Loudspeakers How to size speaker for a venue !

[OTO1702]

Hi every one,

I have search in the forum without luck ! So here is my question :

How can I size the good amount of power and the kind of speakers I have to use for a venue. Here is an example :

The room is a large cafeteria of minimum 100 x 400 feet. The stage is 40x30.
The type of music is Rock \ Metal kind of 90' cover band
The venue will have between 1000 and 1200 persons
The seeling is 15 feet High.

Now I would like to learn about how to calculate the power needed or at least see the first steps. The speaker type seems to be pretty important. I was thinking on using 4 TX9S subs and 4 SRX725 because that's what I have, everything is crown powered ( MA and MT)

Am I wrong ? What about using powered tops like the HPR122i (I have 8 of these also) could it be better with the Yorkville subs ? Because I really like the qsc's tops

Thank you !!

 

[BillESC]

If the stage is on the short wall, you should really consider a line array.

 

[museav]

How can I size the good amount of power and the kind of speakers I have to use for a venue.

It's not just for the venue, it's for the applications. While the physical space is a critical consideration, so are the expectations for the system. What are you looking for as far as level, response, coverage, etc.?

The room is a large cafeteria of minimum 100 x 400 feet. The stage is 40x30.
The type of music is Rock \ Metal kind of 90' cover band
The venue will have between 1000 and 1200 persons
The seeling is 15 feet High.

I would check the dimensions, 400'x100' is a very large space, about the size of 8 full size basketball courts, and 30 to 40 square feet per person is a pretty large area per person. Are you not filling the space? Since you noted a ceiling height, are you planning on flying the speakers, either from the structure or on truss, or are you limited to ground stacking or on poles? And as Bill noted, where is the stage?

Now I would like to learn about how to calculate the power needed or at least see the first steps.

It starts as noted before, with determining what levels, etc. you need to achieve. Need to know the desired results before you can figure out how to get there.

The speaker type seems to be pretty important. I was thinking on using 4 TX9S subs and 4 SRX725 because that's what I have, everything is crown powered ( MA and MT)

Am I wrong ? What about using powered tops like the HPR122i (I have 8 of these also) could it be better with the Yorkville subs ? Because I really like the qsc's tops

Probably the biggest issues will be coverage, avoiding having very high levels up front and much lower levels at the rear or sides of the room, and the level. Unless you have the right speaker system and can properly fly it, to get reasonable coverage of that large a space and audience for that type of music you may have to consider using delay fills. What signal processing and amps do you have available?

 

[OTO1702]

Well !

I have verified and the room is approx 320' x 120'

The stage is on the 320' side.

We Won't have any truss system on the Front stage. My expactations are to cover in off the room so every one can easely here what is going on. Around 95db at the FOH.

The amplifiers are from crown : MT2400 and ITech2000 and Itech 4000 I thing. There is no processors, the itech take care of it.

Thank you !

 

[museav]

"My expactations are to cover in off the room so every one can easely here what is going on." is not really that useful, they will hear it but do they need to understand what is said? Should the entire audience be getting about the same level or is it acceptable to be much louder near the stage and maybe 20-30dB lower in some areas? If the speakers are at the front corners of the stage that makes the furthest listener up to 166' away. Trying to cover that distance with pole mounted or ground stacked speakers is going to be a challenge. If you aim the speakers at the most distant parts of the audience you are going to end up with much of the sound hitting the walls and ceiling rather than the audience. With a 15' ceiling and nothing flown you are going to have difficulty having much evenness of coverage over the entire audience area.

With a 30' deep stage in a 120' deep room and 140' of space off to either side of the stage, will there be audience to either side of the stage that you want to cover or are you only concerned about the 90' in front of the stage?

Are you planning on running stereo? Getting stereo for such a large space with both channels covering the entire space with some uniformity will be even more difficult and will definitely affect the speaker system.

95dB at FOH, but where is FOH? Is that flat, A-weighted or C-weighted? Is that the peak level or average level? In my experience, that would most likely be an average level with probably more like 105-110dB peaks desired. If that is A-weighted that could mean wanting up to around 130-140dB from the subs, so you're probably going to be a bit short there.

On the amps, how many do you have? If you have one of each that would limit the options. Tuning the overall system response using processors in each amp can be difficult and the MT series do not have internal processing.

Perhaps the most important issue is whether your question is indeed what you need for the application or whether it is actually what can you do with what you have? Those are two different questions.

 

[mixmaster]

Hi every one,

I have search in the forum without luck ! So here is my question :

How can I size the good amount of power and the kind of speakers I have to use for a venue. Here is an example :

The room is a large cafeteria of minimum 100 x 400 feet. The stage is 40x30.
The type of music is Rock \ Metal kind of 90' cover band
The venue will have between 1000 and 1200 persons
The seeling is 15 feet High.

Now I would like to learn about how to calculate the power needed or at least see the first steps. The speaker type seems to be pretty important. I was thinking on using 4 TX9S subs and 4 SRX725 because that's what I have, everything is crown powered ( MA and MT)

Am I wrong ? What about using powered tops like the HPR122i (I have 8 of these also) could it be better with the Yorkville subs ? Because I really like the qsc's tops

Thank you !!

Application specific question not withstanding, here's some math to think about:

JBL SRX 725s have a 99db@1watt/meter efficiency. you say you want 95 db as your target db, and we'll assume that's at the furthest point from stage. Add about 10 db of headroom for peaks gets you to 105 db. Plug those numbers into the calculator on the crown website
Amplifier Power Required Calculator
and that comes out with needing almost 17K watts of power....seems a bit much but that also includes 3 db headroom on the amps.
Now, the SRX725s are only rated about 4800 so you would need 4 to handle that much power. For your subs, I'd find those same specs, plug them into the calculator, but take them with a big grain of salt. You need plenty of power for subs.

Now, all of that being said, this is just a figure for how much power you need to fill the room with a stack of speakers sitting in the middle of the stage in an empty space. This won't help you figure for reflections off the walls, a room full of people absorbing sound, directivity or pattern control for intelligibility, or how much extra SPL you might need to get above the stage volume. I assume this is also based on a point-source system, and I don't know how well something like a line-array would hold to these measurements.

Matt

 

[BillESC]

For that space and application I'd use three of these:

EVA-2082S/906 - Electrovoice

And three of these:

EVA-2082S/920 - Electrovoice

Mounted as a single source three point array.

 

[TimmyP1955]

Sounds like a job for nothing less than Danley: Danley Sound Labs - Home of Tom Danley - Innovative Designer of Pro Loudspeakers & Subwoofers

 

[FMEng]

It sounds like you have limited resources and a difficult space to work with. If this type of event is not commonly done in that facility, it might make more sense to hire a sound re-enforcement company to come in and do the gig. If you have 1200 people at the show, there should be some money available to hire a properly equipped expert to come in and do it.

It seems to me a waste of money to buy equipment that won't really be up to the challenge, for a one time thing. Spend money on the in-house system to do the usual stuff very well, not the unusual stuff badly. Then, do the rest with a hired system.