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Old 16th December 2005, 11:53 AM   #1
el`Ol is offline el`Ol  Germany
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Default double-TL useful?

Hello everybody!


I am using M. King`s sheet (original version without offset) to construct an enclosure for the Ciare HX201 in an "omnidirectional" setting (driver looking to the ceiling). What I don`t like so much about a standard folded TL is the direct line from the driver to the bottom, which should make a lot of dampening necessary. So I also considered to separate the box into two TLs. I started with the special case of a diagonal through the box separating the box into two identical TLs. I expected the peaks and holes to become more extreme with two identical resonators in series, but the opposite happened.
An other effect is that the rolloff is more flat and starts sooner.

Can I trust these results?

Oliver
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Old 16th December 2005, 12:21 PM   #2
Rudolf is offline Rudolf  Germany
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Default Re: double-TL useful?

Quote:
Originally posted by el`Ol
[B]I am using M. King`s sheet (original version without offset) to construct an enclosure for the Ciare HX201 in an "omnidirectional" setting (driver looking to the ceiling). What I don`t like so much about a standard folded TL is the direct line from the driver to the bottom, which should make a lot of dampening necessary.
What IMHO will make a lot of dampening necessary is exactly your straight line with the driver at one end. Any other version (folded, offset driver or mass loaded will reduce the necessity for dampening.
Quote:
So I also considered to separate the box into two TLs. I started with the special case of a diagonal through the box separating the box into two identical TLs. I expected the peaks and holes to become more extreme ...
Diagonal separation will reduce lateral resonances in the line.
Quote:
... with two identical resonators in series, but the opposite happened.
From your description I would expect the resonators in PARALLEL. What did I miss? You probably need to a supply a drawing of your construction.

Rudolf
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Old 16th December 2005, 01:54 PM   #3
el`Ol is offline el`Ol  Germany
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Here it is.
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Old 16th December 2005, 03:07 PM   #4
Rudolf is offline Rudolf  Germany
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Aaaah, I see!

But I donīt believe, this will work as wanted. The influence of the second half of the line as a "resonator for the resonator" is negligible.
The only workable arrangements for the partition would be the ones shown in the second and third drawing.
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Old 16th December 2005, 04:46 PM   #5
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Agreed. I'd go for drawing 2 by the way.

Yes, you can trust the results from martin's worksheets (understatement of the decade there), but remember, they can only model what you put into them...
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Old 17th December 2005, 04:33 AM   #6
el`Ol is offline el`Ol  Germany
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Meanwhile I also favour the standard folded TL, because it goes deeper in bass. With some wool at the bottom it shouldn`t be a problem.
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Old 17th December 2005, 02:00 PM   #7
Rudolf is offline Rudolf  Germany
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Old 18th December 2005, 06:54 AM   #8
el`Ol is offline el`Ol  Germany
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I simulated both versions more detailed with the "sections"-sheet using minimal values for the closed end. Rolloff is similar, frequency response of the double-TL is still slightly less peaky.

The main difference is in the terminus velocity.
In the standard folded TL it is continuously falling. In the double-TL there is a steeper decline first and over 100 Hz it is fairly constant with slight peaks and holes.

What does the terminus velocity tell us?
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Old 19th December 2005, 12:04 PM   #9
el`Ol is offline el`Ol  Germany
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Default Visaton B200

I did some more simulations, you need a BR if you really want to get above the infinite baffle response. The superiority of the double-TL is probably just because the HX201 is not really a TL-driver.

When I do the simulations with the Visaton B200 the superiority of the classical TL is obvious (really really nice responses). And maybe the B200 also works as an omnidirectional because of its rising frequency response.
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