(GrizZz here, wife's PC)

I wouldn't bother using the subsonic at all in a sealed box. Or, put it at it's bare minimum to reduce amp feedback/noise.

I used mine for many many months, in my ported box, improperly. Mine's a little different though, I can't set the slope it uses. I can set the frequency that the subsonic begins at, and up to 10dB of boost. So, with my box tuned to 33hz, to set the filter I'd run a 33hz tone, crank up the boost to make the tone peak very obvious, and then set the filter to that tone. Then I'd reduce the boost to 3Db or less, so that it didn't sound "off". This is how my owner's manuals said to do it, set to port frequency and then up boost to wherever you like it.

All seemed fine. Except there was no gut wrenching low-end bass.

So finally, I decided to mess around with it some more. First, I shut it off and ran like that for a while. There's my gut wrenching lows that have been missing for so long! But there's amp hum and other goofy noise coming though now too.

So next, I just turned it on at it's bare minimum settings. 20hz, and 0 boost. That cured the hum/feedback/"ultra-low bass irritants".

So a week ago, I decided to mess some more. Not using a tone, I turned the freq. up a bit. Dunno how high, might be 25, might be 28. Then I turned the boost up to about 3dB of boost.

All seems great. I can notice the slight boost, it makes music sound nothign but better.

So, experiment. Just try different things like I have been, and when you're trying something skechy, just don't give the sub full power, use common sense when experimenting.

 

Not true. I've set up many vented systems with no infrasonic filter. I can play mine without as well - it sounds the same either way though so I figure why not save the current

 

Yes,but low freq are hard on the woofer and like you say,save the power for music you can hear.

 

Actualy Im having some fun playing with the infrasonic ****, the only moment i see the infrasonic usefull is at very high sound level otherwise it's better not using it in my setup cause (SQ in mind with a sealed box) this cut some wanted low frequencies.

 

Yup, with a sealed box I'd say play with it and see what you like. I found with mine I also found the most benifet at higher volume levels. I use it now but only as a safety feature. Basically my sub is wearing a seatbelt to keep it in its seat during performance driving lol.

If you're interested mine is set at 18Hz. but everyone's subs/boxes/cars are different.

 

That's what car audio is all about....playing with your set up until...who am I kidding, you'll never be satisfied!!

 

^^^^^ Lol X2

 

Same for me around 15 - 20Hz

 

Considering that infrasonic filters were initially used to eliminate(reduce ) the ultra low frequency that was caused by a warped vinyl LP (that's analogue disc to the newbies), and were always set at 15 Hz (@ up to -64dB/oct), because the lowest note attainable by a "MUSICAL" instrument is 16Hz,and it'd be a large pipe organ.
Today's recordings IMO, do not require the addition of any filters, especially on a sealed sub box.

 

^^then don't use it! Many inventions were designed for one purpose, but later found to be useful for others. I like the way my system sounds with it on, so I think it's necessary for me.