlier post or this one based on my opinion.
Generally subs for our larger screens and this larger crowd or area size are a waste. That is unless you are bringing enough.
This is totally counter intuitive. Wouldn't you would a bigger, louder system capable of deeper bass and longer throw for a larger crowd?
Of course you would want a bigger, louder system capable of deeper base. I'm not disputing that nor is that the point of my statement.
A quick example: 20' screen I would recommend at a minimum 4 center clustered subs, more as you go up in screen size.
A recommendation for a specific number of unknown speakers based solely on screen size with no consideration for the size of the area or number of audience members is not very valuable.
There are general rules for potential audience sizes in relation to screen size, it can also be assumed that the venues will wide open outdoor spaces. DigitalDevice was speaking about an 18 Mackie Thump sub... So if we are looking at a 20' screen, an potential max audience size of 50 - 300ish, and a wide open park then I feel very comforatable with the statement that 4 center clustered subs would be a good starting point.
Also realize pro-audio subs really aren't subs as most people are familiar with from their home theaters, very few extend down deep.
This depends on what you consider deep. There are professional level subs capable of chest-pounding, pants-flapping brutal force. Most don't have much output below 25Hz. Plus, they usually have handles, casters, and a tough exterior finish that all come in handy when you are repeatedly setting-up your system.
What is deep? Well most quality subs from companies like SVS, HSU, Rythmik, Velodyne, etc have subs being measured down to 20hz, thats deep. I can't name a single pro sub that reaches those depths, its not their job to reach down that deep. Pro subs are being used for live sound applications or recorded audio and their isn't much content that deep outside of pipe organs etc. This is in contrast to movies which have lots of content down in those ranges. In most of our budget ranges you can look at the JBL PRX618s-XLF, my personal choice of subs. These are 1000 watt 18" subs that have a stated spec of 30Hz, its doubtful that they are reaching this in reality. The Mackies are at 35Hz and the QSC HPR's are quoted at 45hz. Of these specs the QSC are the most realistic and most likely where the Mackies are at.
Running 4 of the JBL's, center clustered in front of the screen, the effect was minimal at 60' out and almost none at 100'.
What does them having handles, casters, and tough exteriors have to do with their performance or output?
Subs for a commercial enterprise are difficult. They are heavy, you need a lot of them, and customers generally ate not willing to pay the extra cost in involved.
You don't need a lot of subs. Any sub will allow a system to play lower and potentially louder. Yes, many customers want the cheapest package and are unwilling to pay for an option or upgrade regardless of its value. But every indoor movie theater has subwoofers. Do you upcharge for the center and surround speakers also?
I like bass. I like a lot of it. I'm also practical. Many times I choose to run a pair of 15" 2-way speakers for my BYT - no sub, center, or surrounds. It depends on the situation.
You ABSOLUTELY need a lot of subs in an outdoor environment if you are trying to increase your perceptible bass output! One sub for a typical movie in the park type of event is going to do nothing for anyone past the first row.
Center and Surround speakers in a "typical" movie in the park type event are almost unheard of for several reasons. The first is COST. Second, surround sound in a large open field is more then difficult to pull off and the scope is well beyond 99% of commercial operators. Really think about what your trying to do and how people typically spread out at one of these events. People spread out over a football field size area with the left speakers putting out only the left content, same for the right, and surrounds. Except for a small percentage in the center who will get some of the effect, the rest are going to have an very difficult to understand movie to listen to. Can it be done, yes, but again the scope of equipment and work is large. So do we up charge for this, um yes...
Do we up-charge for subs, um yes. If I'm bringing out 4 - 8 large subs, with power cords, xlr's, etc I'm going to charge for it. It takes extra room in trailers and trucks and time/man power.
Yes movie theaters have subs, multiple subs. They are also an indoor venue where the effect of air pressure, boundaries, etc all come into play. Your ticket price and concessions all go to pay for every bit of equipment in that facility. A theater doesn't say, ya know subs should be standard so we won't count them when we figure out how much we have to charge to stay in business and pay for everything.
We're not talking about backyard stuff, backyard you can get away with 1 sub, you have smaller groups and everyone is typically sitting much closer. When we throw up a 20, 30, or 40 foot screen people are starting to sit, typically, 40-50' back from the screen.