do i need a Subsonic filter

[Naxis2k1 10+ year member]

hey guys i got a friend whos got 15 xxx ported running it off a mtx 1501d does he need a subsonic filter? cuz i know the mtx doesnt one right. so how would i go about do this?

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[Acidburn 5,000+ posts]

what is the box tuned to?

and where in phoenix are you?

 

[Naxis2k1 10+ year member]

box is tuned to 35hrz and i live on 43rd and bethany home ruffly

do you really need a subsonic filter i know it filters out feq's that the human ear cant hear so if you cant hear them wtf does it matter? i guess my real question is is it going to hurt anything not to have one?

 

[g30ffr3y 10+ year member]

you should use it so the subs dont unload

at tones beneath the port frequency...

 

[Naxis2k1 10+ year member]

you should use it so the subs dont unload at tones beneath the port frequency...

ok but how do i get one? the mtx amp does not have one built in if iam not mistaken

 

[g30ffr3y 10+ year member]

got me... im not even sure of what, what i said means...

from what i can figure though the SSF should be

set lower than the port tuning so you may be

able to get away with not having it... but i am

in no position to advise you more than that...

im sure there are external filters that can keep

you safe though... wouldnt a high pass filter

set to ~35hz do about the same as a SSF???

 

[Acidburn 5,000+ posts]

you should set an SSF to 3/4 of an octave below tuning frequency so on octave below 35 is 17.5 so you should set it to about 30-31 Hz

this means if none of your songs go below 31 Hz, you'll be fine

and yes, you can buy an external SSF

 

[ANeonRider 10+ year member]

The subsonic frequency should be tuned to 1/2 octave below tuning.

What is an octave you say?

An octave does not have a predetermined value. A change in frequency of a multiple of 2, means a change of one octave. An octave has to have a starting point. If the starting point is 1000hz, one octave up is 2000hz. One octave down from 1000hz is 500hz. Equalizers commonly have one octave spacing between their slider controls.

So in your case, set the SSF to 35-[(1/4)35] = 26.25Hz

 

[ANeonRider 10+ year member]

haha, we have two conflicting posts now, lol

 

[Acidburn 5,000+ posts]

is it half an octave? i dont really remember so it could be a half

 

[ANeonRider 10+ year member]

ya, its 1/2

http://www.caraudio.com/vb/showthread.php?t=70405&highlight=1%2F2+octave

JMAC approved, lol

 

[g30ffr3y 10+ year member]

sealed boxer dont need worry 'bout no math

 

[themainjam 10+ year member]

without a SSF if you play a frequency below the port tuning your sub will act like it has no box. it will be free air. this can damage the sub and burn the coils. so ssf yes although most song dont have 20-30 Hz frequency its just to be safe.

 

[Acidburn 5,000+ posts]

actually playing below tuning freq is even worse than playing it free air, all the air that used to help to control cone movement now is helping to push it farther

 

[ANeonRider 10+ year member]

yup, unloading the sub makes it emit that very distinct odor that is magic smoke.