24" Stealth Build: Stereo Integrity Audi A4 Avant

[BigAl205]

Any rough idea what a shop would charge to cut and modify a typical car like this for mounting this SUB?

8 hrs?

There's weeks of fabrication and welding in the back of that car to get the sub in the way I did it.

I'm not sure if banshee meant how much they would charge to reproduce what you did, or just mount a sub true IB. Hell, you've got more than 8hrs in just mixing expanding foam

[dumdum]

I'm not sure if banshee meant how much they would charge to reproduce what you did, or just mount a sub true IB. Hell, you've got more than 8hrs in just mixing expanding foam

Peters Honda Accord which he did install himself has well over 40hrs in it for his two 18’s with steelwork fabrication and making the manifold for the two 18’s

my manifold for two 12” was a bonded and bolted in steel framework which then has an 18mm birch ply manifold fitted above it to funnel the pressure down and out, it has approx 30hrs work, I basically did the IB frame, woodwork and base layers for amps in a week, so maybe 60hrs with threaded inserts for subs, amps and dsp etc

[BigAl205]

Peters Honda Accord which he did install himself has well over 40hrs in it for his two 18’s with steelwork fabrication and making the manifold for the two 18’s

my manifold for two 12” was a bonded and bolted in steel framework which then has an 18mm birch ply manifold fitted above it to funnel the pressure down and out, it has approx 30hrs work, I basically did the IB frame, woodwork and base layers for amps in a week, so maybe 60hrs with threaded inserts for subs, amps and dsp etc

That has absolutely nothing to do with what Jason said. Would you have felt better if he said instead, "I could have just bolted in a baffle like the one Peter showed on his channel"?

[JasonInAugusta]

Peters Honda Accord which he did install himself has well over 40hrs in it for his two 18’s with steelwork fabrication and making the manifold for the two 18’s

my manifold for two 12” was a bonded and bolted in steel framework which then has an 18mm birch ply manifold fitted above it to funnel the pressure down and out, it has approx 30hrs work, I basically did the IB frame, woodwork and base layers for amps in a week, so maybe 60hrs with threaded inserts for subs, amps and dsp etc

Cool. Now we're having a conversation.

I never said anything negative about Peter or his work. Peter does some nice work and has built some neat stuff. That build with (I think) 500 individually addressable LEDs is killer to look at.

I'm not sure if banshee meant how much they would charge to reproduce what you did, or just mount a sub true IB. Hell, you've got more than 8hrs in just mixing expanding foam

When I started this I liked the car so much I told Nick I was looking for an Avant so I could build one for myself. Yeah...nah. There is a monstrous amount of work in this car - only for it to look stock when done.

I seriously don't want to replicate the amount of work that's been done to this car to build one for myself. You've seen the Chevelle, the pro-touring Camaro, and other projects that are here. My time is much better spent there.

The foam pour was actually surprisingly quick. An hour tops. There's a short period of time between mixing part A and part B before it starts expanding. The most concerning/worrying part of it all was estimating how much would need to be poured in. Since I didn't know, the common sense thing to do was to mix small batches and monitor expansion progress with the thermal imager. Worked out perfectly.

The major thing I kept in mind while designing/building the sub "enclosure" is the fact that this isn't a sub enclosure you can build outside the car and drop in it. It's literally a permanent, structural part of the car. It had to be built so that it doesn't fail in any way at any point in the future. If any weld cracks or fails it's a MAJOR issue to repair. So...I erred on the side of overkill. The way the back of this car is built you could bolt a plate to the sub baffle and pick this car up and swing it around with a crane if you wanted.

I don't have an exact estimate of time spent on the sub install. I do know that Sumo was here for weeks welding and fitting pieces to the car. One pass around the sub baffle would be a day of welding (had to work a bit at a time and constantly jump around to different areas to reduce heat build-up). We made three full perimeter passes on the top side, three on the bottom side, and then spent time doing more welding to visually blend the baffle to the car so that everything that is seen is metal. No body filler to make it look nice. Weld, grind, weld, grind...

Then there was the work done on the inside and the wall we built. Since there are eight of those 3/4" square tubes connecting the 3/16" baffle to the lower 3/16" ring the steel we had rolled to build the interior wall was cut to fit each section of the wall. What was cool about that was we had the metal rolled as a cone so we could use our templates to cut each section and weld it in.

We tried to make that wall as smooth as possible, but having eight points around a circle - even though the metal was rolled - meant that the inner wall wasn't as perfect as I wanted. We made multiple passes with the welder to build up and add material to the low areas at each of the panel joints where the square tubes are and get it looking nice, but I still ended up running a skim coat of filler at each of those joints to make the interior wall of that space perfectly smooth. Reality is that it's completely unnecessary because no one will ever see it, but I want every part of this build to be a completely finished piece that will stand on its own as a quality product and for people to continually be impressed as they dig deeper into the install.

I don't want someone to see the finished install be impressed with it looking nice with the trim pieces and beauty panels installed. I want them to be just as impressed when the beauty and trim panels come off and they see the inner workings of the install and what's going on behind the trim panels. Every part of the build should be something that can be displayed and stand on its own as something of quality.

I want Audi techs to be impressed with the build quality and ease of maintenance when the car goes in for service.

Sumo is a boilermaker so he's used to working with heavy wall pipe. I'm more accustomed to welding sheet metal so there was a learning curve to him running the MIG and not blowing through the factory sheet metal as he welded that 3/16" plate to it. I gave him grief that while my welds didn't look as nice, I didn't blow through the sheet metal.

He had also not done sheet metal forming or body work. So all of the work under the car cutting that spare tire tub and the hammer/dolly work to blend it into that lower 3/16" ring had to be done by me. It's a lot of fun laying on your back welding above you. I didn't get video of me doing the metal fab under the car with the air saw and hammer/dolly, but once that portion of the metal work was done and I had tacked it all to ring the way it needed to be, I did get video as Sumo ran the perimeter of the ring and zapped it all together. That's the bit you see in the video where I left him to it and came back later to check his progress and we discuss running more passes to (again) add metal to low areas so we could knock it down and have one smooth, continuous piece of metal with no body filler.

And looking back it's crazy that we did (more appropriately I demanded) that level of work under the car where no one will ever see it. There's no body filler where that ring joins the spare tire well. No seam sealer. No need.


Today I'll wrap up the metal work I'm doing to the passenger rear wheel well (to install an amplifier of all things) and update the thread tonight. Again, same thing there. No filler. Just metal. I will run seam sealer on the exterior where I'm joining this piece, but only because there are 90 degree joints (inside corners) on this piece where it joins the body of the car. The 90 corners on the piece I made are fully welded on the exterior and smoothed with no need for filler or seam sealer. I have days on just this portion of the build.

Then there's the hours and hours of sound treatment.

Heck, I have over 8 hours over the course of two days cleaning the carpet that was in the car. It needed it. And it'll get cleaned one final time before I deliver it.

Monstrous amount of time. Speaking of...I need to get to work.

[dumdum]

Well now we are on common ground and we’ve worked out Peter didn’t do the install you gave him credit for and would very much have done exactly what you did that’s all good!

I took a different approach, I welded up a frame and having a car made of tinfoil I did kind of take a leaf out of the boot it in book… however I also took a leaf out of modern car manufacturers book (Audi and Ford to name but a few), basically I used the same sort of adhesive to bond a mild steel frame to the bottom of the wheel well after cutting out a square and basically bonded it to the well with 16 m6 bolts, my take on it was if you’ve ever seen thin metal that’s been welded to thick metal you will invariably see the thin metal break where it’s been ground back and then super heated by welding, it’s a common failure mode and one various cars over the years have suffered with, and also one that’s considered for good and bad reasons in engineering

i chose to go with a 25mm box section frame, drilled 4 m6 holes per side and then cut approx 20mm inside the frame and zip disc’s the corners, then applied a generous layer of pu sealent to the frame and bolted it down with 90mm long bolts going upwards with repair washers under the car and smaller washers on the steel frame, then basically panel beat the 20mm lip up the frame squishing the sealent out, clamping it where needed, this way it avoids the stress points and spreads the load and makes the frame very much a part of the spare wheel well, it still took a few days, but in my car I felt it was definitely strong enough for a pair of twelves once I’d also made the manifold flush to the floor and then put 3mm of closed cell foam down, it basically put everything under tension and made it immensely solid, you could indeed do the crane test with the frame and support the car on it… infact I have jacked it up on it numerous times and nothing moves… well apart from the car away from the floor

then I created a few more layers of wood going up so I could clamp the manifold down on those 90mm bolts I left sticking up, it worked very well and sounds pretty damn good… I am contemplating a trio of 18’s in a tiny euro hatch just because I can and maybe cut the boot floor out between the chassis rails pretty much to let them breath… it would likely do 50’s at 20 I reckon if the doors didn’t fall off… the roof is all good as that’s stainless strips bonded to it also making it 4-8mm think in places

no offence intended or taken bud, it’s all good

[JasonInAugusta]

Well now we are on common ground and we’ve worked out Peter didn’t do the install you gave him credit for and would very much have done exactly what you did that’s all good!

My take on it was if you’ve ever seen thin metal that’s been welded to thick metal you will invariably see the thin metal break where it’s been ground back and then super heated by welding, it’s a common failure mode and one various cars over the years have suffered with, and also one that’s considered for good and bad reasons in engineering

no offence intended or taken bud, it’s all good

The trick to welding thick and thin materials together is to control heat exposure to the thin metal by keeping the puddle on the thicker metal and allowing just enough overlap of the puddle to fuse the two. To keep heat down you do a very small section at a time and jump around the perimeter.

It's that reason that one pass on the perimeter of the baffle would take a full day.

It was also the reason that the welds we intentionally added to be knocked down smooth were called "birdshit welds with no penetration"

Overall, it was great to have a certified welder on hand for this.





Making progress and shooting video. Working on multiple things at one time and shooting/editing two separate video projects on the car along the way.

Last thing I did today was start the process of stripping the factory interior panels for the left and right sides of the cargo area. Fun stuff.

Messy process. Fibers everywhere.

When I get the 2nd panel stripped it’ll be time to rebuild and re-upholster them.

Run the 3" Roloc to start the process of sanding into the factory carpet and, if you're lucky, you'll sand an "edge" in the carpet that will allow you to start pulling/tugging/yanking it off the backer. If not, just keep running the sander. Fibers everywhere. Wearing a mask and running air filtration for sure.

When I get these rebuilt the entire interior will get new upholstery from the window line up as well as the entire cargo area.