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[Tom Petrusky]

I have to ground stack 6 vt4888's as flying is out. How stable are they with what I propose in the plotting software, or do I need to arc back a bit to make them stable. Venue will be 6' below the bottom box and about 100' deep flat and level with no grandstand or elevated seating in the back.

[Riley Casey]

If the calculator is happy you can be happy.  Sand bags on the back of the frame will help if you feel nervous about traffic around the stacks.  When we ground stack on scaff we ratchet strap the backs of the frames to the scaff.  Stacking that high is a substantial PITA.  Having something to stand on on either side of the stack for dropping the pins in is a big help.  Think big subs or low scaff.  Doing it in the dark is an even bigger PITA. Plan accordingly.

[Scott Holtzman]

I have never ground stacked higher than three and we normally only stack four to a tranaport cart.

Keep in mind these are 30 poinds lighter than the 4888. 

I decided since we were using the big truck I might as well stack all 6 and the bumper.

It was a huge pain in the ass with just two of us.

After the third cabinet getting the next ones up and the pins set is tough.  If you are standing on a stack of subs it will be that much harder.

Sent from my VS996 using Tapatalk

[Luke Geis]

Do you really need 6 to do the job? This really sounds like a conventional box type of job. A flat plane viewing audience and only 100' deep is not entirely large or difficult to cover. The top 2 boxes are shooting into space, while the 4th box is shooting straight back into walls and space 10' over every ones heads. Only the three bottom boxes are doing any of the actual work. I could see the possibility that the upper three boxes help " shape " the near field so it is more consistent with the far field, but literally half the energy is not shooting at anybody's heads.

Not my place to say, but I just think this is a job more suited for point source boxes.

[Tim McCulloch]

I'm not a fan of such deployments but customers hand me money to do them.  I'm not sufficiently ashamed to refuse it.

My only concern beyond COG is getting enough 'bend' to the rear hinge bars between the bottom box and array frame.  You're going to need 8-10° of down tilt (maybe less if the audience is further away from the PA).  That will also push your COG further forward.  If you haven't done so, I suggest you attach a box to the array frame and experiment.

[Steve Eudaly]

If you haven't done so, I suggest you attach a box to the array frame and experiment.

Agreed. I haven't worked with VerTec in a minute, but used to do this deployment often when there were no other options [the client was willing to pay for] and it worked well enough to get the job done.

I applaud you looking for options other than the infamous "six boxes pinned at zero" stack that I see all too often.

[John Sulek]

Agreed. I haven't worked with VerTec in a minute, but used to do this deployment often when there were no other options [the client was willing to pay for] and it worked well enough to get the job done.

I applaud you looking for options other than the infamous "six boxes pinned at zero" stack that I see all too often.

It is possible (but not any fun) to build and pin this on the ground and then stand it upright and slide into place. Not my first choice but sometimes you have to do things the harder way.
You need about 8 humans to do this and put some ropes on the top to be the "bridle"to slow the horse down a bit.
If you can try this at the shop, practice there first.

We used to do this at a venue in town all the time with 3 x 4889 on a sub and frame.
I have done 6 x 4889 this way and that is as far as i would ever go.

[Steve Eudaly]

It is possible (but not any fun) to build and pin this on the ground and then stand it upright and slide into place. Not my first choice but sometimes you have to do things the harder way.
You need about 8 humans to do this and put some ropes on the top to be the "bridle"to slow the horse down a bit.
If you can try this at the shop, practice there first.

We used to do this at a venue in town all the time with 3 x 4889 on a sub and frame.
I have done 6 x 4889 this way and that is as far as i would ever go.

This is exactly what we did when we had enough room for it. Much faster than stacking one by one but requires ample humans.

[Helge A Bentsen]

FWIW groundstacking large linearray elements seems to behave better than smaller ones in the same applications.

Best groundstacked rig I've ever used was four as side d&b J, that was really nice. IIRC 4888 is about the same size as J.
A few years ago I did a lot of groundstacks with 4886, that was decent, but the boxes always ran out of gas in the low end first.
Larger boxes seems to suffer a lot less from this.

Beyond and above all, get some degrees between each box. 0 degrees sound awful in a groundstack.

[Todd Friemuth]

I've had to do this quite a few times as well. Typically in small theaters that have no points anywhere downstage, or the small festival stage with no fly bays. What has worked best for me on these types of days has been to ask my lighting guy to drag his feet getting his downstage truss built so I can use his motors first. I build the 6 boxes as normal if I were to fly it, I pin everything at zero, then I use a spanset and wrap the bottom box (or top box when the stack is inverted) and use a lighting motor to stand it up. I float the stack and land it on a chunk of commercial carpet runner with the rubber side up. This facilitates being able to slide or walk the stack into position more easily. Then I just go through and touch up the angles by hand. It's a chore, but it can be done. I also make a point of making sure no one climbs on them. Nothing worse than stacking the PA like that and having the local Eddie Vedder wannabe crawling around on them all night.

[ProSoundWeb Community]