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186 Horn measurements don't add up?

Printed From: Speakerplans.com
Category: Plans
Forum Name: 1850 and 186 horns
Forum Description: Discussion / Questions about the 1850 and 186 horns
URL: https://forum.speakerplans.com/forum_posts.asp?TID=92922
Printed Date: 26 February 2024 at 8:44am
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com


Topic: 186 Horn measurements don't add up?
Posted By: dmr
Subject: 186 Horn measurements don't add up?
Date Posted: 06 August 2015 at 9:38pm
Hi all,

I'm starting my first build; the 186 Horn plan posted on this website.

Upon marking out, the front part that is 350mm (angled part sorta on the left) does not add up to the 310mm height and 195mm width using the Pythagorean theorem (its 16mm out)

Do I go by the 350mm (its length), or by the height/width of where it starts and ends in relation to the side panel?

In retrospect should have chosen something simpler but hey ho its a bit late now!

Cheers!



Replies:
Posted By: djeddie
Date Posted: 08 August 2015 at 12:42am
Cut the main side panel to the exact size then 'draw' the plan on that side. You can the measure each piece as you go.


-------------
Chas n Dave : it's like Drum and Bass but with beards.             E=mc² ±3dB


Posted By: dmr
Date Posted: 08 August 2015 at 10:51am
Yeah that's what i'm doing, its just that if I measure 310mm in from top and 195mm in from left and place it there; the piece is no longer 350mm as specified on the plan. If I cut a 350mm piece and place it relative to the previous, it is no longer 310mm in from top and 195mm in from the left.

I continued regardless and just made a compromise half way between the two extremes, it has changed the shape of the horn slightly...


Posted By: DMorison
Date Posted: 08 August 2015 at 12:55pm
Originally posted by dmr dmr wrote:

Hi all,

I'm starting my first build; the 186 Horn plan posted on this website.

Upon marking out, the front part that is 350mm (angled part sorta on the left) does not add up to the 310mm height and 195mm width using the Pythagorean theorem (its 16mm out)

Cheers!

6mm out, not 16mm. You need to subtract the 20mm offset from the front edge of the box from the 195mm dimension before calculating Wink.

Am still surprised it's out by that much though, would've expected it to be within a reasonable rounding error (ie nearest mm).

Good luck with your build anyway, if your compromise is only a few mm I doubt it'll affect the end result - you're dealing with sounds having much longer wavelengths than that after all.


Posted By: b grade
Date Posted: 08 August 2015 at 2:05pm
yeah I get 356 mm mathematically too. 175 by 310 on the sides of the right triangle. I also double checked against the 1850 plans which are nearly the same. That part on the 1850 is labelled as 353 mm, which is closer, but I would have thought still about 3 mm short.


Posted By: dmr
Date Posted: 09 August 2015 at 8:48am
Originally posted by DMorison DMorison wrote:


6mm out, not 16mm. You need to subtract the 20mm offset from the front edge of the box from the 195mm dimension before calculating Wink.


Ahhh damn that's caught me out so many times, it doens't help that the guy at B&Q cut the side panels 10mm too short!



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