Linearteam WinISD Pro
Since the release of WinISD, many emails have been received from folks pertaining to many issues of the program. While most of these issues are in fact discussed and explained in the Help File itself, most people (myself included) don't actually get around to reading Help Files unless we get stuck. So, with that in mind, I will continue to update the Help File with this FAQ section based on actual popular questions.
Q. You had the EBP text bass-ackwards in the Help
File.
A. from JJ Richard (JJRichard@linearteam.org)
Yes, I most certainly did. Thanks to Choong for pointing that out to me. (5/26/99)
Q. How do I change the units of measurement from metric
to standard etc....
A: from JJ Richard (JJRichard@linearteam.org)
After you load a driver, simply click on the name of the unit over and over until your unit of choice is displayed. For example, if the unit is shown as 15 mm, then click on the "mm", and it will toggle through all available units! Easy, huh? WinISD will "remember" which unit you choose, and will subsequently default to that unit in the future. (5/26/99)
Q. What happened to vent mach calculator?
A. From Janne Ahonen (janne@linearteam.org)
Vent mach calculator was replaced by much more useful tool, vent air velocity graph, which gives not only the value of velocity, but also the frequency, where you could expect problems, if any.
Q. Does WinISD add brace/driver/port displacements to
calculated box volume?
A. From Janne Ahonen (janne@lineateam.org)
No. WinISD doesn't do guessing, and therefore shows net volume for your box. It would be hard to predict, how you are going to mount your driver. Or the port. Or how much and which kind of bracing you are going to use inside your box. For example, you could mount port completely external to the box, which case "usual" guess would be completely wrong. Bottom line is, that you must calculate and add any displacements by yourself to calculated box volume.
Q. What calculated port length means? How it is
measured?
A. From Janne Ahonen (janne@linearteam.org)
WinISD calculates port length assuming that there are one flanged and one free end, i.e. port is mounted to the wall of the box, and another end is freely inside the box. So end correction factor is 0.732 by default. Port length in box wall is counted to port length. If you want do convert the result to different end correction, then add 0.732 times diameter of the port to calculated port length. This gives you needed acoustical length of port. Then add end correction as you like. See also article about port terminology.
Q. Why driver editor calculates different value for
Vas/Bl or some other parameter than in driver's manufacturer specs have?
A: from Janne Ahonen (janne@linearteam.org)
Most common reason why this is happening are the air properties. Since Vas depends on current air properties, there is no absolutely "correct" Vas value existing. So every time you'll adjust your room temperature, air properties will change, and your Vas will be different. My advice is to avoid entering Vas whenever possible. I also have personally found out that manufacturer's specs are not always in complete accordance with T/S model. So when in doubt, it is best that you verify parameters from driver manufacturer.
Q. Why WinISD calculates different result for plot x with
driver y in enclosure z?
A. from Janne Ahonen (janne@linearteam.org)
Most differences come from different input parameters. For example, vented box has quite a few other parameters than just box volume and tuning frequency. More complicated explanation is probably that calculation may use different model or different source parameters. If you go through all the relevant parameters, and still can't find the cause, please e-mail me. I'll have look at it then. After all, it is not at all impossible that we have made some mistakes somewhere.
Q. Why frequency range is limited to low frequencies by
default?
A. From Janne Ahonen (janne@linearteam.org)
That is limitation of used equivalent circuit models. They are valid only in pistonic range of driver, or about 200-300 Hz. Anything beyond that, is very inaccurate. Possibility to change the plot frequency range is provided just for convenience.
Q. Why there is no option for nonlinear simulation?
A. From Janne Ahonen (janne@linearteam.org)
This is not a trivial topic as it may first seem. It is very hard to make accurate
non-linear simulations, because for example considering the nonlinearities in the driver
would require much more extra parameters to input to be able to simulate accurately. There
are so many kinds of nonlinearities in drivers, that you would be running on the walls before
you finished entering all the parameters. Hysteresis and thixotropic effects in
spider/surround, inductance modulation due pole, Bl and Cms nonlinearity, you name it. Driver
is not only source of nonlinearity, box air compression is adiabatic process. Vent air flow
becomes nonlinear at some point. And so on. Because there are no consensus, how the
nonlinearities would be best described driver manufacturers won't generally give you any hint
what kind and how much nonlinearity is expected from particular drive unit. Therefore,
without the info, it would be just guessing, which is not good thing. There are actually some
programs which calculate "nonlinear simulations", but if you don't have option to enter extra
information about nonlinearities, the results are somewhat questionable. Yes, they are
closer to the reality, but still they are inaccurate because lack of nonlinearity
information. Furthermore, if the cone moves non-sinusoidally, then we'll have harmonics. Now,
what should be plotted in SPL window? Just the fundamental or combined SPL considering
fundamental and harmonics? Many kinds of questions arise.