Transmission Line Modelling Software

[wmb]

I did some groundwork, investigating the WinISD driver file format to see what it would take to translate to TL format. Lo and behold, it was completely trivial. WinISD .wdr files say, for example,

Sd=0.00375

while TL .lsd files say:

Sd 0.00375

There are three spelling differences: Model vs. Title, BL vs. Bl, and Le vs Lvc. Other than that, all it takes is to replace the = with a blank.

The units appear to be the same.

A C program to do the translation is attached. I expect that letting TL read .wdr files would be a no-brainer - just change the line parser to delimit on = instead of space and accept the alternate names (BL really should be all caps anyway).

[schmeet]

OK.. More good suggestions. Want a job as a beta tester? :-)

I'll have a look tomorrow, I'm pretty sure they are all pretty quick modifications

Thanks again.

[schmeet]

Didn't see you post above wmb, I have already altered the program to allow it to read wdr files. Thanks anyway though...
I'll upload the update when I get a chance.

[schmeet]

Originally Posted by schmeet

Didn't see you post above wmb, I have already altered the program to allow it to read wdr files. Thanks anyway though...
I'll upload the update when I get a chance.

Sorry haven't had chance to upload the updates yet. Don't have access to a pc!!

[schmeet]

Ok i have uploaded 3.6.1.7

When altering a Start/End Area in the Geometry Display Window, holding Ctrl will also change the area of adjoining elements and branches if they originally had the same area

When a new element or branch is created it is now automatically selected.

The driver library can now read .wdr (WinISD Driver) files. We suggest that you copy these from your WinISD directory to your folder library directory as this application will not have permission to write to files in the WinISD folder.

Recently accessed files can now be opened via File -> Recent Files.


I have also setup a twitter account @leonardaudio where I will announce any relevant news/updates. Follow if you want.

[wmb]

No problem! I can easily convert any driver files I need with my program. My intention is just to help you refine your fine program so it's as easy to use as possible. Perhaps you can make a little money from donations or sales or wherever you decide to go with it.

Using TL has already changed the way I think about ported boxes. By moving the port, you can either "pick off" or suppress different cabinet resonances, and by moving the driver you can avoid exciting some cabinet modes. Lumped-parameter approximations are okay for almost-cubic boxes, but when the box starts to look like a pipe, things get more interesting.

[wmb]

Another great update, thanks! The new feature work fine.

Are you getting tired of my suggestions yet? In case you aren't, here's another: A control that would adjust the boundary between two elements, keeping the total length of the pair the same. The areas would change along the existing taper lines. If that's not clear, I can try to say it a different way.

The use case is what I have been doing for the last 3 hours - moving ports and drivers to adjust the "pipe resonances". As it is, you have to adjust the left element, then make the inverse adjustment of the right element, and that gets tedious in a hurry.

Maybe it could just be invoked by holding Ctrl while using the length control.

[schmeet]

Hi,

Only have my phone to reply on so can't go into much detail but the last update i did had something very similar. If you split an element then you can 'drag' split point between the two elements so the total length remains the same. However this can currently only work with elements that have a consistent taper and can be represented by one element...

[Keriwena]

Originally Posted by wmb

Using TL has already changed the way I think about ported boxes. By moving the port, you can either "pick off" or suppress different cabinet resonances, and by moving the driver you can avoid exciting some cabinet modes. Lumped-parameter approximations are okay for almost-cubic boxes, but when the box starts to look like a pipe, things get more interesting.

Originally Posted by wmb

The use case is what I have been doing for the last 3 hours - moving ports and drivers to adjust the "pipe resonances". As it is, you have to adjust the left element, then make the inverse adjustment of the right element, and that gets tedious in a hurry.

I was doing the same thing a few days ago. I got a couple of errors, and haven't had time to nail them down, but since you mention it....



Changing the position of the port does seem to affect the output, and I also found harmonics (esp the 2nd) could be reduced by making two ports, one with a length about half the length of the other one.

Thing is, the results don't match WinISD (the ports are always longer than WinISD predicts) and I'm concerned that TL.app (really, time for a better name) is including the port length in the overall calculations. I also suspect it's seeing the ports as additions to the total volume.

Now, Peter, while that might be a big bear to deal with, our results are flying in the face of what's been "known" for over 30 years - "port position does not matter and two ports always sum as one". If it turns out that our results are right, you could revolutionize bass reflex design. Well, at least add something new to the discussion.


To be clear - I think there needs to be a way to make an element internal. That is, not added to the total length, and subtracted from the volume of the element it's associated with.

[wmb]

My preliminary results, which I'm planning to write up formally:

Assume a bass reflex cabinet that is long compared to its cross-sectional area, i.e. essentially a "pipe". It is well-known that closed-end pipes resonate at half-wavelength frequencies. 1/2 lambda, 1 lambda, 3/2 lambda, 2 lambda, etc.

If you put the driver at the point 1/4 of the way down, it cannot excite the 1 lambda resonance, because that resonance has an antinode at the 1/4 point. Then, if you put the port at the halfway point, it cannot emit at any of the N + 1/2 lambda resonances, because they all have antinodes at the halfway point. Thus, in one fell swoop, you eliminate port radiation at the first three cabinet resonances (1/2, 1, and 3/2 lambda), as well as all of the odd-numbered higher-order ones.

The 1/2 lambda (first) resonance shows up in the driver output, but can be pretty well damped by adding short sections of heavy stuffing at both ends.

It works the other way too, with the driver at halfway and the port at 1/4. The 1/4 point for the driver probably works better for positioning the driver at ear level, for most reasonable cabinet sizes.

The "port position does not matter" mantra is correct insofar as the low-frequency extension effect is concerned, but it does affect port radiation at higher frequencies.

Keriwena, I do not share your concern that the port length affects the overall length as far as the base calculations are concerned. I convinced myself by looking at the structure of the high-order peaks in the port output. Those peaks occur at the N/2 lambda points of the overall length. Changing only the port length affects the bass-extension resonance, but does not affect the frequencies of those cabinet-resonance peaks. That is the intuitively-correct result.

It is true that the port length affects the model length that is displayed in the Model Info panel, but I don't see any evidence that that displayed number is itself used in the response calculations.