Subwoofer install not playing frequencies lower than 40hz? Potential causes?

[bestgio]

Hello there,

I drive the 2012 Audi A4 and it's the non b&o model with no navigation/ami. It just says Audi concert on top of my CD tray(factory radio).

I have a single 12 inch JL audio sub (12W1v3-2), 300 watts rms installed in my trunk and it's about 5 weeks old so far. It's in a ported box and connected to the Rockford fosgate p400x1 amp with the audiocontrol lc2i installed as well. I'll admit I'm a car audio noob as this stuff is still very new to me. We checked to make sure the box and sub have matching specs which it did and a friend of mines was able to install the subwoofer for me and everything works great so far. However on paper it says the sub could hit as low as 22hz, but that doesn't seem the case when I'm playing tones ~40hz or lower, the sub is basically non existent.(especially after testing the classic "put on" from young Jeezy song to really test how low the subwoofer can go). I can feel the vibration from the sub starting around 40hz and above however after playing those frequency test ranges.

What could be the cause of this? I have quite a few songs that can hit pretty low frequencies in other cars but this sub seems to have problems reproducing that. Is it the amp settings needs to be looked at again? Specifically the lc2i?? I set my amp to use the low pass filter on 80hz, and the lc2i is around the middle for the accubass. Or is it the head unit that's filtering out these low low notes?(factory radio)? If that's the actual cause, that'll be a tough situation because the factory radio has a specific design that goes along with the car. Any aftermarket would make it look awkward imo. I'm pretty sure this sub is more than capable of playing the low lows but that doesn't seem to be the case. Or is there something additional I would need to install to have this additional sub perform what it's capable of?

I spent quite a lot on this set up considering I'm a student. I'm still very happy with the results as the more common bass tones are definitely more solid, but I'm a little bit disappointed with the low lows being non-existent so far especially with all the hype of getting this additional 12 inch sub. Pretty stumped on what to do after asking 3 different forums with no luck..

Any help/feedback is greatly appreciated!

Cheers!

TL, DR: Installed additional subwoofer in trunk attached onto factory radio. Subwoofer does not play low as it advertises. Anything playing lower than 40hz is non-existent. Causes and advice on what to do to get the most out of the sub?

If this isn't the appropriate place for this question, I would happily move it somewhere else!

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[LoudSound]

I see the LPF on that amp begins with 50hz. That means it won't pass any signal below 50hz to the sub.

You have to turn off the filters on the amp and use an external filter if you want anything below 50hz

 

[bestgio]

I see the LPF on that amp begins with 50hz. That means it won't pass any signal below 50hz to the sub.
You have to turn off the filters on the amp and use an external filter if you want anything below 50hz

Thanks for the advice! Exactly how would you disable the filters on the amp?? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

What do you mean by using an external filter? Is that an additional device connected after the amp and then to the sub?? Sorry, I'm a noob when it comes to car audio so any help is greatly appreciated!

EDIT: It looks like there is an "AP" switch on my amp, which I think it means "all pass"

 

[BOOMINGRANDPA 5,000+ posts]

I see the LPF on that amp begins with 50hz. That means it won't pass any signal below 50hz to the sub.
You have to turn off the filters on the amp and use an external filter if you want anything below 50hz

lol.. the low pass filter should be set around 80-120hz., it stops high freqs from getting to sub not low freqs (make sure lowpass is on)

 

[LoudSound]

lol.. the low pass filter should be set around 80-120hz., it stops high freqs from getting to sub not low freqs (make sure lowpass is on)

i had a brain fart. yeah set the amp to lpf and around 60hz

 

[shizzzon 10+ year member]

What is the box specifications the subwoofer is in?

The box will play a LARGE role in what the sub can and cant play.

 

[staan]

could be tappin the lc2i into some channels that are hpf @ 40

 

[BOOMINGRANDPA 5,000+ posts]

id move it closer to 100hz but yeah if u have a tiny box it won't play to 40hz (lot of small truck boxes have no real low end)

 

[Jeffdachef 5,000+ posts]

stock factory decks limit any output below 40 most of the times. Cant expect a subwoofer to play low frequencies when your head unit doesnt even allow it to begin with. This is why people use aftermarket head units with a dedicated sub output which actually process a subwoofer signal rather than trying to get signal from speaker level outs that dont even have a sub signal and forcing it to be amplified. COUNTLESS AND COUNTLESS friggen issues with LOC setups and it never stops.

 

[bestgio]

i had a brain fart. yeah set the amp to lpf and around 60hz

Your original post is correct, I looked into the manual of the amp and enabling the lpf starts from 50hz-however high you set it! I found a way to disable the filter for experimentation and now the sub is going way lower than before. Easy fix, but rather dangerous as it's not filtering out the higher frequencies.

 

[bestgio]

What is the box specifications the subwoofer is in?
The box will play a LARGE role in what the sub can and cant play.

The box is quite large. It almost perfectly matches the sub's requirements. It's a ported box with the volume is 1.6 cu feet, tuned to 33hz. (Sub's requirement for ported is 1.6 cu feet tuned to 32hz)

 

[bestgio]

stock factory decks limit any output below 40 most of the times. Cant expect a subwoofer to play low frequencies when your head unit doesnt even allow it to begin with. This is why people use aftermarket head units with a dedicated sub output which actually process a subwoofer signal rather than trying to get signal from speaker level outs that dont even have a sub signal and forcing it to be amplified. COUNTLESS AND COUNTLESS friggen issues with LOC setups and it never stops.

I totally understand. My factory radio DOES have a subwoofer so we got the signal from there. It turns out that disabling the amps filters allowed the additional sub to go ~10hz lower (now I can actually feel the subwoofer kicking in as low as 30hz after running some frequency tests). It seems like my factory radio isn't too terrible after all, but rather the factory subwoofer was just lacking! Nevertheless, I'll look into some head units in the long run!

 

[Jeffdachef 5,000+ posts]

I totally understand. My factory radio DOES have a subwoofer so we got the signal from there. It turns out that disabling the amps filters allowed the additional sub to go ~10hz lower (now I can actually feel the subwoofer kicking in as low as 30hz after running some frequency tests). It seems like my factory radio isn't too terrible after all, but rather the factory subwoofer was just lacking! Nevertheless, I'll look into some head units in the long run!

if the stock unit has a sub out then it should be okay. A proper head unit will have a low pass filter to filter out the higher frequencies so that would be on your agenda later on most definitely. Or a proper monoblock subwoofer amp that has a low pass filter built in along with a sub sonic filter.