ported/vented box for 2 kenwood kfc w3011

aznboi had a typo above:  meant to say 12.56 sq in.  You can see, as he pointed out, that it takes a total of  four 2" openings to equal one 4" opening (4 X 3.14 = 12.56).  If port noise is okay with that then you had too large of a port opening modeled in the first place (not that there's anything wrong with that, it just takes up precious space needlessly).  You should also look at WinISD's calculated port square inch opening area when you are working under the "vents" tab in the project window.  It is shown as "cross area".

You are experiencing modeling difficulties that proves why slotted ports are popular in car audio.

Thanks for the replies.  You know, this designing business is ALOT more complicated than it would appear!  I do not know what version you are using Stevdart, but I do not see a "cross area" tab or anything on mine, I am running version (.44).  Here is what WinISD shows me for both sizes of ports.  The volume difference of the boxes is because I have subtracted the volume displacement for the port(s).  I have found some flared 2.5" x 8.5" ports, and that is why I have those instead of the 2" x 5" ports.  It would appear that I will get better sound and less noise using the two 2.5" x 8" ports per chamber.  DYohn, you told me that WinISD is a software that I could "believe" the results that it showed me, do you think what it is showing me right now is right or wrong?  Please let me know what you think.  Thanks guys!

Driver            : KFC-W3011

Driver            : KFC-W3011

Number of drivers : 1

WinISD version I use and a link to version history is covered in my WinISD Guide stickied in this forum.

Your results here are similar to the manufacturer's data:  +6 db peak in the 60 - 70 Hz region.

No, I don't believe it would sound good.  When there is a 6 db peak, you have to consider all else as relative to that level.  And depending on the vehicle this is going in, there will most likely be a further increase in that freq range due to cabin gain.  "Flat" is when all usable freqs run along roughly the same db level.  The 0 line is a point of reference.  Only if 30 Hz were close to being along the same db level as the other freqs would it be considered flat (with a +6 db bump at 60 to 70 Hz, the 0 reference line is the same as -6 db).  And...decibel step increments are equal whether they are below or above the reference line.  There is just as much of a difference in sound level from 0 to -6 db as there is from 0 to +6 db, or from -3 to +3 db.

If I were to allow a peak when modeling a sub that I intend to "sound good", I would keep the peak at less than 1.5 db, and at a lower freq than 60 Hz.  It is the subwoofer selection that allows you that latitude and nothing else is as important.  This model is an entry level SPL sub.  Like I said at the beginning of this hybrid thread, this sub will sound pretty much the same no matter what type of box you build for it.  You just might be able to get it louder.

Alright, that helps.  But, I was thinking that if my sub is rated at a SPL of 90, then it will play anything that is close to 90 db within 1db really good, and anything that is above that it will play better (as in how loud it gets at that level.)  When I plot 400 watts (in WinISD) it shows that my subs will play a 30 Hz note at 115.66db, when my sub is rated to play good at 90 db.  That is not  an inaudible db level at all, regardless of the peak at 60-70Hz level.  Also, doesn't the peak just mean that it will be louder at this level than at any other level throughout the audio spectrum.  The way you describe it, it is like the peak becomes the new 0db line.  If that is true, then why would they put the red and purple lines there in the first place?  

Thanks

Thanks for that Anzboi3064.  No, I didn't look there, but I have looked at other places.  Don't know why I thought that?  Now that you mention it, it does sound kinda crazy.  However, what I am trying to say is that since 30 Hz is REAL close to the red or 0db line (-0.36db,) then my subs will play that frequency at normal volume, and it will play the rest of the frequencies louder than normal. (Normal being 90db with 1watt of power applied to them.)  Also, the 6 db peak at the 60-70 Hz region just means that it will be louder than normal at those frequencies, not necessarily meaning my subs will ONLY play the 60-70 Hz region and the frequencies with 3db of it well....right?

thanks