Thoughts on my isobaric "TL/Horn"box design: - diyAudio
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Old 31st August 2011, 03:10 PM   #1
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Default Thoughts on my isobaric "TL/Horn"box design:

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 p-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!

And thanks to 60ndown for showing me the site
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Old 31st August 2011, 05:34 PM   #2
oublie is offline oublie  United Kingdom
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have you used any modelling software such as horn resp?

do you know the thiele/small parameter of the driver?
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Old 31st August 2011, 05:44 PM   #3
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Scott & i did up a modern TL for B139. Three versions are here Transmission Line Speakers (Note: factory data is on the same site)

I would take the straight one, make the cross-section 1/4 to accomodate an isobarik pair, then fold and adjust as necessary to fit the driver. Or the triangular line and decrease cross-section by a factor of 2.

If that is too big to fit in your space, you will likely need to look at a different kind of box.

dave
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Old 31st August 2011, 05:54 PM   #4
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Oublie: No modelling software used to date, though have looked at hornresp and the maths looks preferable to learning how to use hornresp! Have used BBpro for years, but this is a new realm to me.

Planet10-thanks will have a look. Haven't been able to find the spec for these particular varient of the B139-though do have a woofertester so just need to pull the specs off them myself.

thanks for the advice
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