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-   -   New Project Beta 12LTA Fostex FT17H in a TQWT (http://www.diyaudio.com/forums/multi-way/28674-new-project-beta-12lta-fostex-ft17h-tqwt.html)

MIKET 21st February 2004 10:57 AM

New Project Beta 12LTA Fostex FT17H in a TQWT
 
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Just starting up my new speakers, Beta 12LTA Fostex FT17H in a TQWT. I found this drwing posted for the TQWT on the net at
http://home.pacbell.net/tullius/home5.html
but the site is now gone.
What do you think?

GM 22nd February 2004 02:17 AM

I think you need to study up a bit on Ml-TQWT theory and use MJK's Mathcad worksheets to design a much better one: http://www.quarter-wave.com/ Of course post Qs here as required to get through it, and unless it just needs to be short, then a straight untapered pipe with a standard round vent will work fine with this driver and be much easier to build/tune.

GM

MIKET 22nd February 2004 02:18 AM

furtue details
 
I intend to epoxy Oak or maple stuts to stiffen the frame since it is stamped metal and cover the whole mess with Mortite to deaden it. The crossover will be the same as
http://melhuish.org/audio/super12.html
Cabinet constructed from Baltic Birch
Puzzle Coat on the cone, dammar on the wizzer.
Caps by Mundorf.
#14 wire for inductors.

MIKET 22nd February 2004 02:26 AM

Quote:

Originally posted by GM
I think you need to study up a bit on Ml-TQWT theory and use MJK's Mathcad worksheets to design a much better one: http://www.quarter-wave.com/ Of course post Qs here as required to get through it, and unless it just needs to be short, then a straight untapered pipe with a standard round vent will work fine with this driver and be much easier to build/tune.

GM


I don't have or can afford Math Cad, The drivers specs are at :
http://www.partsexpress.com/pdf/290-409.pdf

Can you possibly run the numbers? If not then I guess I will be going with what I have.
They are sitting in the closet waiting for warmer weather. As soon as it is tolerable in my garage I will be out there sawing som plywood.

GM 22nd February 2004 02:47 AM

There's a free demo version on his site you can use, though you can't save the design. FWIW, ebay usually has older versions dirt cheap: http://cgi.ebay.com/ws/eBayISAPI.dll...&category=3789

GM

BrianGT 22nd February 2004 03:02 AM

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I ran some numbers for this driver a while back, since it is relative inexpensive from PE. I found that it required a huge enclosure to get a good response from. Here is the response that I got from a 9.32 ft^3 enclosure (35" high internally, 450 sq in cross-section)

Here is the response that the ML TL mathcad sheets give me:

--
Brian

BrianGT 22nd February 2004 03:03 AM

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Here are the numbers that I used for running this:

--
Brian

BrianGT 22nd February 2004 03:05 AM

I ran some numbers on the cabinet referenced in the first post, and it doesn't seem to go very low. The driver really needs a large enclosure to have good bass response.

--
Brian

MIKET 23rd February 2004 10:11 AM

Box designed on MLTQWT worksheet
 
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Here is what I came up with unfortunately with a 6" vent 1.5 " deep as calculated by WinISD the vent Mach would be .07 and a frequency of 37.05 Hz which is a bit high. Going to a rectangular vent of 5" X 12" rectangular 6.25" deep gives the same frquency but a vent Mach of .03" see below.

MIKET 23rd February 2004 11:25 AM

VOIGHT variation on above
 
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What do you think?


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