Omnitop 12

[Bill Fitzmaurice]

I`m planning on building a few OT12s.How many of them can be stacked per side for an audience of say 2500,and how are they to be stacked,straight or vertical?

Stacked vertically.

For a rock concert for 2500 of your closest friends, I'd look for a setup to have between 16 and 24 OT12's.

I'd say 6 to 10 per side, with eight to twelve T48s. Depending on the stage configuration perhaps a couple for center fill.

[Paul Norman]

I plan on having 12 OT12's. 6 on each side of a 40ft.x4ft. high stage outdoors with 8 T48's. Crowd size about 1,000 to 1,800. I was planning on a melded cross fire array in the bottom OT12 in each stack. Is this going to give me enough horizonal coverage? Thanks.

[Bill Fitzmaurice]

I plan on having 12 OT12's. 6 on each side of a 40ft.x4ft. high stage outdoors with 8 T48's. Crowd size about 1,000 to 1,800. I was planning on a melded cross fire array in the bottom OT12 in each stack. Is this going to give me enough horizonal coverage? Thanks.

It will except possibly stage center at very close range, say within 10 to 15 feet or so. But I'd try it with the stacks alone before doing center fills. With 50 feet or more between the stacks center fills would be a must, unless there is no audience close in.

[mloretitsch]

I`m planning on building a few OT12s.How many of them can be stacked per side for an audience of say 2500,and how are they to be stacked,straight or vertical?

Looking at the chart we could probably take 102db 1w/1m as a sensitivity figure for the omnitop12. I will figure 125 watts driving each speaker (headroom is good).

6 per side at 1500 watts:

25 feet = 126.9db

at 100 feet = 114.9db

at 200 feet = 108.8db

10 per side with 2500 watts:

25 feet = 131.3db

100 feet = 119.3db

200 feet = 113.3db

10 per side should cover any serious metal act that I've done.

[Bill Fitzmaurice]

I`m planning on building a few OT12s.How many of them can be stacked per side for an audience of say 2500,and how are they to be stacked,straight or vertical?

Looking at the chart we could probably take 102db 1w/1m as a sensitivity figure for the omnitop12. I will figure 125 watts driving each speaker (headroom is good).

6 per side at 1500 watts:
25 feet = 126.9db
at 100 feet = 114.9db
at 200 feet = 108.8db

10 per side with 2500 watts:
25 feet = 131.3db
100 feet = 119.3db
200 feet = 113.3db

10 per side should cover any serious metal act that I've done.

That's not how you figure it. Sensitivity goes up when cabs are stacked, to a maximum of about 116dB/watt, which ten cabs would get you. Then you calculate total output based on total array power. Being very conservative for ten boxes we'll say 1000 watts. The resulting 1m figure is 146dB. Add another 3dB for the second stack. Then you must account for the nearfield, where SPL drops at 3dB per doubling of distance instead of 6dB. With ten cabs the line is about 12 feet high, so at 500 Hz the nearfield will extend about 30 feet out, at 1kHz 60 feet, etc., before the 6dB rule kicks in. This is why line arrays are so much smaller and use so much less power than cluster arrays. The higher they go the more efficient they are.
BTW, metal acts don't corner the market on dBs. Many of todays country acts are just as loud, and since the preferred tone of metal is a scooped midrange the country acts can subjectively sound louder.

[gdougherty]

So maybe run 8 OT12's (10ft stack) with 8 T48's, put the subs out to the side 50ft apart and run separate sets of 4? Or go up to sets of 6 with 12 T48?
I have to say, it's pretty kick-ass thinking about running a cluster of 6 -T48 with a single amp running 3 per side. The QSC PLX3602 should easily run 58V into 3.3ohms each side. Considering the small festival rigs I've seen with their pair of double 18's and couple double 15's running a rack of Powerlight's per side, the difference is rather astounding.

[jbell]

After many questions, and help from all -- this is almost exactly where I ended up for my stadium project this summer. 8 OT12's per side(well, actually 4, OT212) and then subs. Since my project will be 100% recorded music and permanent install, 36" wide T36's, not T48's.

My goal was 142db at 1m.

can't wait till it gets warm and I get to install...

[gdougherty]

Pictures of the sealed up boxes without corners from the last time I swapped all the tweeter elements.

[Tom]

Where are you getting the grills, and are you cutting and bending the metal to do it?

I have a few cab building projects starting up, and hope mine end up looking as good as yours!

[gdougherty]

Where are you getting the grills, and are you cutting and bending the metal to do it?

I have a few cab building projects starting up, and hope mine end up looking as good as yours!

I purchased a pair of Dayton 22x30" 6mm grill pairs from PE that Leeland since figured he could have saved me $10-20 on. I used a jigsaw and metal blade to cut along a guide board making a pair of 21x14" grills from each sheet. The package would cover either OT2x12's or a pair of 1x12's.
I roughly measured the length on the 45 degree bend, clamped the grill between my plywood work surface and a guideboard then gently used a hammer, working my way up and down the edge, to slowly bend it down. Screws and 15' of distance to the closest listener will take care of any minor imperfections in the work.

[gdougherty]

Oops, wrong posting. The metal grills are for the white speakers I'm building to install at my church. The grills pictured here are a doubled up bit of pet screen stapled onto a frame built out of strips of 1/2" plywood. I offset the pet screen by half a weave so the openings don't line up. It was cost effective, but I prefer the look and stability of the metal grills on the new pair. The pet screen sags a hair at points and some of the corners bunch up where I've had to jam them into the front spacing. These have all kinds of misfit imperfections on the grills and rear covers as compared to my latest build. My attention to detail went up quite a bit though since the church is footing the $500 component cost on them and it's not coming out of my own play money. I also figured they might get a higher degree of scrutiny in an install than at a temporary outdoor gig.

[Tom]

Thanks!

Sounds like Leland is full service, from all of the postings.

If I still had a metal shear and brake I would be making grills for sale. Too bad I don't have access to that gear any more - I used to have access when I had an office in the hangar at the airport.