Linearteam WinISD Pro
Start by loading a driver into WinISD as follows: Click on File, then New Project (or, simply click on the New Project icon, which is the second icon from the left on the Tool Bar). The New Project window (below) is presented.
Click on the down arrow in the drop down menu box, and you will be able to scroll through and choose a driver from the Program (WinISD) database (see Creating Your Own Driver Database for details on how to Create and Manage your own personal database). Putting a check mark in the 'Show driver parameters' box will cause WinISD to show you the Thiele/Small parameters of the driver that you have selected. This way you can see whether or not this particular driver is what you're looking for before you load it into WinISD as shown below. Note that you can change between standard and metric measurements simply by clicking on the desired measurement system (mm, in, etc..). You can also change any value the same way.
Choose a driver to work with (for demonstration purposes, choose the JL Audio 10W1-4 driver...you can either scroll down the menu until you find it, or you can type the beginning letters "JL..." and the window will "scroll to" accordingly. Click NEXT, and the Driver Usage window will appear:
Here is where you decide whether you're going to design the driver(s) to be configured as Standard or Isobarik. You can also choose the number of drivers you are going to put into the box. Don't worry, all of these parameters can be changed "on the fly", even after the driver is loaded (plotted on the graph). If you made a mistake and chose the wrong driver on the previous screen, click on PREV to go back to the New Project window. For demonstration purposes, choose 1 driver in a Normal configuration (placement). Click on NEXT to bring up the Box Type window:
Here, you can choose whether you are planning to build a Sealed, Vented, or Bandpass box (these are referred to as the box types). Use the vertical Efficiency Bandwidth Product (EBP) bar indicator as a guide to determine which box type is best suited for this particular driver. If the bar is high, then this driver is best suited for installation in a vented box (or a 6th order bandpass). Conversely, if the bar is low, go with a closed type box (or a 4th order bandpass). If the bar is near the center (as it is here), then the driver will likely perform equally well in either a closed or vented type box.
The choice you make here is not changeable later on but you can, of course, load this driver simultaneously multiple times in different box types. Choose a box type by clicking on the down arrow next to the drop down menu box, and click on the desired box type. For demonstration purposes, choose Vented. Click FINISH, and you will then be presented with the Plot Window, with the plot of the JL Audio 10W1-4 driver as seen below. The "plot" is the curved (green,in this example) line:
Also displayed on your screen will be the Project Window (below). Position the Project Window to a comfortable position, and then click on the Box tab of the Project Window, which will now display the Volume and Tuning Frequency of the box:
Clicking on the 'Parameters' button will open a drop down menu which will show you the Thiele/Small specs of the driver, and will also allow you to make temporary changes to those values and their system of measurement (as outlined in the first paragraph above). The green color bar corresponds to the green plot on the plot window (clicking on the green bar will open a window which will enable you to change the color of the plot, if you so desire).
What the information here in the box tab is telling you is that in order for the JL Audio 10W1-4 woofer to produce the sound that is indicated by the green plot in the plot window, it must be placed in a 90.30 liters box, and that this box must be "tuned" to 23.81 Hz (vented or bass-reflex boxes are "tuned" by the number of, diameter of, and length of the "ports", which are usually tubes of PVC pipe built into the box and "vented" to the outside air, as demonstrated by the two horizontal lines in the diagram below the words "Box Shape" in the Project Window).
The initial green plot shown, as well as the initial Box Volume and Tuning Frequency data (in the Project Window) shown, gives us the smoothest calculated attainable plot for this driver. Notice there are no "peaks" or "dips" in the green plot. The green plot is the ACTUAL REPRESENTATION OF HOW THIS SPEAKER WILL SOUND IN A COMPLETED BOX.
WinISD will always default to show you the smoothest (well, at least quite close) attainable plot when you first load a driver (sometimes, if a driver that was designed to be installed into a sealed box is loaded into WinISD in a vented box configuration, the initial plot will look like a roller coaster...however this doesn't necessarily mean that this driver won't work in a vented box, since some drivers are designed to work in both types of boxes). Some drivers have very low Qts values. With them, it might seem that they can't reproduce any bass in default box. However, you can adjust the box as you watch the transfer function magnitude-plot. Notice that I did not say that the initial plot is the "best" or "ideal" plot, only that it is the smoothest plot. The reason I avoided those words will soon become clear.
You can change the plot (which, of course, will change the way the speaker sounds after it's built), by changing the Volume and/or the Tuning Frequency of the box. If you lower the Volume of the box (which makes for a smaller box), you must give back something in exchange, the price here being low frequency response.
Notice that the green plot crosses the -3dB horizontal line at 23 Hz (left clicking in the plot window and dragging the mouse will activate the Trace Cross hairs, give it a try) . This purple line is the -3dB (or half-power, or cutoff) point. This line represents the frequency at which the usable bass output of the box "runs out of steam". Any frequencies below the intersection at the -3dB point simply won't be reproduced very well by the box. In our case here, that frequency is 23 Hz. Most low bass speakers are designed so that the -3dB point is somewhere around 35 Hz. Since we are dealing with a particularly well designed (expensive) woofer, we are subsequently being blessed with some room to play with! We are in the enviable situation of having to RAISE the -3dB point of the box! Since this is done by LOWERING the Box Volume, we're in a win/win situation (remember, as I said, this is an expensive, high quality woofer we're dealing with here, so don't expect to run over to Joe's Flea Market and find such a woofer).
Now, let's say that we want this box to cutoff around 35 Hz. Double-click on the numbers below the words volume, and change the volume to 1.5. Also change the Tuning freq: to 30 the same way. This, of course, tells WinISD to recalculate the woofer when placed in a 1.5 cubic foot box tuned to 30Hz, and to display the corresponding plot. Note that this is less than HALF the initial given box size...we've traded some low bass response (that we didn't even need in this case...remember we went from a cutoff of 23 Hz to a cutoff of to 32 Hz) and ended up with a much smaller box!
By lowering the box volume, we've brought up the cutoff point of the box. That's a nice curve, albeit a challenging box to build due to the small enclosure and LOW tuning frequency (rectangular vents are probably in order).
"Ok, that's all nice and fine, but how did you know what numbers to plug into WinISD to achieve this plot?", you ask. Well, here's where you're gonna learn about the true power of WinISD, my friend. Position your mouse cursor over that diagram of the speaker (below the words Box Shape) in the Project Window (under the Box tab, if you've gone astray). Click and hold your left mouse button. Move your mouse. "Draw" the plot that you want. Release the rodent. Observe the new displayed Box Volume and Tuning Frequency data. Now, wasn't that easy? Want a little secret about drawing your plot? Click here.
If you like the looks of the plot, then run out to the garage, build your box, and you're done. Congratulations, you've just designed and built your first speaker which in this case, by the way, would be a very awesome speaker. And all this made possible by this kick-ass (sorry, kids) little freeware program called WinISD!
All of the features we've covered here so far and more are covered in detail in the Designing your Box Help section. Go ahead and load some more various drivers and play around with the plots (to change the color of a plot, click on the colored bar at the bottom of the Project Box). You'll soon see what I mean about the quality of the driver we were just working with. There are other manufacturers who specialize in manufacturing drivers as serious as JL Audio's (these drivers are designed mainly for car audio competition), but not many.
Many lower-cost drivers perform admirably in their own right, however, and it's not always necessary to spend the big bucks to get a great sounding speaker, especially if you're willing to settle for a larger box! Now that you have the ability to actually "build" the box before you buy the driver, you can actually take different drivers for a "test drive" before you open your wallet. Search around on the net, and just plug the Thiele/Small specs of any drivers that interest you into WinISD and check out the plot vs. box size. Sooner or later, you'll find that "perfect" driver for your application, and all without ever leaving the house or dealing with salesmen!
Note that the author of WinISD (nor myself or any others on the WinISD team) are not in any way affiliated with JL Audio, or any other speaker manufacturer. I simply chose to use the 10W1-4 for the above help demonstration to illustrate a point.
The old adage "Haste makes Waste" applies more to speaker building than perhaps anything else on earth! From the very first speaker building thought in your mind all the way to the end product, haste will most certainly make waste. And alot of waste, at that. Each and every step along the way must be carefully planned/thought out as you go. "Fruition Day" will most certainly underscore your faults more than your achievements. I hate to sound so pessimistic, but you need to approach the speaker design task in the correct frame of mind. Don't cut corners while mentally thinking "ah, it'll be alright, nobody will know". This thinking will at best result in a box that YOU know isn't performing at its best. And that thought will haunt you every time you crank it up. If you're gonna invest the time and energy to do it in the first place, then by all means, take the time to do it right!!!!