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?
http://home.pacbell.net/tullius/home5.html
but the site is now gone.
What do you think?
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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
GM
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.
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.
GM said:
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.
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?ViewItem&item=3661458191&category=3789
GM
GM
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
Here is the response that the ML TL mathcad sheets give me:
--
Brian
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Box designed on MLTQWT worksheet
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.
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.
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Re: Box designed on MLTQWT worksheet
That looks like a washing machine to me... similar dimensions. I would seriously consider a different driver. There are many drivers out there that can go lower in a much smaller box, and a smoother overall response.
I couldn't imagine having to accommidate large sized enclosures like that. I know that my significant other would raise hell if I tried to build those things and put them in the living room. I built a subwoofer that was 24" x 24" x 40", and it just looked ridiculous in my living room...
--
Brian
MIKET said:
That looks like a washing machine to me... similar dimensions. I would seriously consider a different driver. There are many drivers out there that can go lower in a much smaller box, and a smoother overall response.
I couldn't imagine having to accommidate large sized enclosures like that. I know that my significant other would raise hell if I tried to build those things and put them in the living room. I built a subwoofer that was 24" x 24" x 40", and it just looked ridiculous in my living room...
--
Brian
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Hey Brian,
This driver was the subject of much tweaking sometime back on the fullrange forum and different cabs were tried, but I forget what folks liked best. No one measured a driver so published specs was used in each case IIRC. They must be close though since tuning was very close on those that were measured with an SLM.
A max flat is ~9.91ft^3/36Hz and I calculated a 47.25" length with rp = 3.38", Lp = 0.75", and driver down 20.88", which yields basically the same FR as yours except for a very slight increase in box efficiency due to the larger Vb.
WRT alignments, I'm not a big fan of WP's 'Pi Align' because it gives up too much useful BW with today's higher excursion drivers, but for FR and other underhung drivers it's really the 'Hot Ticket' for best overall performance since it maximizes midbass efficiency and is well damped over a wide enough BW that EQ can be used to boost the low end within its meager power/excursion limits without resorting to a huge cab and fiddling with the vent to find an acceptable audible distortion curve:
Vb = 2.453ft^3 (alpha = 1.961)
Fb = 33.09Hz (H = 0.7353)
rp = 1"
Lp = 1.38"
Your sub looks familiar, is it the one I saw in Rob Cheng's basement during the last DIY meet? I don't mind large, my mains are somewhat larger than this, but if not in a corner then they do look out of place unless finished off to look like a complementary piece of furniture. I once did a pair of 30ft^3 cabs and the owner's wife had them finished off by a furniture maker to look like antique French Provincial cabinets. With some 'hanging gardens' style greenery perched on top, they were very impressive (and expensive).
MIKET:
If you do a sim of the 'Voigt' style horn you'll see that it won't perform any better than Brian's straight pipe down low and the high taper ratio will push the driver somewhere between 5/8-3/4 down to get an aceptable tradeoff between LF extension and upper midbass/lower mids smoothness. Unfortunately, the excessively large/long vent will make a choppy mess of them, so overall, not a good design IMO.
Again, to get superior performance with pipe designs with the least effort, MJK's worksheets will save you a lot of time/$$.
HTH,
GM
This driver was the subject of much tweaking sometime back on the fullrange forum and different cabs were tried, but I forget what folks liked best. No one measured a driver so published specs was used in each case IIRC. They must be close though since tuning was very close on those that were measured with an SLM.
A max flat is ~9.91ft^3/36Hz and I calculated a 47.25" length with rp = 3.38", Lp = 0.75", and driver down 20.88", which yields basically the same FR as yours except for a very slight increase in box efficiency due to the larger Vb.
WRT alignments, I'm not a big fan of WP's 'Pi Align' because it gives up too much useful BW with today's higher excursion drivers, but for FR and other underhung drivers it's really the 'Hot Ticket' for best overall performance since it maximizes midbass efficiency and is well damped over a wide enough BW that EQ can be used to boost the low end within its meager power/excursion limits without resorting to a huge cab and fiddling with the vent to find an acceptable audible distortion curve:
Vb = 2.453ft^3 (alpha = 1.961)
Fb = 33.09Hz (H = 0.7353)
rp = 1"
Lp = 1.38"
Your sub looks familiar, is it the one I saw in Rob Cheng's basement during the last DIY meet? I don't mind large, my mains are somewhat larger than this, but if not in a corner then they do look out of place unless finished off to look like a complementary piece of furniture. I once did a pair of 30ft^3 cabs and the owner's wife had them finished off by a furniture maker to look like antique French Provincial cabinets. With some 'hanging gardens' style greenery perched on top, they were very impressive (and expensive).
MIKET:
If you do a sim of the 'Voigt' style horn you'll see that it won't perform any better than Brian's straight pipe down low and the high taper ratio will push the driver somewhere between 5/8-3/4 down to get an aceptable tradeoff between LF extension and upper midbass/lower mids smoothness. Unfortunately, the excessively large/long vent will make a choppy mess of them, so overall, not a good design IMO.
Again, to get superior performance with pipe designs with the least effort, MJK's worksheets will save you a lot of time/$$.
HTH,
GM
Can't do washing machines but will fridge-freezers do?
An externally hosted image should be here but it was not working when we last tested it.
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