Need a little help interpreting some WinISD data

 

New member
Username: The_cobbler

Post Number: 6
Registered: May-11
I just started to use WinISD pro to help model a ported enclosure I'm trying to build and I modeled the subwoofer and everything and I think I understand what the graphs are telling me but before I go and build anything I want to double check and see what you guys think of the model I have created. Unfortunately I'm not sure how to upload the graph onto here to show you but I can tell you values I have. The peak rear port velocity is at 7.6 ft/s @ 35 Hz. Now I believe that this is a good port velocity as it is quite low and will cause little noise. What I don't understand is what the x-value (Hz) tells me in relationship to my air velocity. For the function magnitude graph it's hard to really give any key points because i don't know what are key points on the graph so if someone could show me how to post an image of the graph that'd be a great help.
 

Silver Member
Username: Kaerfpl

Spencerport, NY USA

Post Number: 968
Registered: Jun-06
The best way to get accurate info off this program is to input as little info as possible, and let it auto fill in the rest of the information.

If you would like to get a screenshot to show us, on your keyboard press "print page" while you values/graphs are on the screen to take a picture. Then open up paint or photoshop and click on "edit" then "paste". Make sure to save the picture and then upload it here.
 

Gold Member
Username: Drant19

TX

Post Number: 2256
Registered: Aug-07
what subwoofer? chances are someone already has some input on a proper enclosure or knows where to find the information for you.
 

Silver Member
Username: Alonzoub

Post Number: 145
Registered: Apr-10
7.6 ft/s is insanely low port velocity, are you sure thats right? Make sure you put in the power that your setup will be running off of under the "Signal" tab. What the x-value (Hz) represents is at what frequency that velocity will be reached.

As for magnitude, this graph is really to observe the overall frequency response of your design. A key value on this graph would be the -3dB line that should be in purple, this is the point where your boxs output will begin to rolloff at a very steep rate, its also called the "F3".

Another key value to look at is the ripple or gain your design creates. Here is a screenshot of a couple designs I was messing with yesterday.

Orange: Two IDQ10v3, 3.18cu.ft, 30Hz, 1kWRMS (my current setup)
Green: An Fi Q 15, 4 cu.ft, 30Hz, 1kWRMS (maybe a future setup)

Upload

As you can see the F3 for my IDQs is exactly 30Hz while the F3 for the FiQ15 is more like 26 Hz. As for gain, you see the red line at 0dB, that is the reference, due to the box designs both setup present a 1dB gain, my IDQs gain is around 48Hz, while the FiQs is around 37 Hz, but both cover a rather large bandwidth.

When comparing the output of 2 setups (in the same car) I usually use the SPL graph. This will take into account the power that you put into the Signal tab, the subwoofers sensitivities, and the frequency response function to estimate the output of each setup. Like this one:

Upload

Do not take the dB numbers on the left to be accurate though, other factors such as the transfer function of your car and positioning will effect the output so only use this graph to compare. For example, as you can see I used the tracing feature to get as close to 30Hz as possible, The FiQs output claims around 118.7 dB at 30Hz, I can compare that to the IDQ's output at 30Hz, which is around 116 dB and simply conclude that the FiQ will have roughly 2.7 dB higher output at 30Hz when compared to the IDQs int he same vehicle.

I kinda taught myself how to use this program though, so if anyone disagrees with what im saying please call me out, I don't like telling people wrong information.
 

New member
Username: The_cobbler

Post Number: 8
Registered: May-11
Ok I think I understand now. I got, what I believe, is a more realistic port veloctiy because for whatever reason something I did gave me an unrealistic value before. is ~90 ft/s too high of a port velocity?
 

Gold Member
Username: Drant19

TX

Post Number: 2257
Registered: Aug-07
there are plenty of box builders (bassman3 comes to mind) that would help you with an enclosure to suit your needs. winsd is a good program but nothing beats real world experience.
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