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Old 23rd October 2012, 07:39 PM   #81
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you're speaking about GM's ?

TL is by dimensions and driver & port position

read this , for amusement : 6moons audio reviews: Stephæn's Altec 604 Dream Speaker
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Old 23rd October 2012, 08:00 PM   #82
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A TQWT can shorten this path by using a narowing line.
No, a TQWT has an expanding squaresection, a shrinking pipe is a transmissionline and those two work in entirely different ways, except the quarterway resonant behavior.
The tl principle has as primarily goal to achieve maximum linearity through damping while sacrificing efficiency.

A TWQT instead uses the qw resonances to raise efficiency in the low end by the impedance transformation that is there on account of the expanding pipe, naot att all to the same extent as a real horn but still enough to make som dB gain, this is then carefully contolled with sparse damping in the pipe to milden the inherent unlinearity all qw systems suffer from.

Well executed they, `TQWT´s`can be very well extended, dynamic and,IMO, very nice speakers for music.
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Old 23rd October 2012, 08:05 PM   #83
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When speaking of taper, the dircection we speak of is from open end to closed end?

As for TL, with a speaker 42" tall, doesnt that mean it is tuned in the 80Hz region.
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Old 23rd October 2012, 08:44 PM   #84
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No Buzz, we regard the taper from closed to open end.
A tqwt is growing larger as we approach open end, a tl is shrinking as we go there.

A 42" tall box without inner walls to make a `pipe´, with a port, anywhere, is a bassreflex, shure it has a quarterwave resonance, as has all boxes with parallell walls , size determines frequency.

A proper tqwt or tl is either very tall or folded, the entire pipelength determines lf qw frequency.

A tqwt with the driver properly positioned in the pipe lengthwise gains from the same kind of impedancetransformation as a proper horn but to a much lesser degree, but also in a somewhat more linear manner, corectly done You gain efficiency in the low end of the combined system, box+driver, with decent linearity and without damping to much of the dynamics.
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Old 23rd October 2012, 09:08 PM   #85
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My bad, Thats what i thought. I was incorrect in my understanding of a TQWT. A Tl can also be constant with no taper or expansion, correct. I could have sworn GM said that horn is expanding and tqwt is tapered, but just read "inverse" tapered. Duh! THanks Ingvar.

I case of BR or MLTL, I thought line/pipe length is what determined frrequency, assuming astated Vas. Guess I did not consider that both parameters are involved. What happens to tuning with two different boxes, both same length/heighth, but one with less Vb. Are we just talking rate of rollof, or complete change of response.

Geez. I gotta go read MJK stuff again. UGH!.
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Old 23rd October 2012, 09:41 PM   #86
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A pipe, wichever type, should have, at least, about the same vb as a br cab for the same lf tuning, wich will almost always automatically be the case, the pipe will be larger, but once in a while senile old men do silly misstakes.

Click the image to open in full size.

Here the pipes, TQWT, are 420cm long but the vb is just too small so they still
died down at around 100Hz, the rectified version, slightly more than twice as wide, produce just what they were supposed to do.
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Old 23rd October 2012, 11:15 PM   #87
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I can see my kids draggibg that to their bedroom and using it for recreational purposes : D
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Old 23rd October 2012, 11:58 PM   #88
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Quote:
Originally Posted by TerryO View Post
Greg,

Thank you for mentioning Bill Eckle. He was a first class guy that helped many people.

Best Regards,
TerryO
My pleasure!

Indeed he did, I was one of them. He mailed and later emailed me various info I was interested in and we would occasionally 'bench race' W.E./Altec design.

Did you know Bill personally?

I only knew him through the local Altec distributor and of course later on the early audio BBs, then some web forums before he 'disappeared', resurfacing every once in awhile on the Altec User's Forum to post pics of speaker projects he'd done.

GM
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Old 24th October 2012, 03:48 AM   #89
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Quote:
Originally Posted by buzzforb View Post
Care to explain how high Zo changes things. Amps are not a problem, if there is justification for a certain type.
It raises the system Q for one, lowering damping and if it’s transformer coupled it creates a ‘smiley face’ [with a tooth or two if there's an XO] EQ as it tracks the system impedance with all the good and bad performance potential this implies.

GM
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Old 24th October 2012, 04:59 AM   #90
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Originally Posted by buzzforb View Post
Withot being able to see the inside of the cabinet, this desing sorta resembles the Pensil's by Scottmoose. He call them a resonant air coupler. I would expect a horn like path inside, but there is noting of the sort. What turns it int the a TL, the port? Everything I have read about TL's is that they have to do with quarter wavelength, which increases the lower you wish to tune. A TQWT can shorten this path by using a narowing line. Is this what the squaer port is doing?
Which one? Westend’s? It’s just a high aspect ratio vented cab [MLTL] with some bracing.

The Pensil is called a RAC because its net Vb is many times larger than the driver’s Vas, so is basically a vented I.B. which in turn must be well damped to make it ~aperiodic to get good performance.

A TL is either a 1/4 or ½ WL resonant pipe, so no vent [1/2 WL resonator] to mass load it, ergo like the RAC in that it requires considerable damping to be smooth.

Correct, venting [mass loading] a TL reduces its path-length somewhat for a given Fp[Fb].

GM
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