Array Deployment Question

D

David Sturzenbecher

Junior
Jan 15, 2011
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Hello, I have more of a hypothetical question concerning line array deployment not pertaining to any specific box. The situation I am questioning is a typical arena concert, playing half to 3/4s of the room. The array has been designed to cover from the floor to the upper seats. Attendence is not good so the upper seats are not filled and have been blocked off. In this senereo would you turn off the boxes towards the top of the array, turn off the highs/mids only at the top of the array to keep the length longer at lower frequencies, or just leave it alone? (or something else all together? ie go back to the model and see how things look without a rehang) Just looking for some opinions on this.
 
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Re: Array Deployment Question

"It depends."

If I know in advance that the seats are not sold before I even load in, I'll make sure I don't waste boxes firing into nothing. Instead, I'll shoot the top box at the last seats sold, and readjust my angles as needed to cover the rest of the room. If I find out about the lack of sales after the PA is up and doors are open, well, then I'll just kill the mids and highs in the top boxes to keep unwanted sound in unwanted places. Lows always stay on.


Evan
 
Re: Array Deployment Question

There is a club in Baltimore with 3 levels that frequently shuts down the upper levels when ticket sales are low to mid range. This place may also have the world record for hard reflective plans in awkward places. Each time I have asked the SE to turn off the top of the array, it has greatly improved clarity on the floor.
 
Re: Array Deployment Question

I try to cover every seat in the venue, regardless of whether or not it is sold. The reason is that I learned my lesson the hard way by listening to promoters and venue staff who tell me that a section isn't sold, not covered it, and then had people end up sitting there. If, at the start of the concert a section is empty, I would shut off that zone of PA. I probably wouldn't do that with a line array though, as the whole system response would change. Perhaps in an arena with 12-16 per side I would turn off the top two or three boxes if the potential gain of not having extra energy bouncing around would outweigh the issues by having a system whose performance might change from how it sounded at sound check.
 
Re: Array Deployment Question

Good question, let's take a look at this in simulation and see what the consequences would be. Here's a purely imaginary room that I just happen to have a reasonable model for at 200Hz and 4kHz, frequencies that I think represent the LF and HF behavior of the array well.

4792fb39.jpg027b0693.jpg

Here's what happens if we just turn off the top 5 boxes, again at 200Hz and 4kHz.

df476caa.jpga25dc480.jpg

Well, that's not great at all! If you imagine FOH around the 80' mark, that's going to change things a lot, and we've still got 8 boxes out of a 13 box array left. As you can see, line arrays do not behave like the simple model you may have in your head. Even at a relatively high frequency you still need to consider the effects of the entire array on your frequency response, and without the top part of the array dragging the pattern up at low frequencies your response changes even more below 1kHz.

Turning off the HF section in the top boxes isn't the worst solution, although that top lobe that was firing into drapes is now firing into your audience. What if you can't do that, since you have powered boxes, or boxes with an all-in-one amplifier solution that makes it difficult, or you don't have enough DSP control? Here's the effects of a 500Hz 2nd order BW LPF, shown at 200Hz (I didn't show 4kHz since it's almost identical to just turning off the top boxes). You have to be careful when messing with line array phase!

0b6b3c21.jpg

Long story short, if I knew those seats weren't sold I would hang differently. Maybe less boxes, certainly different angles and processing, but once that array's in the air I'm not modifying it.
 
Re: Array Deployment Question

Bennett,That is an interesting set of models and looking at it made me think just how out of the ordinary the example I initially thought of was. In my example, neither of the hangs is long enough to show much line behavior anyways and are mostly set for the upper floors of a short but tall room. FOH and the floor are for the most part covered by trap fills at stage level. Not a classic example by any means.And it should be clear that I don't make system changes if I can at all avoid it. I much prefer to ask the SE for a particular result and then let them figure out the best way to achieve it. I would hope that my little bit of knowledge just helps me check if their solution is reasonable.Some fleshing out of those models may leave you with another interesting article.
 
Re: Array Deployment Question

Bennett,

You said 'Well, that's not great at all!' when showing the plot of the reduced array size.
I find the second plot, with top 5 boxes muted, EXACTLY the solution for the presented problem.
Sure SPL is different, but polars are hand in hand with 'new' venue occupancy.

... Or am I reading something wrong ?

w/r

Btw : quote : "You have to be careful when messing with line array phase!" .... PLEASE DON'T is my final answer
 
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Re: Array Deployment Question

Bennett,
I'd be curious to see an array modeled after an "arena" hang. Your hang has the top boxes pointed toward the ground, basically covering a flat area(IE- an outdoor area or theatre). Most times in arenas I either have a J hang with the top boxes straight back, or the top few boxes up a few degrees, depending on the available trim height. I'd imagine the lobes to be a lot different in these situations.


Evan
 
Re: Array Deployment Question

I thought placing the very top plot (all boxes @ 200Hz) and the second from the bottom graph (~2/3 boxes at 2k) looked pretty smooth as well representing the "just turn off the HF/MF sections of the box. At least it looked pretty smooth when I was only viewing the floor, before I saw the dotted line representing the "pull out arena seating behind FOH"
 
Sorry, that dotted line is much harder to see in these images than when I drew it. If this were a real prediction for a real venue I would also have truncated it properly to show that the seats don't start at the floor, and that there is a 10' wide walkway at the top.
 
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