where to set subsonic filter

So I've never really seen anything on where you're actually suppose to set  a subsonic filter with relation to a ported box's tuning frequency.  I know that the sub begins to unload below it's tuning frequency but do you put the filter at that frequency or slightly below it?  If it is below it, how much is safe, assuming you're not clipping the sub of course?

I dunno, but using WinISD you can figure out where the optimal point is for your setup. The post "guide to using winISD" in this forum (its a sticky) will tell you how to do this sort of, if you read the whole thing.. For the setup I was just playing with, it looks like I should set the subsonic filter around 35hz or so, but again that is jut for the setup I mocked up in WinISD. On a related note, is there any good sources for subsonic filters if your amp doesn't come with one already? Online sources preferably so I can get an idea of pricing.

The "subsonic" filter is normally set at the same frequency as the port tuning frequency.Support the12volt.com

i've ran without a ssf filter without problems...and thats with 112.5 sq inches of port tuned to 40hz...never even came close to bottoming it...I wouldn't worry about losing low end if I were you since your tuning is 28Hz...if you mean losing low end as in output in the 20Hz range which you will rarely find music with information this low than don't worry