Is my sub bottoming out? or?

[butterMilk 10+ year member]

When my sub is hitting hard and low, 26hz. It makes a bit of a funny sound, almost as if there is a little engine running in there, bit of a rattling sound. The sub is only a few months old and still in very good condition. I dont think its getting a clipped signal(i have a smd dd1). It is in a sealed box, recommended is about 1.5 cu/ft, its a lil bigger than that, about 1.75 cu/ft. I am 99.9% sure nothing is rattling in the box.

My equipment:

sub- JL 12 W7 in a custom fiberglass box

Amp-1200 watts, JBL Grand Touring Series Class D Monoblock Amplifier

RMS Power Output:

4 Ohms: 787 watts x 1 chan.

2 Ohms: 1114 watts x 1 chan.

HU- Pioneer AVH-P8400BH

Electrical- Yellow top Optima under the hood. 1 run of 0g + to a dist block, 4g from that to the amp.

- Grounds- Chassis

Is it maybe because my amp sux? I have found out that it has a damping factor of 6, which I think is quite low, could that maybe be the problem?

Any help would be much appreciated, Thanks guys!

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[nkrell11 10+ year member]

You could check this by turning your subsonic filter up and then playing the same song or frequency again at the same volume and if you no longer hear the sound you were probably bottoming it out.

 

[butterMilk 10+ year member]

Thanks, my amp doesn't have a subsonic filter though. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

Maybe its time to invest in a better amp?

 

[mat3833 10+ year member]

ok, get some test tones. 20hz to ~30hz. play them one at a time and then turn the volume up SLOWLY. start with the 30hz tone. in reaity the 12W7 should have no issues with that in a sealed box unless you are severley overpowering it.

Matt

 

[AnthonyO 10+ year member]

If its a rattling sound, then I would say you are more than likely hitting XMax/Bottoming out.

 

[butterMilk 10+ year member]

Ok thanks, so if it doesn't make the sound at 30hz, but does make the sound at 25hz. Does that mean I'm bottoming out, and I need a amp with subsonic filter?

Or would you say its a normal W7 sound? Without being able to hear it lol.

 

[butterMilk 10+ year member]

If its a rattling sound, then I would say you are more than likely hitting XMax/Bottoming out.

So basically im pushing it too hard? If I made the box a little bit smaller do you think that would help? Damping factor on the amp has nothing to do with it?

And how bad for the sub is it to hit the Xmax

 

[cdc351jeferson 10+ year member]

shouldnt need subsonic filter on a sealed box. would be looking into to over excursion maybe?

 

[AnthonyO 10+ year member]

So basically im pushing it too hard? If I made the box a little bit smaller do you think that would help? Damping factor on the amp has nothing to do with it?
And how bad for the sub is it to hit the Xmax

How did you adjust your gains? Any bass boost turned up? And continuously bottoming the sub will do damage.

 

[Kingstroker 10+ year member]

try adjusting your bass boost on your amp, not sure if it is the same as sub sonic filter

 

[cdc351jeferson 10+ year member]

try adjusting your bass boost on your amp, not sure if it is the same as sub sonic filter

subsonic controls how low a frequency your amp will let yoru sub hit . boost is well more boost

 

[zako 10+ year member]

Bottoming out means that subwoofer runs out of physical excursion. At this point the voice coil is likely hitting the back plate and this is consistent with the sound you hear. As others pointed out, it seems it is unusual for a sealed box subwoofer to bottom out. At the same time, I guess this depends on the material that you play. Most music doesn't have much content below 30-40Hz region.

 

[butterMilk 10+ year member]

Bottoming out means that subwoofer runs out of physical excursion. At this point the voice coil is likely hitting the back plate and this is consistent with the sound you hear. As others pointed out, it seems it is unusual for a sealed box subwoofer to bottom out. At the same time, I guess this depends on the material that you play. Most music doesn't have much content below 30-40Hz region.

The song I was playing was USDA white girl, but they had remixed it and slowed it, and they said it hit 26hz. The sub rattles on other songs that hit really low.

For the gain setting, im quite sure I have it a little bit too high. I set it with a DMM and then went a lil past what JL recommends. Basically the amp is turned up the most that I can without any distortion, also set with SMD DD1.

Bass boost is turned up about 5-10% because I found that I could turn up bass boost without adding any distortion.

If im only bottoming out when it hits really low, could my box be a little bit too big? Would it be worth the effort to secure a piece of wood on the bottom of the box, to take up maybe .2 cu/ft ? Or did I answer my own question by telling you guys the amp is turned up a lil over what JL recommends?

 

[Fi-brations 10+ year member]

Same thing happened to me before, i was overexcurting the sub on lower frequencies because my subsonic was set to low. Setting it higher fixed it.

 

[butterMilk 10+ year member]

Same thing happened to me before, i was overexcurting the sub on lower frequencies because my subsonic was set to low. Setting it higher fixed it.

Thanks. Im am looking into getting a better amp with a subsonic filter. Mind me asking what you set it to to fix your problem?

Even though I have a sealed box, and its said that subsonic filter is for ported boxes. If I had a amp with a subsonic filter could this help my problem?