So i'm trying to "model", if that's the correct term, a subwoofer in WinISD and BBP6 as a comparsion between the programs.. They both tune the enclosure super low. WinISD picks a net volume; BBP6 didn't have a specified net volume. Neither suggest port area.. Whats going on?

EDIT: BBP6 tuned to 23 Hz (super low), WinISD tuned to a reasonable 34 Hz (but net volume was like .5 cuft)

Edited July 6, 201015 yr by Im Hung N ur Not

Don't use the programs to do that kind of stuff.

I just use them to tell me how long a port has to be to get a specific tuning, and the airspace for certain dimensions.

Don't use the programs to do that kind of stuff.

I just use them to tell me how long a port has to be to get a specific tuning, and the airspace for certain dimensions.

Same here, normally.. Now, I'm just fooling around to see what kind of results they yield. You, of all people on SSA, know that I am curious.. lol

Don't use the programs to do that kind of stuff.

I just use them to tell me how long a port has to be to get a specific tuning, and the airspace for certain dimensions.

Same here, normally.. Now, I'm just fooling around to see what kind of results they yield. You, of all people on SSA, know that I am curious.. lol

Oh I know!! lol

It usually has to do with creating a specific modeling curve. Sometimes they want the frequency response curve to be flat, within 3 db across the whole thing. Others have a specified curve shape that they try to conform the model to. Others may have a specific -3db point it tries to hit.

These suggestions work for some subs and not for others. Just use what the manufacturer recommends, not a box program. And no, none of them recommend port size. That's just not part of the program.

Main thing I have found is they they seem to model in a perfect listening enviroment therefore giving you the flattest response curve.

In WinIsd click the optimum and then input what the manufaturer recommends and compare graphs. Should see a big difference.

As a general rule modeling programs try to get the enclosure design as close to a .707 Q as possible. The basic premise is to achieve the flattest response, and the lowest F3 possible.

But in a vehicle, or any room really, cabin gains will take effect, fattening up the bottom end of the response curve, and again creating peaks at the cabin's resonance frequency.

This is an example of an in car TF graph. You will notice the peaks from 30-40Hz, the roll off, then the vehicle resonance frequency spikes again between 60 and 70Hz. If you take a flat .707 design from an anechoic based program the end result in this car will be a peaky response at resonance, and climbing again down at 30-40Hz. The bottom end peak will be less evident, of course, as we will see roll off from the cabinet, but it will still be fattened up because of the gain.

So use these programs and consider their response plots with a grain of salt. They really just provide baselines for us to work from, nothing is set in stone.

You will only get that freqeuncy response in the open air, not in a car or in a room.