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I have a 12-in ported subwoofer box, the box is tuned to 31.7. What should my subsonic be set at? I was told 25-30 Hz but I am not totally sure.

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I've heard, like you said, a couple hz below tuning. I've also heard a half octave below tuning. (32÷2=16 hz is one full octave 16÷2=8 16+8=24 hz is half an octave below 32 hz).

The subsonic filter is there to protect your subs. Basically, when you hit frequencies below the enclosure tuning, your subs will "unload". Basically losing back pressure and the suspension parts can lose control of the voice coil, causing the sub to reach its mechanical limits. 

In my opinion, 25-28 hz is safe. If you listen to basic, normal music the majority of the time, it's kind of rare for songs to hit that low of frequencies anyway. I think you'll be happy with that tuning 

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Thank you! 

 

One other question. Would the subsonic be changed if my lpf slope is at 24 on the head unit and set to 80hz? 

Skar Audio SDR 10" x2 (Sealed Box)

Skar Audio 1500.1D (1 Ohm) x1

Skar Audio TX525c (Front with dash tweeter) x1

Kenwood Excelon KFC-X173 (Rear Coax) x1

JL Audio 360.4 (Mids & Highs Amp) x1 

DEH80-PRS

XS Power d3400

Singer Alternator 275A

98 Jeep TJ 4.0 5 Speed

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36 minutes ago, CommonSyns said:

Thank you! 

 

One other question. Would the subsonic be changed if my lpf slope is at 24 on the head unit and set to 80hz? 

No. That just means that anything above 80 hz will be dropping off at 24 db's per octave

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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Try and think about it like this. 

Infrasonic filter is your High pass, and together with your Low Pass Filter, the middle,.. is your pass band. What you want played. If your box is in fact tuned to 32, and don't play in the low 20's, you most likely don't even need to use your "High pass" filter.  Like home boy above said, its for protection of the driver. Same as a high pass for a tweeter. You dont want your tweeters playing XXX.XX hz/freq to protect them. Same shit, just on the low end of the range. 

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I always set them with math similar to what Dafaseles said, only I multiply the enclosure tuning by .75 (it's a lot less work!). If you want to play it safe, set it 1-3 hz higher than your result. Being tuned to 31.7, I don't see any issues setting it at 25. If you start hearing the sub bottom out, raise it a notch.

 

For daily drivers that have amps without subsonic filters, I build their enclosures between 29-32hz. Higher tuned (40's) boxes, the subsonic filter is especially important.

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12 hours ago, CorNut said:

I always set them with math similar to what Dafaseles said, only I multiply the enclosure tuning by .75 (it's a lot less work!). If you want to play it safe, set it 1-3 hz higher than your result. Being tuned to 31.7, I don't see any issues setting it at 25. If you start hearing the sub bottom out, raise it a notch.

 

For daily drivers that have amps without subsonic filters, I build their enclosures between 29-32hz. Higher tuned (40's) boxes, the subsonic filter is especially important.

Yerrrr.... Tuned that low, if he in fact is, and using any driver with a hill of shit, and not playing slowed (Decaf, DJ Rusticals) music, you can normally not even run a infrasonic filter, .... not much music out there (that hasnt been played with) that drops to 18hz. I have some symphony music, that can see some stupid low shit in my house, but, thats not real common. And your all over it again, its mainly for the suspension of the driver, or slapping the former from out of control suspension travel. Goooood shit yo. 

 

 

Now, if you go buy a shit enclosure thats tuned to 40000000 hz ,.(like most of your basic bitch prefabs) ... the infrasonic filter can absolutely save your ass, where the driver will get out of hand, playing mid or even upper 30s,....  and where many run into the problem to begin with.

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