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Modifiction to HD15 Flare

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    Posted: 19 November 2009 at 10:06pm
Does the HD15 flare need to be curved?
I've noticed quite a few around with 5 or 6 straight sections making up the  flare but why not less say 3 sections.
For example:


if the chamber volume is the same as the original curved flare what adverse effects could this have?

edit:spelling



Edited by HighLift - 19 November 2009 at 10:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fat_brstd Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2009 at 12:38am
general concensus is that 5 straight sections is the closest and easiest way to get very close to the original shape of the curved section. I believe Heathrow B Line did a pdf file which shows you how to cut the wood to get use 5 straight bits of wood instead of the curve. I cant remember the length of each one but the angle was an 81 degree mitre on both ends of each of the 5 panels. If you search in this section you should find i.

edit: found it - http://www.bl-online.org/users/lasse.lukkari/hd215/HD215.pdf
its 124.7mm outside edge and an 81 deg mitre on both ends for the 5.

I dont know if anyone has done a 3 sectioned one before but i doubt it. Have you calculated the change in chamber volumes and horn flair rate?certainly be interested if you have.


Edited by fat_brstd - 20 November 2009 at 12:41am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cravings Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2009 at 12:57am
i think someone did one where they cut (can't remember how much tbh) about 12mm through a single piece of wood in 4 places and folded it slightly on the cuts.. to get the 5 piece sectional curve.. can't remember who... mykey may have been in the thread, or he may have even suggested it...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote HighLift Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2009 at 6:57am
Originally posted by fat_brstd fat_brstd wrote:

general concensus is that 5 straight sections is the closest and easiest way to get very close to the original shape of the curved section. I believe Heathrow B Line did a pdf file which shows you how to cut the wood to get use 5 straight bits of wood instead of the curve. I cant remember the length of each one but the angle was an 81 degree mitre on both ends of each of the 5 panels. If you search in this section you should find i.

edit: found it - http://www.bl-online.org/users/lasse.lukkari/hd215/HD215.pdf
its 124.7mm outside edge and an 81 deg mitre on both ends for the 5.


Cheers FB: This'll be a plan B

Originally posted by fat_brstd fat_brstd wrote:


I dont know if anyone has done a 3 sectioned one before but i doubt it. Have you calculated the change in chamber volumes and horn flair rate?certainly be interested if you have.


Well the chamber volumes wouldn't be a problem to calculate so they're the same as the original HD15, but the horn flare rate is what I'm worried about.
I was planning on just dividing the (roughly) quarter circle into three, so that the joints on the straight parts are equidistant.

I'll get some drawings up of a design proposal, but to be honest I don't have a clue what considerations need to be made concerning the flare rate.

Any advice in this department would be much appreciated.

Originally posted by <span id=userPro329315 =showDropDown'userPro329315', 'proMenu329315', 160, 0; =msgSidePro title=View Drop Down>cravings</span> cravings wrote:


i think someone did one where they cut (can't remember how much tbh) about 12mm through a single piece of wood in 4 places and folded it slightly on the cuts.. to get the 5 piece sectional curve.. can't remember who... mykey may have been in the thread, or he may have even suggested it...


Hi Cravings: I tried that but birch ply snaps pretty easily and I'm not really up for MDF. I have access to a good table saw that can cut angles well so I don't have a problem cutting the individual parts and gluing them with PU glue.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote HighLift Quote  Post ReplyReply Direct Link To This Post Posted: 20 November 2009 at 3:10pm
Here's the draft:



You can just make out the outer face line (R395mm) of the original curved flare in red.

The 3 parts are 212mm on the longest face and each part has 75° angles both ends.
A bit has been chopped of at the throat area to keep consistency with the original design.
There's a chamber volume difference from the original curved design of +20cm3. These cm3s will be taken up by handles ;-)

Now the question remains...
Could there be any adverse effects of this design modification???

Anyone done an AB test of the curved design against the 5 sided one from HBL???
If so, any noticable difference??

Should I just go for it????


Edited by HighLift - 20 November 2009 at 3:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote schiller Quote  Post ReplyReply Direct Link To This Post Posted: 22 November 2009 at 8:55am
Originally posted by HighLift HighLift wrote:

Does the HD15 flare need to be curved?
I've noticed quite a few around with 5 or 6 straight sections making up the  flare but why not less say 3 sections.
For example:


if the chamber volume is the same as the original curved flare what adverse effects could this have?



None. even if you build it with 3 straight sections

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Post Options Post Options   Thanks (0) Thanks(0)   Quote HighLift Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 5:02pm
Done them with 3 sections. Shocked




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Post Options Post Options   Thanks (0) Thanks(0)   Quote backlash Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 5:07pm
WOW that looks impressive!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 5:10pm
The three section thing would be fine, i really like the look of it also
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Post Options Post Options   Thanks (0) Thanks(0)   Quote backlash Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 5:21pm
I think a 2 section would look cool, much more like a funktion one style band pass just got to make sure the driver fits and the internal volume of the rear chamber stays the same!

<or 1 section might be nice >
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djyves Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 9:40pm
yea 1 section 1 curved sectionTongue

Edited by djyves - 30 December 2009 at 9:40pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote backlash Quote  Post ReplyReply Direct Link To This Post Posted: 30 December 2009 at 10:20pm
Originally posted by djyves djyves wrote:


yea 1 section 1 curved sectionTongue


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