2014 Sierra aftermarket sub problem

AW22 · February 9, 2014

Had my local installer who does a ton of high end work (Afterfx in Stamford CT) install 10" Sub under rear passenger seat with amp behind the seat, and sub volume controller mounted in dash in place of one of the 2 cigarette lighters. I will post pics once I get a problem sorted...There is random feedback coming from sub that sounds like gain control is too high. We adjusted sub controls but noise still comes and goes almost randomly. the 6.2 liter with Bose audio has the active noise cancelation, and I am wondering if that may be the problem...trying to compensate for new sub acoustics? Anyone with 6.2 and Bose that has done aftermkt audio run into this problem, or have an opinion if it could be the cause? Is it possible to turn off noise cancelation on the Bose perhaps?

MotoMedic · February 9, 2014

How did they connect the amp to the truck's stock audio?

AW22 · February 9, 2014

Not sure exactly. But I drove around today and there is zero doubt it's the noise cancelation from the factory Bose causing the sub to put out a heavy gain sound when the cancelation kicks in. And it does it mostly when the truck is lugging at 1400-1800rpm, and it's worst on the highway as AFM is trying to go into economy 4 cyclinder mode. There must be a way to either shut off the noise cancelation, or as your question suggests, isolate the amp and sub in some way.

Separate but related issue, I would prefer not to have AFM at all on my truck for the majority of the miles I put on it are not highway miles. Rather have the 6.2 liter V8 working 100% of the time. I came from a 510hp supercharged V8 Range Rover Sport. So my Sierra mileage without AFM 4 cyclinder mode would be an improvement. But this post is about Bose noise cancelation and my new sub not working properly together...

AW22 · February 17, 2014

The fix was to disconnect just the rear interior cabin mic (apparently there are 3) for the Bose noise cancelation feature. They also added an additional ground wire for the battery to the passenger side of the engine compartment which they said can only help in eliminating any electronic interference. I will ask them for more specifics on how they disconnected the mic and how they connected the sub and amp. The equipment is:

Hertz compact power amp 700watt "hcp1d"

Hertz 10" subwoofer "es250d.5"

AudiControl active high voltage OEM line converter "lc2i"

AudioControl sub volume control " lc8remote". Which they installed in place of one of the factory cigarette lighter on dash. It is same color as factory black plastic surround and is really slick. They built a sub enclosure that is under the rear passenger half of the folding seats, with matching black carpet, so there is still some room under drivers side to stash stuff. Amp is mounted on rear bulkhead behind drivers side passenger seat. It is a huge improvement over factory sound, and its nice to be able to control sub volume from small dash volume controller based on what music is playing.

jdthomas24 · March 2, 2014

Interesting. Just ran into this type issue today. With an lc2i on kicker 400 amp and probox 10 sub and enclosure. Seemed as if I was getting some type of feedback even when the truck was not running. Almost an echo in the sub e on different levels. Moved to single mono input on lc2i since it's a mono amp and it seemed to get better. One thing we have noticed with the new wiring is that it seems backwards from previous years. Didn't know anything about Bose cancelation mics in these trucks.

Any more info you have on disconnecting the rear mic?