subsonic filter

[f150_on_32s 10+ year member]

I read that when using a ported box you should always turn you subsonic filter on. why is this. i know it x-overs 20hz and below and that you cant' hear this, but thats what makes the car shake, and the back window flex. is it to preserve the life of the sub or is it just another "car audio rule".

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[Moocow16 10+ year member]

most subs can't play music that low. actually, off the top of my head i can't think of any that can play lower than 20hz. anways, without a subsonic filter, the sub tries to play these tones, and since it can't, it can damage the sub. with the filter on, the sub doesn't try to play these, and it will last a lot longer as to why you should use it in a ported box and not a sealed, i have no idea why.

 

[f150_on_32s 10+ year member]

thanks

 

[Wonderbread 5,000+ posts]

here is whats going on...

In a ported box, excursion below tuning frequency increases greatly...

if you do not set a SSF at a point near (prefereblly before) the mechanical limits of the drivers motor structure, and play super low frequency test tones at full power, you run the very serious risk of overexcursion.

Basically, your drivers cone goes too far and will usually damage something.

Your tinsel leads can snap, your voice coil and sieze, and in short, your driver won't work very well anymore, lol.

If you have one, set it a little below the tuning of the box... if you don't have one, be careful (ie - don't be stupid)

 

[Alphafrog1 10+ year member]

I have a 15" XXX in a ported 6 cuft box and i am gonna hook a PPI PCX-2350 up to it, which i am pretty sure doesn't have subsonic filter. I plan to compete with this setup and am wonderin how important a SSF would be. If it is vital, is there anywhere i can get one to add to my amp, or are they only built into the amp?

 

[Wonderbread 5,000+ posts]

some of the AudioControl products have them built in...

let's put it this way... Loyd does not run one....

basically, if you are not stupid "don't play 15 hZ test tones at full power for any kinda time" you will be fine...

 

[Geminidj2000 10+ year member]

so u shouldnt use your subsonic filter..... in a sealed box........ im running 2 12idmax v.3 in a 1.3 cuft box with a hifonics hercules amp should i not use the subsonic filter?

 

[Wonderbread 5,000+ posts]

there is no way that a SSF would help you in a sealed box..

do not bother...

 

[Wonderbread 5,000+ posts]

well, for a properly made box...

you should be ok, lol.

 

[Moocow16 10+ year member]

alright, i'm getting confused, what's Qtc?

 

[Alphafrog1 10+ year member]

Originally posted by Jmac Qtc is the total Q of the speaker in an enclosure including all system resistances. A Qtc of .707 is the most common and generally produces the flattest frequency response with approximately a 6dB/octave rolloff. Higher values of Qtc will give a peak in the output with a sharper rolloff. A lower Qtc will start to roll off earlier and will roll off at a slower rate.
B] [/b]

Gee nice explanation... kinda like usin a term to describe itself... lol //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[Alphafrog1 10+ year member]

Originally posted by Jmac I was lazy and copied it straight from eatel.net

 

And now I'm too tired to describe it (I've been up since 6 am, afterall)

Understandable, i got 3 hours of sleep last night and am about to pass out.

 

[Moocow16 10+ year member]

i know Q has something to do with quality right? but what about the rolloff thing, what's a good rolloff?