Whiterabbit's 2015 Mercedes GLA 45 AMG

I was hoping to go to a local show and surprise the guys with a new car and install, but with shelter in place, that's not happening any time this year. So I may as well post up my car. It's incredibly plain, but maybe one or two of the small tricks can help to inspire others for some aspect of their car.

Anyway, on with the car! It's the first performance car I've owned, and it's pretty doggone fast!

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Just a rinky-dink 4 cylinder engine, but it makes some good power. The real eye opener was that it comes with a bunch of Benz tech that I had no idea I needed. It sticks to the road like glue, and even more now that I have Potenza RE-71R's on it. differential AWD with torque steer, a Dual-Clutch transmission that shifts ridiculously fast. The turbo lag is extreme, but still theoretically gets me from 0-60 in near 4 seconds. Which means though the 0-30 time is awful, the acceleration from 30-110 is warp-ridiculous to compensate. It's a hoot to drive! And the hatch means I can still move some small cargo, fit my kids in the back comfortably, etc.

After I put a piggyback computer on it, I was able to find a local tuner shop with a 4-wheel dyno willing to help me out

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The internet consensus is that the AWD/rear differential sap 18% of the crank HP. Assuming that is true, I'm putting about 420 HP down at the crank. I like the thought of being in the 400 club... :)

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Regardless of the power level, it's fun to drive! I drove from San Jose to San Diego two years ago and took 14 hours to do it, by taking only super-windy backroads until I hit PCH above Malibu. I was totally tense and tired when I arrived at my destination, but it was an absolute joy.

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Anyways, on to audio, the interesting part!

The install is uber-simple, and no-fluff, so you guys might find it a bit boring in design. Hopefully there's something of interest in the execution to make it neat and fun:


Source:

OEM. Besides being easy, and good enough, it also has a USB input, an ipod input, and an SD card input. So, I put all my WAV on a giant ipod, all my MP3 on an SD, and my wife's entire music collection on a USB stick. Now I have ALL my music in my car at the push of a button, and all my wife's music too! And bluetooth is still there for Pandora. So my bases are covered!


Signal processing:

Factory - I use it as a MOST adapter. That's cheaper than buying one :)
JBL MS8 - deconstructs the 8 outputs of the factory amp, cleans me up, gives me 7.1 upsampling (I'm using 5.1), and gives me a basic tune.
miniDSP HD - I am using two of these. 4 inputs, and 8 outputs. They post-process my mains, center, and sub. HD because apparently these two letters make it better, and they are cheap enough. This gives me all the processing power I could want. The rears stay processed only by MS8. It's enough.


Amps:

JL HD 600.4 and 900.5. 9 channels total cover the entire car. I have come to really like the JL technology in the HD amps, and the form factor is hard to beat. Also, I like the input terminals and locations on the amp. All in all, it's a great sounding amp with good packaging.


Speakers:

Center: Scanspeak Illuminator tweeter, Focal Be3 midrange, and tangband midbass of some flavor.
Mains: Morel Elate Ti 6.2 component set
Rear Midbass: Rainbow Reference (patched in as Mains via separate channels of the miniDSP to experiment with midbass support. Fun reading: https://www.diymobileaudio.com/threa...visited.74088/)
Surrounds in C-pillars: Fountek FR88EX 3's
Subwoofer: Phase Linear Aliante 15SI 15" flat subwoofer. I'm going to be buried with this darn subwoofer.

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Some notes of undocumented stuff:

Standard power wiring. There's an access panel in the trunk that I mounted the D-block in, no fluff.

The OEM wiring was large gauge, so I used it. I cut the factory speaker output wires behind the trunk carpet. 8 speakers, 16 wires. I then crimped on molex pins and 2 pole/4 pole headers so I can reconnect them. That maintains the factory stereo 100%. But now, I unplug them and plug in my own molex pigtails. the amp outputs go to the MS8 inputs, and the JL HD amp outputs are routed to the molex tied to the car wiring. 100% clean and the stereo takes 15 minutes to electrical de-integrate it, and restore the factory condition.

SUPER simple.

On with the build!

Amprack

Trunk looks like this under the floor:

Attachment 12647

Not my car, but it's the same. No spare! Ouch! Just a bottle of goop and a 12 volt compressor. Well, no use crying about it now. OK, so, how to use the space? First, move the goop and compressor out. That gets stored elsewhere. The rest is reintegrated since it's the stereo stuff anyways. Factory amp, and factory sub. OK! trunk gutted, easy enough. Let's start with the amp rack.

I have feeble welding skills, but it's enough to get a job done. Maybe one day I will be a farm quality welder! Here is the base:

Attachment 12648

It gets a cross beam, sheet aluminum is screwed to that to serve as amp platforms, and that leaves just enough space under the rack for a project box to hold the miniDSP. Onward!

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Now fit into the car. The whole thing is cantilevered from the seat mount bar, and floats. It's super-tight packed, and is the max for space efficiency possible. I need the space, I'm putting a 15" under here!

Attachment 12650


OK, so for some reason I have lots of pics of the miniDSP HD case, so here we go with that. I bought the raw PCB's because again, cheaper. I like cheap :) So, need to plan for the board height, and punch the face for the interface.
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Power molex. I love molex plugs. Cheap, secure, easy to crimp, and available in the right sizes needed.

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2x USB for control, DB25 for signal in and out (4 in, 8 out, = 12 RCA = 24 wires), and the 4 pin Molex for power.

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USB bulkheads wouldn't fit with converter cables, so I needed to cut the cables and solder directly to the terminals of the miniDSP. no problem:

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OK, button everything up, it's GTG

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Location us under the center amp. It sits on three standoffs. So, screw the standoffs to the chassis, insert under the amp rack. Put the amp plate in place. Screw the miniDSP chassis to the amp plate. Screw the amp plate to the amp rack. Screw the amp to the amp plate. Done. Serviceability is "OK". good enough, takes 30 minutes to pull apart. But no need to service, the whole thing was built to be reliable.

Note the rubber bumpers between the rack and amp plate. Non-welded, it's important to make sure stuff doesn't rattle. And no-welding ensures I can use a different plate in the very off chance I change amps. These things are cut 1/4" undersized so everything looks like it is floating. No universal compatibility, here.

Attachment 12661


And, done!

Speakers

This is the boring post. Everything is very plain.

Sadly, I guess I didn't take any pictures of the work on the center speaker. Oops! Well, it's straightforward. Car trim came out, traced onto hardboard. Cut the hardboard with a jigsaw, and same it until it is PERFECT. Then use that as my template.

Speaker is recessed, the tweeter was installed off center.

I made a passive network for the tweeter, 12 db/oct. the Focal Be3 rolls off naturally. Overall it makes everything sound very natural.

Attachment 12666
Attachment 12667

No, you didn't see this. Move on.

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Stock doors. Painful! They are not screwed together. They are riveted! I had to drill out 40 rivets to get the panel off. The SPEAK is rived in place with plastic rivets! I had to drill out three plastic rivets to remove the speakers! That's just crazy. Oh, and the big rivets at $1.50 each at the dealer, so that's $60 in RIVETS just to replace some speakers. Holy cow.

Obviously, the design makes it so that in the future, the 6" speaker comes out and ALL access is now done through the speaker hole. No more rivet replacing!

You wouldn't believe how ridiculous it is to clean up a drilled out rivet.

Attachment 12673

Clean inside the door, but we can do better. Couple SDS tiles, butyl rope, and button back up.

Attachment 12672

KISS rules for speaker rings. I use MDF because it is dense, dimensionally stable, and reasonably waterproof. They hold screws, both wood and machine. They are stuff, which you cannot say about the plastic material!

For extra waterproofness, I spray with filler primer then coat with my favorite automotive/not automotive paint. Chalkboard paint. This stuff rocks, it makes wood look like ABS plastic. Good enough for most automotive behind-the-scenes aesthetics!

Attachment 12678
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And there you have it. Rainbow reference in the rear doors, and Morel Elate Ti in the front doors. No muss, no fuss.
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Next, the tweeters. These are also super simple. Pop out the sails, cut as little as possible, high-temp hot glue in place, make sure they are fully supported, add my favorite molex terminals, and re-install.

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Blasphemous, but I used the passives for the front. KISS, this car, and I have tons of processing power on tap to get as close as I can to nirvana without separate control for the tweeters. I can manage. These guys get tucked up above the kickpanels, out of sight, out of mind.

Attachment 12685

Rears

For some reason, I took lots of pictures of these. Probably because of the machining involved with the mount. But other than that, this is the least fussy part of the install.

Rears are held in with rubber friction cups, and I elected to maintain that mounting system for these drivers. That meant the material had to be stronger when thin than MDF, so I used a hardwood. It all looks the same when covered with filler-primer and chalkboard paint anyways. I'll let the pictures tell the (simple) story.

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Sub box

Let's see if I can coax this into some semblance of sense. it's simple in concept, but there's lots of test fitting needed. The goal is simple: Look like the OEM box. Sort of. But that's what the inspiration is. Some bland old ABS box that has a speaker in it. That's it. THAT is true "stealth" if it could be called that. Anyways, here we go!

The walls are 2 inch thick MDF:

Attachment 12696

Following the same OEM design, with a shelf for the OEM amp, neck down the top, just big enough for a 15" subwoofer.

Attachment 12697

Attachment 12698

Minimum clearance on all sides, but still, I MUST have clearance, or else it will look like it's "flowing" into the car, which is not the OEM look we are after! We want something that looks like a roto-moulded box that is bolted in place.

Attachment 12699

Prepping the glass.

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This stuff is cool. It's like an open cell foam designed for glassing. Like an i-beam, it adds thickness without bulk, raising stiffness to a huge degree without adding weight.

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I like this stuff. It is not glass matting, so it conforms to 3D surfaces, But it is SOOOO thick. it drinks resin and bulks up huge. At the same time, it is matted enough to ensure zero pinholes. Sweet.

Attachment 12704

Make sure the box clears. 1/8"? yep, that clears!

Attachment 12706

whew! That dog will hunt!

Attachment 12707

Looks pretty? I used some standard fiberglass weave. No matting, no fancy whatever. The FIRST layer is a standard 4/6/8 oz weave. It is the best material for conforming to 3D surfaces, and leaves a finish so clean, it's used to make fancy wooden canoes and kayaks. On top of that, the bulk 14Oz glass cloth. On top of that, that foam sheeting. On that, more 14Oz cloth. On that, a final layer of standard weave. Makes it look pretty!

On top of that go the rings of course. Glassed right in.

Attachment 12705

Now build up the rest of the layers

Attachment 12708

Test fit. The subwoofer is surface mounted on one board

Attachment 12709

Second board is cut over the OD of the subwoofer so it looks flush mounted. Then put the waffle grille over the subwoofer for protection. Then, cut another layer of 3/4" MDF to sit over that. The backside of the top MDF gets rabbeted out so that the rabbet acts as a clamp, and clamps the grille onto the subwoofer. It's also cut to be a tight fit to the grille so it doesn't slide around.

Attachment 12710

Maybe it's 1/2". Can't remember :)

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Now we start adding the body filler. This will be painted, so can't have so much as a single gap to show, and ruin the look.

Attachment 12712

Finishing the sub box

Filler primer until it's an automotive quality finish

Attachment 12716

Chalkboard paint, then polish with 800 grit wet paper. The other secret to making it look like ABS. That, and using rounded corners on EVERYTHING.

Attachment 12717

Original, new.

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Only thing left is to stuff the box (it's on the small size of what I want, but works), and install!

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Obviously, waffle grilles are ugly, but if I hadn't documented the fact, you'd never know it was a $10 waffle grille after I put the grillecloth on.

Also note the false floor is upholstered on the bottom side with CCF. Not shown, but the bottom side of the subwoofer box is upholstered in CCF too. When I measured the 1/8" clearance, BOTH of these were taken into account, or else I'd be in trouble when I put it all together!

Attachment 12721

I lose 4 dB of volume with the floor down vs up. This is OK because this subwoofer can easily blow over all my speakers, so I can compensate without issue.

Two things not shown here.

#1, The grille bolts. I used, I think, 5/8-24" machine screws, 3/4" long. I used brads to stick the grille to the top of the box. Then I countersunk, drilled, and tapped the top of the box for the 4 very large bolts. I bought black chromate screws from fastenal so they colormatched. Then I used the filler primer and paint and sanded the box to perfection. THEN I use a flathead screwdriver to pry off the grille, clean up the edges, re-spray the brad holes, re-finish the box.

That way, when I screw the grille on, the sides line up perfect, right down to the thickness of the paint.

#2, the wiring. The wiring was cleaned up with cloth electrical tape. That's what Mercedes used for the OEM wiring behind the panels, so that's what I used. The ribbon of wiring across the top, today, is wrapped up in cloth electrical tape, identical to the OEM harnessing. Ditto forthe remote wire an any other wiring travelling elsewhere in the vehicle.

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Well, that's it. There are some other clever things I did but have no documentation for. A pigtail with the MS8 and 2x USB cables wrapped up in the side panel so I can tune from the drivers seat. the D-block. The piggyback ECU tied into the OEM harnessing so cleanly, no smog tech will be able to see that it is aftermarket. my cell phone holder with a wireless charger integrated so I don't need to use cable chargers in the car. Simple little "clever" things.

Anyways, I hope you enjoyed it. I've done crazier installs, I've done installs that earn more points in IASCA, but this one is simple and clean. It lets me tune in REW to my heart's content, play with FIR filters, run 2.1, 5.1, 7.1 (though the sides are midbass only, so that's stupid). Let's me play with midbass arrays. Let's me try 1-way, 2-way, 3-way center. Gives me a ton of bottom-end. Gets loud and boogies. And leaves me with a spare Be3 in case I blow the first one :)

Fun little car

To damn tired tonight to comment. But subscribed. Looking good. Rock N Roll Wabbit :).

Ge0

Are you going to do any custom steering wheel controls this time?

nice and clean,.... but most important... How does it sounds?

ah ha! I will totally build a crazy car again with all the bells and whistles I can think of, but if I do it'll be an older car where I'm "more free" to put on my creative hat and go hog wild.

How's it sound? Overall, the sound is excellent. Despite being 5.1, the car IS a 1-seat car. tuned for no-compromise in the driver's seat, so there is some right-side steering for the passenger. Inevitable.

The strategy is simple. Use the MS-8 to clean up the OEM amp to flat, and provide the basic tune. It is expected that this will properly set the time alignments too. After that, to use the miniDSP to fine tune and fix any measurement issues with the sound using a calibrated mic and REW. It also allows for experimentation with FIR which is a really neat feature. Basically, miniDSP for me is just a really fancy EQ.

The center channel is crisp and planted. It's 5.1, so lots of time was spent here aligning the response with my selected room curve. EVERYTHING follows from this, so it has to be right. The center is like a mono-car, dash level and with reasonable distance from the listening position.

The mains are tuned via miniDSP to match the center. Lots of time spent here too. The overall result is a handsome sounding car. There are fundamental design issues that can NEVER be compensated for in a build like this. The stage is never PERFECTLY distributed from far left to far right, there is still some compression between extreme sides and the center. But the DSP power I have gets me much farther than I could with a more traditional signal path setup. One surprise is the width of the car. The stage width leaves nothing to be desired.

That means the midbass array concept is a largely wasted concept. I've played with it, but it's either not needed, or I'm not tuning it right. Overall, it only muddies the waters. The truth is I have them at -15dB and they contribute basically nothing to the car. But I can turn them back on in a matter of minutes and tune again anytime I want. I have the mini DSP channels for it ready to go!

The rears are not post-tuneable. If I were going ground up, I would add another miniDSP and tune these also. However, it's really a waste of time and money to do so. The transparency to the stage is not 100% perfect since the stage has fine tuning and the rears do not. However, all I have to do is drop them 2-3 dB or so and I get the same effect. If they are not transparent, they just drop out and I get less room-effect with them. It's good enough because let's be honest, the surrounds are a fun gimmick to enjoy, not a critical part of the enjoyment.




Overall, zero complaints, and were I to go to competition, unless something has changed, I believe I'll easily be in the top 5 and possibly the top 3. I have a garage full of silver medals and 2nd place trophies, so I make no grand illusions about taking first here, we got some way, way good cars. Or at least we did 8 years ago when I was competing more regularly!

First of all nice work. Mi gusta!!!!

Now for my first round of questions:

1.) You built your own miniDSP to save a few bucks. Damn that's dedication to taking the cheap way out :). Have any more pictures of that? You fabricated your own aluminum box? I would have thought the cheap way out would be to order a cheap ABS plastic project box from Digikey :).

2.) You seriously sacrificed additional subwoofer box volume so you could mount a factory amp that you are not even using? Wow, committed to a factory look even though you have two JL Audio amps and an MS-8 floating around back there :)

3.) I'm a little confused about the fiberglass material you used for the sub woofer floor. You mentioned some really cool open cell stuff that soaks up resin. But then you also mentioned regular weaved matt. Did you use both?

4.) I really like your subwoofer design. It came out fantastic. Question about the stacked ring construction though. Does each ring require it's own sheet of MDF? I see going through a lot of material.

5.) Please take a few snap shots of the completed center channel. I'd like to see how the bezel blends in with the car.

Thanks for taking the time to post your work.

Ge0

1) it is an aluminum project box. i wanted metal for durability and grounding. A raw circuit board in a non-EMI case in an automotive environment? That screams "NOISE!" to me! It had racks on the inside so I could slide in printed circuit material inside. The original intention was to make custom boards that the DSP were soldered to on standoffs. Then I realized that it was way overkill and totally unneeded. All I needed was perf board, cut to size so they fit into the box. The DSP PCA are secured to the perf board, and the perf board slides into the project box. They are held front to back by the case covers.

I got the box at Fry's, so I guess that makes it impossible to duplicate now ;)

2) The factory amp is being used as a MOST converter. I could buy a MOST converter for $650, and get some more processing, or just use the factory amp. I chose to use the factory amp. It converts MOST to Analog, then I use the analog from there.

3) I'll try to make a post about this

4) Each ring requires its own MDF the size of the footprint used. I think the box is 22 inches wide, so I can get three layers out of a 2'x4' sheet of MDF. So, that box in total has 2 or 3 sheets of 2'x4' MDF in it. The construction is straight forward. The first layer is cut and sanded to perfection. Then the next layer is rough cut ti within 1/8", pined on with 2 pins, the cut with the flush cut or patternmaker bit. A screw driver is used to pry the pieces apart and needlenose pliers remove the pins. Same as any jig. If I don't need to take apart the stack, then I can glue and pin it right there, then buzz it smooth. Because of the contour chosen here, I elected to unpin the whole box and reconstruct it as needed. As I said before, the human hand can feel a gap of 0.001 pretty easy, and sandpaper and bodyfiller take care of the rest to get it as smooth as glass.

Bigger issue is the entire box is "end grain" of MDF which is a SERIOUS PAIN to fill for a painted finish! I've learned to use regular bodyfiller first, then followup with filler primer. First time I only used filler primer. I used alot of filler primer!

5) Car is ugly now. So be prepared for a far less impressive install :) Problem for the center channel is the grillecloth I used faded in the sun. Not good! If you have a recommendation for a fade-proof grille cloth, I am all ears. but I'll show you my car's arse, if you want to see it.




Let me grab more pics for a later post.

ugly pictures incoming :)

Here's the side hatch in the trunk
Attachment 12722

The long pigtail is plenty to have the laptop in any seat in the car. 2x USB and the cable for the MS-8 screen. Most of the time it is coiled up inside the panel. D-block is also seen, floating on some sheetmetal bolted to the unibody via machine screws.
Attachment 12723

Current trunk, taken today. The wiring has been cleaned up with fabric E-tape.
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And center channel as she sits now. I like and use dash mats, they work when tuned in place. (same with the subwoofer, trunk panel has to be down). Dash mat aesthetics are the best China could come up with.
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Unfortunately, sunbaking faded not only the black grillecloth, but also the Focal Be3 grillecloth. Only where the dash mat was open. Seen, obviously, in blue.
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Sooooooooo ... the dash mat obviously lives in place to prevent this ugly fading from being seen.

(I wonder what the speaker cones and domes would look like if I DIDN'T have grille cloth covering!) =o

Quote:

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Originally Posted by Whiterabbit

ugly pictures incoming :)

Here's the side hatch in the trunk
Attachment 12722

The long pigtail is plenty to have the laptop in any seat in the car. 2x USB and the cable for the MS-8 screen. Most of the time it is coiled up inside the panel. D-block is also seen, floating on some sheetmetal bolted to the unibody via machine screws.
Attachment 12723

Current trunk, taken today. The wiring has been cleaned up with fabric E-tape.
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And center channel as she sits now. I like and use dash mats, they work when tuned in place. (same with the subwoofer, trunk panel has to be down). Dash mat aesthetics are the best China could come up with.
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Unfortunately, sunbaking faded not only the black grillecloth, but also the Focal Be3 grillecloth. Only where the dash mat was open. Seen, obviously, in blue.
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Sooooooooo ... the dash mat obviously lives in place to prevent this ugly fading from being seen.

(I wonder what the speaker cones and domes would look like if I DIDN'T have grille cloth covering!) =o

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I have high hopes for using the wireless adapter for my Helix DSP. No cables to tune or change settings. Woo Hoo!!!

As far as the sun fading. Now that there is strange. but in a sense kind of a pretty pattern. I'd be inclined to leave it :)

Ge0

Quote:

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Originally Posted by Ge0

You built your own miniDSP to save a few bucks. Damn that's dedication to taking the cheap way out :). Have any more pictures of that? You fabricated your own aluminum box? I would have thought the cheap way out would be to order a cheap ABS plastic project box from Digikey :).

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Three more pictures of the ugly details. Ugly because rather than using a custom PCB sled to mount the DSP, I'm using perf board because it was good enough.

The project box is something like 2"x3"x5". Try to find a 4 in, 8 out signal processor on the market in that size, that can do all pass and FIR! Anyways, the box had shelves in it. Perfect for holding perf board or straight up PCB. Each board is mounted to perf strategically cut to fit exactly into the box. Additional cutouts are made to clear the cable connectors.

You can see the white wires which are cut to length, DB pin crimped on, and then soldered to the RCA connector. They sit inside the grounded enclosure, so they are "loose". Outside the box, they are twisted pair for noise rejection. The length is specific to allow the panel to be mounted and the boards slide into place. The remainder is internally organized after board installation.

The tricky part was USB soldering because of the size of the USB connector on the board. But thank God, it was still through hole, so soldering was easy enough and structure was in place not to tear components or traces off the board when stressed during install.

Overall, it works. The ugly perf board vanishes once the cap is put on, and the only thing left is an aluminum box with a proper bulkhead on it with the needed conectors, shown above.

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Quote:

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Originally Posted by Ge0

3.) I'm a little confused about the fiberglass material you used for the sub woofer floor. You mentioned some really cool open cell stuff that soaks up resin. But then you also mentioned regular weaved matt. Did you use both?

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So, let me start with a recap of what is used in 90% of cases that I see online for homemade fiberglass boxes. They are made out of 100% chopped mat cloth

https://images-fibreglast-com.s3.ama...%20ounce-2.jpg

This stuff is strong and unidirectional. But it has a couple problems that we deal with:

1. It doesn't conform to compound corners. so we cut it into strips or small squares so we can make complex shapes. Besides the extra work, that's messy!
2. It falls apart pretty much as soon as resin touches it. This leaves a mess of stray fibers everywhere. These often turn into little hypodermic needles waiting to stab you on the surface of your completed layup.
3. It is hard to impregnate, so we deal by overcompensating with resin. This results in the correct strength, but at the cost of excessive thickness and way too much weight!

Other than that, it works great and makes a strong box.

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So, the bottom of MY sub box is made up of three layers of material. Actually 4 since the bottom is upholstered in CCF as a cushion and to prevent rattling. But that's on top of the cured fiberglass panel.

So, the fiberglass panel consists of three different materials, layered. Each has a purpose.

Material 1. standard twill.
Attachment 12735
https://www.tapplastics.com/product/...ified_twill/84

This IMO is actually the best material to use for a glass box. It is easy to impregnate, takes just as much resin as needed, conforms to compound corners with ease, and has superior strength, due to having the proper ratio of glass to resin. But there are issues.

1. It pinholes like crazy.
2. Solve the pin holes by layering, and it makes finishing painful. Filling the weave takes FOREVER. worth it when you are working on a wood kayak with a piano finish. but it's not the work we want to put into something that's never seen.
3. To get the strength, we need tons of layers. That costs money, and takes time to layer up.

I use it for the exposed layers. Imagine that chopped mat cloth box above. Imagine laying over some twill cloth on top after the layups are done. The twill will stamp flat any chopped fibers sticking up and provide a fine surface. So I use it on the bottom of my box, the first layer I put down, to confirm to the trunk floor surface, and on the top layer, to give me a fine finished surface.



Material 2. Knytex X-mat
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https://www.tapplastics.com/product/...nytex_x_mat/91

This stuff is great. It is only slightly thinner than woven roving, so it provides an immense amount of bulk in a single layer. stitched to it is a very very thin layer of chopped fiber. The chopped fiber adds non-directional stability. But they made it thin enough so the chopped fibers move when flexed, so the material conforms to compound corners. But the chopped fiber is stitched in, so it doesn't make a mess.

These are my "strength" layers! They eat resin like twill, conform to compound corners, keep the chopped mat in order, and give me the bulk of woven roving. All of that in just one or two layers so I save lots of money on having to layer up! I put these just under the surface. 1-2 layers is plenty even for a 15" subwoofer.


Material 3: Coremat (I think?)
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https://www.tapplastics.com/product/...ics/coremat/93

I got it at Tap, so I think it's the same. all it does is drink up minimal resin and separate layers of proper glass fabric by 2mm while still bonding them together. Imagine the strength of thin cardboard vs the strength of foamcore board. The coremat is like the foamcore. I put one layer in my layup.

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Overall, I had planned the following layup for my subbox:

twill
x-mat
x-mat
coremat
x-mat
coremat
x-mat
x-mat
twill

But after three layers, it was so clear that this layup was SO RIDICULOUSLY OVERKILL I abandoned that. I made my box:

twill
x-mat
x-mat
coremat
x-mat
twill

And it will survive the nuclear holocaust. The strength is ridiculous, and because there is no wasted resin in the panel, it's light. I save the weight for the 2" thick MDF walls :)

Quote:

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Originally Posted by Whiterabbit

So, let me start with a recap of what is used in 90% of cases that I see online for homemade fiberglass boxes. They are made out of 100% chopped mat cloth

https://images-fibreglast-com.s3.ama...%20ounce-2.jpg

This stuff is strong and unidirectional. But it has a couple problems that we deal with:

1. It doesn't conform to compound corners. so we cut it into strips or small squares so we can make complex shapes. Besides the extra work, that's messy!
2. It falls apart pretty much as soon as resin touches it. This leaves a mess of stray fibers everywhere. These often turn into little hypodermic needles waiting to stab you on the surface of your completed layup.
3. It is hard to impregnate, so we deal by overcompensating with resin. This results in the correct strength, but at the cost of excessive thickness and way too much weight!

Other than that, it works great and makes a strong box.

--------------------------------

So, the bottom of MY sub box is made up of three layers of material. Actually 4 since the bottom is upholstered in CCF as a cushion and to prevent rattling. But that's on top of the cured fiberglass panel.

So, the fiberglass panel consists of three different materials, layered. Each has a purpose.

Material 1. standard twill.
Attachment 12735
https://www.tapplastics.com/product/...ified_twill/84

This IMO is actually the best material to use for a glass box. It is easy to impregnate, takes just as much resin as needed, conforms to compound corners with ease, and has superior strength, due to having the proper ratio of glass to resin. But there are issues.

1. It pinholes like crazy.
2. Solve the pin holes by layering, and it makes finishing painful. Filling the weave takes FOREVER. worth it when you are working on a wood kayak with a piano finish. but it's not the work we want to put into something that's never seen.
3. To get the strength, we need tons of layers. That costs money, and takes time to layer up.

I use it for the exposed layers. Imagine that chopped mat cloth box above. Imagine laying over some twill cloth on top after the layups are done. The twill will stamp flat any chopped fibers sticking up and provide a fine surface. So I use it on the bottom of my box, the first layer I put down, to confirm to the trunk floor surface, and on the top layer, to give me a fine finished surface.



Material 2. Knytex X-mat
Attachment 12734
https://www.tapplastics.com/product/...nytex_x_mat/91

This stuff is great. It is only slightly thinner than woven roving, so it provides an immense amount of bulk in a single layer. stitched to it is a very very thin layer of chopped fiber. The chopped fiber adds non-directional stability. But they made it thin enough so the chopped fibers move when flexed, so the material conforms to compound corners. But the chopped fiber is stitched in, so it doesn't make a mess.

These are my "strength" layers! They eat resin like twill, conform to compound corners, keep the chopped mat in order, and give me the bulk of woven roving. All of that in just one or two layers so I save lots of money on having to layer up! I put these just under the surface. 1-2 layers is plenty even for a 15" subwoofer.


Material 3: Coremat (I think?)
Attachment 12736
https://www.tapplastics.com/product/...ics/coremat/93

I got it at Tap, so I think it's the same. all it does is drink up minimal resin and separate layers of proper glass fabric by 2mm while still bonding them together. Imagine the strength of thin cardboard vs the strength of foamcore board. The coremat is like the foamcore. I put one layer in my layup.

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Overall, I had planned the following layup for my subbox:

twill
x-mat
x-mat
coremat
x-mat
coremat
x-mat
x-mat
twill

But after three layers, it was so clear that this layup was SO RIDICULOUSLY OVERKILL I abandoned that. I made my box:

twill
x-mat
x-mat
coremat
x-mat
twill

And it will survive the nuclear holocaust. The strength is ridiculous, and because there is no wasted resin in the panel, it's light. I save the weight for the 2" thick MDF walls :)

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neat thanks

Quote:

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Originally Posted by Whiterabbit

Three more pictures of the ugly details. Ugly because rather than using a custom PCB sled to mount the DSP, I'm using perf board because it was good enough.

The project box is something like 2"x3"x5". Try to find a 4 in, 8 out signal processor on the market in that size, that can do all pass and FIR! Anyways, the box had shelves in it. Perfect for holding perf board or straight up PCB. Each board is mounted to perf strategically cut to fit exactly into the box. Additional cutouts are made to clear the cable connectors.

You can see the white wires which are cut to length, DB pin crimped on, and then soldered to the RCA connector. They sit inside the grounded enclosure, so they are "loose". Outside the box, they are twisted pair for noise rejection. The length is specific to allow the panel to be mounted and the boards slide into place. The remainder is internally organized after board installation.

The tricky part was USB soldering because of the size of the USB connector on the board. But thank God, it was still through hole, so soldering was easy enough and structure was in place not to tear components or traces off the board when stressed during install.

Overall, it works. The ugly perf board vanishes once the cap is put on, and the only thing left is an aluminum box with a proper bulkhead on it with the needed conectors, shown above.

Attachment 12729
Attachment 12728
Attachment 12730

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So your housing is an aluminum extrusion with end caps. I've designed many products this way.

Ge0

yeah. I got it at frys, but they are pretty ubiquitous.

https://www.zoro.com/box-enclosures-...si/i/G1125144/

This install is fascinating and encouraging! I love how you straight up did it YOUR way and enjoyed the process and results! Great stuff!!!

Oh golly, I have always done things my way, and my IASCA scores for install showed it. A little creativity and practice yield lots of capability. I'm also lucky to have been around for the Maker Movement before it blew up and became this weird corporate burning man thing. When it was starting, it was just a collection of tinkers showing off their home projects on folding tables in a warehouse. Lots of free flowing ideas from amateurs.

This car is a shadow of wild ideas executed in the past. Last car had a 4x12 processor in the form of two DCX2496's converted to 12V operation. fed by a DEQ2496 with digital EQ, compression/expansion, 100 db/oct filters for feedback control (but were amazing notch filters), etc. I ran a Nakamichi CD player who's design was based on all the faceplate buttons being on a resistor ladder. So I installed no less than 15 buttons in my steering wheel and ran them through the same clockspring wire as the existing steering wheel controls and hacked the Nak unit so I could control 100% of the CD player (21 buttons or so) from the steering wheel. I could go on for days about the alarm.

This car I keep simple, mostly because it's an AMG :) TOO fancy in the aftermarket messes up the flow of the car. And at the end of the day, the flow of the car is what it's all about!

Quote:

---

Originally Posted by Whiterabbit

But after three layers, it was so clear that this layup was SO RIDICULOUSLY OVERKILL I abandoned that. I made my box:

twill
x-mat
x-mat
coremat
x-mat
twill

And it will survive the nuclear holocaust. The strength is ridiculous, and because there is no wasted resin in the panel, it's light. I save the weight for the 2" thick MDF walls :)

---

So you made a composite ... composite? Very cool, I like how you chose the best material for each sub-job.

Ends up cheap too because its just a yard of each.

most important is zero post-layup sanding. Zero. Been there, done that, destroyed the t-shirt.

Quote:

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Originally Posted by Whiterabbit

Ends up cheap too because its just a yard of each.

most important is zero post-layup sanding. Zero. Been there, done that, destroyed the t-shirt.

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So let's talk Resin. I'm thinking about glassing a sub box for my Porsche install. However, was also considering switching over to Epoxy resin vs. Polyester due to the reduction in dangerous out-gasing. Do you have an opinion one way or another?

Ge0

No opinion from me. Use what floats your boat. We aren't using these resins for their unique properties, and all are strong enough. We're not making surfboards that take a UV beating, or protecting fine woodworking and need a clear color, and 99% of us are not using the right glass-to-resin ratio for optimum strength, so we don't even need to consider strength since we're using the Russian principle of 'overbuild it' anyways.

I think the next box I glass might not even use fiberglass cloth, just a slurry of cheap resin, chopped fibers, and cab-o-sil. Then just paint it on. How bad could it turn out?

:)

Quote:

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Originally Posted by Whiterabbit

No opinion from me. Use what floats your boat. We aren't using these resins for their unique properties, and all are strong enough. We're not making surfboards that take a UV beating, or protecting fine woodworking and need a clear color, and 99% of us are not using the right glass-to-resin ratio for optimum strength, so we don't even need to consider strength since we're using the Russian principle of 'overbuild it' anyways.

I think the next box I glass might not even use fiberglass cloth, just a slurry of cheap resin, chopped fibers, and cab-o-sil. Then just paint it on. How bad could it turn out?

:)

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I won't have a lot of space to build up numerous layers. So, the layers that I do lay down must be solid. I watched a few of the TAP Plastics tutorial videos. Between that and your write-up I think I have an idea. Iit will be a tight squeeze but I think I can make it work. Worse case, I go back to my baffle.

Ge0

Easy. You can get away with < 1/4" I am sure. 1/4 is overkill when you do it right.

Use standard woven fabric, and try to get the 70%/30% glass-to-resin ratio for max strength. You don't have to weigh anything, just squeegee it untill you barely (but completely) wet the cloth. That will give you maximum strength with no waste. if you see resin pooling anywhere, it's wasted material, doesn't help strength, and just weighs you down. 70/30 is essentially glass fibers close-packed with resin in between and no

If you do it this way, you have to do the whole layup in one shot or you're done, so you have to make sure your glass is all cut and ready for layup. Not sure how many layers will do it, my guess is 5-7 depending on what thickness fabric you choose. You'll want a middleweight so you can layerup for your thin overall thickness. Maybe 6 or 8 ounce?

The resins I like for this are the kind without a wax for surface cure, and SLOW cure with long pot time, to ease your layups. I prefer not to add thinners, that's just an opinion. I still don't worry about epoxy vs polyester. If you want it to be maximum pretty, you pick medium cure epoxy or surfboard resin. Both cure clear, unlike the resin I picked which cures baby-shit brown.

Nice work, I applaud your skills!

For your next all-out older car, do you have a vehicle in mind? I've always been fascinated by the thought gutting a vehicle to use solely as a car audio platform.

I've been dreaming or a rear or mid-engine car. VW bug up to Porche-anything. Karmann Ghia. I think it would be so neat to put the subwoofer under the hood in a really fancy 6th order band-pass box, with the port "ported" into the cabin. Ditto for midbass placement, utilizing space far, far forward, with unlimited space for backwave management.

It'll never happen. But a guy can let his imagination fly high.

Quote:

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Originally Posted by Whiterabbit

Ends up cheap too because its just a yard of each.

most important is zero post-layup sanding. Zero. Been there, done that, destroyed the t-shirt.

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I am curious about actual price comparison. I did the math..well maybe...im actually trash at math but if im right. The Knytex is .75oz for around $0.68 a square foot. I can get 1.5oz chopped strand from a local boat repair shop for around $0.72 per square foot. So basically the same price but my local stuff is twice as thick...and your way is actually more expensive per SqFt when you start factoring in excessive shipping cost.

For something like a 100% FG sub enclosure where you need 5-8 layers of chopped mat to get the desired 1/4" thickness, do you think that Knytex/coremat/twill would end up being cheaper even with the Knytex being half as thick as mat? Would total resin consumption of knytex/coremat vs mat offset the costs towards your way?

There is much more to glass than thickness, but you knew that already.

Chopped matting has some key advantages. The primary advantage being the non-directionality of the fibers. This provides superior pinhole resistance, unlike a weave which can pinhole with the fibers get spread in an area, compromising the box seal.

There are two very key disadvantages to chopped matting. First is it cannot conform to compound corners. If I wanted a flat panel, I'd just use MDF anyways. We work around this by cutting strips or squares, and in extreme cases using loose fibers to make a slurry. Second, it DRINKS resin and fibers separate. This makes it super-easy to get a target panel thickness with a minimum of material, but super-hard to do it with the strongest glass-to-resin ratio. Weave or roving doesn't puff up, so you need more fiber to get it thick. But the strength is higher because all your strength of course comes from glass, not from resin. So matting is a false economy.

Beyond that, matting is a nightmare to finish. I remember many a discussion on CAF, ECA, and DIYMA about the best body fillers to use, the best techniques to pre-grind the box, obtain a smooth surface for filling, etc. What a nightmare! Doubly so when the matted fibers start poking up during the layup, creating a surface layer that looks like pinhead form hellraiser, and just as unpleasant to handle. That's fixable my making the surface layer a cloth mat, but it's going ot be bumpy because the under layers are a hodgepodge of matting squares. You'll probably find you don't even need to add resin to the surface cloth layer, it'll soak in from underneath because there is so much extra unused resin pooled into the matting.

------------

None of this was your question. Your real question, was is it cheaper? my guess is from a materials perspective, no. However, I used ZERO body filler on my box, and would have needed zero bodyfiller even if I had exposed fiberglass in compound corners on the top side. Good bodyfiller is expensive, so we're getting closer to parity.

Factor in labor hours, even though it's a labor of love, and it's not even close. I did the whole thing in ONE layup, and I was done after that. No building up layers, no sanding, grinding, filling the weave, fussing over this or that. It was: make the layup, press the base wood rings into the layup, ensure the wood is soaking up enough resin to adhere, and let cure. Pop out and done. No followup, no "milkshake", no fuss. Just filler-primer and paint.


I am blessed to have several TAP plastics close to me, so I don't pay shipping, only sales tax which in California is about 75-90% depending on your county and city.
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NOW, the elaborate material stackup was just for fun on my part. I could have easily bought a few yards of 8 ounce woven cloth and used only that material to build up my layers to get the desired thickness and off I go. I would have ended up with the same result. But it was more fun to experiment with novel materials, because this layup was frankly so easy. small compound corners, a relatively flat surface. It makes it easier to experiment with materials so I have the working familiarity with them should I want to do something more advanced in the future, tight compound corners, vertical surfaces, etc. So it was fun.

But you WILL NOT make a panel as strong as mine using only chopped matting, unless you make your panel thicker, heavier, and uglier. But yeah, it'll probably cheaper before you start using bodyfiller.

That's definitely a fair assessment. I did some google searching last night about using coremat. From what i could gather from old diyma, and 12 volt forums. It was that Coremat really wasn't a great idea for enclosures. I never found an actual reason but the guys who were "glassing pros" all unanimously said don't use it.

I also did some YouTube searches of coremat and it looks like it may be a little bit tricky to actually use on anything that wasn't a fairly easy curve.

What i did find was that most people recommended using a base of 2 layers of mat for a solid mould, then knytex then mat(to absorb extra resin from knytex) then Knytex and repeat until you get desired strength.

Coremat will not easily conform to compound corners. Most of those "pros" are likely glassing corners far tighter than the compounds I'm dealing with in the photos above. The panel I made is highschool-level glassing, which is why I can get away with using it. Those pros are likely tackling top-tier difficulty projects, which is why most of them end up looking like kindergarden-grade on the inside and need so much followup to clean up the structural mess.

No matter what the stack, there can't be any air bubbles for peak strength! We're not making airplanes here and can tolerate some bubbles, but big gaps are definitely a waste. That's likely where those guys are coming from.

I still prefer to add a layer of twill on top and bottom even if the next layers are knytex. Maybe it's aesthetic overkill but it is just so much easier to get a nice surface with a standard cloth, then put the thick stuff in the middle. The knytex has a thin layer of matting (thin enough to conform to compound corners), and I've been stabbed by needles of stray matting enough in my life. I want that stuff LOCKED up deep inside any layup I ever do. Ever.