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Old 16th April 2014, 07:05 PM   #1
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Default Transmission Line surface area

Lets say I have a bass driver and a CAD tells me this particular driver needs 60 liter, a line length of 180cm with a beginning surface area of 400cm2 and ending surface area of 270cm2.

Now, what would happen if I decrease the volume by decreasing the surface area to, say 300cm2 and 200cm2, but keep the same 180cm length? Isn't it the length that decides what frequency it's tuned to, or is the surface area equally important?
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Old 16th April 2014, 07:12 PM   #2
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Area is equally important, make it smaller, lose bass (in general).
dave
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Old 16th April 2014, 07:28 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

The CSA (cross sectional area) needed is related to the size
of the driver for for a given line length *, and if its not right
it simply won't work well, you cannot reduce it ad-hoc.

rgds, sreten.

* Its more complicated then simply driver size, related
to the drivers parameters, but very related to optimum
sealed box size for the driver, if that makes any sense.
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Old 16th April 2014, 07:35 PM   #4
GM is online now GM  United States
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Right, regardless of how it's shaped, less net box volume [Vb] = less LF output. Note that with horn shapes, taper comes into play also, so when scaling, Fb rises for a given path-length unless you either increase it and/or the taper ratio to account for it.

GM
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Old 16th April 2014, 07:49 PM   #5
GM is online now GM  United States
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Quote:
Originally Posted by sreten View Post
.....but very related to optimum
sealed box size for the driver......
FWIW, IME it's related to a max flat vented alignment with a fudge factor to increase net Vb and why I still use the Margolis/Small HP calculator program from '81 to design the various ML-TL alignments.

The only vented alignment based on sealed that I'm aware of only works well over a narrow Qts range, so much too limited for me.

GM
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Old 16th April 2014, 08:34 PM   #6
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Ok, thanks for the input guys.
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Old 16th April 2014, 08:57 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by GM View Post
FWIW, IME it's related to a max flat vented alignment with a fudge factor to increase net Vb and why I still use the Margolis/Small HP calculator program from '81 to design the various ML-TL alignments.

The only vented alignment based on sealed that I'm aware of only works well over a narrow Qts range, so much too limited for me.

GM
Hi,

Yes you can fudge factors, but generally optimum sealed volume
is about half optimum vented volume, and drivers not suited to
vented (due to high Qts) in any real respect can still be TL'd
with low enough TL tuning in the right TL.

YMMV, its just generalisations.


rgds, sreten.
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Old 16th April 2014, 09:16 PM   #8
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I do believe GM might be aware of this. Probably rather better than the rest of us on our good days.
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