2015 Corvette Z06 Z07 build log - petite speaker upgrade
 

Warning, it usually takes me years to finalize a sound system. I'm going for 6 months this time but the need for finalized pictures and test results won't be met for quite some time. This will be a slow slow process.

Problem: Maximize output while minimizing distortion such that the following constraints are met:

1. no component hinders the driving experience: no speakers in direct view, no speakers reducing leg room (I mean it this time!)
2. the targa top can still be stowed in the back of the car
3. weight gain <150lbs
4. current draw < OEM alternator capacity (150 amps?)
5. car can be returned to OEM state (I mean it this time!)
6. modular construction - 80% of the weight removable for track use
7. time needed to remove/reinstall amp rack and sub rack < 5 minutes
8. stealth when parked for safety
9. sources: GPS, Bluetooth Audio, USB, MP3 CD, Radio, Aux
10. trunk and doors can be opened during rainfall
11. > 120db fullrange
12. > 130db below 100hz
13. properly delayed, band limited, and mixed rear fill
14. no audible vibration or rattle
15. <1% THD full range @100db
16. >1,000 hz at ear level for high soundstage
17. < 10db variation around target FR separate left and right 20hz-20khz


The car is a brand new 7th generation Chevrolet Corvette Z06 with the Z07 pack. I got it in December 2014 with less than 5 miles on the odo. I bought it because it's a perfect all purpose car: track car, great for audio builds, comfortable, practical. But most importantly this is one of the last uber-fast cars to come with a proper manual gearbox. I like it for its rear drive, manual transmission, and power to weight ratio. It's also stunning to look at imo. It's not the most raw experience, but I can defeat traction control, stability control, row my own gears, enjoy the open top motorsport, and listen to the rage of that 6.2L supercharged V8 unbaffled.

@ Laguna Seca
http://i6.photobucket.com/albums/y21...28db274119.jpg
http://i6.photobucket.com/albums/y21...03ddeba2b7.jpg
http://i6.photobucket.com/albums/y21...961093f470.jpg
http://i6.photobucket.com/albums/y21...31dba05b8d.jpg
http://i6.photobucket.com/albums/y21...20-%20Copy.jpg

@Thunderhill
http://i6.photobucket.com/albums/y21...u/GBMA4232.jpg
http://i6.photobucket.com/albums/y21...u/GBMA3336.jpg
http://i6.photobucket.com/albums/y21...u/GBMA4351.jpg
http://i6.photobucket.com/albums/y21...u/GBMA5937.jpg

Door layout
I'm going to dedicate the next few posts to show what I found by taking apart the door panels. I'm listing the space available for speakers and the strengths and weaknesses I see. Overall, this is the best door of all car doors I've seen! It's an utter waste to keep the OEM system as there is so much potential.

First I'm going to post a 3rd party picture of the panel from the outside. Mine is all black so it's hard to see what's going on.
http://www.corvetteblogger.com/image.../062913_17.jpg

The panel (on the driver side) is held on by two bolts at the top, two bolts at the bottom, and some push-pins. Unlike the push-pins you'd find on a Honda for example, these suckers hold on much better. The door is about to break at the time they release. No joke.

Here is another DIY to augment mine with some nice photos to boot:
HOW TO: Image Lights C7 specific - Corvette Forum

I am writing this from an audio enthusiast perspective so here it goes.

I. Gone is the manual door latch. This is great news! Mechanical door latches usually require rods which resonate easily with speaker output. This sucker is all electrical. There is the risk that the button will vibrate but I haven't seen that happen yet in this car. The one button that opens the door is popped off to reveal a screw. There is also no motor in the door! The motors are mounted onboard the car. Again one less thing that can rattle is taken out of the equation. The second benefit is that there is more room in the door and therefore we have a larger speaker box. The bigger the better.

http://i6.photobucket.com/albums/y21...126_184000.jpg

The screw behind the button:

http://i6.photobucket.com/albums/y21...126_184220.jpg

There is a triangular beauty panel that hides the second top screw here:

http://i6.photobucket.com/albums/y21...126_190354.jpg
http://i6.photobucket.com/albums/y21...126_190229.jpg
http://i6.photobucket.com/albums/y21...126_190409.jpg

2. The bottom two screws are found in the small dimples of the door. This is a welcome addition if you load the door with too much dynamat, ensolite, or the like. My last car only had clips and I had a tough time putting the door panel back on and keeping it there.

http://i6.photobucket.com/albums/y21...126_185346.jpg
http://i6.photobucket.com/albums/y21...126_185123.jpg

I used my fingers to pull the rest of the door off which was a huge challenge. I didn't want to scratch the paint or panel.

3. There is nothing to be gained by shaving the door panel. GM and Bose mounted the woofer as closely as possible to the door panel and left just enough plastic at the bottom of the door to maintain panel stiffness and seal up the front of the woofer from the inside of the door panel cavity. The sealing is important because: the midrange is mounted on the door panel! This means the space between the door panel and the door itself is the midrange enclosure. A rather bizzare arrangement that only works because the midrange is tiny and lacks any real excursion and output. The good news is that the woofer cone is unobstructed by any panel plastic piece. Crossing the door bass woofer up to 1,000 hz should be easy to do without major deflection from the door panel. The only reasons I can see GM isn't doing the same are that 1) the Bose inverted woofer design cannot reproduce midrange frequencies, 2) GM marketing sounds better with more speakers so they added that tiny midrange in the panel to up the numbers. After all the Viper has 18 speakers! 0.0

http://i6.photobucket.com/albums/y21...126_191357.jpg

Midrange mounted on the door panel folks:

http://i6.photobucket.com/albums/y21...126_191337.jpg

The net size of the opening is 9." Better make sure the surround and cone fit in that. The truncation at the top is another challenge.

http://i6.photobucket.com/albums/y21...126_191321.jpg

4. The factory door frame openings are sealed from factory. You can see this in the bottom left corner where GM is using a ruber/plastic cover that is glued on and on the top right corner where there are two small patches covering any air leaks. This is a major step forward for OEM, since it provides the woofer with a nearly leak free speaker box. It makes me want to skip adding Dynamat to the door!

http://i6.photobucket.com/albums/y21...126_192235.jpg

5. The speaker location is ideal, mounted as low and forward as possible. In fact, the whole dash is truncated to fit. Brilliant!

http://i6.photobucket.com/albums/y21...126_192226.jpg

Instead of standard foam sealing rings for the speaker to mount on, GM/Bose is using a black substance akin to a pure glue. There is clear intent here to seal any holes and provide an air tight speaker box. Every wire going through uses a grommet, and the hole above it is glued shut.

http://i6.photobucket.com/albums/y21...126_192259.jpg

6. This is the money shot. The available depth and diameter of the speaker opening are great! The window support does not span the full length of the glass, which means more depth is available, especially for small magnet speakers (NEO) and tapered speaker baskets.

http://i6.photobucket.com/albums/y21...126_192902.jpg

Measurements:
9.75 cutout
1.125" top depth (limited by door panel)
3" bottom depth to the window mechanism
4" max bottom depth to the glass (varies along glass surface by .25")
10.5" maximum speaker diameter (limited by door panel)

What fits?

It seems that many standard woofer 10" will fit, there is no need to use a shallow 10" with a trick motor. I presume Bose did because that's all they have to use across all vehicles. Their shallow woofers are also light because they use neo magnets. However, many HiFi woofers will not fit because the basket is too large, or the depth is too high.

Seas Excel 10" don't fit because the diameter of the woofer is too large and the surround does not clear the door panel
Scan Speak Revelator 10" don't fit because the speaker is too deep and cone needs room for excursion.

Top choices that I could find, in order of preference:
B&C 10NW64
Scan Speak Classic 10"
Usher 1001A
Peerless 10" XLS MAC (for a subless or 3 way system)

Here are some pics of the stock Bose woofer. Since there is literally twice the depth available, I'd say Bose did not optimize this location. They could have gotten 2 to 3 times more excursion with a deeper driver of the same type or even with a conventional driver. Oh well, at least they carved a nice door for us to work with. I am very pleased. :D

http://i6.photobucket.com/albums/y21...126_193102.jpg

http://i6.photobucket.com/albums/y21...126_193150.jpg

http://i6.photobucket.com/albums/y21...126_193050.jpg

http://i6.photobucket.com/albums/y21...126_193021.jpg

http://i6.photobucket.com/albums/y21...126_193041.jpg

http://i6.photobucket.com/albums/y21...126_200421.jpg

Test fitting door woofer

I forgot to take the Scan Classic out of the attic so I only had three candidates. The Classic is the smallest anyway. In order from largest to smallest:

Scan Speak Revelator 10"
Seas Prestige 10" (same basket, surround and motor as Excel)
B&C 10NW64


The Revelator is way too deep. I would need at least another inch of depth. If someone is willing to live without lowering the window ever they can fit them.

The Seas can be stuffed in there but it will touch everything: the back window, the back window mechanism, the door panel with the surround, the door switch with the basket. The Seas is basically the size of the opening exactly. That means the next two fit perfectly.

B&C 10NW64 fits! The magnet diameter is reasonable so it doesn't get near the window mechanism. A 1/2" spacer clears the window with 5mm to spare. The woofer and surround are sunk in the basket and the surround is double roll so it has a very flat profile. I will use speaker foam and Dynamat to raise it slightly until the foam on the basket just seals with the door card. It's also much lighter due to its NEO magnet and fits the sporty nature of the car and also its wrath with 10db of output over the hi fi drivers.

Scan Speak Classic fits! This I haven't tried but it's smaller in every way compared to the B&C. I might have to use a 1/4" spacer so that the tall surround has enough clearance. Unlike the B&C it's not likely I can get this one to seal with the door panel because the surround will touch the plastic ring on the door panel.

From left to right Seas, Scan, B&C
http://i6.photobucket.com/albums/y21...601_223559.jpg

From left to right B&C, Scan, Seas
http://i6.photobucket.com/albums/y21...601_223610.jpg

B&C basket side view. B&C is great for car doors. The cone and surround are sunk in, the surround is double roll and therefore low profile, and the basket has a rubber/foam gasket mounted on top perfect for sealing with the car door or bottom mounting.
http://i6.photobucket.com/albums/y21...601_223626.jpg

Seas basket side view. Seas is a typical HiFi driver with a tall wide soft surround. Unfortunately this is the reason it doesn't work for this car. The surround is just too wide and too tall to clear the door panel. Some Seas drivers will fit, just not the best Seas drivers.
http://i6.photobucket.com/albums/y21...601_223650.jpg

Side by side Seas and B&C. The Seas needs that extra 1/2" of depth I just don't have for comfort.
http://i6.photobucket.com/albums/y21...601_223844.jpg
http://i6.photobucket.com/albums/y21...601_223858.jpg

Side by side back view. It is also apparent the Seas has a larger basket and a larger magnet.
http://i6.photobucket.com/albums/y21...601_224131.jpg
http://i6.photobucket.com/albums/y21...601_224217.jpg
http://i6.photobucket.com/albums/y21...601_224411.jpg

Some more observations.

Here is the Bose factory driver on top of the B&C. The Bose has a super tall basket frame. 1.25" in total. That's what allows the use of a 1/2" spacer in the 'Vette with the B&C. You can also see the large mounting diameter although the outer diameter is quite small except for the 4 mounting point. Almost any 10" will fit in the door cutout but the outer diameter can hit some of the door panel things like switches and mounting points. Careful with the outer diameter but no sweat on the inner. About half the foam on the Bose compresses to meet the door panel.
http://i6.photobucket.com/albums/y21...601_225502.jpg

The door panel plastic sealing ring is 9". The ring actually fits inside the B&C gasket so it is easy to center the speaker on top of the panel to see where it would land if mounted. This is the tough part about fitting HiFi 10" as the soft rubber surrounds are usually 9.5" wide.
The B&C has a waterproof coating that ends up picking up all the dust.
http://i6.photobucket.com/albums/y21...601_225827.jpg

B&C fits with only 1/8" inch to spare around the switch and other door protrusions.
http://i6.photobucket.com/albums/y21...601_230039.jpg
http://i6.photobucket.com/albums/y21...601_230050.jpg
http://i6.photobucket.com/albums/y21...601_230055.jpg
http://i6.photobucket.com/albums/y21...601_230114.jpg


As a result the B&C will go in first. Although it's very likely I'll try the Scan Speak Classic as a Hi Fi competitor and see what I like best. Seas Excel and Scan Revelator are out of the picture as they cannot fit.

This will be the first midbass to go in whoop whoop!

http://i6.photobucket.com/albums/y21...601_230344.jpg
http://i6.photobucket.com/albums/y21...601_230352.jpg

Seas doesn't photograph as well due to shiny basket but here it is. It's a bit of a monster compared to the B&C in size. The surround was bending sitting on the door card as it won't fit through the 9" ring.
http://i6.photobucket.com/albums/y21...601_231321.jpg

Day one synopsis: I hate kerfing

I got a membership at Techshop, and got access to a table saw, router, and other good stuff. I figure I should try to keep my garage clean this time and work in a shop.

Brought all the gear and got cranking. Mostly MDF of different sizes, using old fashioned 3/4" board for the sub box and 1/2" for amp rack.

http://i6.photobucket.com/albums/y21...215_130351.jpg

The top of the box has to fit under the roof when stowed in the back which gives me only 10.5" of height in the middle and about 9" in the corners. So I decided to try my luck kerfing. Job one was to get it out of the way.

Try 1: no pic take, cracked when I tried to flex it after 5 slots were made.

Try 2: 99% bent to satisfaction and then ... cracked. This time I made huge slots and left only under 1/8th of MDF of the outer skin.

http://i6.photobucket.com/albums/y21...215_154626.jpg
http://i6.photobucket.com/albums/y21...215_162120.jpg

So I lost my time at the table saw to some other guy who insisted on working on it for many hours. I changed to making router cuts for the subwoofer box:
http://i6.photobucket.com/albums/y21...215_203103.jpg

Try 3: At about 9pm the guy who was rudely hogging the table saw all day cut his finger in the blade. The safety mechanism kicked in and dropped the motor and forced the blade to stop by breaking it. $250 later we got a new blade so I went back at it for the third try at kerfing.

http://i6.photobucket.com/albums/y21...215_230612.jpg

I have not tried to bend this one to assemble the box. I'm going to try to bend it slowly over the next week to get it to bend without breaking. I've also left more material in there because the last one had massive gaps to fill with glue which looked very unprofessional/sloppy.

Any tips on making these kerf cuts to work are deeply appreciated!

Interesting!

Why no updates? :confused:

Car got broken into :( Waiting on a new window.

If I ever end up going to jail it will be because I caught some jack hole doing something like that to my car :willy:

I know what you mean. The first time my car got broken into I was pretty chill about it. The second time not so much. I garage this car at home and at work and I pretty much never take it out except for track days, 99% garaged and already had 2 break ins. Fixing it ain't as cheap as other cars and the paint job gets it all the time from the broken glass moving on the door.

Window fixed, time to pick up where I left:

Kerfing try number 4

There was a better blade on the table saw this time, a flatter profile and fairly sharp. I left only a small amount of MDF on the edge, but not too little so that when bent it remains a very smooth curve. Here is the table saw and the MDF getting sliced up.

http://i6.photobucket.com/albums/y21...229_204252.jpg

This time around I took out material over a very large surface, the glue heavy technique but less risk of cracking.

http://i6.photobucket.com/albums/y21...229_205358.jpg

http://i6.photobucket.com/albums/y21...229_205404.jpg

http://i6.photobucket.com/albums/y21...229_205404.jpg


Then I bent it into a fairly low stress position and bolted it fixed overnight. I hope if it stays like this for 24 hours there is less chance of cracking.

http://i6.photobucket.com/albums/y21...229_224818.jpg

http://i6.photobucket.com/albums/y21...229_224848.jpg

http://i6.photobucket.com/albums/y21...229_224908.jpg

http://i6.photobucket.com/albums/y21...229_224947.jpg

As you can see from the pic below it's not ready for prime time yet. I have to push down on the top to get a more aggressive bend and lower box height.

http://i6.photobucket.com/albums/y21...229_225022.jpg

The fourth kerf is holding strong, so the project moves on!

I took out the temporary holders and laid down a heavy box of tools on top to get the box closer to the right shape. Leaving it overnight to stretch a bit seems to have worked well. I also added some tape on the sides so I can start adding glue without permanently gluing the sides of the box which are not finished yet:

http://i6.photobucket.com/albums/y21...301_191853.jpg

It worked so well I was able to force it down enough to mate with the face panels so I screwed in 6 temporary screws to hold it into shape:

http://i6.photobucket.com/albums/y21...301_200449.jpg

This is basically the bottom of the box, the side without any rounding:

http://i6.photobucket.com/albums/y21...301_200500.jpg

It's still a bit too round on the sides, the kerfed piece is about an inch too long but it does fit in the car. I'm now adding glue little by little while adding some weights on it to straighten up as much as possible where I need it to be straight:

http://i6.photobucket.com/albums/y21...302_014233.jpg

Very nice. I'm subscribed and interested in your results.

Thanks for being very detailed in your posts!

I'm applying the research criteria, which is the work has to be easy enough to understand to replicate by anyone. Glad to know it's helpful. :D

Not much to update except applying tons of tons of glue. No, really. This thing took up 52oz of Gorrilla Wood glue so far and more will go in. Looks like at least 70oz total! $45 bucks in glue alone. I don't know where it goes.

Since the first layer of glue has between 12-24 hours on it I'd say the piece is now held by glue and the chance of cracking is nearly 0%. In the clear!

Box held down by at least 60 lbs to flatten out the top of the box profile:

http://i6.photobucket.com/albums/y21...303_093854.jpg

First layer of glue after 12 hours:

http://i6.photobucket.com/albums/y21...303_093911.jpg
http://i6.photobucket.com/albums/y21...303_093918.jpg

Second layer of glue applied earlier this morning:

http://i6.photobucket.com/albums/y21...303_095144.jpg
http://i6.photobucket.com/albums/y21...303_095150.jpg


Next update the box will be trimmed, braced, sanded, and prepped for coating.

Update

Test fit the box in the car. It fits between the wheelwells with about 1/4" left on each side. GM is to thank here for allowing 42" of width in a car like this. Unlike any other car the Corvette rides on composite leafsprings which means it has no traditional springs, and the wheelwells only have to hold the shocks, which are thinner and take up less space.

http://i6.photobucket.com/albums/y21...306_105353.jpg

The corners need to be trimmed to fit the round profile. The round profile in turn is needed to clear the carbon fiber targa top when stowed in the trunk. I had to get the basic round profile of the top of the box before trimming so the order of operations is important.

http://i6.photobucket.com/albums/y21...306_123004.jpg
http://i6.photobucket.com/albums/y21...306_123009.jpg

Once marked for destruction, the corners were trimmed off:
http://i6.photobucket.com/albums/y21...306_132421.jpg

One side of the box will have 4 ten inch subwoofers firing inside the box, while the other will have 4 ten inch subwoofes firing outside the box. This is an acoustic and mechanical push-pull! But that means I have to find a solution to keep the box stuffing from pressing against the woofer cone. So one side got a grille made out of wood rods:

http://i6.photobucket.com/albums/y21...306_135350.jpg

Now that the box faces are off you'd think the kerf would hold its shape right? It has been gluing for 4 days. Not the case, it was still bending under its own weight. And look at all that glue still fresh.

http://i6.photobucket.com/albums/y21...306_125559.jpg

I decided at this point that there is no reason not to screw/glue the box together, so I went for it. Mechanical push-pull requires a very strong box in the direction the woofers act against eachother. For that reason I added 6 large wood rods the length of the box.

http://i6.photobucket.com/albums/y21...306_190108.jpg
http://i6.photobucket.com/albums/y21...306_191320.jpg

The top almost fits over the box. I have to round off the corners and hopefully that will do it.

http://i6.photobucket.com/albums/y21...306_190926.jpg

Subscribing. Thanks for all the detail. :rock:

Hi George,
Maybe I missed it, what subs are you planning to use ?

in for the win!

Craig! It's been a while. Look, I got a 'vette! :D

I will be using the Vifa NE265HS.
http://www.parts-express.com/tymphan...aker--264-1140

I special ordered 8 of them in 8 ohm with the additional heat sink as seen here. All 8 arrived with an 8 ohm coil but two don't have heatsinks. :( I guess two will be used as a fuse! Better to lose two than eight.


https://cimg9.ibsrv.net/gimg/www.cor...7729475946.jpg