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WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro)

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#1 ·
WinISD Pro Tutorial
By Andrew Vaserfirer​

What is WinISD?

WinISD is a freeware program that allows one to use driver specifications to model how this driver will act in a specific alignment [sealed, ported, passive radiator etc..)] given a certain volume and/or port size.

Differing drivers have different specifications requiring variations in box and/or port design. Use of WinISD Pro is a relatively easy way to ensure that the optimal cabinet is designed for the specific subwoofer in use.

You can download WinISD Pro via this link.

Requirements

To use this program you will need a computer that can run WinISD [virtually any PC will do] and the driver T/S specifications [coming soon]. Please see the Home Theater Shacks database of T/S specifications [coming soon].

Starting with the Program

Before starting there is one extremely important word of warning: While modeling at low frequencies is fairly accurate there is one large, erroneous, assumption made. That is that the driver being modeled will act in a linear fashion at moderate to high SPL/excursion. This simply is not the case for the majority of the drivers on the market. Of course, one specifically chooses a well designed, high quality unit, that has been proven via credible measurement to have these attributes that is a different case.

Open WinISD. Your screen should look like this:



Click the 'New Project' button to get started. This pop-up will display and give you some options:


Now you have some choices:
  • You can click the drop down arrow and look through the database supplied to see if WinISD already has the driver you want entered.
  • You can go to the Home Theater Shack T/S data base [coming soon] and see if we have the driver already in a WinISD Pro file for you.
  • You can enter the driver data yourself.

If you fall under the first two options you can skip the next section as it will go over entering driver data in WinISD as well as what all the T/S specifications mean.

Meaning of Thiele/Small Parameters


T/S specifications are electromechanical properties that essentially define how a driver will perform. A quick overview of the more common T/S parameters and their meaning follow. Please note this is not a comprehensive list or definitions.

Fs: Resonance frequency measured in Hz. is the frequency that the moving mass and suspension of the driver is reinforced by cone motion to the maximum amount.

Bl: Force factor (magnetic strength) measured in Tesla-meters.

Mms: Mass of everything that moves within the driver, measured in grams.

Rms: Measurement of the drivers losses in its suspension/moving system.

Cms: Inverse stiffness measurement measured in meters per Newtons.

Qts: Combined dampening of the driver - both mechanical and electric.

Qms: Mechanical dampening of the driver.

Qes: Electrical dampening of the driver.

Vas: Free air stiffness, of sorts, of the driver - measured in liters.

Sd: Effective area of cone diaphragm measured in meters squared.

Vd: Volume of the displacement measured in liters.

Re: D/C resistance of the coil measured in Ohms.

Le: Inductance of the voice coil.

Hc: Coil height

Hg: The height of the air gap

Pe: Power Handling

For more detailed information on TS parameters... see our TS Parameters thread.

Inputting Parameters in WinISD Pro

From the new project pop-up click the 'New' button beside the drop down arrow. Once this is done a new screen will pop-up. This screen is fairly straight forward - Just enter the brand, make and model of the driver whose parameters you plan on entering. Then click the 'Parameters' tab and you will see something like this:



Ensure that 'Auto calculate unknowns' is on even if you have all the data. This is recommended because WinISD Pro can be very picky about the data and if it is even 1/1000th off it will reject the data so it is just easier to let it do the work. You might notice some small differences in the values from the calculated and the provided, but very rarely are these large enough to substantially effect modeling.

This is the recommended method for entering driver parameters [if at any point you need to change the unit of a parameter simply click on the displayed unit and it will change]:

  1. Enter Mms and Cms which results in Fs being calculated. If Mmm and Cms are not known enter Fs. If Fs and Mmm or Cms are known enter Fs and the other known value.
  2. Enter Sd, Bl and Re. This will result in more auto calculations being made, but Qms and Qts will be blank. If Re is not available, go ahead and enter Sd and Bl.
  3. Enter either Qms or Rms, whichever is available, generally Qms is available.
  4. If Mms and/or Cms were not provided for input, now input Qes. This will cause some other fields to auto calculate.
  5. Enter Hc, Hg and Pe if available. These are not required, however Pe (RMS Power Rating) will give a good idea of how much power signal input to model with.
  6. Enter the number of voice coils. NOTE: Drivers using dual voice coils may cause the Bl and Re parameters to change when changing the connection wiring from parallel to series. Be sure to monitor these when changing the connection option, but WinISD should automatically change these values properly.
  7. Correct Znom (nominal impedance) if needed. Many times this will change to 6 and should be 2 or 4... or the ultimate resistance (in ohms) you intend to run based on the voice coil configuration and your connection setting (parallel or series).
  8. Enter Xmax and any other missing parameters if known and continue. DO NOT change any of the blue auto calculations. If they are only slightly different, this is okay. If they are off significantly, contact the manufacturer or vendor of the driver.

If you want you can also tab over to the dimensions page and enter 'Dimensions'. Don't worry about the 'Advanced parameters' tab.

The steps outlined should cause parameters to be calculated such that they can be saved without error. If there are problems saving then too many parameters were entered that are likely very close to the calculated value, but WinISD wants the mathematical ideal. Just delete one of the problem values it shows up and try to save after it has been calculated and keep trying until it works. In my experience only Fs needs to be calculated to continue.

Time to Start Modeling

Once all your data has been entered hit the 'Save' button and save the file with a representative [of the driver] file name. Now close the driver editor and click 'New Project' again. Go to the drop down menu and look for the driver you just entered. Highlight it and click next. You will see a screen like this. Choose the number of drivers you plan on having sharing the same airspace in a single enclosure [this can be changed later] and you will probably want the 'normal' bullet chosen.

Click next. You will now see the next tab that will let you choose the alignment. If you already know what type of cabinet you want to build choose one. If not its time to research the merits of each style. A quick run down:

Sealed: Typically result in smaller cabinets that are easier to build. The cost is of low end extension, more distortion and less overall SPL capabilities compared to ported/PR.
Ported: Typically larger cabinets that are harder to build and design properly. These usually have more extension, SPL and lower distortion than sealed cabinets.
Passive Radiator: These have the capabilities of a ported enclosure, but can be built smaller due to use of the passive radiator. These typically cost more because high quality passive radiators are rare. A little more build work than sealed and possible more than ported depending on the type of port used.

Please note this guide will primarily focus on the sealed and ported alignments as they are the most common.

Click next once you have decided on what style cabinet you want to build. After this you will see a screen that asks what type of alignment you want. Just go with whatever is the default as it will rarely be the optimal choice for your application. You will now see something that looks like this:



From this point there are essentially two point of control. On one portion you can control aspects of the driver and from the other you can see the different graphs that model is performance.


Under the 'Box' tab you can control the size of the box as well as the tuning frequency if you are using a ported. The box size will directly effect performance in a number of ways. If you are using a ported alignment the next tab will be the 'Vent' tab this allows you to control the number, size and shape of the vent(s) used. The next tab of interest is the 'Signal' tab, it is notable because it allows you to adjust the amount of power being input to the sub. Enter the amount you plan on feeding the sub to get accurate modeling of certain parameters. The last tab of interest is the EQ/Filter tab. This tab allows you to model how certain filters will effect the response of the sub as well as other areas of performance.

Now if you click the other source of control you will see this:



There are some graphs available here that will be very important to you and others that will be meaningless this will depend mostly on what alignment you have chosen.

For a sealed alignment the main graphs are:

Transfer Function: this is essentially the modeled frequency response of the subwoofer
SPL: This is the SPL that the subwoofer is modeled to be capable of with the amount of power specified in the previously discussed signal tab.
Cone Excursion: This is the total movement of the subwoofers cone. You typically want to keep this within the boundary listed by the manufacture.
Impedance: This is the resistance to current flow of the driver. Depending on the amplifier you have it could be an issue if it drops to low.

Along side the previously listed if you are using a ported alignment the 'Rear Port - Air Velocity' tab will be of importance to you. This will show you how fast the air will be moving into and out of the port. The lower the better. To decrease this number the port surface area must be increased, but as you do this you also decrease the level at which the port resonates. Due to this a balance act must be had where you minimize port air velocity [at its fastest 20-25m/s should be accepted] and keeping first port resonance out of audibility range. If you plan on crossing your subwoofer over at 80Hz with a 4th order crossover [typical of modern receivers] having first port resonance modeled at or above 120Hz is safe an explanation can be found here of why this is 'safe'. There are two reasons why port air speed is important. If it gets too high it will create port chuffing [audible and annoying noise from the port] as well as port compression [there is too much impedance to airflow caused by the port resulting in nonlinear performance at high SPL].

How to prevent a sub from bottoming out

This aspect of designing a cabinet is very important. Not only can bottoming out damage your driver it just sounds bad. Proper use of an infrasonic filter is the best way to do this. Fortunately, you have the tools to model this in WinISD Pro under the 'EQ/Filter' tab. Click the 'Add' button and choose a highpass Butterworth filter. Cutoff frequency is the frequency at which the filter starts [you will typically want it at or slightly below tuning in a ported enclosure] and Q is meaningless in this case. Order refers to how steep the slope is:

1st order 6dB/oct
2nd order 12dB/oct
3rd order 18dB/oct
4th order 24dB/oct
etc...



The following are graphs of a modeled subwoofers transfer magnitude, cone excursion and port velocity with [gray] and without [yellow] a highpass 2nd order Butterworth filter at 20Hz:





Now that you have an understanding of what is going on try and play with the program seeing how changing the box/port size effects modeled tuning and response.

If you have any questions or need any help feel free to create a thread and ask questions. There are many members here who are willing to help the inexperienced learn to design and build subwoofers.
 
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9
#3 ·
How to enter data in WinISD - A video

Even with our guide, some people still find it difficult to input data into WinISD, so upon scouring the web I found this little video which helps put a visual representation to the help files, and decided to put it on here.

The guy inputting the data in this video is doing so in the same way the help files show you, so its a good guide. Note, the input of data needs to be done in the order shown in the video (and stipulated in the guide). Any of the auto calculated data needs to be left alone (WinISD doesnt do any guess work and calculates exact figures), and as long as those figure closely match the published figures, then its ok to leave them. Any huge changes should flag up in your mind as there being an error somewhere along the line, which would need to be checked. Typically, I found errors arise when the units for any given measurement are different, so they should be the first thing to check in the odd occasions errors arise.

Below is the video link, as well as a quote from the help file.

Hope its helps out anyone who might be struggling.

http://www.youtube.com/watch?feature=player_detailpage&v=Iz06TL33m9I

Ensure that 'Auto calculate unknowns' is on even if you have all the data. This is recommended because WinISD Pro can be very picky about the data and if it is even 1/1000th off it will reject the data so it is just easier to let it do the work. You might notice some small differences in the values from the calculated and the provided, but very rarely are these large enough to substantially effect modeling.

This is the recommended method for entering driver parameters [if at any point you need to change the unit of a parameter simply click on the displayed unit and it will change]:

1. Enter Mms and Cms which results in Fs being calculated. If Mmm and Cms are not known enter Fs. If Fs and Mmm or Cms are known enter Fs and the other known value.

2. Enter Sd, Bl and Re. This will result in more auto calculations being made, but Qms and Qts will be blank. If Re is not available, go ahead and enter Sd and Bl.

3. Enter either Qms or Rms, whichever is available, generally Qms is available.

4. If Mms and/or Cms were not provided for input, now input Qes. This will cause some other fields to auto calculate.

5. Enter Hc, Hg and Pe if available. These are not required, however Pe (RMS Power Rating) will give a good idea of how much power signal input to model with.

6. Enter the number of voice coils. NOTE: Drivers using dual voice coils may cause the Bl and Re parameters to change when changing the connection wiring from parallel to series. Be sure to monitor these when changing the connection option, but WinISD should automatically change these values properly.

7. Correct Znom (nominal impedance) if needed. Many times this will change to 6 and should be 2 or 4... or the ultimate resistance (in ohms) you intend to run based on the voice coil configuration and your connection setting (parallel or series).

8. Enter Xmax and any other missing parameters if known and continue. DO NOT change any of the blue auto calculations. If they are only slightly different, this is okay. If they are off significantly, contact the manufacturer or vendor of the driver.

If you want you can also tab over to the dimensions page and enter 'Dimensions'. Don't worry about the 'Advanced parameters' tab.

The steps outlined should cause parameters to be calculated such that they can be saved without error. If there are problems saving then too many parameters were entered that are likely very close to the calculated value, but WinISD wants the mathematical ideal. Just delete one of the problem values it shows up and try to save after it has been calculated and keep trying until it works. In my experience only Fs needs to be calculated to continue.

Read more: WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com
 
#10 · (Edited)
What are the guideline's for tweaking the Qa in the advanced rear chamber tab?
(Qa is the system's Q at Fb due to absorption losses.)
Default is 100, from the WinIsd Pro tutorial
Qa, absorption losses. These are produced by losses in enclosure. Any stuffing will increase the absorption loss. With no stuffing inside the box, 100 is typical.
Heavily stuffed enclosure has this about 3-5.
I am putting stuffing in my box and desire to model it correctly.
When I put 5 in there it went from a Qtc 0.86 to 0.697.
So, what does a "5" mean for stuffing? 1/2 lb fill per cu ft?
(yea, I also was tweaking between 2.25 cu ft and 2 cu ft, the basic question is still valid)


[edit Feb-24-2013]
surfin the web I found some info:
For Qa (box stuffing) I use the following:

No fill : Qa = 100
Minimal : Qa = 50
Normal : Qa = 10
Heavy : Qa = 5
I take it "minimal" means lining the cabinet sides only.

I've seen 1/2 lb fill per cu ft of volume recommend from Parts Express for their Acousta-Stuf Polyfill 5 lb. Bag, http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-330
Acoust-Stuf™ is a sound absorption, dampening fiber which will deepen bass, provide cleaner midrange and improve the dynamic extension of any speaker system. Acoust-Stuf will outperform Dacron, foam, and fiberglass. There are no health hazards with Acousta-Stuf and no mask or gloves are needed when using this product. Most sealed and vented enclosures require 1/2 lb. of dampening material per cubic foot of enclosure.
So that's the baseline for "normal", Qa=10, for that specific type of material, how much more to get to "Heavy"?
 
#14 ·
:doh:I am trying to model a SI HT18 d4 and when I have the SPL graph up and start to set signal source settings like system input power the readings go off the chart. I plan on using an inuke 3000 with 2 ohm load to 2 subs. I am trying to compare various sizes and closed vs. ported but just can't get it right. I read through this post as well as the winisd help files but I'm still doing something wrong but can't figure out what it is.
Any help will be highly appreciated especially if it comes before I'm completely bald.
 
#16 ·
Hmm, the old alpha version was 'right click' on the chart, but the latest 0.7.0.900 requires clicking the 'wrench' option, then choosing 'plot window'.

GM
 
#21 ·
I loaded the parameters perfectly with your guide (very comprehensive thanks) created a project for 2 qxw6 woofers, 125W rms each on a sealed box, everything was good until I noticed the "Signal" section was calculating for 1W and 1ohm, I changed it for 250W and 16 ohm as thats the woofers impedance and rms consumption in series. But now the excursion and port velocity are way out of hand, my woofers would obliterate themselves unless I seal them in an unrealistical 3L (0,1 cubic feet) enclosure... what can I do? Did I misinterpret the meaning of signal, should I leave it on its default value? Thanks for helping this noob
 
#22 ·
i have followed every step in this and i still get negative vent length...... can anyone help? i have read the thread many times and i still can't figure it out. my parameters are 100% correct (if the manufacturer is to be believed) and i still get a negative port length
 
#23 ·
I haven't used it since my last entry in the driver database 'sticky' and didn't know this was even possible, just assumed it would show an error, but the only way this makes since to me is if you start with too small a vent area, i.e. the vent area [Av] should normally be at least 1/3 driver effective piston area [Sd] and if a high Xmax driver, then at least [Sd]/2 and some need to be [Av] = [Sd] and will be quite long.
 
#25 ·
'Stuff' happens! ;) I don't remember this option on the original PRO or the latest PRO 0.7 or why it would make a difference unless the rules governing a low vent mach is 'loosened' or just removed.

Regardless, glad the problem was easily solved.
 
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