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Old 3rd December 2012, 02:37 PM   #421
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OK. So I think i got my head rapped around this thing a little better, but have some questions. In a TL, the thing that determines whether it is expanding or tapering is the location of SL or the open end. If open end is larger, then it is an xpanding line/horn. If the open end is smaller, it is a tapered line or Tqwt. Driver positioning is always relative to the SO or closed end.
Using the open TL worksheet is easy peasy. Where things get hairy for me is when we get into a ML TL worksheet. The ML portion simply means that there is port somewhere on the acoustic line. Am I correct in thinking that it is this port that now determines the open end of the design, taking the place of SL in the open TL worksheet. It would seem that the MLTL sheet is geared more towards designing a BR, although interestingly enough, the response i get from the MLTL shhet does not match that from WinIsd.

I am going to try and model the same system in both worksheets and see what i get.
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Old 3rd December 2012, 04:19 PM   #422
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do you want me to make a box sketch of that sim I made ?

GM influenced me enough to abandon slot opening , so I think I got solution to have both square port and folded TL ( xpanding , as you call it )
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Old 3rd December 2012, 06:21 PM   #423
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I think i got it, just trying to confirm. Let me figure mine and we can compare....only if you promise to use as teaching exercise and not running joke

As for port. In my sims, moving the port around did make significant difference in ripple and cancellation of resonant frequencies. Bob Brines talks about the possiblity of canceling both 3rd and 5th resonant frequencies and I believe MJK has an example in his TQWT paper, but i cannot find the stupid link. Oddly enough, I cannot find many examples where people try moving the port. They mostly just change driver position. and shove the port to the bottom, i guess trying to take advantage of length to gain LF extension.
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Old 3rd December 2012, 07:58 PM   #424
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GM influenced me enough to abandon slot opening , so I think I got solution to have both square port and folded TL
Hmm, sorry to hear this as I'm not against them, just like anything else it just depends on the needs of the app as to what to use.

BTW, the pioneers of audio apparently understood the value of moving the vent location back up a [ML]TL as some would put the mouth of a rectangular or K-slot ducted port at the bottom and box in duct up the inside of the baffle, which is no different than if the port was located at this height from an acoustical design POV.

Where do you think I learned about such esoteric design considerations? Not much new, if anything, in [TL] speaker design.

Oh well, got to get back to gutter replacement.

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Old 3rd December 2012, 08:07 PM   #425
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I didn't said that you're against them (slot openings) , but I understood that with square one I'll need less tweaks later

or - in other words , no need for test boxes
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Old 3rd December 2012, 09:20 PM   #426
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I bet I can replace a gutter better than you ......Although I dont know if that is something to brag about.
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Old 4th December 2012, 01:28 AM   #427
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Originally Posted by buzzforb View Post
In a TL, the thing that determines whether it is expanding or tapering is the location of SL or the open end. If open end is larger, then it is an xpanding line/horn. If the open end is smaller, it is a tapered line or Tqwt. Driver positioning is always relative to the SO or closed end.

Am I correct in thinking that it is this port that now determines the open end of the design, taking the place of SL in the open TL worksheet. It would seem that the MLTL sheet is geared more towards designing a BR, although interestingly enough, the response i get from the MLTL shhet does not match that from WinIsd.
Correct and these definitions are mine and some others use to differentiate them, while others stick to the strict electrical definition of just 'TL', requiring further description that isn’t always included, sometimes causing considerable confusion as to who is recommending which TL alignment.

Right, the ‘TL’ is a ¼ WL resonator and the ‘ML’ [vent] is a ½ WL resonator in series to cause a summed tuning somewhere below these two differently tuned acoustical systems. As the vent is moved up, the path-length increases due to reflecting off the bottom of the cab, but the trade-off is reduced ¼ WL loading of the vent with a notch in the response that can become audible if moved too close to the driver.

Of course! A typical reflex program assumes a ~uniform particle density of the cab’s trapped air mass ‘spring’ whereas a MLTL has more powerful [stiffer] ¼ WL resonant action exciting/damping the vent with the trade-off that the MLTL must have a high aspect ratio and greater net Vb to have a comparable frequency response.

GM
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Old 5th December 2012, 02:37 AM   #428
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Seems I only know how to design BR speakers. As GM said, I can stuff it flat, but seem to be failing at getting it clean without. Maybe this is good. Sure as hell is big, coming in at about 16ft^3. Probably too big. I am open to further correction again.
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Old 5th December 2012, 02:20 PM   #429
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Like most folks, you look at any speaker sim not billiard table flat as unacceptable, but the reality is that only a vanishingly low percentage of folks living in today’s society of high ambient noise have the ability to hear well enough to notice these small phase ‘burps’ and even then most are female and lose it before adulthood and why I relied heavily on my daughter and other young women to ‘voice’ my critical listening builds and do audible perception experiments.

Anyway, FWIW, Altec recommended a minimum 8 ft^3 sealed up to around 18 ft^3 vented if tuned to Fs, but the latter assumed a high output impedance, so today this equates to a ~ 9-10 ft^3 tuned to 35-40 Hz alignment. If a matching impedance, then sealed Vb = Vas up to IB, so you’re still thinking ‘small’ for this driver if you want it ‘to be all it can be’.

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Old 5th December 2012, 02:35 PM   #430
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Apparently I am not going to be all I can be. I could narrow front and deep sides, but i would lose 4 feet of room if i want to pull them out any. I sitting here looking at a tiny 20' x 28.8" x 40", 13.5 ft^3(inside) and thinking if I can pass it off. What would you recommend in the 10-13ft^3 range?

Nother thought that came up last night in regards to big enclosure. What about stuffed U Frame. I grew up listening to old Alnico Guitar speakers in crappy little uf rame boxes with a back and they had plenty of tone and low end. I believe I have read that the Altecs like some dampening and wondered if somthing like this would work.

Dunno wha to do. Wna tt let these babies sing, but it has to be presentable or I will listen to them all the time because I am sleeping on the couch.
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