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Old 9th March 2004, 10:52 PM   #1
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Question Short TL design

In another thread that I almost hi-jacked Sreten posted this picture. I'd like to know how the cross-sectional area is determined in a design like this. It seems like a very narrow pipe. In back-loaded horns the top of the pipe starts out similar to this but gets wider as it nears the terminus.
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Old 9th March 2004, 11:07 PM   #2
sreten is online now sreten  United Kingdom
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I'd suggest the intention is for each vertical section to be
narrower, as you move towards the terminus.

But by introducing a shielded bass driver they had to tweak
the first divider giving a line profile not in any textbook.

You can't see the half depth of the box but I estimate
the CSA of the line to be ~ = to Sd of the bass driver,
in the first section of the line.

sreten.
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Old 9th March 2004, 11:46 PM   #3
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Thanks, I thought that it was about Sd but it's hard to tell from the picture. I'll have to play around with this. Folks seem to like little boxes.
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Old 9th March 2004, 11:58 PM   #4
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Hmm, all I can do is lay a scale on the screen, but it sure appears to be a constant cross section from the first fold to the terminus, and once you subtract out the drivers, probably the first section also. The terminal cup/XO causes a constriction in the pipe, though how much of one depends on how dense the foam is.

Anyway, more than likely it was determined by the decades old rule-of-thumb to make the line's effective cross sectional area = Sd, but as MJK's work has shown, this isn't the Hot Ticket to good overall performance for most drivers. As for short, well this just means a relatively high Fb if it's not reverse tapered.

Browse MJK's TL design tables to get some idea where to start.

GM
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Old 10th March 2004, 01:42 AM   #5
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I played around with So and SL equal to Sd and got some unpleasant results. I'll keep trying.
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Old 10th March 2004, 01:59 AM   #6
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Try whatever the max flat Vb is for whatever Fb you chose.

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