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 Post subject: Airshow
PostPosted: Wed Sep 06, 2017 9:46 am 
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Joined: Sun Jul 15, 2012 9:24 pm
Posts: 168
Location: Dayton, OH
Here are a couple of photos from an event we did yesterday. My friend's band played during dinner and during the intermission of a private corporate airshow. We knew that the crowd would be large but I think it was a bit bigger than anyone expected. We used my four T39s and four OT12s plus the bands QSC K12s for side fill and another pair about 250 feet away where the dinning tents were located. There was really only room to lay the subs across the front of the stage but that worked fine. If anything we really needed more mains. Four more OT12 would not have been too much. The sound was good from the stage to about the halfway point in the crowd. After that is dropped off pretty fast which was okay since most people were there for the airshow but could move up if they wanted to hear the band.


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File comment: Crown taken from the stage during airshow
crowd.jpg
crowd.jpg [ 37.75 KiB | Viewed 387 times ]
stage.jpg
stage.jpg [ 84.5 KiB | Viewed 387 times ]

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4 x T39 - 20" - 3012LF (Built 2)
4 x OT12 - 2512 - Melded/D220Ti
1 x TAT - GTO804
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 Post subject: Re: Airshow
PostPosted: Wed Sep 06, 2017 1:55 pm 
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Joined: Wed Jul 30, 2008 10:18 am
Posts: 583
Location: Kankakee, IL
Bill, would there have been any low end benefit to standing them all up, side by side, facing the crowd? Maybe less low end cancellation? (It would have obscured the band's knees and shins, no big deal.)

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2 DR250s, 2 27" Lab15 T-60s, 2 30" Neo Titan 39s, 1 Autotuba...and looking for more!


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 Post subject: Re: Airshow
PostPosted: Wed Sep 06, 2017 2:11 pm 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
Rich4349 wrote:
Bill, would there have been any low end benefit to standing them all up, side by side, facing the crowd? Maybe less low end cancellation? (It would have obscured the band's knees and shins, no big deal.)


No cancellation as long as they are within a quarter-wavelength......if I remember what Bill said a long time ago.

I've laid mine down like that with no problem.

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6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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 Post subject: Re: Airshow
PostPosted: Wed Sep 06, 2017 9:51 pm 
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Joined: Sun Jul 15, 2012 9:24 pm
Posts: 168
Location: Dayton, OH
The most hilarious part of the day was the power that they had for us. Before we got there they told use that we would be running on a generator. Always a little concerning since you never know what to expect. When we were ready for power I got one of the maintenance guys to show me how to start it up. He walks me around to the other side of the hanger where there was a 55kW, 100HP, 5000 lbs diesel generator. Not for the whole event, just for the stage. Okay, that'll do.

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4 x T39 - 20" - 3012LF (Built 2)
4 x OT12 - 2512 - Melded/D220Ti
1 x TAT - GTO804


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 Post subject: Re: Airshow
PostPosted: Thu Sep 07, 2017 2:27 am 
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Joined: Thu Mar 24, 2016 1:11 pm
Posts: 19
Location: Austin, TX
Bruce Weldy wrote:
No cancellation as long as they are within a quarter-wavelength......if I remember what Bill said a long time ago.


Is that measured center-to-center or edge-to-edge?

I'd assume edge to edge, as a quarter wavelength at 120Hz is about 28 inches... and some BFM horns are wider than that.


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 Post subject: Re: Airshow
PostPosted: Thu Sep 07, 2017 2:58 am 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
alexk wrote:
Bruce Weldy wrote:
No cancellation as long as they are within a quarter-wavelength......if I remember what Bill said a long time ago.


Is that measured center-to-center or edge-to-edge?

I'd assume edge to edge, as a quarter wavelength at 120Hz is about 28 inches... and some BFM horns are wider than that.


Edge to edge.

And a cancellation at 120hz is usually a good thing! :mrgreen:

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6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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 Post subject: Re: Airshow
PostPosted: Thu Sep 07, 2017 3:13 am 
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Joined: Thu Mar 24, 2016 1:11 pm
Posts: 19
Location: Austin, TX
Bruce Weldy wrote:
And a cancellation at 120hz is usually a good thing! :mrgreen:


What are you doing up at 3am? :p


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 Post subject: Re: Airshow
PostPosted: Thu Sep 07, 2017 4:37 am 
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Joined: Fri Nov 27, 2009 11:37 am
Posts: 6092
Location: New Braunfels, TX
alexk wrote:
Bruce Weldy wrote:
And a cancellation at 120hz is usually a good thing! :mrgreen:


What are you doing up at 3am? :p


One of the consequences of old age, I guess. Once a week or so, I wake up and can't go back to sleep. Thanks goodness I don't have to get up and go to work!

_________________

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."


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 Post subject: Re: Airshow
PostPosted: Thu Sep 07, 2017 9:43 am 
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Joined: Sun Jul 15, 2012 9:24 pm
Posts: 168
Location: Dayton, OH
From the sub placement guide: "The basic rule is to have them either less than a quarter-wavelength apart or more than two wavelengths apart for their pass band, which for 40 to 100 Hz means less than 2.8 feet or more than 56 feet."

I did have a v-plate in the trailer and consider stacking and plating for a few more dB. But laying them out across the font was definitely the most workable arrangement. It's not obvious in those pictures, but there had been nearly 3" of rain a few hours before we arrived. The grass was full of standing water. The driest area was the front of stage and still we had to put the subs on tarps to keep them dry. Also there are pieces of plywood under the rear speaker stand legs to prevent them from sinking into the ground.

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4 x T39 - 20" - 3012LF (Built 2)
4 x OT12 - 2512 - Melded/D220Ti
1 x TAT - GTO804


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