is this bad?

[ccrider540]

i think i read somewhere that its bad to have your subsonic filter set below the tuning frequency of ur ported box because it can damage your subs. is this true?

[Robert8252]

Simple example. If your tunes to 33hz you want your subsonic filter around 31hz. If you let your box play tones a lot lower even around 29-30hz in a 33hz tuned box you can bottom your sub out.

[DirtyD78]

wow never knew

[EclipseChris]

Dang i never knew that either, i thought tunin it to 33 hz would be low enough to play decafs music with no second thought.

[TLEJ]

Never knew either.. Good question

[Robert8252]

Ok. Before everyone takes what I said as fact. I know I've seen what I said mentioned here a few times so I'm going off of what I've learned here on the forums. Please someone who knows this for a fact post to back it up or if I'm wrong

[Robert8252]

I did a little more searching to stand behind my post and I am 99% I'm correct. The problem is, if your subwoofer is playing hz below its boxes tuned frequency distortion happens really fast and this is where damage can be caused to your sub. Still would like a more knowledgeable person to chime in though.

[tacomabanga1986]

lol, how do u find out what the box is tuned to to kno what to set the ssf to?

i built some ported boxs mtx recomends for my 15's and for fun i designed the same box on teh re box calc and it came out to 26htz tuning so i unno wtf is up with it

but it never played lows, just notes around 40htz plus, but no lows, when it tryed to i guess it didn't have enough port area

and my ssf goes from 20htz to 50 and i had it set to like 30 just to be on the safe side but my subs never bottomed out, i guess i dont have enough port area for the air to flow out good, prolly why they didn't bottom out

when it played low notes the sub barally moved tho with the ssf set to 20htz so i unno

[ISO]

its called unloading and when your sub plays below the tunning frequency it acts like it doesn't even have a box.

[finkster]

I have heard several different theories. I hear some people say to set it to 1/3 octave below tuning.

There is a more technical process, heres a quote that sums up a good way to set the ss filter.

"The port works as a bandpass filter, so the first thing you must to do is verify the frequency response of your sistem, you can use a decibelimeter or a rta beginning with the lower tone you can use, you must to draw a chart. with the values of your response, with this you will find the peak frequency of your enclosure, once done this you can determinate the frequency -3 dB of the port,

From this value to the lower frequencies, your enclosure works as a infinite baffle, thus there is no damping to the cone, the excursion increases, and the control is minimum. decreasing the amount of sound.

for example: if you detect that the -3dB point is set at the 26 Hz in your chart, you have to use this frequency with a tone generator, and do the next, identify in your chart the peak value for your port and take that value. we can say 90 dB.

use your 26 Hz tone and calibrate your system to get the same 90 dB measured with your dBmeter or RTA, now begin to adjust your subsonic filter up to the position where the amplitude gets 3 dB below your initial value, that is 87 dB. with this action you have adjusted your subsonic filter to the exact frequency where the information begins to waste power with no benefits."

Credit goes to RENAULT10 on diyma. I did fix some of the spelling errors, but even with them he seems to know his stuff.