JBL W12GTI mkii: Bottoming out?

[mc71]

I have 3 w12gti's & 1 of them, at higher volumes, will hit a bass note & make this popping sound. I listen to EDM & at a certain point, like after a buildup & the bass comes back in, the kick drums will become this distorted "bok" "bok" "bok" (call me for exact pronunciation) sound.

Or sometimes it happens on a sudden higher-pitch bassline note...if the bass is generally low freqs.

While my first assumption is it's bottoming out....it's a gti mkii! (known to be able to take tons of power & has the DDD "brake"ing system built in, etc).

I should mention, it was bought used & I've noticed the voice coil terminals can be twist-tightened to the point they'll keep twisting (like the bolt on top could be tighter). It's not loose, but still...could be tighter....& yet that top bolt isn't easy to get to.

With these 3 w12gti's (each in JBL spec 2.25cu ft, 1" MDF, triple baffle, aero-ported at 30hz) I'm still not playing the volume I've previously gotten with just 2 10" Alpine type-R's in a Crutchfield prefab box.

Currently I have my amps' SSF's set at 23Hz...initially I had 30hz RCA SSF's plugged in-line.

Is it possible the bass notes could be loosening my wire connections & causing this distortion?? Because it's odd that sometimes it happens on a high-bass note, odd that it still happens with 30hz SSF's, & odd that it's happening on a w12gti (with way more power than my 10" Alpine, yet not as much actual volume).

The box I have these subs in is heavy as hell & snuggly fits in my SUV...it's not easy to get the subs in & out of the car. So I'm just wondering anyone's gut reaction.

Any thoughts??

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[ciaonzo 5,000+ posts]

If it happens on low frequencies as well as high, and it the sound comes through all three drivers, it could be the amplifier hard clipping.

 

[hispls 5,000+ posts]

If it's only 1 driver acting funny you have a problem with the sub, the box, or even the sub is out of phase with the other two.

 

[mc71]

Thanks, I think it's only the one sub & I do think the sub is the problem..

[i set amp gains with a dmm. I doubt it's +/- phase (wired parallel...final ohm checked with dmm). I spent a month building/sealing the box (3 chambers, 1" MDF, triple baffled, several coats fiberglass inside/outside, seams siliconed)].

Maybe I'm grasping at straws hoping the sub's +/- connections are getting bumped from the SPL (vs facing reality the sub is bottoming out) :-/.

It's just weird my first sub having this problem is a GTI mkii (& not any alpine, JL, Memphis, Audiobahn, etc I've had in my past). Although the mkii's voice coil terminals do get bumped more, fitting through box cuttout hole, they seem to stick out more.

Guess my real question is, has anyone had a "bottoming out sound" that turned out to be a loose connection?

I'll pull the one sub and see what happens....also double check my gains...I'll just recheck everything lol. thanks again.

 

[will3 10+ year member]

I would bet money one or all are wired wrong , very common with the GTI

They use a split coil , unlike normal DVC subwoofers both postives are on one side and both negatives are on the other, you should also have the terminal jumpers included with the drivers , if you are aware of this than you probably have one out of phase if not , you need to go to JBL.com and download the manual and make sure everything is like it should be in the diagram