critical dimensions for the Dallas II (or III)?

jmroach · 9th January 2013, 06:01 PM

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

Dallas II vs Kirishima

jmroach · 9th January 2013, 07:02 PM

Quote:

Originally Posted by secanbj

here are some better drawings

Dallas II vs Kirishima

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

planet10 · 9th January 2013, 08:24 PM

Quote:

Originally Posted by secanbj

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

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.

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.

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

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9th January 2013, 06:01 PM	#1
jmroach diyAudio Member Join Date: Jan 2013	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

9th January 2013, 06:29 PM	#2
secanbj diyAudio Member Join Date: Sep 2003 Location: Gothenburg	here are some better drawings Dallas II vs Kirishima

21st January 2013, 08:15 PM	#6
jmroach diyAudio Member Join Date: Jan 2013	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. note that the divider is "floating" in the last picture.