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Discussion Starter · #1 ·
I am a noobie here so the answer may be obvious. I am interested in building a couple of subs using the new SI DS4-18.

On their web sites a couple of their specs are:

Fs 17
Mms 561 g
Cms 128.3

However if I input the Mms and Cms into WinISD the Fs is calculated as 18.76

Which should I believe, or maybe a better way to say it is which input should I over rule?

Thanks
GM
 

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When entering T/S parameters for a driver you should let WinISD calculate its own Mms and Cms. If you dont let it calculate it the parameters wont add up and wont let you save the file. I use these parameters:
Fs
Qts
Qes
Vas
Re
Le (if known)
Xmax
 

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Discussion Starter · #3 ·
In the instructions for WinISD it says to input the Mms and Cms and the program will calculate the Fs

When doing that the Fs comes out different than the specs on their website 18.96 vs 17.

If I input the Fs and Mms then the Cms is different than the specs. Same for the Mms.

I am going to contact them to get a clarification.
 

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Am also fairly new at these things but I've always been thought to work with the results of WinISD calculations rather than wholesale use of manufacturer's data and it seems to have worked well so far. In any case it should not differ enough to substantially affect your simulations. Perhaps in a sealed or vented alignment, a difference of 1.9hz in Fs may not cause a large difference in the final result?
 

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FWIW when I copied Nick's post on AVS (at least pretty sure it was Nick's post) with the T/S parameters it indicated FS of 18.75.
 

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Discussion Starter · #6 ·
That's what I saw also. That's why I was surprised when on the web site for this driver it is listed as an Fs of 17
 

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Hopefully Nick can fill you in....and then you can fill us in!
 

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I wouldnt worry about Fs being off by 1hz. Lots of variables can change when each driver is made. I dont mean huge changes but slight differences are just fine. A few grams here and there and Fs change of 1hz ect ect.

You will see all this will you simulate the driver and see what the response shape is when very small changes are made. Fs, Vas, Le and Qts are my main concerns. If I wanted a custom driver to be built for a certain purpose I might worry more about Cms and Mms.
 
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