combine ports from dual to single

No, ports do not work that way.  You calculate the proper vent size to attain the desired tuning with the net enclosure volume.  So, if your net enclosure size is 2.5 cuft and you want, say, a 30Hz port tuning frequency, build the vent, say, 6" diameter and 29.5" long.  Use the port calculators on this site to help.Support the12volt.com

I have used the port calculator on this site but it differs from the WinISD program.  For some reason it usuall differs to a 4" port all the time.  Is this accurate.  If i use 12" subs, 10" subs, 1 or 2 subs, the WinISD always recommends a 4" port.  Am i doing something wrong? And correct me if I'm wrong, theres nothing wrong with tuning fairly low (28Hz) is there?  I am trying to obtain the smoothest curve as possible(sound quality) using the WinISD program.  A sealed enclosure in my 05 accord coupe just doesnt seem to give me that low end that I'm looking for.   

Thanks for all your help.

The tunning of the box is really preference. However 28hz is really low. if you have 10" woofers they will need to have a REALLY high excursion to have a chance at playing that low. As a general rule of thumb I use a 55hz for 10" 45hz for 12 and 35hz for 15". But its really a preference of the listener. Also when calculating the port, make sure you take into consideration the displacement of the woofers themselves and any bracing that you have in the enclosure. So you say the net is 2.5Qft. is that including the woofers already inside? if your target is strictly 28hz, the displacement of the woofers may change the port's tunning frequency by as much as 5hz.

The program is not "recommending" a 4" port opening.  That's the default port size...work with the program to suit your needs.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

MikeHusain wrote: I have used the port calculator on this site but it differs from the WinISD program.  For some reason it usuall differs to a 4" port all the time.  Is this accurate.  If i use 12" subs, 10" subs, 1 or 2 subs, the WinISD always recommends a 4" port.  Am i doing something wrong? And correct me if I'm wrong, theres nothing wrong with tuning fairly low (28Hz) is there?  I am trying to obtain the smoothest curve as possible(sound quality) using the WinISD program.  A sealed enclosure in my 05 accord coupe just doesnt seem to give me that low end that I'm looking for.    Thanks for all your help.

https://www.the12volt.com/installbay/forum_posts.asp~TID~74558~PN~1

Support the12volt.com