Odd sub problem - bass dropping out and can't figure out why

[sci85]

Hello,

I recently bought a 2017 Impala Premium that comes with the Bose 11 speaker center point system with active noise cancellation. The system doesn't sound bad, but having installed many audio systems in my cars over the years, I really wanted some additional punchy bass. So, I put in my 2 10" subs, amp and a LC2i LOC since this bose system uses the new MOST digital signaling from the head unit so you have to come off the speaker outputs POST bose amp. Now, I understand this amp contains active noise cancellation and probably some additional signal processing.

So hears my issue. The subs sound excellent but only if the trunk lid is OPEN. If I close the trunk lid, the sub output is cut significantly. The ANC is not supposed to be active unless the car engine us running so I'm not convinced it has anything to do with that. However, I've checked everything I can think of including checking the phase, the LC2i LOC, etc but nothing I do makes any difference.

So, I'm not sure where to go from here and hoping someone has possibly run into this issue before.

Anyone have ANY possible ideas? I'm open to anything at this point.

Thanks.

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[Boomin_tahoe 5,000+ posts]

Sounds like he bass is "trapped". Your issue may be to let the bass into the car by simply cutting a hole in the rear deck. Or if you have a ski hole, drop that sucker down and should get some bass.

 

[bandit_kb]

Or lower your seats if you can. See if it improved. May need a way to let the bass in.

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[sci85]

I've tried dropping the seats. That had no affect. I haven't tried moving the sub box around or removing the rear deck speakers. That's my next step when I get back in town tomorrow. I found something about bass wave cancellation that can happen in sedans. I've never actually had that problem before in the past but maybe the newer cars it's more of an issue? Anyway, hopefully it's something as simple as that. Will report back results tomorrow. Thanks.

 

[BOOMINGRANDPA 5,000+ posts]

check sub phase

 

[audiobaun 5,000+ posts]

I've tried dropping the seats. That had no affect. I haven't tried moving the sub box around or removing the rear deck speakers. That's my next step when I get back in town tomorrow. I found something about bass wave cancellation that can happen in sedans. I've never actually had that problem before in the past but maybe the newer cars it's more of an issue? Anyway, hopefully it's something as simple as that. Will report back results tomorrow. Thanks.

It would serve better to remove the rear deck speakers to get some of the sound you are missing.Even so..If those rear speakers in the rear deck are not enclosed/sealed off from that SHARED trunk air space as those sub woofers, those rear speakers will eventually become damaged/ trashed and later will admit some unwanted noise from destroyed cones.I myself experienced that back in the early 90s.

 

[BOOMINGRANDPA 5,000+ posts]

sub firing rear in trunk or towards backseat?

 

[Boomin_tahoe 5,000+ posts]

I've tried dropping the seats. That had no affect. I haven't tried moving the sub box around or removing the rear deck speakers. That's my next step when I get back in town tomorrow. I found something about bass wave cancellation that can happen in sedans. I've never actually had that problem before in the past but maybe the newer cars it's more of an issue? Anyway, hopefully it's something as simple as that. Will report back results tomorrow. Thanks.

I would try removing rear deck speakers and play around with positioning of sub enclosure before buying anything. Those alone will and should dramatically improve things. If not, step 2 it is.

 

[sci85]

I've checked the phase (all good) and disconnected the rear 6x9's on the deck. Right now, the subs are firing forward. I will move the box around and try out different placements as suggested and provide an update. Thanks!