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Old 12th March 2005, 07:13 PM   #1
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Default Quick help for TL design

i'm working on a TL design for:
DAYTON DC160S-8 6-1/2" CLASSIC SHIELDED WOOFER
http://www.partsexpress.com/pe/pshow...=295-306&DID=7

with:
TANG BAND 28-847SA SHIELDED NEODYMIUM DOME TWEETER
http://www.partsexpress.com/pe/pshow...number=264-822

in anycase, my box dimensions are:
48" inside height, 6.5" inside width, 8.5" inside depth.

there will be one devider located at a bottom corner and moving to the cented of the depth, and at a height about 6" below the top of the box. this is a voight pipe IIRC.

this seems like a length of approximately 85". this should be long enough, but i fear it may be too long. i have heard that making the opening larger i can increase the tuned frequency. right now i've calculated the opening to be 4" x 6.5".

any tips. also should i make the opening larger?
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Old 12th March 2005, 07:52 PM   #2
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Did you use MJKs worksheets?
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Old 12th March 2005, 08:11 PM   #3
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no, just a book i have that has very little on this. the size had to be what i had given the wood.
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Old 12th March 2005, 08:52 PM   #4
qwad is offline qwad  Australia
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l can understand someone wanting to do their own thing, but why go to all the trouble when there is a similardesign in parts express diy speaker section very similar to what you propose to do...... sorry cant give you a link, just do a search...... cheers TC
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Old 12th March 2005, 10:03 PM   #5
GM is offline GM  United States
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Greets!

Just plugging in all the details and calcing the actual acoustic vent length and using Weems formula for calcing the driver position (~39.96" down from pointed end), I get a 60Hz Fp with lots of gain/broadband 'ripple' to beyond 1 kHz. Typical Voigt pipe performance and no need for any BSC.

Shifting the driver position to ~21.25" lowers Fp to ~45Hz, but increases the 3rd harmonic notch and shifts it down into the ~110-200Hz BW, so probably not a good plan.

Shifting the driver to ~51" and reducing the vent to 2.5" dia. x 2" long yields a flat, smooth enough response to a ~45Hz Fp. To go lower requires a rethink of the design, with much reduced efficiency and the need for BSC if not up against a wall.

GM
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Old 12th March 2005, 10:27 PM   #6
RJ is offline RJ  United States
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Here's the link to what your intending to build;
http://www.d-web.com/dbrown/db616tl2/db616tl2.htm
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Old 12th March 2005, 11:19 PM   #7
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well, i only have 1 speaker and the box looks different.

the mathcad sheets are poorly commented. i have no idea what n_open, n_closed, or driver position ratio are.
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Old 12th March 2005, 11:25 PM   #8
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Quote:
Originally posted by theChris
the mathcad sheets are poorly commented. i have no idea what n_open, n_closed, or driver position ratio are.
They are not obvious, I'll give you that! to get the benefit you really need to study the pdfs on Martin's site, print them out and read through them as you go through the worksheet. It's worth it in the end
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Old 13th March 2005, 12:00 PM   #9
RJ is offline RJ  United States
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Two of the better programs for modelling subs;

http://www.pvconsultants.com/audio/eq/boxcircuit.htm
http://www.diysubwoofers.org/prt/

Two more programs that'll give you a quick model;

http://www.pvconsultants.com/audio/boxmodel/unibox.htm
http://www.linearteam.dk/default.aspx?pageid=winisd
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Old 14th March 2005, 03:54 AM   #10
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Quote:
Originally posted by theChris
well, i only have 1 speaker and the box looks different.

the mathcad sheets are poorly commented. i have no idea what n_open, n_closed, or driver position ratio are.
Took me awhile to figure out the sheets. But it's very much worth it. You can do it. Building speakers about physics/math, so if you work with the sheets you a lot better off.
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