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Author Topic: hockey arena sub configuration recommendations  (Read 1786 times)

Jean-Pierre Coetzee

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Re: hockey arena sub configuration recommendations
« Reply #10 on: June 29, 2018, 03:33:03 am »

I would look at something like Dave Rat's vortex setup on the sides with a usual cardiod setup through the middle.

He mentions some stuff about it here. just search for for vortex it should come up.
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Word & Life Church

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Xandy Whitesel

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Re: hockey arena sub configuration recommendations
« Reply #11 on: June 30, 2018, 01:49:13 pm »


Thanks you'all for these comments...all tidbits of information are helpful.

Responses:

As Steven mentioned, looking at the polar plot is indeed a good thing to point out and keep in constant mind.   In fact the basic spaced virtual arc looks pretty crap at 80Hz and above (presumably because of the wide line length and also the decrease in output of a B22 at the freq) but comes together below that and looks more powerful, thought at 65Hz it still doesn't look great to me considering it's not pushing hard in the +20 degree and -20 degree directions.  But the coverage below 65 is very very even.

I answer the frequency response questions probably the same as everyone else.  Yes, I want a big tight 65hz-ish push for rocking kick drum.  Yes, I still need the rest of the frequency range, the lower stuff for the songs that are bass synthy, the higher stuff for the 2nd kit's kick drum, the whole range for the bass gtr on the rock songs.  Yes, the musicians are most bothered by low end that is lobe-y on stage or that clouds up their mix (80-120) beyond discernability.  The weight of my kick moves around some, room to room.  If 70-100 is tight in that particular room I like it higher.  If it's not I'll go lower.  Super low kicks (40-50hz) kind of irritate me but I'll do it if I have to.  What I'm saying is that I think we all probably tailor decisions and compromises we make based on what is happening in the room that day.  If 40hz is a floppy mess that goes on for 10 seconds then if we're smart we avoid it.

Steven, why do you say that the "virtual arc of cardiod stacks...will likely narrow vertical coverage"?  I would like to understand the physics of that statement.  I've done a few measurements in theaters of 2 high stacks vs. 3 high that indicate that the top sub of a 3 high stack increases low end on the floor 6db but doesn't do anything for the balcony.  Is your reasoning related to this?
 
RE money seats... from the response I've received from my PM/BMs, seat cost goes down with elevation, which doesn't help us much with decisions: we still need wide and even coverage. 

It is hard to know what the ideal ratio of forward to side coverage is; I guess it will really depend on the shape of the venue.  1-1 sounds actually too wide to me, at least in a normal oval shaped arena where the PA will be setup to throw farther than wider, though in Oslo spektrum 1-1 looks desirable since the venue is kind of even depth to width and very wide.  I think that (in the sub frequency range) rear cancellation is just as important as coverage in an arena setting.  If sub freq is bouncing around the back of the arena then the entire venue sounds like mushy wet dogdoo.

end responses, begin notes.

My thinking has distilled down to the desire for two options.   The status quo option is: spaced and cardiod stacks across the front of the stage delayed to arc the coverage, augmented by a flying cardiod hang to widen side coverage.  Is there an alternative setup that looks as good or better if you add up and weigh all the compromises involved?  I think I may have found one, described later, but the proof will be in  the pudding.  If I have a total of two setups to audition, I can find the time, gumption, and manpower to set up and dial in them both, and decide which one seems better.

Attempting to improve on the status quo, I made a new file for the spaced arc keeping the line to 40' wide but turning the outside cardiod stacks 45 degrees.  This seems to tighten up the polar plot in the 90 degree off axis region, bringing in that lobe at 80Hz and maybe improving rear cancellation.  It would still be weak on the sides; enter a flown hang of J-subs into the equation, toed out and hung to cover 60-90 degrees off center.  But how is the lobed coverage you'd get from a flown side hang interacting with a center covering arc any different from the lobed coverage from a Left pile interacting with a Right pile?

The vortex plots seem to look promising.  But what is going on in there?  What is the vortex exactly?  How does it work?  I've distilled it down to this: it's a two dimensional end fire.  If you setup a square of subs all pointing in the same direction, and think of it as an end fire in the forward direction and another end fire in the sideways direction, you can end up with a plot resembling the vortex.  But the vortex actually has something else going for it.  With the subs oriented in different directions it has somewhat varying distances between each pair of acoustic centers.  This morphs it a bit away from end fire and a smidge towards delay steering, but also dissipates comb filtering (in the forward direction) and cancellation (in the backwards direction).  And also makes you look at the thing and wonder what the hell is going on happen when you turn it on.  What all is getting ignored, including that sub energy from one box actually has to go around the box in front of it, and can you really treat a 3'x4' box as a single point of acoustical center?  Not only that, but B22 subs are different dimensions and directionality than SB28s, so the math between my model and DR's model is not the same.  When I nudged the B22's locations to be a closer match to the acoustic center of an SB28, the plot looks worse.   If I put in delay numbers that match closer to what DR describes, the plot looks worse.  Currently the delay numbers are what arraycalc came up with to get the most forward steering, and arraycalc actually decided to use a different sub stack as it's timing start point than DR's calculations.  Which is all fine, I guess.  We're dealing with some kind of squishy seeming math anyway.

In my attempt to understand how the vortex worked, I made various models of subs in various orientations, as I said, and ended up deciding that the theory is based on an end fired end fire.  Then I stumbled on a setup that looks similar to a vortex, but simpler, and in my opinion better, at least with the B22 subs that I'll be using.  Finally, this plot looks like a potential competitor to the status quo.  And it might be slightly easier to understand and set up.  It's still a square-ish shape of 4 stacks of subs; the inner 2 stacks face out, the outer stacks face forward.  This offsets the acoustical centers somewhat, naturally steering the array slightly towards the outside.  It's about 9' deep and 8' wide.  Mucking with the delays, I arrived at a plot that looks very wide cardiod, and the rear cancellation looks excellent.  (You can widen or narrow it a bit with delay times, but rear cancellation changes along with it.)  Add everything together and the compromises still look reasonable.   (The squeeze in 40Hz off axis coverage on the LR polar plot is a freq/distance specific hole.  Or is it a crack?)  I feel good about it, but what do I know?  I know I want to know what you'all think.  Can you'all please pick this apart and point out the goods, bads and uglies of this solution?

plots in accompanying posts.

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Xandy Whitesel
Bon Iver FOH
Denver, CO

Xandy Whitesel

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Re: hockey arena sub configuration recommendations
« Reply #12 on: June 30, 2018, 01:50:27 pm »

new awesome setup??
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Xandy Whitesel
Bon Iver FOH
Denver, CO

Xandy Whitesel

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Re: hockey arena sub configuration recommendations
« Reply #13 on: July 09, 2018, 12:26:57 pm »

new awesome setup??

Had some time and space and gear after a rehearsal a few days ago, so I set this up with 4 Qsubs and walked around.  No measurements, just pumping a track and getting a seat of the pants impression, and also be convinced that math in a fancy prediction program actually translates to the real world with real subs inside a real room.  It was quite perceivable and appeared to obey the plot, super punchy in front and a lot of cancellation obeying the wide cardiod pattern.  The 80-100hz lobe in back was also noticeable.  It seemed like the pattern might be a little narrow actually, if I set this up again the times can be massaged/lowered to widen the pattern a bit if necessary.
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Xandy Whitesel
Bon Iver FOH
Denver, CO
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