# 2015 GMC Sierra System Upgrade



## speakerman99 (Apr 18, 2016)

Greetings All, 
As they say long time listener, first time poster. I'm working to install a new system in my 2015 GMC Sierra Crew Cab with Bose (no sub). It's actually not bad for factory, but anyone on this site knows factory is never good enough. 

Have already purchased most the new toys. Going with Helix P6MKII to run active 3way system. AudioFrog GB25 in factory dash location. Hertz Mille 1600 in doors, Hertz Mille 280 in factory sail panels. 2 JL audio 10tw3's under the back seat powered by my old trusty Rockford Fosgate P1000x1d. I'll post photos to get caught over the next few days.


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## charles.beener (Mar 31, 2016)

Looking forward to seeing it.


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## 5829bmg (Nov 20, 2009)

charles.beener said:


> Looking forward to seeing it.


Tuning in for this also


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## Jdmeyers (Jul 16, 2015)

It took a fair amount of time but I was able to fit L3se in the dash. The GB should be quite smoother.


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## speakerman99 (Apr 18, 2016)

Guys, I know it's been forever since I started this build log. My apologies. I have the bulk of the system up and running. I've spent a lot of time learning to fine tune the Helix DSP system. Let's call that a steep learning curve for a newbie. 

Apparently I need to spend some time learning to upload photos to DIYMA! I'm going to attempt a few photo adds and hope for the best. If someone has the cliffnotes please share!


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## speakerman99 (Apr 18, 2016)

One more try at pics. Here's the back wall with a little knoKnoize sound deadener. Note the factory bose amp and rear window door motor on the left.



The plan was to mount a piece of carpeted plywood to the back wall. I wanted to retain the factory MLV layer if at all possible. Most guys just cut this stuff out. I like to do things the difficult way as following post will attest. 



First mounting ideas was taken from another forum member. That was to mount elevator bolts (large flat head) to the rear wall with epoxy (jb weld, not the industrial stuff



Looked pretty solid. Sanded to bare metal. Applied pressure for a few hours. Let cure for 24 hours. Popped like a coke can the minute I started tightening down on the nuts. Remember I'm putting plywood on top of the factory mlv/padding which is supper cumbersome and anything but play. I thought the longer bolts would help me get the nuts started and allow me to compress the mlv stuff to a reasonable depth. Wrong.


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## speakerman99 (Apr 18, 2016)

How not to successfully mount plywood to the back wall of your truck 

What not to do:
1)JB Weld and Elevator bolts.
2)JB Weld and plywood blocks (more surface area, but dangerous to screw into the back wall!) Managed to get a few screws in the plywood block without catastrophe. One stayed. One popped off once pressure was applied again. I don't think I took a picture of this attempt, but you can see the large extremely clean and bare sheet metal square that was left in the aftermath.



3) the Photo above shows the 3rd harebrained idea. T-Track and industrial epoxy. I really thought this would have worked. Again same result once pressure applied. 



I can't be this enept......After a weeks worth of nights working and waiting on epoxy to cure; I decided I was wasting my time with adhesive. Unfortunately I can't weld, but I can bend metal so I decided to mold some 3/8" steel brackets. That should hold it! Here's the finished product prior installation. I used existing bolts in the floor (seat belt/tire tool) and a couple of 1/4 rivet nuts in the top of the bracket. 



Here's the finished mounting board. 

You'll notice that I beat up the MLV padding pretty good with all of my failed installs. Also had to notch a big area out for clearance of the seat belt mechanism. This seat belt was grumpy and did not work with any bit of extra pressure applied from the back. Removing the seat belt bolts is not for the faint of heart or low on resolve. There is no clearance for a socket so it had to be removed with wrench and 1/8th turn at a time. 

Also read a few other forum post that said the shiny reflection of sound deadner could be seen after the seat was installed so I painted each bolt location with flat black paint. 

Here's a quick pick of the sound deadening going in full tilt. I was able to unbolt the seats and slide forward or back inside the cab without removing the front seat belt mechanism that looked a bit too unwieldy to tackle during one of my late night work sessions. 



'

Yes that is a dumb bell. I used two different weights to apply pressure to the various attempts to glue something on the back wall. 25lb on the floor, 15lb on a diagonal 1x4" did the trick. Well apparently not.....When does the fun stuff start?:laugh:


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## Old Skewl (May 30, 2011)

Wow! Rough start to the build. Looking forward to seeing the rest of the install. Just sold my 03 Silverado SS. Leaning towards a Sierra All Terrain Crew Cab or a tundra crew cab. When I did my Silverado I used liquid nails to glue (4) 1x3s to the back wall. Very solid. Screwed though carpeted 1/2" MDF into the 1x3s with 1 1/4" self tappers.


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## speakerman99 (Apr 18, 2016)

Rough start indeed. Kind of had me questioning some life choices for few days!

I drove a 2004 GMC for 11 years before buying this truck. I was able to take advantage of some advantageous placed factory bolts on its rear wall and sort of just cam clamped the whole assembly into place. I've really enjoyed this 2015 GMC update. That is part of the reason it took me year to decide I needed to tear it apart. It was inevitable, just surprised it took me this long! Here's a pic of the truck. Maybe the international guys will appreciate it. 



Liquid nail would have been way too easy. I almost tried that before bending the flat metal. On the plus side I was able to keep the factory MLV padding so I've had zero road noise issues. 

In the middle of waiting for all of this epoxy to cure aimlessly, I did manage to bang out a breaker rig for the electrical. Here's a pic of the finished main breaker for the system. I decided to purchase a flush mount unit and mount inside a NEMA water tight box. Overkill, but it dang near looks factory.



Here's a shot from the inside of the box. I got 99 problems, but dirt and water in my fused breaker ain't one. :laugh: 



I'll get into the electrical in a later post, but for starters the plan was to run 1/0 cable in black techflex through the firewall in front of the driver's seat. A quick youtube search resulted in an excellent how to remove the various wire harnesses and assemblies that made the job much easier.


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## cmusic (Nov 16, 2006)

The next vehicle I plan to buy is a truck, and I'm primarily looking at a crew cab Sierra like this one. My dad has a 2015 Silverado crew cab Z71 and it looks like the interior of these trucks can handle a high end install without too many modifications.

In the past when attaching blocks of wood or bolts to the metal of a vehicle, a silicone based glue called Goop has worked extremely well for me. Goop can be found at Walmart, Lowes, Home Depot, and many other places.


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## speakerman99 (Apr 18, 2016)

Didn't someone once say that doing things the hard way builds character?

Thanks for the tips. I used to fix work shoes with GOOP. Never thought about it for this application. I'll definitely file that away for the next project.


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## speakerman99 (Apr 18, 2016)

One of the things that bugged me the most about placing amps on the back wall of my 2004 GMC was the inability to get anything without pulling the seat. Found this mod in a few forum post. here's my version of clipping the rear seat bracket so that the top seat folds down. Hands down one of the best tricks I've learned to date. This has easily saved me hours of pulling seat bolts by now!

The idea is to clip the rear bracket just enough that it fully engages except at the very top when the seat bottom is nearly folded up. To find the appropriate length just install the rear seat (passenger or driver side, not both) and watch the bracket slide up and down with the rear wall bracket. Make a few marks with a sharpie and break out the cordless hacksaw. I was paranoid about accidentally cutting the seat back so I placed a small piece of 1/2" plywood underneath each bracket. Worked like a charm.



A little black paint to clean things up.


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## speakerman99 (Apr 18, 2016)

For anyone crazy enough to follow in my footsteps here is the video that shows how to run the power cable through the firewall. The under-dash info was particularly helpful. 

https://youtu.be/spG6oFvVOOk

www.youtube.com/watch?v=spG6oFvVOOk


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## speakerman99 (Apr 18, 2016)

With the amp wall finally in place it is time to move on to something more fun. I got into woodworking several years ago and spend more time in the wood shop than the garage most of the time. It's great when the two hobbies intersect.

I had real concerns about having to overly modify the factory dash speaker area. There are only a few high-end drivers that I could find that would stay within the factory 2.5" footprint. The Hybrid Audio L3SE was on my short list, but I just couldn't risk cutting up the dash if it was too big. The AudioFrog GB-25 was a near identical match for the factory Bose speaker. Here's a very detailed review of the mid-range. http://medleysmusings.com/afgb25/

Again, I'm trying to keep any mods to something that could be bolted on/off without too much trouble. Pictured below (top) factory speaker (bottom) exact duplicate copied with pattern router bit made from 1/4" black ABS that I found on Amazon.



Here's another pic installed. Had to screw the driver to the bracket and then used 2 factory bolt locations to fix the abs bracket. Worked like a charm. 


I read a few other build logs that talked about some nasty reflections from under this dash trim piece that covers the speakers so I applied a combination of dynamat or kno knoize CLD strips to add weight to the panel and also shaped a scrap piece of Stinger road kill for rear wave damping. 

For good measure I stuffed some polyfill in the recesses behind and below the driver. In restrospect, low end extension for the GB25 might have benefited more from trying to seal off the area better. Has anyone tried this?

Final dash pic: better picture of the cld mat, damping mat around the driver. Note that only a small portion of the speaker grill is actually perforated so if you are considering adding tweets up here like I was it will take some more work.


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## speakerman99 (Apr 18, 2016)

I should also add that the Frog's are obviously a finely machined loudspeaker. I've always been a speaker snob and these are some of the best looking speakers I've ever seen. However, I was a bit disappointed with the extremely small allen head set screws that hold the speaker wires. I nearly rounded off one of the heads and one even snapped off  but thankfully after it was tight. Probably my fault. At 2am you let such things slide so I will worry about fixing it if or when I tear back into the dash.....


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## brumledb (Feb 2, 2015)

I have a 2014 with GB25's in the dash. I put down a strip of RAAMmat behind the speaker for the backwave and added polyfill, but didn't think to add CLD around the speaker grills. This picture shows the response of the left and right mid with crossovers set but no EQ. I have the HPF set at ~400hz. I think the response looks pretty good.

One pretty big caveat though, I am bypassing the bose system. I am using an 80prs directly into Helix DSP. Within the next couple of days I will test the response using the OEM signal into the Helix and see how much they differ.








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## speakerman99 (Apr 18, 2016)

brumledb said:


> I have a 2014 with GB25's in the dash. I put down a strip of RAAMmat behind the speaker for the backwave and added polyfill, but didn't think to add CLD around the speaker grills. This picture shows the response of the left and right mid with crossovers set but no EQ. I have the HPF set at ~400hz. I think the response looks pretty good.
> 
> One pretty big caveat though, I am bypassing the bose system. I am using an 80prs directly into Helix DSP. Within the next couple of days I will test the response using the OEM signal into the Helix and see how much they differ.
> 
> ...


Brumledb, It looks like we need to compare notes! I'm actually much farther along with this build. Just trying to return the favor and post pics I took along the way. I've been playing with the Helix DSP for months now. Check out my post from tonight on this thread I started about tuning with the Helix. 

http://www.diymobileaudio.com/forum...1098-perfect-rta-but-midbass-gets-flat-4.html 

I've run the gb25 down to 200Hz, which I can get away with so long as I use -24db HPF. Recent conversation with BlackHHR convinced me to move it to 300Hz. From the looks of your response curve you get some spikes between 600-2khz too. Well, spike may not be the proper term. Anyway, I'm surprised at how much I've had to eq to flatten all of that out. Here's just the GB25s, but with heavy eq.



Finally, I had to give up on the factory bose high level inputs. I just couldn't get good sound from them. Seemed to be more trouble than it was worth, so I added an apple airport express. I play everything over airplay to the APE which then runs digital to the P6. The APE integrates surprisingly well with all the existing hands free/factory screen etc. I do have to use The Director for volume.

Also, just bought a pair of the SI subs. How do you like them. Curious what phase setting you came up with? I set my distance to zero and phased to -348.5 degrees.


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## brumledb (Feb 2, 2015)

I have had issues getting the proper amount of midbass and bass also when using generic curves. Even when I used the Whitledge curve which has more midbass and bass than most reference curves, I still found myself turning up the gains on the processor for my midbass and subs. So now I have a curve that I have adjusted from the Whitledge that gives me the amount of bass and midbass I think is right. 
My acoustical crossovers are Subs(90), Midbass(90-400), Mid(400-3000), Tweet(3000----)








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## brumledb (Feb 2, 2015)

As for the SI subs, I really like them. They are the only item that remains from my initial setup in this truck.

I do not have any delay or phase adjustment to the subs. My current method of tuning has not required me to adjust the phase on the sub or midbass in order to get the bass firmly on the dash.


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## speakerman99 (Apr 18, 2016)

I found a better picture of the GB25s in the mounting brackets. 



Finally moving on to the doors here. Ran out of knukoncepts deadner on the rear wall and floor so I decided to try second skin deadner for the doors. The two door kit wasn't enough to cover the inside of the exterior door skin so I mostly used my remaining dynmat exteme sheets to cover inside door panels. The second skin is thinner and lighter. Provides a cleaner finish. I'm hoping that the thinner lighter version holds up and works as well as the others. 

I debated about fabbing hard panels to cover the larger interior openings of the door. In the end, I decided to just double up on the dynamat and I think it worked pretty well. 



From the beginning of this build I have been obsessed with getting great midbass from these doors. Previous attempts have had mixed results. Decided to try a little rear wave deflection via the SS audio "speaker tweaker". Unfortunately there is a brace located directly behind door speaker location. To create a flat surface to mount the deflector I used another piece of that 1/4" ABS, popped a couple rivet nuts in the door brace and slobbered enough glue between the two that will hopefully hold up to the summer heat in Georgia. 



To mount the Hertz I fabbed a mounting bracket from 3/4" ABS sandwiched together to bring as close as possible to the door panel. Total height 1.5". Not much to spare. 

Don't ask me how I know but there is zero margin for error when aligning brackets to the door. I let the bracket slide maybe 3/8" off center and the door panel wouldn't fit.....First one is always the hardest. I eventually had to remove and move the bolt hole.


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## speakerman99 (Apr 18, 2016)

Sound deadening these doors has really flared up my OCD. These trucks are pretty quite to begin with, but I did have a little rattle from the door panel with the factory 6x9s. So....Max coverage, some double layers on the exterior door skin, interior door skin , and door panel. Literally spent hours cutting, fitting, rolling anything that could be deadened. 

I also added a layer of the SSaudio luxury liner. I was not sure it would fit, but once I got that clearance issue with the midbass bracket resolved everything fell in place.



Also fitted a few pieces inside the midbass recess. Seems to have worked well. 

Next it was time to run the speaker wires. Boy did I make that hard. I searched the internet high and low and found only bad or worse options to get past those new molex connectors. Most guys recommend drilling the couple of unused pin locations. I'm not usually lucky enough to pull that off and...... I bought this 12ga twisted pair speaker wire from knu koncepts that is super thick. Would have contemplated drilling if I was running normal 16ga wire. Anyway, I decided the "best" way to run wires was to bypass the molex connectors all together. There is an unused hole location already drilled above the molex. I just had to drill the door side, which required taking the door off. Only 5 bolts and not super hard with some help from my wife, albeit somewhat begrudgingly



After filing burrs, and applying touchup paint to the bare metal all it took was few rubber grommets and rubber door jamb wire loom. Not to shabby I think.
Except the first loom I bought (below) was too short. 
https:

Had to replace with this model for the required length. The molex (bottom)was replaced in this photo.




//www.amazon.com/Keep-Clean-10620-Door-Rubber/dp/B00H8JW4FK/ref=sr_1_1?ie=UTF8&qid=1470456925&sr=8-1&keywords=rubber+door+jam+loom


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## optimaprime (Aug 16, 2007)

Balls you have are huge for removing the door and drilling a hole !!! Get it !!


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## What? (Jun 5, 2008)

I have removed three sets of F250 doors to do the same thing. Thankfully, the F250 doors line back up without any adjustment needed.


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## speakerman99 (Apr 18, 2016)

optimaprime said:


> Balls you have are huge for removing the door and drilling a hole !!! Get it !!


:laugh::laugh: :laugh: Wish the wife was so impressed!

I grew up in a body shop so I'm probably not as hesitant to tear a new truck apart as I should be. For the record, the absolute worse part was getting the molex connect back in place on the cab side. Door was a piece of cake. 5 bolts and an extra set of hands.


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## Badmunky (Mar 9, 2009)

Any updates?

I am about to start my own install on my 2015 Silverado and am watching you build closely.


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## optimaprime (Aug 16, 2007)

Good stuff man any more updates?


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## speakerman99 (Apr 18, 2016)

Sorry guys. I'm steady making progress, but sometimes life gets in the way. Skip to the next post if woodworking doesn't interest you!

I think I mentioned before that I get into woodworking projects pretty frequently. Had an emergency project jump in lap this summer. Long story short my parents started a bathroom remodel, their contractor dropped the ball with a number of things so I (got) volunteered to build the bathroom vanity. 86" vanity made from Red Oak. 3part stain for weathered look. Lots of fun but I'm ready to get back to my truck!



Here's my first attempt at mitered doors. Turned out pretty well, but probably easier to just build cope/stick version.



Proof that one can never own too many clamps. 



I just installed the doors tonight. Finished the drawers last night. and hope to get everything installed by Wednesday.


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## speakerman99 (Apr 18, 2016)

Were I left off.....Hertz are in the doors. Frogs are in the dash. Now time for some tweets. My initial plan was to use the hertz ML280's that I picked up with the 6.5". Decided to install in the sail panel but wanted to attempt aiming somehow without going full fiberglass kindof involved. 

I should add that I'm pretty particular about keeping things stealth. Never been a flashy mod kind of guy. Flashy is cool, but for any everyday driver flash also draws more attention than I want. 

First attempt to aim the ML280 with an old flush tweeter housing that I trimmed down with a belt sander

Drilling the sail panel with a forstner bit worked great. Tape added for extra tearout insurance.


I don't think I snapped a pick with the Hertz installed in the sails. I just couldn't get over the shiny aluminum now in plain site. OCD is a terrible disease. 

Finally opted to installed my trusty old Diamond Audio Silk tweeters from my old truck. They fit flush and almost look factory. I'll snap a picture and add later.

One final note. When placing the tweeter in the sail panel of these trucks you have to be mindful of the rear bolts for the side view mirrors. One of them actually sits right behind were I wanted to install the tweeters. Luckily the bolt head protrudes about 3/8" beyond the nut. Feeling luck. I grabbed a cordless hacksaw and trimmed the bolt to flush with the nut. I was able to fit the diamonds, which are about 1" deep flush mounted with no problem.


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## speakerman99 (Apr 18, 2016)

As promised. Quick pic of the flush mount diamond audio tweets in the sail panel. Definitely not any danger of winning install of the year awards, but it was painless and effective.
















Low profile. I really wanted to like the hertz. Shiny bevels Just didn't fit my taste. 


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## speakerman99 (Apr 18, 2016)

Great story that happened at about this point in the install. So I'm working till 2am every night trying to get the truck put back together to haul my wife and 2 girls 6 hours to Myrtle Beach for a few days. Nothing like a deadline for motivation! 

I had a big meeting at work on this Tuesday morning at 8am. Planned to pick the family up by noon Tuesday and head to Beach. So of course the Night before I'm working furiously getting all back together. At this point tweets, frogs, and mid bass speakers are installed. Wires run. helix installed, but haven't cut anything over from the OEM headunit. So at like 2amMonday night/Tuesday morning I finally get the last panel in place and it's time to fire this puppy up! ......................Silence




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## speakerman99 (Apr 18, 2016)

Checked the usual suspects and just couldn't figure this one out. All settings were perfect..... So with my meeting coming up in only 6 hours I admit defeat and head off to bed and trying to figure out how I can delay plans long enough to get something working. 6 hour (more like 10 with my girls) road trips with 2 small children and no entertainment system does not make for a happy wife. 

So I'm laying in bed trying to turn my brain off and suddenly EUREKA I know with 100% certainty what my problem is but now it's even later and I'm already in boxer shorts.....I think what would my DIYMA friends do? You get up and go fix your junk at 2am in your boxer shorts! Am I right? 

So long story short. My OEM connection comes in via high level input plugs to the helix. At some point in my gain setting process I unplugged the high level input for the front channels to check for distortion from the OEM Bose amp output. Plugged it up and the system roared to life! Now the tuning fun begins.


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## LiquidClen (Dec 27, 2005)

Good stuff man. Any updates


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## beak81champ (Oct 2, 2015)

This is a very enjoyable build to watch. You have some excellent problem solving skills. I will be continuing my '14 Silverado Crew build shortly, and have learned quite a few great tips to employ from reading this. Thanks!!!


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## speakerman99 (Apr 18, 2016)

beak81champ said:


> This is a very enjoyable build to watch. You have some excellent problem solving skills. I will be continuing my '14 Silverado Crew build shortly, and have learned quite a few great tips to employ from reading this. Thanks!!!




Thanks guys...You might not say that if you knew how long I've worried about this build! Like everyone else; this forum has provided a wealth of knowledge for me so I'm just trying to return the favor, even when the mistakes are stupid and avoidable. I've tried to remember that I care more about this install being DONE RIGHT than DONE. Easier said than done after 3 months....

The next couple of post might not be very exciting. I'm not happy with the finished fit and finish at this point, but given time constraints it's as real world as it gets. Maybe 2 years from now I look back at how far I've come? Suggestions appreciated!

Here's a snapshot of the initial amp wall with Capacitor, fuse blocks, and RF sub amp.









Initial plan was to place the Helix P6 recessed in the dual sub box. After a lot of calculations I decided that I would be happier with the box firing down and without the amp...... So let's just rearrange EVERYTHING!







again, not stoked about the finished product but it had to be done to head out
Of town with the family for vacation.

I bought a bulk pack of the Stinger 4>8ga terminal post to clean up power connections on the reorganization. I'm starting to get picky about that tiny bit of exposed wire that seems unavoidable....


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## speakerman99 (Apr 18, 2016)

Went crazy with the Tessa tape to black the speedwire which varies the high level inputs from the OEM signal. 


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## speakerman99 (Apr 18, 2016)

After living with that rats nest of wires for a while I'm thinking that I could clean it up by building bottom wire trough to relocate the distribution blocks and cap. Has anyone seen any other options?


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## gregrob (Sep 12, 2016)

Love the build! Would you have needed to cut the sheet metal in the dash to fit the L3SE? That's what I was going to use on my 15 Sierra.

Also planning on a sub box / amp rack under the rear seat, and reason not to go that route?

You have captains chairs right? I thought all crew cab Bose trucks with the center console got the sub?


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## speakerman99 (Apr 18, 2016)

gregrob said:


> Love the build! Would you have needed to cut the sheet metal in the dash to fit the L3SE? That's what I was going to use on my 15 Sierra.
> 
> Also planning on a sub box / amp rack under the rear seat, and reason not to go that route?
> 
> You have captains chairs right? I thought all crew cab Bose trucks with the center console got the sub?




The dash location is actually quite spacious but the complicating issues are really two fold. 1) the dash grill is only perforated in a small oblong area MAYBE 4" approx. radius. I may eventually build custom Apillars or mod the grill allow more usable area. 2) I believe that better imaging is achieved by the slight angle on the factory speaker mount rather than simply firing straight up. I could be wrong on that one but it certainly has to help. By the time I added the new dash bracket and the gb25 there was no room to spare at the top which leads me to believe that a l3 would take a lot more work. I've heard of others that made it work so I know it can be done. Another approach I have seen is a bottom mount like this one. Easier, but again I think the angle is valuable.









The amp will fit in the sub box but only if I build out to meet the seat contours. I was trying to keep box depth at the middle seat minimum for an easier build. I get hung up on down firing subs for performance also, but the box would be easier to fire up. In the end, I've recently bought a helix spxl 1000 amp which is larger than the RF so I'm going to have to relocate back to the sub box eventually. 

My truck has bucket seats but the center console just has a jump seat, no sub. On another note, I am contemplating swapping
Out the jump seat for full center console which would yield some more install options! 


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## gregrob (Sep 12, 2016)

Thanks for the info! I'm currently researching options for the sub in the center console. Hoping a 7 or 8 woofer will fit in the factory box at a minimum. May end up building a box for it though.


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## beak81champ (Oct 2, 2015)

Thanks for all the dash issue info. Seems like this is going to be one of the biggest challenges with my truck, unless I attempt to glass some pods for the dash. Great install!


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