Build Log - Sound System Upgrade

[Aarvix]

Been taking bites at this build for a while now, thought I might share it in case it helps other stinger owners, and and see if anyone has any comments/suggestions/advice.

The car: 2019 KIA Stinger GT2.
This is my daily driver and I've already put 50K on her. The HK system is pretty good for an OEM system, but I spend so much time behind the wheel I really want to
a) reduce road noise, and
b) improve the stereo system.

The plan:

• Sound treatment
• replace drivers
• add a real subwoofer
• fully active DSP

Phase 1: sound treatment

I started with the trunk, there's nearly zero OEM sound deadening material back there, and with my MBRP exhaust it's pretty drone-y back there.
CLD on all the flat sheetmetal, followed by 1/64" lead sheet covered by 3mil plastic sheeting and 2mm flooring underlayment (don't judge).

Next I attacked the wheelwell liners. I used Thermozyte (synthetic jute with a foil radiant barrier) followed by 1/16" MLV.
I also lined the inner wheelwell liners in 1/16 MLV.

Now the doors. Used Dynamat xtreme on the outer skins and 1/16 MLV behind the door card. I used 1/16 as a compromise between performance and weight. This is a sporty car after all, and I'm willing to sacrifice a few DBs to continue beating up on Chargers/Camaros/Mustangs.

Lastly the floor.
The stinger floor is so busy I had a hard time getting good coverage and as such, there wasn't really any noticeable reduction in noise. Given the chance I would not do this again.
Pic is WIP, I apparently didn't take one of the finished product.

Results:
Soundproofing is a touchy subject, and notoriously hard to measure, but I tried to get at least SOME objective evidence. Measurements taken with REW and UMIK-1.
NOTE: these recordings were taken on the same road under similar driving conditions, but they were weeks apart and other factors could surely add to error (plus 75 is a busy road and it's a ***** to get a measurement on the same strip of road with no adjacent cars).
First, the noise at idle is definitely, and noticeably, lower.

At speed however, it's harder to tell.
Subjectively I feel like road noise is less fatiguing, but not necessarily lower in volume. This is probably due to the higher frequencies being substantially lower, but under 2K there's pretty much no difference.
The door treatment completely eliminated noise from adjacent vehicles, so it's definitely worth it just for that.

 

[Aarvix]

OK, time for the audio mods.

I'm budget limited, but I think this will strike a good balance between SQ and wallet....for now.

The plan:

• Front Doors: Audiofrog GS10, GS25, stock midbass
• Rear Doors: stock (midbass, midrange, tweeter)
• Center: Audiofrog GB40, GB10
• Sub: Audiofrog GB10D4
• Amp: Helix V12, Toro MR2

First up, Tweeters.
I decided to do sails because I'm too cheap to buy new A-pillars ($100ea), this turned out to be more difficult than I thought.

First I modeled up the pods in Solidworks. I have a small graveyard of PLA templates I made to get the angles and drafts right, but after about 8 "vase mode" templates I got something that fits perfect.

template model, I was able to smooth out that horizontal ridge on the fwd side.

Printed in PETG and wrapped in alcantara. I really suck at upholstery so there's a few seams if you look closely, but the black hides it pretty well. Maybe once I get my voron built I'll re-print in ABS and get it professionally upholstered.

These are a compression fit for the GS10/GB10, and have a notch in the pocket for the wires and a center hole for pushing the tweeter out.
On the back is a counterbored pocket that I JB-welded a 3/4" neo magnet into. The mating magnet is screwed into the plastic sail trim (CSK magnet). It holds very well.

The stock HK system has 3 speakers in the doors, but the 2.5" midrange and tweeter run on the same channel. There is no crossover, only a small capacitor on the tweeter.

I want these frogs to be fully active, so I needed to run an additional wire into the door. This proved to be a much bigger PITA than I expected. KIA uses a bulkhead connector on the door wiring. I do not have the tools to piggyback into this connector, nor do I want to disassemble the dash to get to the inboard side of the thing, so it's onto plan B.


OFF WITH THE DOORS!

I'll be using this little grommet below the main connector. I was able to fish a wire to another hole in the body (where I also added a grommet).

Applied shrink wrap and snuck it into the OEM door grommet, doesn't look too out of place.

Here's a link to the STL for the pod in case another stinger owner wants to print it:
KIA Stinger Tweeter Pod by Aarvix

 

[LordShadow]

You did a great job man!
Just curious, why the multi-layered lead/plastic sheeting instead of using the thicker MLV? It's a bit lighter than what you went with and if you go with the 1/4 stuff it does a damn good job. If it was as simple as "This is what I had access to/laying around," I totaly get it. Either way, nicely done.
Bulkhead connectors are a pita to to do properly since you have to source the pins and figure out which positions are open for use, if any. Had to deal with all the things you did when I did up my last WRX. I will say though, that thing was the quietest ride after I finished with it.
Be happy and proud of the work you did and take the time to really enjoy it.

 

[Aarvix]

1/64" lead is 1# per square foot, same as 1/8" MLV. Lead is also super limp and ductile, and forms easily around complex shapes. it was an experiment more than anything, but I wish I had bought more, because it's much easier to fit and form than MLV.


The interior parts fit pretty tight, and it's tough to get everything back together with an extra 1/4" of build-up (1/8 MLV plus 1/8 CCF). The plastic/lead/underlayment is under 1/8" total.

 

[stoopid]

-10db noise improvement at idle is significant. Not surprised that it didn't translate to highway speeds, it takes a lot of work to isolate the noise coming from relatively thin tires. I suspect suspension/connecting bit mods to soften the vibrations being sent into the frame would be necessary.

The tweeter pod looks good upon completion, but I'd still just use the hole already in the door.

 

[Aarvix]

Yep, lots of structural noise transmission in the stinger, not much that can be done about that.

There's around 3db reduction in the 300-2K hz range, which is audible, but the car will never be "lexus quiet" (at least we're faster!).

A-pillars are probably better for a 2-seat tune (and easier to wire), but the sails are great for the driver.

 

[turboAWD]

That looks amazing.

What's the easiest stuff to use for a beginner? Would consider maybe doing some in the trunk area, but don't know where to start.

Not going to take out the seats, or anything. Taking out door cards always feels like a gamble, because I've only ever done it once or twice, and it felt like I didn't quite get it back together correctly.

 

[Aarvix]

Center channel time.

The stock system uses a single 4" center channel speaker, but interestingly the dash is provisioned for a second speaker on the passenger side. I can only assume base audio system uses it instead of the LH side.

This opens the possibility of installing both a midrange and tweeter in the center dash, there's only one problem: the OEM grille only has holes for the driver side.

Time for some ultra-tedious drilling!

I found a bit slightly smaller than the molded holes and went to work. After drilling I deburred the back side of the holes, then hit the whole thing with a quick pass with the MAPP gas torch to smooth out the drill marks a burrs. Be very careful here, the grille WILL begin to warp, just press it against a flat surface until it cools and viola!

Back to Solidworks for some more 3D printed adapters.
GB40 adapter goes on the driver side, GB10 adapter on the passenger side. No drilling/cutting required, but I did fill the gaps with a little PSA-backed CCF and dynamat (no pic).

I also uploaded these to Thingiverse:
KIA Stinger Center Channel Speaker Adapters by Aarvix

The tweeters come with some slick mounting gadgets. I chose to use the backing plate with the spring to secure the GB10. Unfortunately it's not a very strong spring and makes.....spring noises....I guess.
Wrapped it with a little dynamat and no more noise.

 

[Aarvix]

That looks amazing.

What's the easiest stuff to use for a beginner? Would consider maybe doing some in the trunk area, but don't know where to start.

Not going to take out the seats, or anything. Taking out door cards always feels like a gamble, because I've only ever done it once or twice, and it felt like I didn't quite get it back together correctly.

Doors and hatch are the most bang for your buck.

It's hard to beat Dynamat Xtreme, it's .065" thick but performs better than nearly every .080" CLD (constraint layer damper).
If you want the absolute best, get Resonix.

If you're budget limited, the cheaper products like Noico do work, but just not quite as well (but hey, they're 1/3 the price for ~80% of the performance).

A lot of folks think you need 100% coverage of the Dynamat, but there's some pretty hard diminishing returns after around 50% coverage. At that point you're just throwing mass at the problem and your money is better spent getting a sound blocker like mass-loaded vinyl (or lead in my case).

There are off the shelf products out there like luxury liner pro or Cascade VB-3, but I chose to go the DIY route. Sound blockers DO need as close to 100% coverage as possible.

 

[turboAWD]

Thanks. Not exactly budget limited, more time / experience limited. Also worried about an unknown shop messing things up.

I guess since I don't really drive anywhere close to the amount you do, and it's only helping "some", I may just put in on my "someday" list.

 

[LordShadow]

If you want some really great how-tos from some of the most talented people in the car audio community, go to DiyMobileAudio.com Car Stereo Forum and have a look through the forums and check out the various build logs. There is a wealth of knowledge there.
Most of it centers around SQ (Sound Quality) builds which is my preference. Anyhow, lots of great reading and knowledge to be had. Get in there and get your hands dirty, you will love it!

 

[stoopid]

Center channel time.

The stock system uses a single 4" center channel speaker, but interestingly the dash is provisioned for a second speaker on the passenger side. I can only assume base audio system uses it instead of the LH side.

Nope, base audio has same speaker on left side like yours. I assumed the hole was for access, but now that I'm looking I see the two mounting holes you ended up using and there's certainly an intended purpose for the right side.

 

[Snowwhite]

Doors and hatch are the most bang for your buck.

It's hard to beat Dynamat Xtreme, it's .065" thick but performs better than nearly every .080" CLD (constraint layer damper).
If you want the absolute best, get Resonix.

If you're budget limited, the cheaper products like Noico do work, but just not quite as well (but hey, they're 1/3 the price for ~80% of the performance).

A lot of folks think you need 100% coverage of the Dynamat, but there's some pretty hard diminishing returns after around 50% coverage. At that point you're just throwing mass at the problem and your money is better spent getting a sound blocker like mass-loaded vinyl (or lead in my case).

There are off the shelf products out there like luxury liner pro or Cascade VB-3, but I chose to go the DIY route. Sound blockers DO need as close to 100% coverage as possible.

I've been curious lately about trying to fill the cavities in the A and B pillars with some sort of closed-cell foam. haven't had time to research though.
I got as much of the floor done as I could without removing the carpet and center console, did the back seat, trunk, roof panel, and wheel wells with Noico and MLV, but I agree, there's only so much noise reduction possible on this car. the road noise is just everywhere.

 

[LordShadow]

Do the A and B Pillars have airbags in them? If so, I would say to leave them be, as any alteration there would be dangerous.
Keep up the good work man, nice job on the prints. It was always a bitch when I tried to get my machine printing anything so, mad respect!

 

[Snowwhite]

Do the A and B Pillars have airbags in them? If so, I would say to leave them be, as any alteration there would be dangerous.
Keep up the good work man, nice job on the prints. It was always a bitch when I tried to get my machine printing anything so, mad respect!

Behind the airbags. The pillars themselves are hollow. The airbags attach to the outside of the metal pillars but inside the plastic trim.

 

[Aarvix]

Time for some junk in the trunk.
This is my first time building a fiberglass box, so please don't be too harsh. I think it turned out OK, but some of the contours don't match perfectly, and there's a few gaps that shouldn't be there.
I attribute this mostly to me glassing the interior panel out of the car, where it probably deflected a bit and I didn't notice.

Audiofrog GD10D4, she's a beefy girl, Diet Coke for Scale.

Planning to put this in the hatch behind the driver side wheelwell in an effort to conserve as much cargo space as possible.

Took some rough measurements and I'm a bit shy on airspace (needs .6 ft^3), but I managed to relocate the power hatch module to make a bit more space (the black box on the aluminum bracket used to be much higher). It turned out to be exactly the .1 ft I needed, lucky me!

Taped up the panel and created a little "doghouse" that extends into the newly-created space.

First layer of glass.

Many more layers later. Made some MDF rings then fleeced and glassed the inboard face.
I also filled it with water to check for leaks and measure volume. Came out just over .7 cubic foot, which matches the AF suggested box size.

Check fit after the first pass of glass filler and sanding.

Finished product after more filler, lots of sanding, and carpet.

Needs a grille for thet sub, any suggestions for one that will fit an AF GB10D4?

 

[Aarvix]

Got the Helix all mounted and powered up.

The wiring behind the hatch liner is still a bit of a trainwreck. It's all hardwired at the moment, but I plan to redo the wiring with some kind of quick-releases (deutsch connectors or cannon plugs most likely).

11 inputs, 12 outputs.....sooo many wires. Everything will get soldered, heat shrunk, and sleeved with expanding wire braid.

WIP pic:

fabbed up and carpeted a little panel for the Helix.

Installed.
It sits completely outboard of the wheelwell, so no real loss of cargo space.

I'll probably print a replacement grille for the wire pass-throughs that can utilize some kind of circular or MS21266 caterpillar grommet to limit chafing. Also may install a permanent hidden USB cable for the helix, but this will do for now.

I guess it's time to learn how to tune this thing now...

 

[NIU_Huskies]

Needs a grille for thet sub, any suggestions for one that will fit an AF GB10D4?

Great work! Quick question, are you still able to pick your floor panel up to access the spare and battery or do you have to remove the custom box first?

 

[Aarvix]

@NIU_Huskies I trimmed off the little flap of carpet beneath the box, so the spare tire cover can come out without disturbing the box.

 

[mfenske]

It would be really cool if you could do a press fit or magnetic panel to cover the Helix