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Thread: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

  1. Back To Top    #1

    2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Hello all - this is going to be an abbreviated post from my upload to DIYMA.

    https://www.diymobileaudio.com/threa...g-door.444799/

    Going to be a long read but hopefully enjoyable to follow along with my rapid descension into the rabbit hole of car audio.

    Finally had made arrangements to find a new 2021 6.2L AT4 in Satin Steel Metallic that had a confirmed delivery date to our local GMC dealer. This is a company truck for our family construction business. As most people know, inventory is literally nill nowadays and getting any sort of options on your vehicles (esp. GM trucks) cause major issues with delivery times. We found this truck with production spot but was coming with no options added but the basic AT4 trim is still decent enough. Love the truck and have had 3 of the previous Sierra body types. The 10 speed is fantastic and finally the interior are getting refreshed.

    Before I jump into the audio side of this post, I wanted to briefly show what other mods have been done to the truck:

    Exterior:


    • 20x9 Fuel Vector Wheels
    • 275/60/R20 Michelin LTX Defender Tires (Drive 99% on road and the stock Duratracs are noisy af/also have Nokian winter tires)
    • Magnum Headache Rack
    • OEM Off Road Running Boards
    • Illuminated Black Front GMC Emblem
    • Black Rear GMC Emblame
    • Black CarbonPro AT4 Emblem
    • Black OEM Exhaust Tips
    • Truxedo Lo Pro Tonneau Cover
    • Bed Mat

    Interior:

    • ProClip Phone Mount
    • OEM All Weather Mats

    Mechanical:

    • S&B Cold Air Intake
    • Pulsar LT Programmer
    • J&L Oil Separator


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    On to the audio side of my journey:

    I knew I was going to make some level of audio upgrades because the truck was not coming with Bose system and regardless, the Bose system is a sad system in itself. So I began to research. Hadn't upgraded car audio in anything except high school, had an Infiniti QX4 with Alpine HU, Kicker 700.5, Some Kicker Speakers and CompVR10 Sub. So I started by setting a budget - initially wasn't planning on a sub, just speakers and an amp only and put $1500 as my goal. Long term, boy was I naive on my wants vs price of components.


    I am not going to post the other 3 previous audio builds that I did in this truck before I got the system I am posting here. Definitely check out the link above if you want to peak into the progression of the overall build. In short - I certainly underestimated how much time and effort I would sink into this because I find audio and how perceive music fascinating and a piece of advice to my past self. Save for what you want, buy once, install once - I learned a lot in practice but could have saved myself a lot of install hours and returning/selling items had I spent another few weeks researching and talking with experienced installers/DIY'ers.

    Ok, on to the build.

    My objectives were:

    • As stealth as possible (company vehicle)
    • Retain ability to return to OEM fit/finish upon trade as well
    • Audiophile sound quality
    • Accurate, slightly warm but powerful speakers and subwoofers
    • Ease of use/straight forward integration with factory head unit
    • Reduce/eliminate cabin noise and rattles


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    Parts list with description and reasoning for purchase:

    Speakers:


    • Front Stage
      • Doors - Audiofrog GB60
      • Dash Corners - Audiofrog GB15
      • Long term going to do 3 way - not sure what combination of drivers yet though

    • Rear Stage
      • Audiofrog GS62 - 6" Coaxial

    Subwoofers:

    • JL Audio Stealthbox with two JL Audio 12" 12TW3-D8 Subwoofers, wired to 2 ohms
      • It was between this and a custom box from MTI Acoustics in Texas. I settled on this because of the pocket it provides for the amps, it's sealed fiberglass (extremely well built) and can be installed or removed in under 20 min without any factory modifications. It also ended up cheaper and much faster to ship than the MTI set up. I think I ultimately would have been happy with either.
      • Now that I have them properly tuned and powered with my current Helix P One mono amp (giving them about 900W), they are excellent shallow subs. They play flat down to around 28-29 hz, which I am very happy with considered they are sealed and very thin 12s. I tune towards sound quality with some good low end punch but when I push my sub gain up on the Conductor, they will flex the windows and mirrors on my doors.

    Amps and Controller:

    • Helix V8 DSP Amp with HEC HD Bluetooth Card
      • 75W x 8 @ 4 ohms or 120W x 8 @ 2 ohms
      • Probably the decision I hesitated with the most until talking with Skizer (Nick). The online community seems to have a perception that midbass or midrange/woofers need to be overpowered to get the output folks need to listen loud. While at the competitor level I'm sure can certainly be true, I don't think it is nearly as important at the common car audiophile level. Most folks run their GB60s at 150 watts+, I run mine at 75 watts with the V8 and they get louder than my ears can handle and I listen to music very, very loud in general. Understanding power to SPL ratios helped me settle my brain a lot. And then just hearing them sold me and then some.
      • There is literally no noise in the system, it's so clean and quiet that I think something is wrong at times. It's also a TINY foot print for an 8 channel amp which was important for me to fit all of my amps under my rear seat. Build quality is S Tier.

    • Helix P One Mono Amp
      • 1 x 500W @ 4 ohms, 1 x 880W @ 2 ohms, 1 x 1500W @ 1 ohm
      • My subs are wired @ 2 ohms, rated for 400W, each
      • I scored a great deal from a community member on DIYMA otherwise wasn't actually looking at this amp because of the price tag. I was originally looking at the Helix M One X or the Mosconi Pro 1/10 because of their size.
      • This amp will allow me a ton of flexibility in future builds compared the M One X.
      • When I compare this to 600W I was previously getting from my JL XD1000/5 amp, it is night and day. Output, cleanliness and build quality are much, much better.
      • Also fits extremely well in my under seat location

    • Helix Conductor
      • Controls my master volume, subwoofer gain (0.5 db increments), rear fill volume and several different audio presets
      • It's a sexy little piece of engineering

    Input Signal:

    • Digital (Music) (in order of sequence)
      • iPhone 11 Pro Max to
      • Apple CCK3 Camera Kit (powered from a USB-C to Lightning cable plugged into my center console) to
      • Audioquest Pearl USB A-B Cable to
      • Topping D10S DAC (Digital Audio Converter) to
      • Audioquest Pearl Optical plugged into Helix V8 Amp
      • This is what I use to play music directly from phone while completely bypassing the head unit and avoiding any un-needed digital to analog and analog to digital conversions of the signal. It has made a nice difference, especially on Master versions of tracks on Tidal. The Topping D10S is simple and just works.

    • Analog (OEM Bluetooth Sound, Navigation, Phone Calls)
      • LLJ Customs out of Arizona who specializes in custom wiring harnesses. They make a full plug and play wiring harness that intercept the 4 high level speaker outputs under the glove box and provides a long harness to mount your amps anywhere in your vehicle. I got the Loopback option which also includes an additional set of speaker wires that use the OEM speaker wiring without splicing, it is a massive time saver. I also had them added an extra set of speaker wires for my tweeters as I was going to go active. Overall a great investment for someone who wants plug and play DIY, just take 5-6 weeks to get.
      • The Helix software auto swaps from Digital to Analog when I get a call and back again seamlessly when the call ends.

    • OEM Controls/Carplay
      • If you keep your phone connected to the truck via BT AND use the Apple CCK3 Kit that lets you select which audio output you want, you can have a digital signal out AND retain all OEM controls except master volume. I use the Conductor for the master volume now which actually I prefer over the HU or steering wheel.
      • Carplay - if you have wireless Carplay, same thing. You can retain it via BT but the current iOS software recently screwed up the audio output function and swaps the audio out to Bluetooth every time you swap songs. It is a known issue that supposedly Waze messed up.

    Sound Deadening:

    • Outer Door Shell
      • Resonix CLD - Performance vs value - it's the best. About 75% coverage on outer shell, beyond this becomes diminishing returns
      • Dynamat Dynaliner CCF 1/4" - Added about 50% coverage of the outer shell with some 1/4" closed cell foam I had left over from my earlier builds.

    • Inner Door Shell
      • Soundskins Pro SSK Kits - I bought these as an all-in-one timeaver CLD + CCF deadening solution to seal the inner door shell. The paper is a pain in the ass to peel off during application but they are well made and my doors are literally air tight now.

    • Inner Shell of Plastic Door Panel
      • CLD + CCF @ Speaker Pockets
      • Dynamat Dynaliner 1/4" - About 50% coverage to help with rattles

    • Tessa taped all of body clips
    • Soundskins Rings @ all speakers

    Custom Work:

    • Custom ABS speaker mounts - CNC'ed by Delander from DIYMA - a really nice rigid solution to mount to the doors and speakers with
    • Custom center console Conductor mount - CNC from Delander, assembled and finished by me and honestly my favorite finish piece of the build.
    • Custom ABS amp rack - probably a reach to call this custom but it was a planned and fabbed piece.

    Will be posting the entire build process tonight...hope you folks enjoy!

  2. Back To Top    #2
    Refuses to grow up... mumbles's Avatar
    Real Name
    Eric
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    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Looking forward to lots of pics... I do mean LOTS...

  3. Back To Top    #3

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    So from the top, here we go. Going to post the build in this order. Sound deadening, speaker install, subwoofer install, input signal, amp rack and wiring, Conductor mount and then some final highlight reel shots.

    So first step was getting a full tear down of my doors, A pillars, dash corners and few pieces of my center consoles:

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    Old components: Audiofrog GS60 + GS10 + GS62 (Kept my GS62s for this build but replaced the mounts)
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    Door condition at beginning of build, existing weather barrier, some limited Dynamat CLD at the speakers and I had Dynaliner CCF on the outer door panels (which was useless and a pain to remove but necessary to properly treat the doors this go around):
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    Stripped and ready to treat:
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    All 4 doors have about 75% coverage on the outer door shell with Resonix CLD and Dynaliner 1/4" CCF:
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  4. Back To Top    #4

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Then I moved on to treating the inner shell of the doors with the SoundSkins Pro SSK Door Kit. The paper was a pain to peel but the doors are literally air tight at this point and I am very please with the fit and finish:
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    All 4 doors treated:
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    Nice and clean, air tight opening at the OEM speaker locations:
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    Then I moved on to trimming and cleaning up my inner door plastic panels. I had previously applied some CCF to help with rattles but this time I added from leftover CLD I had to the local surround at each speaker location, trimmed the plastic extrusion to prevent conflicts with my CCF rings and finally tessa taped all my body clips:
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    Panels with CCF and clips tessa taped:
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    I can honestly say, I've yet to hear a rattle in my doors. I can barely hear my tires are highway speeds now, can't imagine what it would be like if I fully treated the doors and rear wall of the truck.

  5. Back To Top    #5
    Noob Stycker's Avatar
    Real Name
    Brian
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    Pittsburgh
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    2020 Subaru Outback XT
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    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Can't wait to see more, great work so far. I covered my Silverado doors like you did. If I had it to do over again I would have sealed up those holes even better with some wood or plastic. That material will still flex under heavy midbass impact. I didn't think I was lacking midbass at the time but now in hindsite I would have deadened even better. Something to think about if you still have the panels off.

  6. Back To Top    #6

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    From here, I moved on to getting my speakers mounted in the doors. I worked with Delander to create the custom ABS mounts for the GB60s and GS62s and some acrylic rings for GB15s. The fitment was great, only needed some minor trimming on the GB15 mounts.

    Here are the mount design and after fabrication (before they were shipped to me):
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    Started with getting the GB60s drilled and tapped on to the mounts before I fit the mount to the door:
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    Didn't take photos of the GS62 prep but same thing. Then I move on to prepping my GB60 wiring. I used the harnesses I got from Crutchfield from my old builds that allow me to plug and play into the OEM harness without splicing:
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    Then finally through bolted the mounts with stainless hardware and lock washers/nuts, CCF taped the opening and mounted the speakers:
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  7. Back To Top    #7

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Quote Originally Posted by Stycker View Post
    Can't wait to see more, great work so far. I covered my Silverado doors like you did. If I had it to do over again I would have sealed up those holes even better with some wood or plastic. That material will still flex under heavy midbass impact. I didn't think I was lacking midbass at the time but now in hindsite I would have deadened even better. Something to think about if you still have the panels off.
    Good to note - May ask Nick to cut me some plastic panels for the front doors openings if I swap to an 8" midbass in the future when I go to a 3 way set up. Project is all closed up at this point but I think I have taken these doors off a dozen times so it wouldn't be a huge deal to add those panels.

  8. Back To Top    #8

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Then added Soundskins CCF rings to all 4 door speakers:

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    A before and after of the doors:

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    From here, I jumped to my GB15s. Started by getting some 47 uf, 100V caps installed on a small harness to each tweeter:
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    Then got the acrylic mounts butyl taped front and back then got the tweeters mounted in the brackets and added some CCF foam rings:
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    Then dropped the tweeters in the dash and wired them up:
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  9. Back To Top    #9

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    Subwoofer: I had installed the JL Stealthbox as part of my previous builds (aka why you are seeing the JL amp and LCQ-1) but wanted to show a few pics of the fitment and unit itself:

    Two 12TW3-D8's wired @ 2 ohms and the amp shelf/pocket.

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    Installed under rear seat (Again - from my old install):
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    Seats down:
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  10. Back To Top    #10

    Re: 2021 GMC Sierra AT4 - Helix, Audiofrog GB, JL, Resonix

    From here, I moved on to my input signal. I have two items here: My LLJ harness for analog and my Topping D10S for digital.

    Here is the LLJ Loopback Harness and where it plugs in under the glove compartment. Has 2 twisted pairs of wires providing high level speaker inputs to my Helix V8 for the factory BT (phone calls and navigation), chimes and FM/AM. Then it also have 6 twisted pairs of speaker outputs - 2 twisted pair each to utilize the OEM wiring of front and rear door speakers and 2 additional pair for the tweeters to bypass the OEM crossovers going to the dash corner locations. It also has a 12V feed and ground for something like a LOC or DSP - I just never used the ground as it caused ground loop noise when I tried it out on my old set up.
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    Digital Signal: It was probably to aspect of my built that was going to the most design on the fly but very happy with the outcome. Decided I was going to mount the Topping inside my center console after trying out a few locations and was hoping to retain some access to the device visually and wiring wise but still keep it stealth.

    Started by drilling holes in the bottom of the console and the console liner. Put some rubber grommets to protect wires:
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    Nice and clean penetration with grommets:
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    Used some VHB, Dual Lock Velco to mount the Topping:
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    Mounted and really like the concealed wiring but easy to get to. Audioquest Pearl Optical and USB A-B cables to a Apple CCK Adapter. Easy to open the console check the sampling rate.
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