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Old 10th September 2007, 03:31 AM   #1
sardonx is offline sardonx  Canada
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Default Closed End Transmission Line

Hi all,
I've searched here but couldn't find anything. Does anyone have any experience with the so called "true" transmission line concept with a closed end? It doesn't seem that many people try this..
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Old 10th September 2007, 07:03 AM   #2
banana is offline banana  Hong Kong
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Like this??

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Old 10th September 2007, 07:28 AM   #3
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A closed transmission line is a 1/2 wave resonator. Best exemplified by the B&W Nautilus pictured above.


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dave
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Old 10th September 2007, 10:22 AM   #4
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Been thinking about this for my upcoming big speakers. With the lower mids at the top and bottom of a big symmetric array that'll probably end up being about 1.75m tall and only wanting 80-100Hz response there should be enough length. Plan is to build a test box from scrap and see if an opening at the closed end makes some difference. I'll get Martin's software and sim it to get me in the right area.
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Old 10th September 2007, 05:03 PM   #5
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Wise man.

They should give you a purity across that region other boxes struggle to match. Nice easy amplifier load too.
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Old 10th September 2007, 08:50 PM   #6
sardonx is offline sardonx  Canada
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I used to work for the guy who made Morrison's transmission line enclosures. They were closed end. What is interesting about the design is that instead of one length, the enclosure has 4 different lines, at different lengths. If you looked at the impedance plot, instead of one big hump at the resonant frequency, there would be 4 gradual ones. I never actually saw a tested graph myself, but can tell you the bass was very deep, and very clean.
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Old 11th September 2007, 12:36 AM   #7
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Quote:
Originally posted by sardonx
I used to work for the guy who made Morrison's transmission line enclosures. They were closed end. What is interesting about the design is that instead of one length, the enclosure has 4 different lines, at different lengths. If you looked at the impedance plot, instead of one big hump at the resonant frequency, there would be 4 gradual ones. I never actually saw a tested graph myself, but can tell you the bass was very deep, and very clean.
Morrison inherited that design from Stu Hegeman. The man was a genius. The enclosure can't really be called a TL thou as the lines aren't really long enuff.

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Old 11th September 2007, 02:20 AM   #8
sardonx is offline sardonx  Canada
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Oh yeah I know it's not Morrison's design.. I guess I should have mentioned that for those that don't know. Those enclosures were built like a **** brick house though.
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Old 11th September 2007, 06:11 AM   #9
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No intent to belittle Morrison. Stu hand picked him to carry on his work and from what i understand he has added his own important wotk to the concept. This is a speaker i'd really like to hear someday. I did sell the Hegemans when i worked hifi in the late 70s and they were special... 30 years of steady development can't have hurt

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Old 11th September 2007, 06:19 AM   #10
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Quote:
Originally posted by sardonx
I used to work for the guy who made Morrison's transmission line enclosures. They were closed end. What is interesting about the design is that instead of one length, the enclosure has 4 different lines, at different lengths. If you looked at the impedance plot, instead of one big hump at the resonant frequency, there would be 4 gradual ones. I never actually saw a tested graph myself, but can tell you the bass was very deep, and very clean.
Interesting. Any idea on the details of the implementation?
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