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Old 4th October 2013, 04:43 AM   #21
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I think it is something similar I mentioned in my rules of thumbs above and use in TABAQ.
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Old 4th October 2013, 09:30 AM   #22
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Slot vents in themselves are fine.

Damping in an MLTL should not significantly attenuate overall SPLs, nor shift the box gain away from what is intended. If it does, then it's not been designed properly. A well designed cabinet of this kind should not have any issues with harmonic modes.
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Old 4th October 2013, 09:32 AM   #23
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I seen a topic that I have not seen discussed. That is, the interference nulls created with transmission line type speakers.
As in pipe harmonic modes? It's mentioned in one way or another in just about every QW thread on the forum.
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Old 4th October 2013, 02:37 PM   #24
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Originally Posted by Scottmoose View Post
As in pipe harmonic modes?
No, in fact the frequency(s) are exactly between harmonics. If you take a transmission line with a driver at zero position (not offset) a null in the far field occurs at 4 times fundamental (between third and fifth harmonic). This wavelength is the length of the pipe, the pressure wave coming from the vent is 180 out of phase with speaker front wave. If you offset the driver (1/4 wavelength of this frequency from the closed end) the vent pressure sums now to zero at that frequency because you now have two separate pressure waves adding inside the pipe. Therefore, there is no pressure wave coming from the vent to cancel the front wave pressure at that frequency. This nulling occurs at all multiples of this wavelength, but the first (or lowest) is the most serious.
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Old 4th October 2013, 04:20 PM   #25
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Here's another way this nulling effect could be mitigated: mount a second driver separated by the distance equal to 1/2 wavelength of the frequency to be eliminated (measured inside the pipe), and the internal pressure wave then sums to zero at the vent terminus for that frequency.
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Old 4th October 2013, 05:59 PM   #26
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The nulling effect is part of the same issue as the peaks with the same solutions. Take the peaks away the valleys go with.

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Old 7th October 2013, 01:47 AM   #27
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Originally Posted by Patrick Bateman View Post
There's gotta be a better way to fix the dip, right?
Attached HornResp data comparing SPL response when the speaker is located near bottom of box, and ~32.8% down from top of a quater wave long box. The selection of stuffing material can also shape SPL response and final sonics. Naturally, not all designs permit flexible speaker location options.

What is the best simulator to add port shape modeling?
?Exporting the HornResp model into AkAbak and then extending that AkAbak model to include detailed port models?


Has anyone successfully modeled multiple ports with X,Y,Z dimensions that control resonance and air flow restriction?
Attached Images
File Type: jpg Box Resonance.jpg (77.7 KB, 477 views)
File Type: gif Stuffing.gif (19.8 KB, 462 views)

Last edited by LineSource; 7th October 2013 at 01:58 AM.
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Old 7th October 2013, 04:52 AM   #28
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Quote:
Originally Posted by LineSource View Post
Attached HornResp data comparing SPL response when the speaker is located near bottom of box, and ~32.8% down from top of a quater wave long box. The selection of stuffing material can also shape SPL response and final sonics. Naturally, not all designs permit flexible speaker location options.

What is the best simulator to add port shape modeling?
?Exporting the HornResp model into AkAbak and then extending that AkAbak model to include detailed port models?


Has anyone successfully modeled multiple ports with X,Y,Z dimensions that control resonance and air flow restriction?
I have successfully modeled port shapes by approximating a 2 dim port as a series rectangular ports of prescribed dimensions. This is how I modeled the Karlson aperture. See post in the Karlson thread here: KARLSON I have also modeled arbitrary ports located at different points along the TL to detune the Q of certain cavity resonance modes. See my thread here: The Flute Pipe TL.

Akabak is very flexible and allows arbitrary xyz (and alpha, theta, phi angular orientation) placement of ports/vents/radiators.
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Old 11th October 2013, 04:55 AM   #29
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Originally Posted by sreten View Post
Hi,



Then Bud Fried came along with a load of unverified nonsense,
but he made it sound good, which it isn't, and was very influential.


rgds, sreten.
Can you please state which exact Bud Fried T-line speaker models you have heard?
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Old 11th October 2013, 05:32 AM   #30
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This might be of some help.
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