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Old 16th December 2012, 04:02 AM   #331
wmb is offline wmb  United States
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For a few designs I have tried, TL and WinISD agree very closely with respect to bass extension, for boxes of the same volume and ports of the same area and length. That is especially true when using WinISD's conventional port modeling. WinISD's transmission line port modeling gives somewhat different results, predicting surprisingly-high Q for the bass-extension resonance. I'm not sure I believe WinISD in that mode.
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Old 16th December 2012, 07:03 AM   #332
schmeet is offline schmeet  United Kingdom
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I'm not aware of WinISD having a transmission line mode. As far as I know WinISD using a lumped parameter mass spring model and so does not take into account box or port resonances.

The more pipe like a box is the less accurate this method becomes and the more reason to use a wave-equation based model such as HornResp, MJK's Math cad or TL.app (I know I know, better name is required!)

Wmb, your findings seem sensible...
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Last edited by schmeet; 16th December 2012 at 07:07 AM.
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Old 16th December 2012, 10:52 AM   #333
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Just a few quibbles:

Sometimes, when clicking on an element to select it, instead the drawing jumps back to the original size and position.

The 'drag the split' doesn't seem to work, at least after there's another element attached - it jumps to one position and won't move from there.

The 'Redo' will go 'round the circle, past the last change and produce the original file loaded. You can undo it back to where you were, but it's weird.

Otherwise, the new changes are very helpful. Great work, as always.
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Old 16th December 2012, 11:53 AM   #334
wmb is offline wmb  United States
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WinISD version 0.7.0.900 has a 'Use "transmission line"-model for port simulation" checkbox on its "Advanced" control page. Checking that box shows the effect of resonances within the port tube in the transfer function, and also, as noted, tends to predict different behavior in the bass extension region. That version was never formally released but a link was posted on Linearteam's (now-defunct, spammed out of existence) forum.

The attachments shows the WinISD and TL models of the same box, driver, and port. It's an Audio Nirvana 8" driver in a 38 liter unstuffed box, 10 cm diameter round (78.5 cm2 area) x 10 cm long (60 Hz) port. The TL model is "boxy", with 929 cm2 area and 41 cm total length.

The green WinISD trace is with the transmission line port model, showing the port resonances starting at 1700 Hz. The red trace is the lumped model.

Adding short sections of heavy stuffing at the box ends on the TL model brings down the port peak so the low-frequency part of the graph matches the red (lumped) WinISD graph quite closely, and also tames the box resonances.
Attached Images
File Type: png WinISD Screenshot.png (51.4 KB, 103 views)
File Type: png TL Screenshot.png (38.0 KB, 102 views)
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Old 17th December 2012, 12:44 AM   #335
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At the present point of development, it is possible for TL to model something like this?
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File Type: gif box sketch.gif (12.5 KB, 94 views)
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Old 17th December 2012, 08:32 AM   #336
schmeet is offline schmeet  United Kingdom
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Quote:
Originally Posted by Keriwena View Post
The 'drag the split' doesn't seem to work, at least after there's another element attached - it jumps to one position and won't move from there.
The drag split seems to work well on mine. For example:
A sealed enclosure with two elements:
Click the image to open in full size.

Then split the first element in two. Note that the split line is a different colour (This shows that you can drag it)
Click the image to open in full size.

Add a port:
Click the image to open in full size.

You can then drag this split, and thus the port, along the length of the two elements:
Click the image to open in full size.
Click the image to open in full size.
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Old 17th December 2012, 04:43 PM   #337
wmb is offline wmb  United States
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I have the same "jumps to a new position problem", even with no other elements attached. It reproduces easily, in the simplest possible case:

a) Open TL afresh
b) Select the initial element
c) Type S to split it (or use right-mouse, it doesn't matter which)
d) Click-and-drag the mouse on the split line, away from the square handle

At the instant you start to move the mouse after down-clicking on the split line, the split line jumps to the far left, showing "Split ratio 0.01" in the status bar at the bottom of the window. Subsequently, the split position cannot be moved from there; if you attempt to drag it, it just stays in the same position.

This misbehavior is very robust for me, to the extent that I have seen many failures but no successes. I have also tried the two-element-plus-port geometry shown in your report, and it fails in the same way.
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File Type: png Split.png (27.0 KB, 18 views)
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Old 17th December 2012, 04:48 PM   #338
schmeet is offline schmeet  United Kingdom
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Hmm.. very strange.

Do you guys use commas or dots for decimal place? (most strange things seem to be because of this!)
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Old 17th December 2012, 04:53 PM   #339
wmb is offline wmb  United States
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I use dots, per US usage. I could try commas if I knew where the setting were located.
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Old 17th December 2012, 04:56 PM   #340
wmb is offline wmb  United States
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I have also tried turning off auto-update, and have tried different settings of both the default units and the displayed units. Nothing seems to make a difference.
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