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4pi Commercial Dinner Theater Build [message #68600] Sun, 17 July 2011 19:02 Go to next message
dutchswan0311 is currently offline  dutchswan0311
Messages: 102
Registered: June 2011
Location: Iowa
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Greetings! I am maintaining a build thread for a new Dinner Theater at our family's winery in Iowa. We are completely remodeling a 5,000 sq ft church build in 1930 into our new winery location. I will post a link to my build thread on the AVS Forum later (I'm typing this on my phone). If you want to see a photo album of our progress on the overall project see "Van Wijk Winery" on Facebook.

Anyway, thought I would keep a diary of my 4pi builds here so that I might get some feedback from the man himself or other enthusiasts better equipped to answer questions specific to the pi speakers.

I started my first 4pi speaker using a 7ply 23/32 Arauco found at Lowes. After making a few errors, such as putting in the rear panel and bracing before putting in the port, I decided to start from scratch and use that first speaker as my learning curve. After sifting through 20 sheets of 13ply North American Birch at Lowes I finally became frustrated and finally did some research on other local lumber stores. I found a woodsmith store literally 4 blocks from my house that sells the Baltic Birch in 5' x 5' sheets for $60/sheet (among other quality varieties). All of this time I thought those knocking Lowes' and HD's plywood selection were just being snobs. But after just a little experience working with some of them, I realize that those other 'big box' lumber stores'lumber isn't even in the same league as the Baltic Birch. So, either I was wrong before, or I am a snob now too Wink

I will post a few pics later, but in the mean time a couple of questions I hope to find quick answers to:

1. I have read a few posts from Wayne about making the center channel sealed. I wanted to see about feedback for our specific application. In addition to the three 4pi speakers being used for LCR duty behind a 180" acoustically transparent screen, four F20 horned subs of lilmike's design using the Reference HF driver will be integrated behind the wall under the creen pointing at the audience. While I will mirror the right channel with the port left of the horn, is there ANY advantage to making our center channel sealed?

2. I notice that the space above the port is 3/4 inch. Is that space supposed to be there? More to the point, is there any disadvantage to sandwiching another piece of 10" x 5" above the port so that it may have extra support by being able to screw into the port from the top as well as the side?
Re: 4pi Commercial Dinner Theater Build [message #68601 is a reply to message #68600] Sun, 17 July 2011 19:49 Go to previous messageGo to next message
petew is currently offline  petew
Messages: 63
Registered: June 2011
Location: Albuquerque, NM USA
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Hey glad to see you checking in here. I've been watching your progress over at AVS. I've got the drivers and other odds and ends on hand to build four of Lilmikes F-20's. Then I plan to build 4 two Pi's for surround duty and eventually build a trio of four Pi's.

As my drunk friend Marvin says: "Ain't life fun?"
Re: 4pi Commercial Dinner Theater Build [message #68603 is a reply to message #68600] Sun, 17 July 2011 21:04 Go to previous messageGo to next message
dutchswan0311 is currently offline  dutchswan0311
Messages: 102
Registered: June 2011
Location: Iowa
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Also, should I screw in the bracing from the outside, or is the PL and preload enough?
Re: 4pi Commercial Dinner Theater Build [message #68604 is a reply to message #68603] Sun, 17 July 2011 22:14 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

The sealed center channel offers no advantage - It's done purely for aesthetics. It actually reduces LF extension; however, having the extra extension in the left and right channels is probably enough overlap for the subs. So while the sealed centar channel provides no advantage, I don't see it causing any real disadvantage either, provided the right and left channels are vented as designed.

As for the braces, glue and a small amount of preload is enough. I actually prefer not to use screws except in places where clamping force is needed and a removable brace is impossible or impractical. For this reason, I only use screws on the 12π hornsub, where they provide holding/clamping force on some panels and internal structures.

Re: 4pi Commercial Dinner Theater Build [message #68607 is a reply to message #68604] Sun, 17 July 2011 22:53 Go to previous messageGo to next message
dutchswan0311 is currently offline  dutchswan0311
Messages: 102
Registered: June 2011
Location: Iowa
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Thanks for the reply Wayne.
Re: 4pi Commercial Dinner Theater Build [message #68609 is a reply to message #68607] Sun, 17 July 2011 23:40 Go to previous messageGo to next message
Dave_S is currently offline  Dave_S
Messages: 28
Registered: April 2011
Chancellor
I have made some mistakes with buying plywood from big box lumber stores myself. My TV stand that I will post in my build thread in the future was a disappointment to me. The veneer was rotary cut (made like a pencil sharpener), so I ended up with a plywood veneer that soaked up way too much stain and the grain pattern was a blotchy mess. For my last project, I opted to pay 3 times as much for cabinet grade lumber. I haven't seen anything that comes close to baltic birch in terms of structural quality.

Maybe I will get to hear your system a few years down the road. My nephew is starting college in Ames this fall, so it may be a side trip. I don't know much about wine, but I am an all grain beer brewer. The thought of working in a winery sounds nice. There is always the voice in my head telling me to start a brewery, but it would probably be tough.
Re: 4pi Commercial Dinner Theater Build [message #68610 is a reply to message #68609] Sun, 17 July 2011 23:48 Go to previous messageGo to next message
dutchswan0311 is currently offline  dutchswan0311
Messages: 102
Registered: June 2011
Location: Iowa
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We are thinking about dabbling in a couple of beers. We already have 18 varieties of wine. Ames is only about an hour from the winery. I got my bachelors and Masters from ISU.
1pi or 2pi for surrounds? (Please send me plans) vs JBL 8320 or 8340A [message #68617 is a reply to message #68600] Mon, 18 July 2011 09:03 Go to previous messageGo to next message
dutchswan0311 is currently offline  dutchswan0311
Messages: 102
Registered: June 2011
Location: Iowa
Viscount
Wayne, may I please have the plans for the 1pi and 2pi? I am considering using one of these for our surrounds in the Winery's dinner theater. How does the 1pi compare to the JBL 8320? How does the 2pi compare to the JBL 8340A? Building either of these models will certainly offer a cost benefit over $500 for a pair of 8320s or $750 for a pair of 8340As.

Keep in mind I am using 4pis for LCR, and four F20s for sub duty. The room is 1,200 sqft with a 300sqft balcony. Total room volume is about 20,000 cubic feet. I want the best bang for my buck, but also want to keep my surrounds as small as possible. The winery will have a 17th century castle feel with stonework, etc. The LCRs and subs will be completely concealed behind a AT screen, so the idea is to walk into the ballroom and NOT think "wow, there sure are a lot of speakers in here."

I will be needing 8 surronds I think.
Re: 1pi or 2pi for surrounds? (Please send me plans) vs JBL 8320 or 8340A [message #68618 is a reply to message #68617] Mon, 18 July 2011 09:31 Go to previous messageGo to next message
justphil is currently offline  justphil
Messages: 114
Registered: December 2010
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Supposedly the 1pis have a smoother response than the 2pis so I would lean in that direction but I am sure Wayne will offer his thoughts =) I would think in an effort to keep the "sound" the same using 1 or 2 pis would be the better way to go. But I know little to nothing except what I have read about speakers.
Re: 1pi or 2pi for surrounds? (Please send me plans) vs JBL 8320 or 8340A [message #68619 is a reply to message #68617] Mon, 18 July 2011 09:43 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Both the one π and the two π speakers are excellent as surrounds for three π or four π mains. Each has the same spectral balance, and so they preserve the illusion of seamless, fluid movement when sounds pan from surround to mains or vice versa.

Really then one π and two π speakers are more similar than different. You could almost consider them to be equivalent speakers, certainly above 100Hz. The only real difference is below 100Hz, where the two π goes a little lower.

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