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Old 18th November 2010, 01:55 AM   #21
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closed end is half-wave.

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Old 18th November 2010, 02:33 AM   #22
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Cheers Dave

Crikey, so the line has to be matched exactly to the Fs - and the length of the closed line, is it measured on the half wave going to the end and returning.. or just one way? 3am, not explaining myself well, apols

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Old 18th November 2010, 03:07 AM   #23
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1/2 wave is 1-way. And it changes if the line is tapered. This Natilus prototype can be shorter because of the taper.

Click the image to open in full size.

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Old 18th November 2010, 03:33 AM   #24
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If it helps, Bob Brines has a discussion about traditional TLs here: Traditional Transmission Lines and here: Small TL's In the 2nd article linked he notes "Small and TL is a relative thing. A TL enclosure will almost always be the largest option for a given driver".

I'm not sure why you'd want to use a TL but hey, much better people have used them than me. For example Nelson Pass used an open-ended one for the Pioneer B20 (BOFU) driver here: Pioneer 8" fun
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Old 18th November 2010, 11:25 AM   #25
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Thanks for your replies
I came up with a design a few months ago(see model pics) which wd use two small FR units in a tapered double TL (and a small sub at it's base).
I wanted to use the little spiderless Jordans (which normally use a sealed box as a suspension). I am hoping a closed TL is a good solution and may also add some benefits.
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Old 18th November 2010, 03:03 PM   #26
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Quote:
Originally Posted by Bill poster View Post
fascinated by closed end TLs but don't fully understand how they work-
Resonances of open air columns

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Old 18th November 2010, 03:44 PM   #27
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Quote:
Originally Posted by Bill poster View Post
I am hoping a closed TL is a good solution and may also add some benefits.
It is, though as already noted it will have to be end loaded 1/2 wave (AKA plane wave tube (PWT)) to keep from having to excessively stuff it to damp its 1/4 WL resonances.

That said and without any detail technical or hands on knowledge of these drivers, IME it will damp them so well if properly designed that they may only be usable over a relatively narrow BW, requiring either a tweeter or CD horn EQ that will significantly reduce its effective efficiency.

As you increase net Vb to allow it to 'breathe', you quickly revert back to being just a near I.B. loading, so of limited use beyond cosmetic.

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Old 18th November 2010, 04:40 PM   #28
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Hm ok, so in general closed TLs offer some benefits but are effectively narrow bandwidth, hence why the nautilus was 4 way?

Last edited by Bill poster; 18th November 2010 at 04:46 PM.
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Old 18th November 2010, 05:28 PM   #29
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Quote:
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Hm ok, so in general closed TLs offer some benefits but are effectively narrow bandwidth, hence why the nautilus was 4 way?
The B&W would have been 4-way with or without the TL.

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Old 18th November 2010, 05:45 PM   #30
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Probably a badly thought out question, but anyhow, do we build the half-wave TL in accordance with the drivers free air fs or, since the driver will effectively be performing in a closed box, do with build to the closed box fs (having found the approximate volume of the closed TL enclosure)? My MJK sheets expired a long time ago
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