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-   -   critical dimensions for the Dallas II (or III)? (http://www.diyaudio.com/forums/full-range/227410-critical-dimensions-dallas-ii-iii.html)

jmroach 9th January 2013 06:01 PM

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

secanbj 9th January 2013 06:29 PM

here are some better drawings

http://www.diyaudio.com/forums/full-...ml#post3237398

jmroach 9th January 2013 07:02 PM

Quote:

Originally Posted by secanbj (Post 3318288)

Perfect! Just what I was looking for. Thanks a ton!

planet10 9th January 2013 08:24 PM

Quote:

Originally Posted by secanbj (Post 3318288)
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

jmroach 10th January 2013 02:28 PM

Quote:

Originally Posted by planet10 (Post 3318428)
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.

https://lh5.googleusercontent.com/-P...62190C1A69.JPG

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!

jmroach 21st January 2013 08:15 PM

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.

https://lh3.googleusercontent.com/-E...3E58A5623D.JPG

https://lh5.googleusercontent.com/-l...EDDDAA4871.JPG

https://lh5.googleusercontent.com/-D...D7BA83FD41.JPG

https://lh5.googleusercontent.com/-x...01E384919C.JPG

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


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