# Thoughts on my isobaric "TL/Horn"box design:



## The Baron Groog (Mar 15, 2010)

I impulse bought some old KEF B139 subwoofers on ebay a while back and have just started playing with ideas for an enclosure for the lounge. Enclosure must fit under some draws, so height and width dimensions are fixed-internal and depth we can play with. Subs must be mounted isobarically as old cathode ray TV above the enclosure will flip out if subs aren't mounted like this. External dimensions are:

H16.5"(fixed) W46.5"(fixed) D18.75" (couple of inches extra won't hurt, but will shift TV out of bay window into lounge and piss off the missus)

Thought I'd have my 1st go at a "T-line/folded horn" type of enclosure and was wondering what everyones thoughts are. 

Line/horn starts at 1.25", increases to 2.5" at 1st bend, 5" at 2nd bend and 10" at final bend, opening in front of sub 20" wide and box height. Total length 160".

Now I have ZERO experience of this type of design, so figured that the line should start small and increase in width as it progresses through each bend, so the air speed should drop by half at each bend, though have seen designs where the pipe is the same diameter throughout or getting smaller towards the opening-but this would just require moving the internal walls so no fuss really!


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## its_bacon12 (Aug 16, 2007)

Try Part-Express techtalk - those guys are a LOT more helpful with this stuff


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## Chaos (Oct 27, 2005)

How did you determine the flare ratio and line length?


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## The Baron Groog (Mar 15, 2010)

"Its bacon"-cheers, in the UK so time zone will be an issue!

Chaos, ultimately I didn't. I just measured up the space available, sketched it on some paper and "worked it out" so it would all fit in with a decent line length. I just figured doubling the "line" area at each bend would half the air velocity in each section and worked the length out to be 160"! No science, just hoping to be bloody lucky!

As I said, total noob with this, have since found "hornresp" so will try modeling on that when I get some clear time at home.


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## its_bacon12 (Aug 16, 2007)

The Baron Groog said:


> "Its bacon"-cheers, in the UK so time zone will be an issue!
> 
> Chaos, ultimately I didn't. I just measured up the space available, sketched it on some paper and "worked it out" so it would all fit in with a decent line length. I just figured doubling the "line" area at each bend would half the air velocity in each section and worked the length out to be 160"! No science, just hoping to be bloody lucky!
> 
> As I said, total noob with this, have since found "hornresp" so will try modeling on that when I get some clear time at home.


If you're patient, the guys at techtalk are very helpful. Also, DIYaudio.com/forums has a lot on horns as well - much is which is far over my head.


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## The Baron Groog (Mar 15, 2010)

The design works! believe it or not I hit the nail on the head with my off the cuff design, will build it when I get the chance, but have modeled it and surpisingly good!


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## The Baron Groog (Mar 15, 2010)

Just in case any of you give two hoots the plans have changed:

Old CRT is gone-yeah, new LCD in it's place So the need for the isobaric mounting has gone with it so I looked at other designs and began experimenting with Hornresponse and chatting with the good folk on diyaudio.com.

Bjorno, a very helpful member, has really helped me out with an 18Hz T-TQWT design which more or less fits in the required space (just got to double check the fold will work, horn volume is low enough)

Here's the modeled output, off 1watt:


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## pocket5s (Jan 6, 2012)

so if I read that graph correctly, that enclosure will play from 18hz up to ~100hz? 18hz in the home is pretty low. nice.

I have hornresp but the interface is, uh, less than friendly...


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