I just installed my new Fi Q12 today, and it sounds fantastic for the most part. But there are a few frequencies that are causing a loud rattling/popping noise. It's in a sealed box, I'm 100% certain I'm not clipping it, or overpowering it. Lower frequencies don't cause the noise, just higher ones around 100 hz I'd guess. The noise only happens at mid to high volume. It sounds like the noise is coming from directly behind the dustcap. Is the problem a loose dustcap? Any input is appreciated.

You shouldn't really be playing frequencies around 100 hz with your sub bass. Your mid bass should take care of it. Do you have a LPF set on your amp?

I do, I have it set at about 120 hz. I'll try turning it down some and get back to you.

I do, I have it set at about 120 hz. I'll try turning it down some and get back to you.

Also, If you have the option, try taking the ssd out the box and free air it on the same frequency that it made the noise on. See if you can see anything unusual.

There is no need for that, turning the lpf down a few hz entirely solved the problem, & I've never felt so stupid in my life. That never even crossed my mind, I've had 3 different 12's with the lpf on this same amp set the same way and never had a problem. I guess the Q is just pickier.

whiling playing music rest your hand carefully on the dusk cap to see if the rattling stops. sounds like it might be loose. 

 

playing a sub over 100 hz isn't the issue at all. certainly isn't causing the symptom . 

 

check the box for leaks at joints or around the sub cutout as well. 

Edited October 16, 201311 yr by lithium

I thought I had the lpf at 120, but it was actually a little higher than that. Now I have it at about 100 and it sounds fine. So the noise I was hearing was probably upwards of 120 hz. 

And it was a very small, specific frequency range, I was listening to 3 mix cd's, and the noise only happened on two of the tracks. But it was very obvious that something was wrong, my girlfriend could hear the loud pops from outside the car.

I can't play the sub loud enough to test it any more tonight, I'll have to wait a few hours. 

Is there a possibility that the lpf set too high could cause these symptoms?

As I'm turning the volume up more, the noise is happening at lower frequencies. I'll get some test tones and try to pin down the exact frequency, but what are the possibilities? I can't really test it by resting my hand on the dust cap because it doesn't do it a lower volumes.

I tried every tone between 70-125 hz, and I couldn't replicate the noise.

I've put a video up here: http://www.youtube.com/watch?v=JyPm-DTero4&feature=youtu.be

I'm certain the noise is coming directly from the sub, and not just something in the car rattling.

Help!!!

that sub enclosure has a divider right? 

Yes, it does.

The prime suspect in my mind is loose dust cap, how can I know if that's it for certain?

 

By the way, all the other frequencies sound great. You could listen to 10 songs and never know there is a problem. The frequency at the beginning of this one is just the clearest example of the problem. The deeper notes that come after sound fine.

Edited October 16, 201311 yr by TJ Fields

Do you have a sub sonic filter?

Do you have a sub sonic filter?

 

its a sealed box so he really shouldn't need one. unless he's throwing a lot of power at it

The prime suspect in my mind is loose dust cap, how can I know if that's it for certain?

 

as i suggested, rest your hand on the dust cap as the sub is making the noise to see if the rattle/popping goes away.  

I do have a subsonic filter at about 20 hz, but like lithium said, I shouldn't really need it because it's sealed. And the lower frequencies aren't even a problem, it's the higher ones. My amp is rated for 1400 watts at 2 ohms, which is what it's at now, but I'm probably only giving it about half of that.

 

I tried resting my hand on the dustcap, but since it doesn't do it at lower volumes, I had to turn it up too much for me to rest my hand on it. When I tried anyway, the sound of the dustcap lightly tapping against my fingers sounded exactly like the sound it was already making, just louder.

Edited October 16, 201311 yr by TJ Fields

Take a good look at the glue around the dust cap for any gaps.

 

You might also see if you can pry it up with your fingers anywhere.

There definitely aren't any visible gaps in the glue, it looks perfect.

There definitely aren't any visible gaps in the glue, it looks perfect.

I would set the low pass filter at around 90hz.

 

Your mid bass should come in around 80hz.

 

Play it hard and see what it does.

I'll keep playing with the lpf, but even if I do have it a bit high, I don't think it should be making this noise. 

Could you take some pics of the box and sub? May be easier to help you.

I'll keep playing with the lpf, but even if I do have it a bit high, I don't think it should be making this noise. 

Need to get some sub experts to answer the question.

Could you take some pics of the box and sub? May be easier to help you.

This sounds like a great idea.

I can take some pics, but I've had same setup (enclosure and amp) for years. It's never done this before, and the only thing that's changed is the sub. I had an Alpine Type-E 12 in the same box in the same setup, and it doesn't do this. I've even taken the Fi out, and put the Alpine back in, it definitely isn't doing it.

 

I was just tinkering with the lpf. At 100 hz, the noise was nonexistent with the head unit volume at 18, but obvious at 19. For each 5 hz I turned down the lpf, it bought me about one notch of head unit volume. All the way down to 50 hz, the noise was still happening, just at about 26 on the head unit.

Anything in particular I should take pics of? The glue around the dust cap looks fine and the dust cap isn't cracked or anything.