Linearteam WinISD Pro
This section of the Help File assumes that you've read the Getting Started section first.
Designing your box (which is also referred to as your project since, hopefully, it will soon be a project in your garage) is accomplished by using the Project Window that is presented once you select a driver and the type of box you plan on putting this driver into from the database. Everything that you need to do to completely design your box (project) is done in the Project Window.
You can load as many drivers as you want (even multiple loads of the same driver if you wish), and each driver loaded will have it's own Project Window which "controls" its respective plot on the graph (each plot represents its corresponding Project Window). Each plot will also have its own color, which you can change by clicking on the color bar at the bottom of that plots' Project Window. The "plot", by the way, is the curved, green line (green in this example, you can make it any color you wish as described above) in the picture below. For demonstration purposes, go ahead and load the JL Audio 10W1-4 driver.
Again, everything you need to do to design your box is done in the ubiquitous Project Window! The Project Window has seven tabs (six if using a sealed box, since no Vents tab is necessary in that scenario, also when designing passive radiator system, the passive radiator has tab of its own), and each of these tabs are described below:
Here you can view or change your driver's specs, as well as change how many drivers that you want to cram into your box, and (if more than one), how you plan to cram them in there...
Also, you can specify how much extra mass you place into each driver's cone. This way, you can make driver's resonance frequency into lower value. But nothing comes free. You lose sensitivity, and even worse, your driver Q-values will rise. That might be untolerable. Anyway, option is there in case you want to try it out. If you want to view or change your driver specs, simply click on the "Parameters" box, and a drop down window will appear showing you the specs of the driver:
You can change the values and/or the units in which the values are displayed simply by clicking on them. This feature allows you to play "what if" with your driver (which can be very educational for learning what the different Thiele/Small specs control...try changing some of them and watching what affect it has on the plot), and is also ideal when using Driver Templates. Keep in mind, however, that any changes you make here are temporary, and will be set back to the default values once you quit WinISD. Note that you shouldn't make values ambiguous.
You probably have noticed the small driver icon besides of the model number entry field. If you want to do more detailed examination of driver data fields, you can "drag" the driver object into driver editor window icon in the "Editor"-button. You can do this by clicking and holding left mouse button in this icon and then dragging the icon into editor. This will open Driver Editor.
In the Placement section of this window, you can choose how many drivers that you want to use in the same box, as well as whether they are to be in a "Standard" or "Isobarik Pair" configuration. Remember that the placement options you choose here are calculated using the box type (ie; sealed, vented, bandpass) that you chose when you initially loaded the driver. You cannot change the box type at this point. If you want to compare how the same driver performs in separate box types, then you must load the driver over again in a different box type. After all, you're gonna want to view separate plots for each type anyway, right?
This is the most powerful part of WinISD! While you can finish what you need to get done here within seconds, you will probably find yourself here tinkering for hours ...read this section carefully!
When this Tab is initially opened, the default Volume and Frequency data is displayed. Sometimes, the "default" box volume is too large to be practical, or maybe you are just building an addition to an existing speaker system, and a different plot is desirable. By manually changing the size of the enclosure (and/or port frequency for bass-reflex), changes in the output plot appear. These changes in the plot represent the real world performance of the completed box.
For bandpass boxes, there are two chambers, front and rear. Rear chamber is that what is normally in rear of the driver.
There are two ways to change the Volume of the Box (from here on out referred to as Vb) and the tuning Frequency of the Box (from here on out referred to as Fb (on vented boxes)). You can either do it manually by double clicking on the numeric values you wish to change, and then typing in new values (the graph changes with each keystroke entry, no need to hit the enter key), or you can do it "on the fly" (dynamically) with your mouse!
To change the values with your mouse:
The power of this feature is that no longer do you have to manually type in changes that you hope will produce the desired plot! You simply "drag and plot" your desired curve and viola, the necessary box dimensions are already calculated and displayed for you! You can also "lock in" one parameter (either Box Volume or Tuning frequency) while changing the other. How? Click here.
This, coupled with the ability to load and view the plots of multiple drivers at the same time, makes choosing the right driver for your application a breeze!
There are other concerns than just the frequency response. One of the most important ones is the mechanical power handling. That means, how much power our design will tolerate without running out of limits of maximum excursion. You can get estimate of this by looking at the "Maximum Power"-plot:
Graph shows us clearly the well known fact about ported boxes, that their power handling is severely weakened below tuning frequency. Best power handling is achieved around tuning frequency, where acoustic resonator represents heavy acoustic load to the driver.
Clicking on the Box Shape button activates the Box Shape calculator:
Under "advanced->", you can find controls for box losses. There, you can see what effect the each loss type will have on your box design (Smaller the value, greater the loss). There are three types of losses:
When you click on the "Advanced->", a popup menu opens, where you can see what current loss parameters are:
When you choose a particular loss type from this popup-menu, a small window will appear:
In this case, I choose "Ql". Here, you can enter new value for loss or you can use similar drag method, by clicking on the white square beside input box. Again, the graph will update in real time.
Clicking on the Vents Tab displays the vent (port) information.
Here, you can decide how many and of what shape you want your vents to be on your box. The ports, of course, serve to "tune" your box to the frequency that you have chosen while you were designing your box in the Plot Window. The size and -3dB (cutoff) frequency of your box determine the size of the ports.
1st port resonance shows frequency of first "organ-pipe" resonance. This helps you to estimate where port becomes undesired radiator.
Very important here is to make your ports large enough, so that peak air velocity won't exceed 5% of sound velocity in air. That is, about 17 m/s assuming normal environmental conditions. You can check it by using "Rear port - Air velocity" graph, by first setting simulation power to anticipated maximum power, see "signal"-tab. In this case, Pe is 125 Watts.
Here, the velocity peaks at 20,8 Hz. Peak air velocity is about 23,3 m/s, which is a bit high value. This might or might not be a problem, depending on your program material; If you don't expect very powerful sounds at vicinity of this frequency, you shouldn't have any problems. However, if you want to play safe, use larger port or several ports.
If your port velocity is too high, the only way to lower it is to either increase the number of or the diameter of the ports. Of course, here comes that dreaded "trade-off" word again! If you make your port(s) bigger in diameter, they will be able to pass more air with less effort. However, in doing this, you have lowered the "loading" of the speaker(s) in the box. This, of course, changes the -3dB point of the box. The only way to get back to your desired -3dB point is to "load" the speaker(s) again. How? Well, you gotta make the new, larger port(s) longer! This forces the speaker(s) in the box to work harder to move the air into and out of the box, and brings your -3dB back to where it should be. THE END OF YOUR PORT(S) MUST BE AT LEAST ITS DIAMETER AWAY FROM ANY INTERIOR WALL OF YOUR ENCLOSURE.
"Ok, so I make the ports larger, big deal?" you say. Well, if you're building large speakers for the home, then that's probably not going to be much of a problem for you. However, if you're building small, car sized speaker boxes, then the increased length of the ports is indeed a big problem, since you will need more port length than your box has room for!
There are currently three ways to combat this problem:
If none of the above options appeal to you, then you must go back to the drawing board and make the sacrifice somewhere else. Remember, a small box tuned to a low frequency will demand a large port design. It's that damned "trade-off" again. Yeah, you can have a small box deliver big sound, but, as you now see, it's requires more thought and more work. But, the good news is, it CAN be done.
You shouldn't try to make too long ports, because they must be very much shorter than wavelength of sound to be reproduced by the system. About 1/20-1/10 is safe factor. Otherwise, they start to behave like organ pipe, which is not desirable. If this proves impossible, then viable solution might be using passive radiator instead of the port. However, it has its own peculiarities, which you can see, when you simulate such a system.
Here, you can set values of several environment variables. This is because sound velocity is dependent on environment values. Default values are ok for casual user. If you try changing the temperature, you'll notice that it affects the port length. As you can see, the effect can be quite great! This is one of the difficulties, what most box-building programs won't deal with at all. Calculated sound velocity is shown also. Calculation of sound velocity and air density is derived from Claus Futtrup's excellent documentation of Driver Parameter Calculator (DPC).
You can also change line color and width.
Signal source has two properties, Power and Series resistance. Term "power" should more correctly be voltage. This term "power" comes from definition by Richard Small, who defined the input power to be P=Eg²/Re (this is to simplify things, because impedance varies greatly depending on the frequency and the box), where Eg is RMS output voltage of your amplifier, and Re is DC resistance of voice coil. Actually, driver's impedance will vary greatly (see impedance graph), depending on the frequency, so this is generally not the power which is taken from the amplifier.
Series resistance is source resistance seen by the driver. This includes your amplifier's output impedance, crossover coils, connectors, interconnect wires. Raising this value will effectively rise the Qes. Default value is 0.1 ohms, which is reasonable default. If you experiment, you'll find out a quite large change in system behaviour.
Distance is distance from imaginary speaker in half-space, assuming far field on-axis conditions. It is not true on very small distances, although some people have quite succesfully simulated in-car SPL levels using small values.
The Project tab allows you to save your Project, complete with all of the changes that you made, to disk for later retrieval.
Clicking in the Descr: field opens a dialog in which you can type some text to describe the project.
Clicking on the Show as text button brings up the Project as Text window:
When you're done, you can either save it in the default directory (WinISD), or you can create a new directory (recommended).
Next time you want to work with this saved project, you can click on File, then Open Project, and then select your project from the folder that you saved it in.
This tab is used only with passive radiator systems. For demonstrating the thing, we must create project for passive radiator system.
Basically, "PR"-tab shows relevant parameters of your passive radiator unit. Parameters are same than any ordinary driver. You can in fact use normal drive unit instead of passive radiator, just remember to leave it's terminals unconnected. Like active drivers, you can place several passive radiator units in your box design. There is also possibility to add mass to passive radiator cone. If there are several PR units, mass is per unit mass. WinISD shows below unit's new resonance frequency with added mass.
This concludes the Designing Your Box Help File section. Be sure to check out all of the articles sections! -JJ