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Old 3rd November 2008, 05:23 AM   #11
simon5 is offline simon5  Canada
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BTW, what is that driver ? It has interesting parameters.

I guess you'll need to use long ports with big diameters to have low vent noise no ?
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Old 3rd November 2008, 05:53 AM   #12
00600 is offline 00600  United States
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Quote:
Originally posted by simon5
BTW, what is that driver ? It has interesting parameters.

I guess you'll need to use long ports with big diameters to have low vent noise no ?

The driver is a late 90's Cerwin Vega Stroker 18", sold for car audio competitions, I have a strong feeling its just a relabeled PA driver.

The ports will be 4" diameter, two ports roughly 34" long, I'll use DWV PVC pipe with a few bends in it.
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Old 3rd November 2008, 07:02 AM   #13
GM is offline GM  United States
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Due to the MLTL's and vent's area/length combined, simplifying it into a TQWT is a better choice overall IMO.

GM
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Old 3rd November 2008, 07:19 AM   #14
00600 is offline 00600  United States
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Quote:
Originally posted by GM
Due to the MLTL's and vent's area/length combined, simplifying it into a TQWT is a better choice overall IMO.

GM

Umm... I just did a quick check, and a TQWT for that driver tuned to 18HZ would be 33cu ft, 18" x 26" X 118"....

Am I missing something?
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Old 3rd November 2008, 08:16 AM   #15
Thawach is offline Thawach  Thailand
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00600,Loud is Beautiful said that' all right.the TQWT is a better choice for 18 hz and it's not difficult to design. But before u build please carefully to check your roof and your floor. because it's very high. sometime may be higher than your roof. About phase and group delay are difficult to explain. u build a lot u will know by yourself.

/TW
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Old 3rd November 2008, 02:14 PM   #16
GM is offline GM  United States
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Quote:
Originally posted by 00600

Am I missing something?
Apparently.

I'm curious, how did you arrive at such a large, long pipe? What program are you using to sim it? None of the typical vented box calculators such as WinISD can do it with any degree of accuracy, especially WRT vent area/length since they assume a ~uniform particle density throughout the cab, i.e. one with dimensions that has a theoretically perfect acoustic ratio.

Regardless, just so we're on the same 'page', TQWT ~ defines the inverse of a simple constant area expansion horn, i.e. just as it needs an increasing expansion ratio (ER) from the throat to the mouth (St : Sm), ergo its length increases with increasing ER, so goes the TQWT's inverse closed : open cross sectional area (CSA) compression ratio (CR), ergo its length decreases with increasing CR.

Bottom line, the TQWT shouldn't require any more net Vb than the sum of your MLTL + vent Vbs and maybe less depending the desired XO point/slope, yet its various performance specs will be superior overall due to better acoustic damping. The trade-off is a deep notch at its 3rd harmonic and strong pipe resonances above it along with a vented alignment's 4th order roll-off , so its effective HF gain BW is much more limited than typical vented alignments without a high stuffing density that will attenuate much of its gain, but for < ~100 Hz XO points it's not a problem.


Quote:
Originally posted by Thawach

.....because it's very high.
That's what multiple folds are for , with the dividers doing double duty as very effective bracing, ergo if void free plywood construction is used it shouldn't be all that heavy for its bulk. I mean you could design it so that the driver loaded the walls/floor corner and the vent the walls/ceiling corner, but a folded one with the driver and terminus (vent opening) at floor level has much more placement flexibility, though of course at the expense of taking up more floor space.

GM
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Old 3rd November 2008, 09:12 PM   #17
Thawach is offline Thawach  Thailand
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LOL GM! because u my joke is not joke. i told very high but u tell me high/2.LOL 00600 if u want high/2 TQWT that u can use speaker calculus program from mhsoft,i ever saw. 00600 please believe me about high+extension=super high LOL okay GM the next project sometime i want the deep bass. it's sure!! TQWT


/TW
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Old 4th November 2008, 02:23 AM   #18
00600 is offline 00600  United States
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Quote:
Originally posted by GM


Apparently.

I'm curious, how did you arrive at such a large, long pipe? What program are you using to sim it? None of the typical vented box calculators such as WinISD can do it with any degree of accuracy, especially WRT vent area/length since they assume a ~uniform particle density throughout the cab, i.e. one with dimensions that has a theoretically perfect acoustic ratio.

Regardless, just so we're on the same 'page', TQWT ~ defines the inverse of a simple constant area expansion horn, i.e. just as it needs an increasing expansion ratio (ER) from the throat to the mouth (St : Sm), ergo its length increases with increasing ER, so goes the TQWT's inverse closed : open cross sectional area (CSA) compression ratio (CR), ergo its length decreases with increasing CR.

Bottom line, the TQWT shouldn't require any more net Vb than the sum of your MLTL + vent Vbs and maybe less depending the desired XO point/slope, yet its various performance specs will be superior overall due to better acoustic damping. The trade-off is a deep notch at its 3rd harmonic and strong pipe resonances above it along with a vented alignment's 4th order roll-off , so its effective HF gain BW is much more limited than typical vented alignments without a high stuffing density that will attenuate much of its gain, but for < ~100 Hz XO points it's not a problem.




That's what multiple folds are for , with the dividers doing double duty as very effective bracing, ergo if void free plywood construction is used it shouldn't be all that heavy for its bulk. I mean you could design it so that the driver loaded the walls/floor corner and the vent the walls/ceiling corner, but a folded one with the driver and terminus (vent opening) at floor level has much more placement flexibility, though of course at the expense of taking up more floor space.

GM

here's a link to the .xls file I used:

http://82.95.237.142/mhsoft/downloads/TQWPmetric.zip

I just changed the blue parameters to match my driver, and changed the 1st harmonic to 18Hz.

I spent two weeks playing with Hornresp last year, trying to model a folded horn for this driver, but the low roll off always ended up worse than just running it in a BR.

I'd like to keep the enclosure as small as possible, 1.5' x 2' x 4' MAX, that way it either has a small footprint, or I can use it as a shelf.

Around the time I was modeling the horn, I was also reading a whitepaper on TQWTs, it seemed like tuning was very hit and miss, and since I didn't have ANY enclosure at the time, and I had never done a slot ported box, I figured I'd take the easy one.

I'm looking for a response curve as flat as possible, as low as possible, around 110-120db to match with my mains.

I was thinking about a Linkwitz Transform, but it didn't seem like the driver was well suited to it either.

I'm just trying to improve upon what works. Though I'd be willing to try a TQWT if I knew more about it.

Thanks again.
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Old 4th November 2008, 12:58 PM   #19
Thawach is offline Thawach  Thailand
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hi 00600

if u build TQWT subwoofer. please show me the pics and i want to know the sound of it. now i interest it. i often see it use with full range drivers. but u don't build the high TQWT.it's not beautiful.

regards/TW
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Old 5th November 2008, 01:20 AM   #20
Thawach is offline Thawach  Thailand
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hey! GM ask a little,i want to know which are good between BIB and TQWT? i know u know about this and has experience. i see BIB and TWQT. it seems like as the same( the basic of horn) but it has a little difference.

queen regards/
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