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Trapezoid enclosures [message #43883]

Mon, 09 February 2004 08:07

Larry Acklin
Messages: 54
Registered: May 2009

Baron

Hi-

Has anyone tried to make a "trap" enclosure out of a 3 or 4 PI? I'm thinking about a couple of pairs for mid-tops in the PA. Would the trap's ability to "throw farther" (myth?) affect how the box is calculated?

Thanks

Larry Acklin

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Re: Trapezoid enclosures [message #43885 is a reply to message #43883]

Mon, 09 February 2004 09:18

Chris R
Messages: 133
Registered: May 2009

Master

Hi Larry,

Could tell me the tale of how the box shape effects how far it throws? I haven't heard it before. Sounds like a myth to me too, but I'm curious to hear anyway.

Thx, Chris

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Re: Trapezoid enclosures [message #43886 is a reply to message #43885]

Mon, 09 February 2004 10:05

Larry Acklin
Messages: 54
Registered: May 2009

Baron

From--
http://www.atr-treehouse.com/PA10.html

start quote

BOX DESIGN SHAPE - Trapezoidal vs. Square
The reason for that "wedge-back" trapezoidal enclosure geometry is to facilitate the creation of semicircular arrays where multiple enclosures are arranged closely side-by-side. Created initially for "flying" in elevated clusters, trapezoidal enclosures have also found their way onto stages all over and are used in small numbers with great success.

Their shape looks a little horn-like leading sometimes to speculation about them having "longer throw" than similar, square enclosures - of course we know better now. However there is a potential benefit in this shape - when properly configured, it reduces internal standing waves which means smoother frequency response and possibly improved phase coherence, a factor which gives the enclosure a "tight","focused" sound. On the other hand, not all trapezoid boxes automatically benefit from this shape, nor do all square boxes fare less than favorably in comparison to them.

end quote

So in an array- better coverage, about 3 db gain by stacking close together, and a possible standing wave issue. Plus they pack better in the trailer.

-Larry

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Re: Trapezoid enclosures [message #43890 is a reply to message #43886]

Mon, 09 February 2004 14:34

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

There's no harm in making your cabinets this shape as long as the cabinet volume is kept the same. All box volume calculations are the same - The Helmholtz resonator formed by the bass-reflex cabinet doesn't care if the volume is formed by a box, a trapezoid or a bottle.

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Re: Trapezoid enclosures [message #43896 is a reply to message #43883]

Tue, 10 February 2004 08:29

JLapaire
Messages: 156
Registered: May 2009

Master

http://www.pispeakers.com/DIY/JohnLapaire_Tower4Pi_and_MK2.jpg

Larry, the Theater 4 stuff makes a great speaker (see mine, above left). I've run 'em wide open, and hipassed anywhere from 80 to 150. They seem to blend with the Omega Pro 18s best at around 150.

John

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Re: Trapezoid enclosures [message #43900 is a reply to message #43886]

Tue, 10 February 2004 13:13

Chris R
Messages: 133
Registered: May 2009

Master

Thanks. I think we were clear before hand. :^)
chris

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Re: Trapezoid enclosures [message #43901 is a reply to message #43896]

Tue, 10 February 2004 13:16

Larry Acklin
Messages: 54
Registered: May 2009

Baron

Good looking mid/tops (to me, anyway). What is the horn flare? Looks to be about 15X6 inches- not an Eminence flare, for sure. How did you handle the crossover and compensation?

Looks like i'm gonna be building 6 for a club/smaller outside jobs rig.

Larry Acklin

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Re: Trapezoid enclosures [message #43904 is a reply to message #43901]

Tue, 10 February 2004 15:45

Wayne Parham
Messages: 18675
Registered: January 2001

Illuminati (33rd Degree)

That horn is a Peavey CH-3. It's one of my favorites.

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Stock Theater 4 parts [message #43913 is a reply to message #43901]

Wed, 11 February 2004 05:40

JLapaire
Messages: 156
Registered: May 2009

Master

I think Wayne used to include the CH3 in the Theater 4 kits - I remember voting on whether we wanted the CH3 or H290 so he could standardize.

The crossover is stock Pi/Eminence with the 10db pad and comp circuit. I'd have to look at the parts, but the HF section is probably right out of the Crossover Document for the PSD2002.

6 of them will be a good project! The full-size version is kinda big to put on stands, though - how are you going to get them up high enough to reach out over the crowd? On second thought, 6 of them in a room should reach everything just fine.

John

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Re: Stock Theater 4 parts [message #43914 is a reply to message #43913]

Wed, 11 February 2004 09:03

Larry Acklin
Messages: 54
Registered: May 2009

Baron

Thanks! I thought it might be a Peavey. My application is usually 2 or 3 traps a side, stacked on top of a dual 15" folded horn sub (2 horns in one box) which is 32" high when laid on its side. That puts the HF horns about 55-60" up, OK for clubs and whatnot. Outside, for bigger shows- (300-500 people) the midbass and mids are a huge EV 90X40 horn, with an EV 12" in a 1 cu ft compression chamber. Big, heavy, but very dynamic.

I do the speakers on sticks indoors, but these would be marginal in weight for the supports I own.

Thanks

Larry Acklin

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