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

[RickWilson]

The amp rack was probably my most pre-planned aspect of the build. Designed the rack in CAD to give myself some additional shelf space behind the V8 for my distribution blocks (wanted clean fuse access) and this was my final layout:


Sourced some 1/4" ABS and got the shape cut out and corners rounded. I ultimately ended up scuffing the surface and putting 2 coats of SEM Trim Black paint as I didn't want the gloss black look. It also helped keep static way down and no more fingerprints


I then mocked up the V8 (covered in packing tape to protect during the install/fab process) and made some final layout adjustments for the holes needed for the connections to the V8:


From here - I began to pre-drill all of the holes I was going to need for power and speaker wiring. Loaded up my drill press and went to town and then mocked up with the distro blocks mounted


Got my new P One amp the next day and then added that the amp rack and confirmed layout. Picked up a couple 90 deg Audioquest RCA adapters that gained me some critical clearances on the input side of the P One.


Then finally, dropped the rack in for a quick test fit, can't lie, this part got me so excited that I ended up working most of the night on the truck:

[RickWilson]

Then came wiring and tidying up the amp rack.

Mounted the amps on some small rubber washers and through bolted them. Trying to isolate them from as much vibration as I can as they are mounted on my sub enclosure:


From there, I wired up the amp rack (to the extent I could outside of the truck) and added a couple layers of 1/4" CCF to the bottom of the rack to conceal the nuts and provide some additional vibration isolation:


Then finally I dropped the amp rack in and wired it all up. Sat for a good half hour after I finished this phase and just enjoyed the view, stoked how well it came out for an amateur install:


Clean and tidy, easily accessible for service.


Getting interrupted from uploading for a few hours but still have the Conductor mount fabrication, "finish product" photos and some tuning to cover.

[mumbles]

Great work... and nice "big" drill press! What brand of distro blocks are those, don't think I've seen them before?

[RickWilson]

Thanks man! - Those are T-Spec Distro blocks - T-Spec v12 Series VDB2 - Ground Block

T-Spec v12 Series VFDB2 - Fused Power Block

[RickWilson]

The Conductor and its mount - this one piece drove a ton a major decisions in my system - swapping to digital input with my vehicle (no NavTV currently offered) meant an alternate control for master volume and I wanted to retain subwoofer gain control up front as well. The Director is nearly impossible to fit without major cosmetic modifications and I didn't care for the look or mounting options of the URC.3 - so the Conductor was my go to piece. I worked through several mounting locations and settled on making a mount in my center console cup holder. Again, another easy piece to remove and place a small plug to cover the small hole I drilled when I trade the vehicle.

This is from concept drawing, paper mock up to final implementation:


Now how we got there. I worked with Delander from DIYMA to take my CAD design and have him make some pieces from polycarbonate that I would then assemble and finish. The design:


Then cut with his CNC:


Then I glued, sanded, testfit, sanded some more and then finally painted (primed with Krylon then used 4 coats of SEM Trim Black:


And the money shot, almost looks OEM:

[RickWilson]

And finally my favorite shots of the final build:







From here - we tuned

[RickWilson]

I started initially using the AutoEQ feature in the Helix Suite with a UMIK-1 and honestly got some decent results. A little boomy in the 500 - 2k hz area but honestly for a 5 min tune, it was very passable.

Parameters for AutoEQ were:
All crossovers were LR 24db/octave
Subs were 20hz HP and 80hz LP
GB60s were 80hz HP and 1800hz LP
GB15s were 1800hz HP only
GS62 in rear were 80hz HP only



I played a bit with it but eventually got a remote tune. I hooked up with Shannon Price this Saturday to knock out a a basic remote tune of the system. He was very competitively priced and figured it would at least be a small crash course in witnessing how he tunes, measures, adjusts, etc. as I have never seen the process done live. He spent a couple hours with me and got me pretty much 90% there and I tweaked the rest of the way to finalize the center of the stage, integrate my rears and global EQ.

In full disclosure, I ran out of time to save my final measurements properly (new REW user) after I integrated my rear speakers and did some final global eq adjusting. The small hole you see @ 50-60 hz is filled and I took a touch off of the hump at 80-100hz to create a much more linear rise from 200 hz up to ~35 hz. I have rears crossed at 155 hz, 24 and 5000, 24 - this helped keeping them from distracting from my front stage at all, just a compliment.

Overall, this was a drastic step up from the AutoEQ but still think the AutoEQ has a ton of value vs time invested tuning.

I had Shannon measure my the autoEQ in red and it is shown here against his final tune (before my rears were added and my Global EQ adjustments) and you can see the big improvement. I had suspected my 200 - 1000hz was off after realizing things sounded a little boomy, esp with lower male vocals, lower end guitar/piano notes and that certainly seemed consistent with the measurements we saw.


We started on the left side - GB60s crossed at 80 hz, 24db and 1800 hz, 24db. This shows left mid, left tweet and both measured together. Had a little hole @ 800hz that we boosted gently to ease the curse but mostly disappeared once we got the whole front stage tied together.


Right side of the front stage. Had a nasty hole at 200 hz that again blended mostly away after we got the whole front stage together.

Left Front Stage, Right Front Stage and Overall Front Stage. Ended up quite balanced.

From there, we added the subs. Ended up inverting the polarity of my subs and crossing them at 64hz, 24 db to deal with some issues we were having at the 80-150 hz area. I have to say the the blending of my bass to midbass and location of where bass is coming from is superior with this tune. Feels like the bass rises universally from the floor of the vehicle.


Overall, the system just gets better with time and break in. I will continue to tweak some really minor things and hopefully can make some time to hook up with Nick for an in person tune later this spring. I think that will be another big step forward but right now, with the tools at my disposal, I am stoked. The ability to hear a bass drum getting hit by the pedal AND feeling it in your chest is hard to explain to the average listener. Or hearing the breath and tongue clicks between words, the strings of an upright bass vibrating off the fingerboard in Lake Street Dive recordings just makes me want to sit and listen to everything again. I also now notice a distinct difference between well mixed music and poor recordings, it's amazing how much more detail you pick up on.

I am currently playing around with adding the bass augmentation because I find at lower volumes (when I have passengers), the low end is lacking without a major adjustment to the my sub gain on my Conductor. I will probably experiment with differential real fill and the stage expander as well to see what it does.

Lastly, this is what my Helix EQ looks like.



Now to begin designing and dreaming about 3 way front stage combinations that fit in these pods:

https://www.instagram.com/p/CBtiKFfp...e-fb3421979177

[BigAl205]

That looks awesome! I love the attention to detail.
One of my bosses has an AT4 with the same Fuel Offroad wheels that I have on my Z71

[mumbles]

Cool, I appreciate the info!

Awesome choice on placement of the Conductor... very clever use of space!

[RickWilson]

Welp 2 way lasted 2 weeks.

Just pulled the trigger on a juicy 3 way from BLAM.

WS8.100 - 2 ohm, 8” mid bass
Multix MS3 - 3” midrange
TSM 25Mg 45HR - 1” Tweeter

Will have the GB60/15 for sale in a few weeks. Looking for $1150 for the combo, will have only a month or so of use.

damn excited to see what this 3 way is capable of, esp with a tune from Nick.