Guesstimating and speaker selection

[Grommet]

As being an all around person i get pulled into things such as "Hey we rented a sound system can you make it work for today?"

And what gets rented is always a bit too small as far as the power it can put out.

I'm want to for future events is force myself into the planing stages a say "we need to rent a _______and a ________with _________watts."
Is there a rule of thumb for system selection for outdoor music for a 100 person crowd, 500 or 1000? or just out doors in general

What about indoors for a non acoustic friendly space for 100 200 1000 person house?

 

[gpforet]

If you're renting from a sound company, provide them with a desired SPL over a specified coverage area and the type of content to be delivered. Also provide descriptions of the physical space and audience size. Lastly, spec the number of inputs, and desired or required outboard, and available power.

There are far too many variables to be able to answer the question with a global answer.

As an exercise, find some speakers, get the specifications regarding frequency response, dispersion pattern, efficiency, and power handling. With this information you can determine the max. SPL you can provide over a given coverage area at a given distance. Additional speakers covering the same area and being powered in the same way will increase your spl by 3db (this does not apply to line arrays). Additional speakers splayed will provide more coverage area. Wall reflections will deminish sound quality.

Like I said, not a simple answer.

 

[Chris15]

Talking in terms of wattage is useless...
If you have one speaker rated at 98 dB SPL 1W, 1m, and another rated to 95 dB SPL 1W, 1m, then it will take double the power to get that second speaker to the same volume as the first...

 

[WooferHound]

In General . . . you will need 4 times the power to do an outdoor show, compared to an indoor show. If you want the Bass to Thump Outdoors you will need more than 2000 watts. This is wildly general as every program is different.

 

[museav]

In General . . . you will need 4 times the power to do an outdoor show, compared to an indoor show. If you want the Bass to Thump Outdoors you will need more than 2000 watts. This is wildly general as every program is different.

I'm not sure how you arrived at these numbers but as already noted, there are so many factors to consider as to make any specific Watt recommendation pointless.

An example, four times the power is +6dB. You could get the same change by using different speakers with a 6dB higher sensitivity. Or have the same level at the rear of the audience if that distance is half as much. Or by having everyone on axis rather than off axis and 6dB down.

As gpforet noted, except when there are specific limitations, it is usually much better to define the results (levels, coverage, intelligibility, response, etc. at the listeners) and the situation (audience size/area, type of music and so on) to the provider than to try to define how they should do it.

Or consider that grouping subs together rather than physically separated can allow them to couple, with a resulting up to 3dB greater output with the same devices and amplification due to mutual coupling and the resulting summation.

 

[WooferHound]

The first 2 words I used were "In General" meaning "Generally Speaking"
The things I said are a good place to start if you are asking the questions that were asked
Sure you can give a nonanswer like "it depends on this and that", I was just giving them a place to start. From there they can learn more about the the finer points from experience. I guess I left out the part about using reasonable efficient speakers.

 

[gpforet]

I'm wondering the same thing....what is this "4 times" based on?

The first 2 words I used were "In General" meaning "Generally Speaking"
The things I said are a good place to start if you are asking the questions that were asked
Sure you can give a nonanswer like "it depends on this and that", I was just giving them a place to start. From there they can learn more about the the finer points from experience. I guess I left out the part about using reasonable efficient speakers.

 

[WooferHound]

It's based on a starting point. Once a person does a few outdoor shows they will have a better idea on what it will take to cover an area of a certain size. But they should know that it takes a lot more power to go outdoors without the reflections from walls. I do a lot of shows in the summer, about 1/4 of them are outdoors. I have the experience to know what I will need for an event, it could be anything between 150 & 3000 watts depending on the program and and the size of the area. But I do know that whatever I would need to cover an area indoors, I would need at least 4 times the power to cover the same area outdoors.

 

[museav]

But I do know that whatever I would need to cover an area indoors, I would need at least 4 times the power to cover the same area outdoors.

I think you are perhaps leaving a critical piece of information out of this statement, which is that it apparently assumes everything else remains the same. Same components, same system arrangements, same result, etc. However, it is quite common for numerous other things to change when moving between comparable indoor and outdoor applications. Compared to a comparable indoor application people will often use more subs, group the subs, use higher sensitivity mains, tune the system differently and perhaps even have different expectations for an outdoor application, all of which could also affect the power required to get the same result.

 

[howlingwolf487]

...The things I said are a good place to start if you are asking the questions that were asked...

Then, the OP needs to learn to ask different questions. I think he's getting the point now.

Here, in order, is what I would ask:
1. How far will the furthest audience member be from the stage?
2. What SPL do you require at the back of the audience area? (This is also a good time to inquire as to the genre of music.)
3. What are the rough dimensions of the performance area - length and width (height, too, if the venue is raked, etc.)?
4. What is your budget?
5. What type of AC power, if any, do you have available at the performance location? (And no, a 6-outlet surge strip does NOT equate to 6 circuits.)

As long as you get the desired SPL and sound quality over the majority of the performance area (it'll never be perfect, unfortunately), the number of people is irrelevant. Waterbags, er...punters will soak up a bit of the sound, but the biggest issue may be keeping the band louder than the screaming fans...

 

[Grommet]

Thanks for all of your input. I think i have enough info to ask the appropriate questions when i talk to the rental company.