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Old 9th January 2013, 06:01 PM   #1
jmroach is offline jmroach  United States
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Default critical dimensions for the Dallas II (or III)?

Hi all,

I'm in the process of building my first set of BLHs (first full-range for that matter). I have selected the Dallas III and have read that no plans for this speaker exist, but that others have just "smoothed" the Dallas II. That's what I'm doing as well.

Here's the issue I've run into: in the only plans I could find, no dimensions I would think to be critical are listed! What I'm referring to mainly are the passage heights at various positions (ie. between the start & end of pieces 2 & 4, 7 & 12, 12 & 15).

Does anyone have this data? All I can think of is comparing these to other dimensions on the print or performing some serious geometry shenanigans?

Thanks in advance!

-john
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Old 9th January 2013, 06:29 PM   #2
secanbj is online now secanbj  Sweden
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here are some better drawings

Dallas II vs Kirishima
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Old 9th January 2013, 07:02 PM   #3
jmroach is offline jmroach  United States
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Quote:
Originally Posted by secanbj View Post
here are some better drawings

Dallas II vs Kirishima
Perfect! Just what I was looking for. Thanks a ton!
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Old 9th January 2013, 08:24 PM   #4
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Quote:
Originally Posted by secanbj View Post
here are some better drawings
Given that that is a snapshot of one ofmy drawings, i will have CAD files if that is helpful -- obviously not finished to my liking or they would be posted on FH.com

dave
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Old 10th January 2013, 02:28 PM   #5
jmroach is offline jmroach  United States
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Quote:
Originally Posted by planet10 View Post
Given that that is a snapshot of one ofmy drawings, i will have CAD files if that is helpful -- obviously not finished to my liking or they would be posted on FH.com

dave
Thanks, Dave. I don't currently have any CAD software installed, but if you think it would be helpful I'm sure I could figure something out. I'm still at a point in the build where I can tweak dimensions.

Click the image to open in full size.

As a more general note-- Do you have a sense for how sensitive the design is (or other BLH designs are) to geometric deviations? For example, would one of the passages entrances/exits being too big/small by 1/16" affect the performance? 1/8"?

Thanks!
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Old 21st January 2013, 08:15 PM   #6
jmroach is offline jmroach  United States
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Thought I would share a few more pictures of the progress. I didn't really find any in-progress pictures of this design before i started. Hopefully these will be useful for someone else who decides to tackle the same project.

Here's a short rundown of the construction: it's 1/8" bending plywood sandwiched on both sides of 5/8" marine-grade plywood. It helps a lot to get the bending plywood damp before trying to manipulate too much. Glue is titebond #1. I tried cutting dados in the 5/8" plywood to accommodate the bending, but it didn't provide enough compliance. Corners are 1/2" to 1" strips depending on the radius of curvature.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

note that the divider is "floating" in the last picture.
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