So i plugged my Icon 10 D2 into WinIsd according to the specs on SSAs site. For some reason it says the best response is going to come from roughly .5 cu ft ported. The optimal suggested on the site is 1.5 cu ft. which is what i built and it sounds great. Of course i wanted to play with the port sizing and the cu ft a little bit and see if I can do better. Are the specs correctly listed? Do i need more than what the site lists to get the program to work correctly? I dont think i could even fit the sub in such a small box!

What is the "best response?"

You likely plugged some value in wrong, or have an incorrect unit.

I would bet the boxes are figured using large signal parameters.

When small signal t/s are done the sub will only move about 1mm. So in reality the T/S parameters don't show what these large drivers do in the real world. But when you do large signal testing (25, 50 volts ect) to get the sub to move in normal working range you see a big difference in the parameters.

For example VAS which is directly responsible for box volume can go from 19 liters on t/s parameters to 30 or 40 liters on large signal parameters.

It has to do with the fact that most of these large thick surrounds resonate very high at 1mm and much lower at high excursion.

Forgive my naivity on the subject, but when i say best response im talking about the curve the program gives. As ive seen that called the response curve. With my box specs it peaks up at about 33/34 hz and drops down sharply to a flat curve. Ill do a screen shot later so you see what i mean. But i am i under the impression we want it pretty flat and uniform as far as the curve goes.

As far as the signal voltage i put in 1200 watts and it automatically calculated it to 34.6 volts if i remember correctly. Which is what i believe i set it to with a dmm. I am going to re check that later as well.

I haven't played with the modeling yet, but define "best" ?

Every enclosure and tuning has a specific goal. The goals set as a priority to recommend the .5cuft enclosure are obviously different than those used by SSA to determine what they recommended as the optimal enclosure volume. Everything is a give and take in this hobby.....when you change things to improve one area, you give up something in another area. There is no "best" enclosure, there are only enclosures better suited to one particular goal or another.

As for small signal versus large signal....that's not what Q was referring to. In WinISD the power is only used to approximate output under ideal circumstances (SPL goes up and down with power). What Q was referring to was the power level used to measure and calculate the Thiele Small Parameters of the driver. What power you plug into WinISD and what drive level is used to measure the T/S Parameters are not related in the slightest.

And you fundamentally did exactly what people who are anti-modeling always do. Hit some "ideal" button and not put in the boundary conditions of your vehicle. If you don't manipulate the ideal and it isn't your ideal it isn't right.

So i suppose for now until i understand better I leave well enough alone.

I went through this for a while of wanting to lean hard on what BBP or WinISD etc. was suggesting. But then there is real world results. So the approach is to take from both.