# 2015 Corvette Z06 Z07 build log - petite speaker upgrade



## cvjoint (Mar 10, 2006)

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


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## Lycancatt (Apr 11, 2010)

looking forward to this one.


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## JoshHefnerX (Jun 13, 2008)

I'm in for this. The new vettes are completely awesome. How about some pics of the interior as it sits? How does the targa top fit in there now?

Josh


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## cvjoint (Mar 10, 2006)

The plan is to go though the build slowly and post everything. I generally strip the car down slowly and measure up the crevices to see what design works better. I'm a big fan of getting a lot of speaker surface area to lower distortion and get realistic output. 

I've taken down the doors and will post all the photos and measurements. Part of the reason I bought this car was the OEM 10" speaker hole in the door. Quite impressive. 

The targa is a one piece carbon fiber roof. it has 4 mounting points in the trunk. I plan to use all the space under the targa to fit the sub so I don't have to modify the frame itself or mounting points.


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## thehatedguy (May 4, 2007)

As I look at grad schools and programs...going for Economics is looking more attractive lol.

Which AMTs are you thinking about going with?


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## Niebur3 (Jul 11, 2008)

Love the car. Have you heard about the new Mid-Engine ZR1 coming out late next year?

C8 Chevrolet Corvette Exclusive! What to Expect from the Heart-stopping Mid-Engined Zora! – Feature – Car and Driver


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## trojan fan (Nov 4, 2007)

Check this car out! A lot more car for $150k than the Mid-Engine ZR1 

Do a google search for more details


Acura | NSX Future Vehicles | Acura.com


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## Niebur3 (Jul 11, 2008)

trojan fan said:


> Check this car out! A lot more car for $150k than the Mid-Engine ZR1
> 
> Do a google search for more details
> 
> ...


I drive an Acura. I am well aware of the awesome NSX coming out. FWIW, the new Corvette is rumored to have 700+ HP and it is cool to me that they are finally doing a mid-engine vette. The Acura is awesome also, but will be around the same price with less HP (550ish). It will be interesting to see the differences between the 2. If GM "practiced" on the new Z/28, the ZR1 should be a spectacular track car. But don't count out the Acura besting it.


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## trojan fan (Nov 4, 2007)

GM hit a home run with the Camaro. Ford has been trying to catch up but falling short



Here's the ultimate road machine P1 GTR McLaren P1 - Wikipedia, the free encyclopedia


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## nadams5755 (Jun 8, 2012)

taken a look at this thread yet? clever solution to big prosound mids. http://www.diymobileaudio.com/forum...llery/172958-mikes-pro-audio-passat-2-0t.html

i kept an eye on the golf forums for totaled cars to buy spare interior parts (kick panels, center console, etc). that way i can easily return to stock


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## few35t (Dec 10, 2014)

subb'd


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## Huckleberry Sound (Jan 17, 2009)

Niebur3 said:


> Love the car. Have you heard about the new Mid-Engine ZR1 coming out late next year?
> 
> C8 Chevrolet Corvette Exclusive! What to Expect from the Heart-stopping Mid-Engined Zora! – Feature – Car and Driver


IF they follow through. The car will have an european flair about it.
Now we are talking!


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## BuickGN (May 29, 2009)

I can't help with the audio but I would love to race it in a couple
months since I think you're right over the hill from me. Nice car.


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## SkizeR (Apr 19, 2011)

BuickGN said:


> I can't help with the audio but I would love to race it in a couple
> months since I think you're right over the hill from me. Nice car.


Ahh look who's back


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## Lycancatt (Apr 11, 2010)

I've got a friend with a syclone in la who'd come join that party..be good to stack the two turbo v6s up for a race.


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## Niebur3 (Jul 11, 2008)

BuickGN said:


> I can't help with the audio but I would love to race it in a couple
> months since I think you're right over the hill from me. Nice car.


He's Back!!!! We missed you!!!!!


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## cvjoint (Mar 10, 2006)

nadams5755 said:


> taken a look at this thread yet? clever solution to big prosound mids. http://www.diymobileaudio.com/forum...llery/172958-mikes-pro-audio-passat-2-0t.html
> 
> 
> 
> i kept an eye on the golf forums for totaled cars to buy spare interior parts (kick panels, center console, etc). that way i can easily return to stock


Oh man, that's a great build. I'll sit down and digest it sometime. It reminds me of the golden days when I had months to burn on audio projects and fiberglassed entire door panels to fit 10"s. 

I can tell you guys that this will be exciting. Here is what I have in store.
1. A pair of 4 ohm B&C pro audio 10NW64. Rated at 300W continuous RMS, fed 350W from a pair of bridged ARC Audio channels. 
http://www.parts-express.com/bc-10nw64-10-neodymium-woofer--294-679
vs. the Hi Fi challenger
2. Scan Speak Classic 25W/8565-00 8 ohm with that sexy SD1 motor but only 100W RMS rated, fed 180W continous off the same ARC amp.
https://www.madisoundspeakerstore.com/approx-10-woofers/scanspeak-classic-25w/8565-00-10-woofer/

Will the most Hi Fi oriented Pro Audio driver usurp one of the all time greatest Scan Speak woofers? Is that little more HiFi spice worth losing 12db of output? Will the Scandinavian drivers cope with my heavy knob turning? Non-considerate testing will decide! 



Lycancatt said:


> I've got a friend with a syclone in la who'd come join that party..be good to stack the two turbo v6s up for a race.


I do advanced group with many HPDE clubs in North Cal. Sonoma, Laguna Seca, or Thunderhill. I can take on almost anyone for a couple of laps and then I cook eggs on the hood. 



thehatedguy said:


> As I look at grad schools and programs...going for Economics is looking more attractive lol.
> 
> Which AMTs are you thinking about going with?


Check these bad boys out:
Aurum Cantus AST25120 Aero Striction Tweeter 8 Ohm

Two per side will give me 101db @ 1 watt with 350w available and 200w power handling. They are less than an inch deep and already have rear wave treatment. The crossover point can be as low as 1,000 hz. The 'Vette pillars are wide, long, but shallow. Perfect spot to stack them. 



Niebur3 said:


> Love the car. Have you heard about the new Mid-Engine ZR1 coming out late next year?
> 
> C8 Chevrolet Corvette Exclusive! What to Expect from the Heart-stopping Mid-Engined Zora! – Feature – Car and Driver


If the rags were reliable my car would have a 5.5L V8 like they expected before seeing the car. C&D released an article lately with max operating temperatures of the Z06. I proved most of them are incorrect just by tracking the car. I think they just make stuff up nowadays to sell a magazine. It's a waste of time to follow their speculation, don't get teased!


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## cvjoint (Mar 10, 2006)

trojan fan said:


> Check this car out! A lot more car for $150k than the Mid-Engine ZR1
> 
> Do a google search for more details
> 
> ...


Honestly, I'd take my old S2000 back before I ever drive that. I don't take too kindly to automatic boxes, hybrid engines, 4wd, or turbo engines. I would cave and drive a (turbo) boosted car if the turbine is electric driven, or mounted in the vee of the engine. Maybe a heavily rear biased 4wd would work too, but you couldn't pay me to drive floppy paddles.


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## Niebur3 (Jul 11, 2008)

Me and the wife have toyed around with the idea of getting a S2000. Love those cars.


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## thehatedguy (May 4, 2007)

You have a hookup for PE?


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## Coppertone (Oct 4, 2011)

BuickGN said:


> I can't help with the audio but I would love to race it in a couple
> months since I think you're right over the hill from me. Nice car.


Hey, welcome back....


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## nadams5755 (Jun 8, 2012)

cvjoint said:


> Oh man, that's a great build. I'll sit down and digest it sometime. It reminds me of the golden days when I had months to burn on audio projects and fiberglassed entire door panels to fit 10"s.


tuning an enclosure for the fs seems like a clever approach to low-end extension, without impacting anything but build complexity. however, if you can get a backup pair of door panels, why not?


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## JayinMI (Oct 18, 2008)

Supposed to have one of these coming in tomorrow. Is yours the 10 speaker audio system? When I was Googling the C7 Corvette Audio System that's all I could find info on, and I thought there was a system w/o the sub. 
My Salesman says that the area where the sub enclosure fits might be different (or non-existant) on ones without.

Jay


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## BuickGN (May 29, 2009)

cvjoint said:


> Honestly, I'd take my old S2000 back before I ever drive that. I don't take too kindly to automatic boxes, hybrid engines, 4wd, or turbo engines. I would cave and drive a (turbo) boosted car if the turbine is electric driven, or mounted in the vee of the engine. Maybe a heavily rear biased 4wd would work too, but you couldn't pay me to drive floppy paddles.


Why would you require an electrically driven compressor (turbine is the exhaust side)? Why in the Vee of the engine? Turbos have pretty much made superchargers obsolete except for cost. Less parasitic drag meaning better power and mpg, lower charge air temps for a given pressure, full boost and torque under 2,000rpm for any decently designed system, more (variable) volume to keep boost pressure constant despite mods or altitude, fully electronically configurable power band if you're not into heaps of torque below 2,000rpm. What's not to like? If you're worried about lag, you haven't driven a properly setup system. My little 6 cylinder made 620lbs of torque to the wheels at 2,800rpm and it probably would have made it down lower but that's what the converter flashes at. Modern turbo tech is s wonderful thing.


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## few35t (Dec 10, 2014)

My old S2000 changed my life.

I'll definitely be in the market for another one day. My even do a simple 2 way active setup and throw a bm mkiv in the spare tire well. =D

This will be a good thread to follow as I may take some inspiration from this build to keep my future s2k trackable and still sounding good.


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## rton20s (Feb 14, 2011)

cvjoint said:


> 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
> ...


I'm definitely in for this one! I'll also believe #1 and #5 when I see it. 




BuickGN said:


> I can't help with the audio but I would love to race it in a couple
> months since I think you're right over the hill from me. Nice car.


Who? 

Good to have you back.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> You have a hookup for PE?


Sending you a PM now. 



nadams5755 said:


> tuning an enclosure for the fs seems like a clever approach to low-end extension, without impacting anything but build complexity. however, if you can get a backup pair of door panels, why not?


No such thing as a free lunch, even in audio. I can think of a few tradeoffs, port noise, time domain response, and robustness (needs exact filters, exact dimensions, exact design). I've always tried to do infinite baffle. When that wasn't possible I did a sealed setup. To me a port design was never worth the tradeoff. I do think it's clever and I enjoy hearing other people's port designs. 



JayinMI said:


> Supposed to have one of these coming in tomorrow. Is yours the 10 speaker audio system? When I was Googling the C7 Corvette Audio System that's all I could find info on, and I thought there was a system w/o the sub.
> My Salesman says that the area where the sub enclosure fits might be different (or non-existant) on ones without.
> 
> Jay


Mine is the 9 speaker. Same as the 10 except there is no subwoofer. Instead of a sub enclosure I just have a cover panel near the rear hatch latch. Here is what you get as a sub:


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## bassfromspace (Jun 28, 2016)

What do you expect the B&C do that the previous Peerless midbass didn't?


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## cvjoint (Mar 10, 2006)

bassfromspace said:


> What do you expect the B&C do that the previous Peerless midbass didn't?


Do you mean the SLS 6.5" that I used in the S2000? It is true some other folks have used it in Corvettes, patching up the larger 10" hole. 

First, the SLS 6.5" has a 18 db output disadvantage compared to the B&C 10. That's like the distance between the earth and the moon. Secondly, the SLS is built to displace air morso that reproduce midrange. There is a massive, and in my opinion insurmountable resonance midband 700hz IIRC. With steep filters you can get away with a 500hz LP but I need a 1000hz LP at the least. 

The SLS 10" doesn't fit. Too deep.


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## BuickGN (May 29, 2009)

Niebur3 said:


> He's Back!!!! We missed you!!!!!


I missed all of you guys too. I'll be contacting you for some amps. Probably going AB on the front stage this time. The silence while driving has been killing me these past several months. Back to the impending Mayweather fight.


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## bassfromspace (Jun 28, 2016)

cvjoint said:


> Do you mean the SLS 6.5" that I used in the S2000? It is true some other folks have used it in Corvettes, patching up the larger 10" hole.
> 
> First, the SLS 6.5" has a 18 db output disadvantage compared to the B&C 10. That's like the distance between the earth and the moon. Secondly, the SLS is built to displace air morso that reproduce midrange. There is a massive, and in my opinion insurmountable resonance midband 700hz IIRC. With steep filters you can get away with a 500hz LP but I need a 1000hz LP at the least.
> 
> The SLS 10" doesn't fit. Too deep.


I was referring to the shallow, motor-above-cone 10" Peerless.


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## t3sn4f2 (Jan 3, 2007)

bassfromspace said:


> I was referring to the shallow, motor-above-cone 10" Peerless.


Can't play high enough I imagine.


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## BuickGN (May 29, 2009)

I know Dynaudio isn't your favorite brand but what about the MW182? 3" deep, the cone area of a 9", 18mm p-p linear travel, 1" p-p travel, but most importantly, it works well as a midbass/midrange, at least until beaming becomes a problem. I've run mine as a 2-way, no subs, just the 182s and tweeters with a 35hz subsonic so I could push them with the full 300w each and a 1.8khz LP. Bass is good. They don't come close to taking the place of a real subwoofer but they will most definitely hold their own compared to most factory subwoofer setups. 

Efficiency isn't up to your standards but they're average compared to other car audio midbass drivers. I prefer the efficient route myself but these will handle a ton of power and they do have good dynamics for a non pro audio style midbass, given the power is there. I believe the Fs is around 40hz, I'm not sure if that will be a problem for you but I assume not, if it's being used as a midbass. I've had mine out past their 26mm rating by a good margin and they never sounded strained, so they should displace more than enough air for midbass duty.


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## cvjoint (Mar 10, 2006)

bassfromspace said:


> I was referring to the shallow, motor-above-cone 10" Peerless.


Motor wise it's about as good as the SLS 6.5", there's just more surface area for greater output. Both Peerless drivers are good for midbass only. With the MAC I suppose you also have to worry about deflection off the motor for upper frequencies. It would be a great choice if I decided to do a 3 way.


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## cvjoint (Mar 10, 2006)

*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.









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. 










The screw behind the button:










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


























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. 


















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.


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## cvjoint (Mar 10, 2006)

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










Midrange mounted on the door panel folks:










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. 










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! 










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










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. 










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.










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.
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)


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## cvjoint (Mar 10, 2006)

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.


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## etroze (Dec 24, 2013)

Sub'd


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## Tnutt19 (Dec 22, 2010)

What about a pair of Illusion audio C10s up front in the doors. Would be tons of upfront bass!


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## cvjoint (Mar 10, 2006)

Tnutt19 said:


> What about a pair of Illusion audio C10s up front in the doors. Would be tons of upfront bass!


The diameter is a a little too large at 271mm. That Bose is really a 250mm driver. With luck you can get about 10mm more before touching the door panel but that's about it. Depth wise it will fit. 

I need something that is low distortion up to 1,000 hz. Otherwise, I will need a midrange which requires a large speaker box somewhere, more processor channels, more amplification etc. If you pick a dinky midrange like the OEM one then it will be the weakest link in the system. 

The C10s compared to an average 10" woofer don't have that much more output. Let's say 1.5db corresponding to moving 50% more air. That's still not enough to move the crossover point lower. Rememeber that my goal is to reach 120db fullrange, and 130db under 100hz. No 10" pair will reach 130db under 100hz. This will be sub duty. 

To be honest I'm not pushing very hard for bass up front. With push-pull and high quality drivers in the subwoofer you can't really localize it.


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## rton20s (Feb 14, 2011)

Tnutt19 said:


> What about a pair of Illusion audio C10s up front in the doors. Would be tons of upfront bass!


I'm a fan of Illusion (you can check my sig), but I don't think a pair of C10s in the doors is what George had in mind in terms of budget or design goals. 

Just from a quick spec a F/R graph spec (not to mention price) I would probably go with the ScanSpeak Discovery 26W/4534G if it fits. But George knows far better than me how to determine which of the drivers he listed best fits his needs.

Edit: Bah! George responded quicker, and much more thoroughly than I could have.


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## papasin (Jan 24, 2011)

Looking forward to hearing it the next time George!


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## cvjoint (Mar 10, 2006)

papasin said:


> Looking forward to hearing it the next time George!


It will be many seasons until this one will fire. I special ordered some subwoofers months ago and no real ETA. 

Someone was kind enough to PM me some useful links to get Corvette mounting baffles made. Maybe I'll start throwing in our midbass candidates in one by one and testing them on the OEM amplifier. Maybe I should check the impedance on those door woofers first. Erin found some that were 0.5 ohm lol.


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## fish (Jun 30, 2007)

I've been looking forward to this one! Those 17 goals you have are some high expectations, but going off of your previous builds I don't see why you couldn't achieve them. 

Those AC AS tweets look like the real deal! It's still a goal of mine to get one of those AC models in my vehicle at some point.

Did B&C change the T/S parameters on that woofer? When I was looking at those for my doors some years back I don't recall the Qts being .2something. Are you concerned at all about such a low Q driver being mounted IB? Which brings me to the question where do you plan on high-passing the B&C? Closer to the tune of 80-100hz?

Oh, & nice ride!


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## Niebur3 (Jul 11, 2008)

Dynaudio MW182 would be a perfect fit!


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## cvjoint (Mar 10, 2006)

fish said:


> I've been looking forward to this one! Those 17 goals you have are some high expectations, but going off of your previous builds I don't see why you couldn't achieve them.
> 
> Those AC AS tweets look like the real deal! It's still a goal of mine to get one of those AC models in my vehicle at some point.
> 
> ...


I've never really worried about too low of a Q. High Q is a bit nasty, with a bump in response and resonance. Low Q is really only low in IB and less than 1 watt. In reality the door adds a bit of air supspension and the Q rises quickly with the nonlinearities of the speaker motor and suspension. It doesn't take much wattage to get a stiff suspension like the B&C's to reach .56 Q. 

I'm going to try 63hz to 100hz. I think 100hz is ideal for high output and to sidestep the resonance ( 2xFS rule of thumb). I'm not sure the door can take lower crossover points, this one I'll have to play by ear.


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## Tnutt19 (Dec 22, 2010)

rton20s said:


> I'm a fan of Illusion (you can check my sig), but I don't think a pair of C10s in the doors is what George had in mind in terms of budget or design goals.
> 
> Just from a quick spec a F/R graph spec (not to mention price) I would probably go with the ScanSpeak Discovery 26W/4534G if it fits. But George knows far better than me how to determine which of the drivers he listed best fits his needs.
> 
> Edit: Bah! George responded quicker, and much more thoroughly than I could have.


Yes I agree, was just thinking by the size of those stock openings that it would almost fit and wow that would be a lot of bass up front but true it would require something very oversized to compensate for mid.

I agree with either a scanspeak or with Neibur on some Dyns 182's which would also be a perfect fit.

Either way I look forward to watching this one unfold. Freakin sweet car and love your goals with the system design.


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## cvjoint (Mar 10, 2006)

Is this the right model: MW 182?
http://www.gattiweb.com/images/dynaudio/MW182.pdf

Some of the things I see:
Pros:
Fits easily
high crossover of 1000 hz easy
No cone edge resonance, well damped cone

Cons:
Extremely small cone, effectively an 8"
Extremely low linear throw, 4.5mm
Stamped basket

Overall, you can get these pros with the Scan Speak Discovery 8", get the same output, but a cast basket and more linear throw. 

I just realized the Scan Speak Discovery 10" has a 272mm basket, it wouldn't fit. However, the Usher 10" would fit.


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## MMC Racing (Dec 25, 2008)

cvjoint said:


> 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.


Ironic. Same exact speaker came out of my GT-R. Funny that a car considered a competitor in the same category uses a shared part.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

BOSE shares parts for just about everything.


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## t3sn4f2 (Jan 3, 2007)

Can't wait to hear what you have planned for those 8 Vifa Ne 10". Some type of LAT style spare tire well IB setup I suppose.


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## fish (Jun 30, 2007)

cvjoint said:


> Is this the right model: MW 182?
> http://www.gattiweb.com/images/dynaudio/MW182.pdf
> I just realized the Scan Speak Discovery 10" has a 272mm basket, it wouldn't fit. However, the Usher 10" would fit.


I have the Usher 10" in my doors now, & by far has the best lower midrange (tonally) out of the 2 Faital Pro models & the Beyma I've tried. Naturally, being a hifi driver I gave up some output. I can't cross them any lower than 63hz @12db without them bottoming out at high volume. In comparison, the Faital 10PR200 (discontinued) had more midbass kick (63-160hz), but above 315hz started to sound very bloated in the midrange. 

I really wanted to try some Scans in the doors, but 272mm was too much , I gotta stay around 262mm.

Have you looked at any of the Faitals?


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> Can't wait to hear what you have planned for those 8 Vifa Ne 10". Some type of LAT style spare tire well IB setup I suppose.


There is no spare tire well this time. The 'Vette has run flats. IB is also impossible since it's a liftback. 



fish said:


> I have the Usher 10" in my doors now, & by far has the best lower midrange (tonally) out of the 2 Faital Pro models & the Beyma I've tried. Naturally, being a hifi driver I gave up some output. I can't cross them any lower than 63hz @12db without them bottoming out at high volume. In comparison, the Faital 10PR200 (discontinued) had more midbass kick (63-160hz), but above 315hz started to sound very bloated in the midrange.
> 
> I really wanted to try some Scans in the doors, but 272mm was too much , I gotta stay around 262mm.
> 
> Have you looked at any of the Faitals?


I went with the B&C because from a technical point of view I don't see why the Faitals would have an edge. Every time I saw a comparison on Voice Coil Magazine between B&C and a competitor pro audio driver the B&C was simply perfected regardless of what the spec sheet was indicating. The Klippel fit in centering, symmetry, and overall shape are consistently better. They also have the resonance lower in the band compared to most. My only point of discontentment is airflow noise. It seems B&C's venting, while effective at cooling down the voicecoil has quite a bit of noise. When playing in free air the Scan Speak Classic sounds like a superior driver in the lower octaves hands down. 

8 or so years ago when the Usher was a popular driver most folks were reporting that it is a Scan Speak Classic copy at a budget price. I'm not sure I'm giving up anything by using the Scans instead but it surely speaks highly of what the Ushers can do. I'm glad they fit as they give me more options. They'd be cheap and fun to try out. Swapping midbass drivers in and out is one of my favorite things to do. The Hi Fi drivers in particular seem to have more character from driver to driver so I'd more willing to try out different Hi Fi options than pro audio. 

In the end I think Pro Audio vs. Hi Fi comes down to a few differences. Output and low compression vs low noise linear suspensions and better damped cones. The money question is will the Scan Speak blow up like the 10" Excels did.


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## Lycancatt (Apr 11, 2010)

so when do I get to hear this? drive down to the angel stadium meet in la and show it off?


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## fish (Jun 30, 2007)

cvjoint said:


> I went with the B&C because from a technical point of view I don't see why the Faitals would have an edge. Every time I saw a comparison on Voice Coil Magazine between B&C and a competitor pro audio driver the B&C was simply perfected regardless of what the spec sheet was indicating. The Klippel fit in centering, symmetry, and overall shape are consistently better. They also have the resonance lower in the band compared to most. My only point of discontentment is airflow noise. It seems B&C's venting, while effective at cooling down the voicecoil has quite a bit of noise. When playing in free air the Scan Speak Classic sounds like a superior driver in the lower octaves hands down.
> 
> 8 or so years ago when the Usher was a popular driver most folks were reporting that it is a Scan Speak Classic copy at a budget price. I'm not sure I'm giving up anything by using the Scans instead but it surely speaks highly of what the Ushers can do. I'm glad they fit as they give me more options. They'd be cheap and fun to try out. Swapping midbass drivers in and out is one of my favorite things to do. The Hi Fi drivers in particular seem to have more character from driver to driver so I'd more willing to try out different Hi Fi options than pro audio.
> 
> In the end I think Pro Audio vs. Hi Fi comes down to a few differences. Output and low compression vs low noise linear suspensions and better damped cones. The money question is will the Scan Speak blow up like the 10" Excels did.


Nice observations! I remember someone on here saying the B&C would make a whistling type of sound through the multiple vents, but at higher frequencies (where you plan to play them) when not given much room to breathe. 

Swapping out midbass drivers?! I'm the same way! They're the one area I like to try out different drivers... I'm on my 4th 10" set.


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> so when do I get to hear this? drive down to the angel stadium meet in la and show it off?


This one will take 3 to 6 months to build. Probably, Richard's or some other local meet.


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## papasin (Jan 24, 2011)

cvjoint said:


> This one will take 3 to 6 months to build. Probably, Richard's or some other local meet.


Just let me know, and I'm sure we can set something up.


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## SWINE (Aug 29, 2008)

subscribed!


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## cvjoint (Mar 10, 2006)

Cracked open the passenger door last night and did some test fitting. 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









From left to right B&C, Scan, Seas









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. 









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. 









Side by side Seas and B&C. The Seas needs that extra 1/2" of depth I just don't have for comfort. 

















Side by side back view. It is also apparent the Seas has a larger basket and a larger magnet.


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## cvjoint (Mar 10, 2006)

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. 









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. 









B&C fits with only 1/8" inch to spare around the switch and other door protrusions. 


































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!


















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.


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## BP1Fanatic (Jan 10, 2010)

Sub'd! My boyee has a C7 Z51.


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> Sub'd! My boyee has a C7 Z51.


These cars have the best speaker-box-doors of any car in production! We are lucky. I definitely recommend what I will use. Either the B&C 10NW64 with a subwoofer, or the Scan Speak Classic subless. From the testing I've done so far I expect the Scan Speak Classic will extend down to 20 hz in door flat.


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## rton20s (Feb 14, 2011)

cvjoint said:


> These cars have the best speaker-box-doors of any car in production! We are lucky. I definitely recommend what I will use. Either the B&C 10NW64 with a subwoofer, or the Scan Speak Classic subless. From the testing I've done so far I expect the Scan Speak Classic will extend down to 20 hz in door flat.


Sounds like these C7s would make a stock class competition killer. DEH-80PRS with the right 10s and 3s in the doors + tweeters on the dash I bet you'd see some of the highest scores ever in stock class. Though $55k is a pretty big chunk of change to drop just for a great competition platform.


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## cvjoint (Mar 10, 2006)

rton20s said:


> Sounds like these C7s would make a stock class competition killer. DEH-80PRS with the right 10s and 3s in the doors + tweeters on the dash I bet you'd see some of the highest scores ever in stock class. Though $55k is a pretty big chunk of change to drop just for a great competition platform.


You should be able to do the JBL 5.1 system pretty easily too. It has rear speakers and a center:


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## rton20s (Feb 14, 2011)

cvjoint said:


> You should be able to do the JBL 5.1 system pretty easily too. It has rear speakers and a center:


Indeed. And I was checking out that same exact image when I posted that. 

I was just thinking "Stock" because it is very limiting and I don't know that I have seen another vehicle that checks as many boxes as the C7 for that class. Once you move beyond that class things start getting pretty flexible pretty quickly and DSP options are virtually limitless. 

On the JBL front, Andy was just posting on FB the other day about building a DSP and his frustrations with what is currently on the market. I'm, sure it will be out a ways but it will be interesting to see what he comes up with and if any of his JBL roots come through to the new AF product.


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## cvjoint (Mar 10, 2006)

My initial design included a 3 way upfront using this sucker instead of the 3" cone in the door. Crossed 500hz to 5,000hz this guy will sound better than any cone alive, and should easily get about 3 times the output of the cone as well.


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## Fernpatch (Aug 21, 2014)

what driver is that? and where can I find the specs on it?


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## rton20s (Feb 14, 2011)

cvjoint said:


> My initial design included a 3 way upfront using this sucker instead of the 3" cone in the door. Crossed 500hz to 5,000hz this guy will sound better than any cone alive, and should easily get about 3 times the output of the cone as well.


Nice! A full ScanSpeak build could be pretty awesome.



Fernpatch said:


> what driver is that? and where can I find the specs on it?


ScanSpeak D7608/92000
http://www.scan-speak.dk/datasheet/pdf/d7608-920000.pdf

The wideflange version (http://www.scan-speak.dk/datasheet/pdf/d7608-920010.pdf)is available from Madisound and is pretty reasonably priced. 
https://www.madisoundspeakerstore.com/approx-3-midrange/scanspeak-discovery-d7608/9200-10-3-dome-midrange-d75mx41/

George, do you know of anyone in the US that sells the version without the wide flange? Looks Solen has them up in Canada. 
https://www.solen.ca/pub/index.php?catalog=description&nodiapo&id=2381&recherche=&numRows=10&manufacturiers=&niveau1=1&niveau2=1&niveau3=4&s1=2&s2=1&s3=2&s4=


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## Babs (Jul 6, 2007)

Looks like scan-speak d7608-920000
http://www.scan-speak.dk/datasheet/pdf/d7608-920000.pdf


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## rton20s (Feb 14, 2011)

Babs said:


> Looks like scan-speak d7608-920000
> http://www.scan-speak.dk/datasheet/pdf/d7608-920000.pdf


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## cvjoint (Mar 10, 2006)

rton20s said:


> Nice! A full ScanSpeak build could be pretty awesome.
> 
> 
> 
> ...


Yeah, that's it. Note the high sensitivity. The coil can also withstand crazy amounts of power. For Scan Speak's 17.1 rating of 80w, the long term 17.3 rating is usually 175w. As long as you don't bottom it out it can get quite loud. 

Generally I would phone up either Parts Express or Madisound. You can special order lots of rare drivers from either one as long as they carry the brand. I special ordered eight 10" Vifa neo woofers with the heatsink option from Parts Express in March. They should be here anytime now. The websites are just for the items they stock but it's not a full representation of what they can sell you. I ordered speakers from outside of US once and regretted it deeply. Use a large US distributor and you'll be much happier. Canada's currency is also quite strong as of late.


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## Babs (Jul 6, 2007)

cvjoint said:


> ...Crossed 500hz to 5,000hz this guy will sound better than any cone alive, and should easily get about 3 times the output of the cone as well.


For real? So maybe not crossing quite as low as a 10F you'd say it would be more better, and louder?  The 10F is a killer little mid. If I enclosed my pillar windows with these flushed in, the install would be pretty slick on axis. Heck I was thinking a 5 incher 15M in there, so this would be the other end of the spectrum maybe on the other spectral side of the 10F.


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## cvjoint (Mar 10, 2006)

Babs said:


> For real? So maybe not crossing quite as low as a 10F you'd say it would be more better, and louder?  The 10F is a killer little mid. If I enclosed my pillar windows with these flushed in, the install would be pretty slick on axis. Heck I was thinking a 5 incher 15M in there, so this would be the other end of the spectrum maybe on the other spectral side of the 10F.


Yep, the only thing you get with a cone is more excursion at the expense of everything else. Unless you need a low cross point go with a dome midrange. It's the closest thing to get the transparency of a planar. Unlike a planar it's quite small for how much output it has. I don't know why people don't use them more often. I've heard quite a few over the years, the ATC, Dynaudio, Dayton, HiVi. I tried the HIVi myself a while back but I didn't have the tuning skills to make it work. They are a bit tougher to integrate, the frequency response needs a lot of shaping.


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## Babs (Jul 6, 2007)

cvjoint said:


> Yep, the only thing you get with a cone is more excursion at the expense of everything else. Unless you need a low cross point go with a dome midrange. It's the closest thing to get the transparency of a planar. Unlike a planar it's quite small for how much output it has. I don't know why people don't use them more often. I've heard quite a few over the years, the ATC, Dynaudio, Dayton, HiVi. I tried the HIVi myself a while back but I didn't have the tuning skills to make it work. They are a bit tougher to integrate, the frequency response needs a lot of shaping.


Possibly just from the posted FR plots.. Might scare people away without considering the dome's other attributes compared to similarly sized cone like the 10F. At first glance it's a bit peaky at 1khz but nice roll-off from there if used on-axis, which I'd want to.

Actually, at 3.84" (10F) vs 5.98" (D7608 flanged), the dome is significantly larger footprint, but a large amount. Actually it's even slightly larger OD due to the flange than the 5" 15F which should easily hit 200hz one would think. Hmm. So it'd be really 500hz vs 200hz as just a crossover point constraint, though I get that the dome could be more accurate. 

Were it not for either having to DIY a smaller waveguide or do the larger flange, and if you had a driver below it that would mate up to 500hz, I can certainly see it. Looks like they still need an enclosure behind them like a mid though really to shine.

D7608 Dome









10F 4ohm









15M 4ohm








Fascinating stuff.


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## HardCoreDore (Apr 30, 2014)

Subscribed


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## rton20s (Feb 14, 2011)

Good info on the special ordering George. I wasn't aware of that. 

I've never heard the D7608s either and when I was comparing 3" midranges they never get a real consideration. Just as Scott suggested in his post above, the response graph played a big part in that. In fact, I ended up ruling out ScanSpeak all together because the D7608 needed a higher crossover than I was wanting and I didn't care for the look of the graph. The 5F is to small, 8 Ohm and not efficient. The 10F, while small for its size is a 4" driver (no larger than a 3" to work in my vehicle in Street class). 

Does anyone have a link to where someone has used the D7608 for a car audio install? Or even for home audio or some independent driver testing?


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## cvjoint (Mar 10, 2006)

Babs said:


> Possibly just from the posted FR plots.. Might scare people away without considering the dome's other attributes compared to similarly sized cone like the 10F. At first glance it's a bit peaky at 1khz but nice roll-off from there if used on-axis, which I'd want to.
> 
> Actually, at 3.84" (10F) vs 5.98" (D7608 flanged), the dome is significantly larger footprint, but a large amount. Actually it's even slightly larger OD due to the flange than the 5" 15F which should easily hit 200hz one would think. Hmm. So it'd be really 500hz vs 200hz as just a crossover point constraint, though I get that the dome could be more accurate.
> 
> ...


Somewhere along the line sound quality started being judged on the high pass filter for speakers at ear level. The race for low crossover points started and domes got sidelined. I got cut up in it too with my last car. The best sounding of all the designs was the one where I allowed the door speaker to cover up to 1khz, the first design. It amazing how much distortion we tolerate with full range pillar and dash setups but that's the odd world of sound quality at this time. The OEM 6.5" in the doors are typically lower distortion up to 1khz. 

Keep in mind that with an enclosure the resonant frequency of the system goes up. In free air 300hz is a low FS point. With a small box it may double so you have to cross 800hz up to get good results.


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## Instaburn (Aug 22, 2013)

For the doors...
What about some old school JBL pro audio 10"s like the 2123H or similar? ..


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## Instaburn (Aug 22, 2013)

Possibly the JBL 2012H as an option

www.jblpro.com/pages/pub/components/2012h.pdf

Found a great write-up here on the 2123's

http://www.audioheritage.org/vbulletin/showthread.php?16962-Field-Guide-to-the-JBL-10-inch-Midbass-driver-2121-2122-2123/page2


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## cvjoint (Mar 10, 2006)

Instaburn said:


> Possibly the JBL 2012H as an option
> 
> www.jblpro.com/pages/pub/components/2012h.pdf
> 
> ...


Honestly, it never occured to me to look at JBL. Let me catch up.


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## cvjoint (Mar 10, 2006)

Instaburn said:


> For the doors...
> What about some old school JBL pro audio 10"s like the 2123H or similar? ..


Ok, so I checked out the JBL yesterday, the newer one that is umm...discontinued already. 

Overall, that is an impressive driver. It's in the same class as the B&C 10NW64, namely it bridges the ProAudio and HiFi worlds. If I could get my hands on two, I'd still want the B&C, here is why:

I. B&C uses a neo motor. The benefits are many:
*higher motor force
*better venting behind the woofer
*6lbs total vs. 20lbs total. This may not seem like a lot but taking off 28 lbs off a door is conducive to long lasting door hinges and it's quite a lot for a sports car. I can't take it off for track days either. To put things in perspective here are two major revisions for the 7th generation Corvette to get rid of 25lbs:

1. Carbon fiber torque tube -13.2 lbs
source: http://gmauthority.com/blog/2014/11/...#ixzz3I6SEwCIl

2. Hollow lower control arms and aluminum rear toe links -11.4lbs
source: National Corvette Museum - 2014 Corvette

*Because the coil is larger at 3" and it has a large ferrite magnet around it I doubt the outter diameter of the magnet would clear the window mechanism.
*smaller motor means more net box room, means closer to perfect IB, and therefore higher efficiency and low end extension

II. B&C has 8mm of xmax whereas JBL has 8mm of xmech! That is B&C is still under the threshold of audible distortion when the JBL is bottoming out. That is the difference between a 63hz crossover and 100hz! 

III. B&C Klippels perfectly. Perfect centering, perfect symmetry, for every plot. I have no idea what the JBL looks like. Big risk here.

IV. B&C has a lower FS, and better low end extension. 

V. 4 ohm coil. How are you going to feed full range, stereo signals, to two 8 ohm drivers to the tune of 300 watts each? 4 ohm coils are a must when you want this much power for a midbass. 

The only upside to the JBL that I can see is that the breakup is moved higher up by about 500hz. However, the B&C's breakup is so high you'd have to play well into the beaming frequency for it to be bothersome. 

Interestingly enough, while the JBL uses 2 or 3 shorting rings, the B&C has an identical impedance curve, and therefore similar inductance profile. This suggests neo magnet + 1 copper Farraday is the same as ferrite magnet + top and bottom plates Farraday shielding.


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> Yep, the only thing you get with a cone is more excursion at the expense of everything else. Unless you need a low cross point go with a dome midrange. It's the closest thing to get the transparency of a planar. Unlike a planar it's quite small for how much output it has. I don't know why people don't use them more often. I've heard quite a few over the years, the ATC, Dynaudio, Dayton, HiVi. I tried the HIVi myself a while back but I didn't have the tuning skills to make it work. They are a bit tougher to integrate, the frequency response needs a lot of shaping.


Some people might disagree with you. 



Abmolech said:


> Warning Abmolech extreme bias against domes.
> 
> So apart from the obvious geometry differences (and there associated modes), what major differences does a dome suffer from.
> 
> ...





Abmolech said:


> You are quite correct.
> So what drivers are not designed to be played on axis?
> Domes.
> 
> ...





Abmolech said:


> The reason for dome mid range unpopularity is there increased distortion, lack of frequency band width, and the requirement to have them off axis.
> 
> Unless your completely stuck, a cone 4 1/2 to 5/14 " mid range will be a superior option.
> 
> ...


Of course the highly regarded ATC dome doesn't fall into this category since it has a spider and has a coil attach more toward the center.


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## cvjoint (Mar 10, 2006)

Lol, I'll have to soak this up too. A few things that I see right off from A's responses:
*He sees a decision between domes up to 3"s compared to cone mids in general. For example, he allows comparisons with 5.25" cones. That's not really comparable in my book, because the diaphragm area makes a huge difference in distortion. The comparison should really be against a maximum 3" cone, which has dismal output due to small coil, and some 10db lower efficiency @ 1watt. 
*He seems to constrain domes to chambered units. The Scan Speak that I posted is open backed, so those arguments again don't hold unless you compare a raw woofer with an enclosed dome. 
*I haven't seen the particular nonlinear distortion that he mentions in domes, but I have seen the particular nonlinear distortion that he mentions in cones. So how is it that we should weigh the dome distortion heavier when it is undocumented? I'm not saying he's wrong, but maybe the right distortion tests are never shown for domes??


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## thehatedguy (May 4, 2007)

I do love some domes.

If you go the dome route and want to try some Hybrid domes, I have a few (4) pair that you could try a set out.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> I do love some domes.
> 
> If you go the dome route and want to try some Hybrid domes, I have a few (4) pair that you could try a set out.


I'm entertaining the discussions, I think it's a fresh way to upgrade the Corvette's system. However, both small cones and all domes are too low output for what I'm going for here. With dual AC AMTs per pillar and B&Cs I should have (per side)

101db @ 1 watt above 1,000 hz (200 watts coil rating, 250 watts amp)
96db @1 watt above 100 hz (300 watts coil rating, 350 watts amp)

Interestingly, that JBL pdf that was linked showed some crazy amount of compression at 300 watts. I have to figure 3 db is lost to heat on the woofer side.


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## Instaburn (Aug 22, 2013)

Thought I would just open the door to a not so popular brand these days.
Those old Pro Audio JBL's 8's , 10's, and 12's were quite good and if I am not mistaken, the BuickGN guy or the infamous other used them for a while or still does use them in the rear quarter panels as a midbass driver.

Of course the old school brings the old ferrite magnets etc... which are hardly weight efficient for track cars etc...


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## funkalicious (Oct 8, 2007)

Eight 10s in a Vette. This I want to see !


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## fish (Jun 30, 2007)

thehatedguy said:


> I do love some domes.
> 
> If you go the dome route and want to try some Hybrid domes, I have a few (4) pair that you could try a set out.



I've always been curious about those Hybrid domes before they even came out. I never really found much feedback on them. What's your take on them?

Sorry for going off track George.


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## thehatedguy (May 4, 2007)

Mine are just sitting there...no time or money to install them at the moment. And like you, I haven't found much info on them.


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## edzyy (Aug 18, 2011)

Not sure if mentioned, but have you considered horns?


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## cvjoint (Mar 10, 2006)

edzyy said:


> Not sure if mentioned, but have you considered horns?


IMO, horns have to be designed well to work. All of them can get high output. None of them that work can fit in a car and be aimed properly imo. Here's an example:


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## Babs (Jul 6, 2007)

I've heard this particular Audi running horns.. Made a believer out of me for sure. 
http://www.diymobileaudio.com/forum/build-logs-project-install-gallery/161201-2013-audi-s6-sq-build.html


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## edzyy (Aug 18, 2011)

cvjoint said:


> IMO, horns have to be designed well to work. All of them can get high output. None of them that work can fit in a car and be aimed properly imo. Here's an example:


The Eric Stevens waveguides work very very well in cars


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## cvjoint (Mar 10, 2006)

Here are the measurements for a rear speaker replacement. Lots of room! 
*Plastic panel cover has a 5" plastic ring that seals with the Bose speaker
*Inside the plastic ring that seals the Bose speaker there is 0.5" depth
*The Bose speaker itself has 0.25" thick basket up top, with a 0.5" foam that seals with the panel
*Top mount depth (not total depth) is 6.5"+ on the passenger side and 5"+ on the driver's side. There are however some odd restrictions behind the speaker.
*Total depth is roughly 7" on the passenger side and 5.5" on the driver's side 
*The speaker cutout, the inner diameter, is 5.15"
*The speaker outer diameter is virtually unlimited, a 6.5" basket would fit

This leaves a lot of opportunities available for rear speakers! 

Some quick shots:

















Now, who's got some intimate knowledge of Pro Logic II or the Alpine H800? What kind of band and output are we looking for?


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## cvjoint (Mar 10, 2006)

*DIY rear speaker assembly*

First, get $5 panel removing tools from Amazon. No panel scratches, no finger bleeding.









Second, observe the challenge eye to eye. A 5.25" Bose speaker is lurking under there.









It looks like a 5" by 6" but it is not. An odd choice for a panel indeed. 









The annoying part of car audio is there there is always twice the work to be done. Here's the driver's side. 









Third, use the plastic tools to pop open the plastic beauty panel that's a different texture and color than the rest. You can't miss it. 








To place less stress on the plastic part dully note where the clips are and pick at it in that neighborhood. 









Fourth, remove the plastic cover from the tie down. It's just there to look sexy.








Unleash the Torx









Fifth, pick up your plastic and finish the job. The panel comes off like so and the Bose speaker is now at your mercy.










The typical Bose high end look:








The typical quarter sized magnets used in OEM these days.


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## cvjoint (Mar 10, 2006)

*Observations *










A jaw dropping speaker job indeed. Immediately you should notice that the speaker is mounted on a composite frame that is entirely leaky. By the seat belt roll, the front of the cone and the back of the cone are nearly open to each other. That is to say, there is no speaker box. This is a free air design, infinite baffle if you wish, but a brainless one. The cancellation that takes place in this speaker design is of epic proportions. Where the wire harness goes inside the composite box, the whole seemed to have be sawed by hand on the assembly line. 

Ok, so what else stands out in this whole affair? Is there anything worse than a speaker that cancels its own output? Well yes, there appears to be an flap vent that equalizes air pressure between interior and exterior right behind the speaker. Look at that:










Bose couldn't seal that speaker box if they wanted too. It would completely seal off the vent. You can see some of the openings in the next photos. Now we know they have to be there to allow air bypass to the vent. 



















The passenger side looks similar but there is no vent:


















*The plan*
Obviously, I am going to seal off those speaker chambers. That should give me substantially better sound and high output in the lower octaves. I have to get clever with the passenger side to maintain the operation of the vent. 

Secondly, I am going to try to fit a Satori 6.5" speaker in there and run it nearly full range, 100 hz to 20,000 hz. The trick is that the Satori has one of the smallest inner diameters of any 6.5" speakers. At only 136 mm ID it should fit with minor trimming of the spacer. 


















It is one of the lowest distortion wide bandwidth drivers on the market. It has a low FS, high sensitivity, and ridiculously good power response to well beyond 10 khz. 










Satoris are on the way. It was an easy choice since nothing other than crappy car audio woofers or Accutons would give me an SD of 119 cm2 or more. If you've noticed a trend with my car builds is that I never give up cone area.


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## Babs (Jul 6, 2007)

I'll bet that's for air-escape in case of an air-bag deployment so you don't blow out your eardrums and eyeballs probably. About all car's have them somewhere now. I'd tread lightly before sealing that little thing. Might be able to do some kind of small chamber in front of it though, leaving space for the vent to do its job.


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## Babs (Jul 6, 2007)

duplicate


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## cvjoint (Mar 10, 2006)

Babs said:


> I'll bet that's for air-escape in case of an air-bag deployment so you don't blow out your eardrums and eyeballs probably. About all car's have them somewhere now. I'd tread lightly before sealing that little thing. Might be able to do some kind of small chamber in front of it though, leaving space for the vent to do its job.
> 
> And bravo on your excellent choice of Satori's. Awesome drivers. Reminds me.. I gots 10F's waiting on me at home! Yay!


I haven't thought about that, good point. 

The reason why I'm surprised to find that vent is that there is another one, that made the news big time:
First it was positive









Excerpt: "Previous Corvettes used what’s called a “motorized actuator” that opened and closed a hatch vent to release air from the trunk. This vent is key because that airflow makes the trunk easy to shut.

The 2014 Stingray ditches the actuator in favor of this smart-shape memory alloy that expands and retracts based on heat, stress, magnetism or voltage. When you open your Corvette’s trunk, heat from an electrical current expands the alloy, which levers the vent open. When the trunk is closed, the current shuts off, the alloy retracts, it levers the vent closed, and that’s that. A mechanized arm replaced with a simple metal strip."

Then it was negative: It's so hard to shut the latch that GM went back to a simple motorized unit on the 2016 model.


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## suzi427 (Oct 6, 2011)

Any update on this? I just bought a C7 myself, and Im looking to do a 3 way up front with sub in rear.


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## cvjoint (Mar 10, 2006)

suzi427 said:


> Any update on this? I just bought a C7 myself, and Im looking to do a 3 way up front with sub in rear.


I just got all 8 subwoofers shipped a couple of weeks ago. The wait was over 6 months for those suckers! Starting the build in a month.


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## vwjmkv (Apr 23, 2011)

looking forward to this VERY MUCH! I'm not th biggest Vette fan but i do love these builds and how creative you guys get with driver placement etc.


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## cvjoint (Mar 10, 2006)

Build has begun. Mock up of the amp rack attached.


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## Lycancatt (Apr 11, 2010)

what amps did you end up deciding on?


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> what amps did you end up deciding on?


All Arc Audio class G/H. No analog to digital conversions and high efficiency. 

Arc KS 2500.1 : 2500watts @1 ohm
Arc KS 300.4: 175watts x 4 @2 ohm
two Arc KS 125.4: 125watts x 4 @2 ohm

I'm running all of them at minimum impedance, so total output is 4,200 watts at 14.4V and less than 1% thd. In reality they make a bit more than rated power but I won't be able to hold 14.4V on the stock charging system, so it's probably just under 4 kilowatts at 12.6V.


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## Lycancatt (Apr 11, 2010)

that's interesting! I knew we thought a lot alike, those are the amps I plan to use for my artcar/meca sq car build in a big ol van.

I plan to use a pair of the ks2500 amps strapped for 2 ohm load to 4 ported eighteens, but with me, plans change frequently.

cant wait to hear what you do with tis car.


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> that's interesting! I knew we thought a lot alike, those are the amps I plan to use for my artcar/meca sq car build in a big ol van.
> 
> I plan to use a pair of the ks2500 amps strapped for 2 ohm load to 4 ported eighteens, but with me, plans change frequently.
> 
> cant wait to hear what you do with tis car.


IMO the Kar series remains Robert Zeff's best amplifier range. The only other line of amplifiers I liked was the Clarion XH also a Robert Zeff design.


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## GLN305 (Nov 2, 2007)

cvjoint said:


> I haven't thought about that, good point.
> 
> The reason why I'm surprised to find that vent is that there is another one, that made the news big time:
> First it was positive
> ...


I'd hate to see you cover those vents behind the speakers as they serve more purpose than making the trunk and doors easier to close. The vents also allow the A/C unit to work without pressurizing the cabin. I had covered the vents in a truck at one point and it made my ears hurt due to the pressure in the cab. Just my 2 cents.


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## cvjoint (Mar 10, 2006)

Yes, I've thought about either leaving the chamber as is and loose the bass output of the speaker or create some sort of bypass for the vents. I'm delaying the install of the rear speakers to think this one through.


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## cvjoint (Mar 10, 2006)

*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. 










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. 


















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:









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.










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!


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## gumbeelee (Jan 3, 2011)

Just checked out your build, looks like u got some nice work going. Definately going to subscribe. Got a question for u what is techshop? I am nit familiar with it or heard of it.


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## cvjoint (Mar 10, 2006)

gumbeelee said:


> Just checked out your build, looks like u got some nice work going. Definately going to subscribe. Got a question for u what is techshop? I am nit familiar with it or heard of it.


Looks like there is one in your town: TechShop is the 1st International Open-Access Workshop -- TechShop Locations

It's basically a shop where you pay a monthly fee to get access to professional grade equipment. They have anything from laser cutters to 3d printers. I got a deal to access the shop for 4 months two classes for $350. You can bring the stuff there or store it onsite for a fee. 

There was a guy making a baby bed next to me. Subwoofer box vs. baby bed! Glad I'm doing the first although the guy was a better carpenter than me.


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## cvjoint (Mar 10, 2006)

Broke the third kerf job...


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## DLO13 (Oct 24, 2010)

Have you considered using steam?


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## jtaudioacc (Apr 6, 2010)

cvjoint said:


> *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.
> 
> ...


you can take as long as you want, but from what i can see, it might break. you should cut it thin enough to bend right then and there. 

when i get some extra time, i've been wanting to join a makerspace. there's a few seemingly good ones around here.


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## cvjoint (Mar 10, 2006)

DLO13 said:


> Have you considered using steam?


I did a little bit of research and it turns out MDF doesn't like water too much. 

What I'm going to do on my 4th try is to:
1) increase the surface area of the slits by 50%. That way there is more play in the board although the shape gets out of hand. 
2) clamp it down to the bottom board of the box. I'll let it sit like that for a week to adjust to the curvature. (steam optional, but will probably skip)
3) add a small layer of wood glue in the slits to strengthen it
4) start pressing down on the top to get the right shape. 

It will be a glue heavy technique but there is less stress on the MDF. 

I'm pretty sure I used the wrong saw blade last time too. The top of the blade cut more than the side of the blade making an optimum crease job.


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## DLO13 (Oct 24, 2010)

I would just do what JT says. lol


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## cvjoint (Mar 10, 2006)

jtaudioacc said:


> you can take as long as you want, but from what i can see, it might break. you should cut it thin enough to bend right then and there.
> 
> when i get some extra time, i've been wanting to join a makerspace. there's a few seemingly good ones around here.


Ah, that was definitely why the first one broke! I've been trying to make them thinner. The blade was all funky cutting a deeper groove in the middle. I was afraid it would cut right through if I lifted the blade any higher.


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## Lycancatt (Apr 11, 2010)

which tech shop did you join? would be funny if it was the one down here in san jose..which is 4 blocks from my house.


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> which tech shop did you join? would be funny if it was the one down here in san jose..which is 4 blocks from my house.


San Francisco one in SOMA. I carried MDF from my house on foot there is so close.


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## Lycancatt (Apr 11, 2010)

I guessed as much, its a handy place to work, but they wont let me take the classes..wonder why? lol


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> I guessed as much, its a handy place to work, but they wont let me take the classes..wonder why? lol


You don't need classes for hand tools.


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## SQram (Aug 17, 2007)

cvjoint said:


> All Arc Audio class G/H. No analog to digital conversions and high efficiency.
> 
> Arc KS 2500.1 : 2500watts @1 ohm
> Arc KS 300.4: 175watts x 4 @2 ohm
> ...


How are you achieving the 2 ohm output on the midbass amplifier? The B&C's are a 4 ohm SVC, or did you go a different route?


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## cvjoint (Mar 10, 2006)

SQram said:


> How are you achieving the 2 ohm output on the midbass amplifier? The B&C's are a 4 ohm SVC, or did you go a different route?


The B&Cs have a 4 ohm coil. I bridge a 4 channel amp to drive them at 350 watts x 2 @ 4ohm. Because the amp is bridged the effective load the amplifier sees is 2 ohms on every channel.


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## Lycancatt (Apr 11, 2010)

technicly, running at 4 ohms bridged puts each channel of the bridged pair at 2 ohms, so that would equate to "minimum resistance."


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## SQram (Aug 17, 2007)

That's what I figured, just wanted to confirm in case I was missing something (autoformers etc.).

Carry on...


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## cvjoint (Mar 10, 2006)

Car got broken into last night. Build will be delayed a week until I get a new window. 

Gotta love how safe San Francisco is. I parked out in the street maybe 20 times total and got broken into twice.


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## BP1Fanatic (Jan 10, 2010)

That $uck$.


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## cvjoint (Mar 10, 2006)

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. 










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





























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. 





































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.


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## optimaprime (Aug 16, 2007)

Hoooo this gonna be pretty . I love me some vette !!! IllhVe one soon I hope . The wood Kerfing is sweet man ! I gotta try it


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## Kellyo77 (Dec 5, 2009)

Beautiful car sir. Anxious to see this build take shape.


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## cvjoint (Mar 10, 2006)

Thanks guys! 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:










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:










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










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:


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## Mless5 (Aug 21, 2006)

cvjoint said:


> San Francisco one in SOMA. I carried MDF from my house on foot there is so close.


Lucky you!
Cool build, cant wait to see more of it.


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## cvjoint (Mar 10, 2006)

Mless5 said:


> Lucky you!
> Cool build, cant wait to see more of it.


I still do a bunch of work at home, like applying glue. I don't leave stuff there overnight. 

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: 










First layer of glue after 12 hours:


















Second layer of glue applied earlier this morning:



















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


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## BP1Fanatic (Jan 10, 2010)

Nice!


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## cvjoint (Mar 10, 2006)

Everyday the kerf gets stronger! But that glue is also taking days to cure so I'm going to post some updates I've done on the car cooling system for track use. 

*Scope of work*
Does this aftermarket radiator work better than the stock unit? If so, how much better? 

This is a presentation of several lab results employing the C&R Denso high efficiency core in my C7 Z06 M7. This core is a straight replacement of the main radiator. C&R constructs 90% of the NASCAR radiators. This core is the same exact core technology used in the infield and short course NASCAR vehicles. The thickness of the radiator is the same or negligibly thicker than the OEM. The trick is in the fin spacing and construction. In any case, I bought it because I believe C&R has the high overhead needed to construct a quality piece and because I thought the DENSO core is the best on the market for roadcourse use. MSRP $1,300, compare this to the $225 cost for replacing the stock unit.

*Background*
The main radiator cools the water and the water in turn cools the oil through a liquid to liquid exchanger. That is, the C7 Z06 only has a single heat exchanger for both oil and coolant for the engine. The C&R piece replaces it. 

I've overheated this car several times in the summer last year so I'm trying to approach cooling with the most effective options available from GM or otherwise. 

The car overheats at 262* coolant, but gives early warning and shuts off access to A/C at 256*. Coolant overheats before oil, I never got an oil overheat although oil did go over 300* at times. 

*Pictures of the install:*






























*Install detail*

Fit and finish is perfect. There was no difficulty in installing the radiator. I had it done at a dealership so that it is done right and all the bubbles are taken out of the system with the right equipment. Water/coolant ratio was kept at 80/20 just like I had done with the OEM core. The car never sits in freezing temperatures so a coolant heavy mixture is not needed to ensure proper operation. 

*Testing conditions*
Testing track: Thunderhill 3 mile
Driver: self
Time: January 24th stock; February 13th C&R
Transmission: manual; I optimize shifts for speed not for cooling; I use 3rd and 4th gears on this track
GPS receiver refresh rate is 10hz
Coolant temperature is read through Harry's laptimer using a high refresh rate OBDII reader and placed into a spreadsheet for the analysis 
I record the max sustained coolant temperature in every lap; I ignore very short time span spikes as they may be recording errors
I drive in advanced group and I am competitive running middle of the advanced pack or slightly above depending on the organizing group. 
Notes: 
(1) The track configuration was w/bypass on January 24th and w/o bypass with C&R so the C&R laps are supposed to be 2 seconds slower; the rest of the track is the same
(2) The ambient temps were higher during C&R testing day, but the ambient temperatures do vary within each day so a proper comparison can be made
(3) The stock radiator runs are shorter at ~16 minutes compared to the C&R runs which are ~25 minutes. Speed SF runs shorter sessions than Hooked on Driving. You pay more with HOD but you get more track run time. Compare accordingly.

*Preview of results*
I do not find a large improvement from using the C&R radiator. I interpret this result as either (a) more data is needed for a proper comparison or (b) the radiator location has to little airflow for any radiator change to make a meaningful impact or (c) the radiator is no better than the stock unit. I'm leaning towards (b) being the most likely scenario. 

Here are two graphs where I think I can display 99% of the relevant information in one go. This way we can visualize a whole bunch of data in the simplest way to digest. I can do a whole bunch more of data tossing around so hang tight. 

On the Y axis (vertical) you can read the coolant maximum temperature in any given lap. On the X axis (horizontal) you can read run time, basically driving at speed on the track for up to 25 minutes. I propose we compare only sessions where the ambient temperature is roughly equivalent. As you can see from the C&R day, the ambient temperature makes a huge difference. I also propose we compare at similar run times since you can see the car runs the coolant higher and higher until it stabilizes. That said we still have to assume my driving is consistent. Since I'm the same guy driving within a 1 month period, basically back to back, I don't think there is much variance. However, I'm not as consistent as some of the best advanced drivers. 






















*Disclaimer*
I will do the best I can to interpret the results and analyze the data. Feel free to correct me if needed, ask for analysis, or to interpret the data in your own way. I do not work for C&R or have any interest in the company. I bought this radiator just like anyone else would. No skin in the game, except to cool my car better and prevent overheating.

*Main results*
Here is what I've been working on for the last week. I'm approaching this from a statistical point of view, throwing all the data all at once into one large model that can answer our big picture questions. 

Let's skip to the results and then go over why it works very well, and of course cover some of the weaknesses as well. Trying to be as objective and unbiased as I can. 

*Question 1:* What is the improvement in coolant temperature from using the C&R radiator over stock?
*Answer 1:* Holding everything else constant, none. There is no evidence that the C&R reduces coolant temperature. There is also no evidence that it increases coolant temperature either. 

*Question 2:* What is the improvement in coolant temperature from using a 20/80 water mixture instead of the stock 40/60 water mixture? 
*Answer 2:* Holding everything else constant, the coolant mixture is on average 4.3 degrees cooler. 

*Question 3:* What is the effect of time spent driving on the track on coolant temperatures? 
*Answer 3:* Holding everything else constant, every minute spent on the track increases coolant temperature by half a degree. At the end of a 20 minute session, the coolant is 11.4 degrees hotter. 
*
Question 4:* What is the effect of ambient temperature on coolant temperatures?
*Answer 4:* Holding everything else constant, every degree increase in ambient temperature increases coolant temperature by 0.83 degrees. In the same vein, every 10 degrees increase in ambient temperature increases coolant temperature by 8.3 degrees F. 



Model results in one shot:










*Data*
I've collected data on coolant temperatures for 159 laps on the track. For every lap I looked up the historical recorded temperature at the time of that session in that location and collected it. I kept track of whether I used 60% water 40% antifreeze or whether I diluted the coolant mixture to 80% water. I've also kept track of whether I used the stock radiator or the C&R radiator. Run, time is calculated as the total spent time on track up to the end of that lap. My sessions are 25 minutes or less.

*The model*
The model is a pretty simple regression model. At the core it is based on correlation. I've removed two datapoints where Harry's Laptimer seemed to give erroneous information. There is a lot of variation in the data which is good for estimation. I drove on a wide variety of tracks: Thunderhill 2 mile, Thunderhill 3 mile (both with bypass and cyclone), Sonoma Raceway, and Laguna Seca. Recorded coolant temperatures are between 199*F and 246*F. Ambient temperatures were between 42*F and 79*F. There are 40 laps with the C&R radiator in the data and 119 laps with the stock radiator. There are 8 observations with the stock coolant mixture and 151 observations with the diluted mixture. 

*Pros of the model*
Multiple regression models are good at eliminating the bias in comparisons driven by other factors. Say we are interested in whether the C&R radiator cools better. We'd like to answer the question without being biased by the ambient temperature effect, or whether we looked at the temperatures after driving for 2 minutes instead of 20 minutes on the track. The model can figure out the effect of each of these individually and "keep them fixed." This is far better than looking at two lines on a graph, unless the two lines you are looking at are the most representative (same run-time, same ambient, same coolant mixture, etc.). 

The model is also good at giving you a measure of variance in the data. Where does variance come from here? Well, it is the traffic on the track, changes in driving style such as picking higher gears, and the different load the track places on the cooling (say Laguna Seca runs the car hotter than Thunderhill). So what does this all mean? For example, the models finds that the C&R radiator runs the mixture hotter by 1.5*F. However, it also tells you that this amount can be driven by all the other factors not accounted for and that we should interpret it as no evidence of an effect. So we can't say from this data the C&R runs hotter. Another thing we can say is that using run time, ambient temp, the radiator type, and the radiator coolant mixture we can predict 60% of the variation in coolant temperatures. The rest is driven by driver, track type, traffic, etc. 

The other good news is that it does not matter whether I'm a great driver or just a good driver, or even that I'm consistent. My lack of consistency is going to show up as high standard error. But given that we can predict the effect to the level of 2 degrees or less that's pretty good level of error we have. 

*Cons of the model*
I would have liked to have variables for type of track used. However, I only tested the C&R on one track, and that exact configuration is nowhere else in the data. So we can't answer today whether Laguna Seca runs the car hotter than Thunderhill. Someday in the future!

The other con is that we only have 8 observations with the stock coolant. I changed away to 20/80 very early so I don't have a lot of data with stock coolant mixture, sorry! But the 8 points seem to be sufficient. We find an effect, although I would have preferred more precision in the results. 

Obviously the data can always be fudged. Say I ran the car with the C&R in higher gears than the rest of the time. Since we don't tell the model what gears I am using it can bias the results. So you will have to trust me that I didn't pick higher gears on purpose!


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## casey (Dec 4, 2006)

Im surprised the C&R isnt dropping the temp. Is there any company that makes ducting/shrouds so that air is forced through the radiator from the grill opening? Vented hood in conjunction with that would probably help a bit


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## cvjoint (Mar 10, 2006)

casey said:


> Im surprised the C&R isnt dropping the temp. Is there any company that makes ducting/shrouds so that air is forced through the radiator from the grill opening? Vented hood in conjunction with that would probably help a bit


The first aftermarket radiator, the DeWitts also failed to improve coolant temperatures. I believe the most likely explanation is that there simply isn't enough air coming through to the radiator. The car is supercharged and the intercooler heat exchanger sits right in front of the radiator covering the entire inlet. 

The shrouding is done well by GM so there is nothing to improve. The hood is also vented taking out 1/3 of the air coming out of the radiator. The fenders are also vented.


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## nadams5755 (Jun 8, 2012)

What makes it a better radiator? Different flow? Different surface area? 

I feel like a higher flow will minimize the time fluid spends in the radiator, thus not allowing it to cool as much. If there's more surface area, then you get more exposure to air and are able to dissipate better (assuming you can get more airflow across it)

Does running the heater help with engine temps? Flip the AC on for a few seconds to get the engine fan to spin up?

Usually the water temp sensors are at the top/exit of the engine, before it leaves for the radiator. Have you measured the delta where coolant comes back into the engine at the bottom? I suppose that would be the best measure of radiator effectiveness.


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## cvjoint (Mar 10, 2006)

nadams5755 said:


> What makes it a better radiator? Different flow? Different surface area?
> 
> I feel like a higher flow will minimize the time fluid spends in the radiator, thus not allowing it to cool as much. If there's more surface area, then you get more exposure to air and are able to dissipate better (assuming you can get more airflow across it)
> 
> ...


It has tighter fin spacing than the stock unit. I believe it also has a slightly large surface area. The fins can also be dimpled or formed in a different fashioned, but I'm not sure if this one has that. It looked more or less like stock except denser. 

The fan doesn't do much above 30mph or so. I think the programming is to shut it off at high speeds as it just impedes flow. The fan housing also has some flaps that open up at speed to let air through. Racecars don't have fans for this reason, they cool better without one. 

I haven't plugged in any other sensors. The thing is the engine goes into limp mode at 262* coolant, so I'm trying to avoid that. Moving the sensor would void warranty I'm sure. 

Running the heater in 100* ambient is brutal! I don't run A/C to help it cool down but running the heater is a bit tough.


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## 555nova (Apr 12, 2014)

For those you that have never driven on the track before you have no idea how hot and uncomfortable it can be, especially considering your in a fire suit of some sort along with neck brace, gloves and helmet.

Cv joint have you looked into water wetter or similar products? I had a big block street car with a small radiator that would over heat on 95*+ days and after using the water wetter it never overheated again. Also have you looked at different thermostats?

Beautiful car by the way, I can't wait to see it finished.


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## RandyJ75 (Dec 4, 2006)

What about the fluid used in the radiator? You said that the fluid was 80 percent water and 20 percent coolant. Don't you think you would have better results if you used more coolant and less water?

Sent from my SM-N910V using Tapatalk


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## danssoslow (Nov 28, 2006)

RandyJ75 said:


> What about the fluid used in the radiator? You said that the fluid was 80 percent water and 20 percent coolant. Don't you think you would have better results if you used more coolant and less water?
> 
> Sent from my SM-N910V using Tapatalk


Water works much better than coolant at exchanging heat. Redline makes a product called Water Wetter that is meant to improve heat exchange; but that may be due to simply providing corrosion protection in an all-water system and allowing the water to do its thing. I'm not completely versed on the stuff.


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## nadams5755 (Jun 8, 2012)

cvjoint said:


> I haven't plugged in any other sensors. The thing is the engine goes into limp mode at 262* coolant, so I'm trying to avoid that. Moving the sensor would void warranty I'm sure.
> 
> Running the heater in 100* ambient is brutal! I don't run A/C to help it cool down but running the heater is a bit tough.


Suppose I should have suggested adding a sensor and measuring vs moving a sensor, then you can measure efficiency. If outlet temps are ambient, then the cooling system has done its job perfectly. However you get to a point where ambient is high enough and you can't cool any further. (How do I make less heat?)

Hard problem for sure. 

I've done emergency cool down with the heater, not something I'd want to do all the time.


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## cvjoint (Mar 10, 2006)

I read the Redline water wetter white paper. Even in their testing the water wetter does almost nothing. The increase in cooling comes from running more water and less coolant. The redline product provides corrosion protection without coolant, and it's also not slippery in case it gets spilled on the track. It reduces some local boiling but I don't see in their testing as doing much at all. It's basically good to add when you're running all water and no coolant. Since I plan to have some freezing protection via coolant I decided to skip the Water Wetter. Some reported it creates sludge in the radiator when used with coolant. That was the second reason I didn't want to use it. 

The aftermarket thermostats made for the C7 Corvette stick so they have to be revised. Even if you were to use one it wouldn't do much on the track unless you reprogram the fans to turn on earlier. I enter the track at 195* coolant to 200* so the stock thermostat is already open and working (starting at 190*). It's the fan that's the key. To change the fan operation you risk voiding the warranty.


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## danssoslow (Nov 28, 2006)

I got bored last night and started reading a bunch of stuff on the net about the overheating issue. I read on page (mind you it was a condescending conspiracy theory kind of read) that, in the writer's strong opinion, came down to three issues:

A smaller (than the ZR1) cfm supercharger being spun outside of it's efficiency zone, an intercooler with a thicker core (than the ZR1), and the cores location ahead of the radiator. The supercharger creates a bunch of heat, the intercooler gets oversaturated and the density of intercooler doesn't allow the airflow to sufficiently evacuate the heat, trapping the heat to be soaked into the radiator.

Maybe his claims hold weight, maybe not; but could a pulley swap and/or change to the ZR1 intercooler possibly be viable options to consider?

Everything else that I read as a consideration to a possible solution seemed to be via the ecu or changing driving styles; none of which appeared to be a solid solution.


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## cvjoint (Mar 10, 2006)

danssoslow said:


> I got bored last night and started reading a bunch of stuff on the net about the overheating issue. I read on page (mind you it was a condescending conspiracy theory kind of read) that, in the writer's strong opinion, came down to three issues:
> 
> A smaller (than the ZR1) cfm supercharger being spun outside of it's efficiency zone, an intercooler with a thicker core (than the ZR1), and the cores location ahead of the radiator. The supercharger creates a bunch of heat, the intercooler gets oversaturated and the density of intercooler doesn't allow the airflow to sufficiently evacuate the heat, trapping the heat to be soaked into the radiator.
> 
> ...


All of those are true. But the elephant in the room is that there is only one radiator and it is stuck behind an intercooler and A/C condenser. The inlet is also quite small, not like something you'd find in a pony car. Changing the intercooler or radiator will do very little. Adding additional radiators is where it is at, moving the intercooler somewhere else, or both.


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## danssoslow (Nov 28, 2006)

I'm sorry to derail the build, I sincerely here this for you. The Z07 has been heavily marketed to do the very thing you are doing with it. I'm pissed you can't thoroughly enjoy it as such. Now that you brought up the front inlet, I remember reading that, too.

I'm curious as to how far from stock the C7R is is concerning such things. Off to research...


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## cvjoint (Mar 10, 2006)

*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.










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.


















Once marked for destruction, the corners were trimmed off:









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:










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.










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. 


















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


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## rton20s (Feb 14, 2011)

Looking good George. Can't wait to see the whole thing come together.


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## unix_usr (Dec 4, 2013)

On the inside of the kerfed corners, try using some fiber glass filler instead of wood-glue; it bonds just as well but adds considerably more strength... I'd also lay a layer or two of cloth and resin inside personally as that adds even more strength still. Not to mention, hardens a lot faster and costs oz for oz likely less than you're spending on glue 

Great build so far though, anxious to see where else this goes...


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## cvjoint (Mar 10, 2006)

unix_usr said:


> On the inside of the kerfed corners, try using some fiber glass filler instead of wood-glue; it bonds just as well but adds considerably more strength... I'd also lay a layer or two of cloth and resin inside personally as that adds even more strength still. Not to mention, hardens a lot faster and costs oz for oz likely less than you're spending on glue
> 
> Great build so far though, anxious to see where else this goes...


Tell me about it. I was 50/50 on whether I should just fiberglass the top of the box and bolt it to the rest. But I thought wood would be so easy...just one piece for top and sides... 

If it doesn't harden sufficiently by the time I'm ready to coat the box that's what I'll do.


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## BP1Fanatic (Jan 10, 2010)

Four 10's are going to POUND in that vette! The box is looking good! I say vent more air to the radiator if you can. My boyz have a 15 C7 Z51 and 13 C6 Z06 Special Edition. They do HPDE's at Mid-Ohio and Daytona. I went with them to Mid-Ohio and they never had any overheating problems. They plan on going to Indy this year! I told them I'd roll with them.


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> Four 10's are going to POUND in that vette! The box is looking good! I say vent more air to the radiator if you can. My boyz have a 15 C7 Z51 and 13 C6 Z06 Special Edition. They do HPDE's at Mid-Ohio and Daytona. I went with them to Mid-Ohio and they never had any overheating problems. They plan on going to Indy this year! I told them I'd roll with them.


Eight 10"s, and if you count the ones in the doors, ten tens 

The Z51s are much easier to cool, no intercooler. With a thick radiator like Ron Davis or LG you can cool that thing and run all day.


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## BP1Fanatic (Jan 10, 2010)

Are the eight 10's going to be mounted isobarically?


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> Are the eight 10's going to be mounted isobarically?


No. They are going to be mounted opposed and inverted. 

Here is a simplified graph using only two woofers that are opposed. This will cancel mechanical force (vibration) if the woofers are connected in-phase. Both push out or both pull in at the same time. I've also seen this referred to as mechanical push-pull. The benefit is that it nearly eliminates cabinet/car vibration.










So mine will be opposed, except I've added another tweak. One side has woofers inverted with the cone facing the inside of the box. This will achieve the traditional benefit of push-pull, which is lower second order harmonic distortion. These inverted subwoofers will be connected out of phase. 

All cones move either all outward or all inward. The design achieves both vibration reduction and distortion reduction. Mechanical and acoustical push-pull.


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## BP1Fanatic (Jan 10, 2010)

Nice, you really gonna pound with all that Sd! I can see that, similar principles as the Porsche flat 6 and Subaru flat 4.


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## audiokid1 (Jul 2, 2014)

Per the suggestion above; if you intend to use the top piece with the current kerfs, then you will want to use fiberglass for reinforcement. As for the body filler...make sure it is a reinforced filler like Kitty Hair or Duraglass. Do not use normal body filler like Rage Gold.
Unfortunately, your current piece has to many kerfs so it definitely needs rigid reinforcement. If you find yourself re-doing the top piece again, then I hoghly suggest switching to 13 ply Baltic Birch Plywood. Here is a sample that I was playing with. You will end up with a stronger piece if you have just the right amount of kerf cuts.

























As for the track...I'm surprised they let you use ethylene glycol at all. I ride the track frequently, but it's on two wheels so we may just go by a different set of rules. I have been running Motul Motocool for the past few years along with distilled water. At the end of each year I drain all the coolant out of my bikes. 

It's been a while, but a few years ago I had to disassemble a Corvette. Thankfully, they are fairly easy to dismantle. Here's is a few photos of the one I worked on. We were asked to add strobe lights to the four corner lamp housings.


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## cvjoint (Mar 10, 2006)

Thinking back MDF was a terrible material to bend. But if I were to do it all over again I would totally do a composite box top. It would be stronger (especially since it is curved), lighter, and thinner which means more box net internal volume. Birch has crossed into my mind but I never worked with that material so I was weary. No doubt it should bend better. 

The glue has been drying for almost a week now and the box feels really sturdy. I've been adding glue to make sure it's airtight. I am foreseeing the first coat of finish to go on it Thursday night. 

For HPDE they won't ask every driver to remove their glycol. I believe it is not a rule to allow more freedom. I agree that it is very dangerous. Compared to a bike though, cars can drift more readily.


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## BP1Fanatic (Jan 10, 2010)

audiokid1 said:


> As for the track...I'm surprised they let you use ethylene glycol at all. I ride the track frequently, but it's on two wheels so we may just go by a different set of rules. I have been running Motul Motocool for the past few years along with distilled water. At the end of each year I drain all the coolant out of my bikes.


I have another boyee with a ZX10R, ZX636R, and R6. We took the R6 to Mid-Ohio for a track day too.


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## audiokid1 (Jul 2, 2014)

I've eyeballed what the guys are paying for track time out west and it's pretty salty.

I haven't ridden at Mid Ohio yet. It's been on my "to do list" for quite some time.

The National Corvette Museum (NCM) track is on my list for this year.

Tracks I frequently ride are Gingerman, Grattan, Autobahn Country Club, Putnam, Braber, NOLA, and Road America. 
Nashville had a fun little course at the speedway, but they no longer hold events.


CV, as for Baltic Birch.....it's a better material all way around and it's easy to work with. It cuts well and doesn't dull blades near as fast, is lighter, the sawdust isn't near as harmful as MDF dust, easy to screw and staple, and doesn't swell up near as quickly as MDF if exposed to water. 
The only advantages to using MDF is that it is cheaper, easier to find, has a consistent thickness, and you can paint it (if the project calls for it). 

I rarely have MDF laying around the workshop anymore. The only stuff I do have is usually 1/4" or 1/2" and it's used for templates.

As for kerfing; Baltic Birch is a better choice due to being constructed of veneer cores vs MDF being made of sawdust and glue.


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## Lanson (Jan 9, 2007)

You can also mix sawdust with glue, and use it as a type of filler in these situations. Though short-strand reinforced filler would probably be my way of doing it.

Another Vette build, nice! The '02 I'm working on is kicking my ever-loving ass.


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## cvjoint (Mar 10, 2006)

I took some of the advice and got reinforced body filler. I have to go back in there and use if for the soft sanding round. 

Here is what it looks like after 4 hours of hard sanding. 

Front









Rear









Sides


















Test fitting with the targa top. Fits this time but very tight. Still have to shave off a bit of the corners.


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## BP1Fanatic (Jan 10, 2010)

That's beautiful work but all that sanding is too much for me! I'm a simple L7 enclosure man. I have never worked with fiberglass either. Shet, it's a PITA just to carpet a box IMO. I'm lazy.


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> That's beautiful work but all that sanding is too much for me! I'm a simple L7 enclosure man. I have never worked with fiberglass either. Shet, it's a PITA just to carpet a box IMO. I'm lazy.


I think you can see the same type of laziness here in that I never counter-sink subwoofers! I'm not doing any additional work unless it's functional. If I don't sand it again the box won't fit snuggly after coating.


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## BP1Fanatic (Jan 10, 2010)

I've never countersunk a speaker either!


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## t3sn4f2 (Jan 3, 2007)

Looking good. You might want to throw in some vertical bracing in there as well.


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## cvjoint (Mar 10, 2006)

The vertical bracing is a good idea. I'm relying on the box being small and therefore quite rigid. It's only 2.5 cubic feet net as it is and braced at least every foot.

*UPDATE*

I sanded the box down until it fit in the car without hassle. This required quite a bit of rounding off in the corners. I used the orbital sander this time to get a bit more precision. 










Wherever there were any gaps between the kerfed piece and the box faces I filled it in with the reinforced body filler. Same for covering screws. That stuff works like a charm. 










Next I realized that the grilles I made to keep the stuffing at bay were resonating loudly when flicked. It only resonated where the ends were terminated in thin air. So I picked up some scrap wood and glued the ends down to the box. So close to doing something silly! 




















Here you can see a 2" hole drilled for the 5 way connection post. It is the smallest heavy duty connection post I could find. As you can see the clearance is minimal in this build. 










I made a decision to waterproof everything in this build inside and out. So I started with the inside of the box. I found this guy at Home Depot which promised to waterproof things. 



















At this point the box is built! On with the coating. 

Typically I just wrap things in carpet and call it a day. This time I wanted to try something new. Duratex fit the bill. I never used it, it's thinner than carpet which helps with fitment under the targa top, it's chip proof, and waterproof. 










First layer, looking really good but mostly rugged and pro-audio flavored. I just noticed my BG Radia 520i 7 foot floor standers at home are also finished with this stuff. Awesome!


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## Lycancatt (Apr 11, 2010)

duratex is the only paint for me when I do cabinets I know are gonna get the crap beat out of them


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## BP1Fanatic (Jan 10, 2010)

Looking good!


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## cvjoint (Mar 10, 2006)

UPDATE

I find that there is at most 0.5 inches of depth available by gutting the a-pillar. That is unfortunate. I was hoping for an inch of depth to mount the tweeters directly to the a-pillar panel. Instead, I will have to make half inch spacers to fit them. That translates to a bit of viewing area loss as well. The good news is the a-pillar is very robust, made out of thick plastic and held down by screws and clips. None of the clips have to be broken to fit the tweeters. The tweeter is an air motion transformer line array, more on that later. 

First, I had to remove the rear view mirror. Twist the base with Thor like strength.










Second, start removing the center trim piece as it it holds the a-pillar ends. Move the sunvisors to the side by dislodging them from the inner mount. Pull down on the sides of the center trim to remove the clips. As you do so a panel pops out on the inner sunvisor mounts revealing a torx screw. Remove the screw. Pull down on the center trim piece to remove. Leave it hanging by the wires enough to get the a-pillars out. 



















Third, remove the sunvisor. Pull down on the beauty cover to reveal the three torx screws. Remove the screws. 











Fourth, unhook cables behind a-pillar and pull to release the a-pillar from the clips. That's it.











So what is there to know about the a-pillars for audio. The plastic is thick and robust. It shouldn't deform if mounting tweeters directly to it. It is held by the sunvisor's torx scrws up top so it can hold heavy loads. None of the clips mount on the big face so it can be drilled and trimmed at will. One thing left to do, find out how much room there is behind it. The frame itself looks like a heavy steel bar with a channel inside to route cables. I took the a-pillar out and drilled it to measure the depth.



















Half inch of depth.


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## BigRed (Aug 12, 2007)

cvjoint said:


> UPDATE
> 
> I find that there is at most 0.5 inches of depth available by gutting the a-pillar. That is unfortunate. I was hoping for an inch of depth to mount the tweeters directly to the a-pillar panel. Instead, I will have to make half inch spacers to fit them. That translates to a bit of viewing area loss as well. The good news is the a-pillar is very robust, made out of thick plastic and held down by screws and clips. None of the clips have to be broken to fit the tweeters. The tweeter is an air motion transformer line array, more on that later.
> 
> ...


loving everything about this build  Go George!!!


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## cvjoint (Mar 10, 2006)

BigRed said:


> loving everything about this build  Go George!!!


:devil:

*UPDATE*

The subwoofer of choice is the Vifa NE265W-08HS. Let's break that down. Vifa is one of the world's largest producer of speakers, a lot of it being OEM product in TVs, sound bars, etc. Vifa as well as many other traditional Danish companies are now part of Tymphany. It seems like they have Danish and Chinese design and like almost everyone they build in China. 

The NE woofers are ideal for this application. Weighing only 5 lbs the woofer is one of the lightest on the market. Eight of them still weigh only 40lbs so that I can lift the subwoofer box easily over the rear spoiler once a month at the track and not break my back. How did they do it? Aluminum frame, neodymium magnets, and titanium coil. That is the winning combination for low weight, cooling, and high fidelity sound. To top it off they implemented copper in the motor for Faraday shielding to keep inductance low and specified an ideal suspension made out of well damped composite and low resonance soft rubber for great transient response. The spider is large, light, looks fairly permeable and has fine etched voicecoil leads symmetrically along its diameter. The woofer is high fidelity enough to be used as a midrange, thanks in part to the asymetrical terminations of the cone and surround mating. See if you can spot them! Here are the specs. 

Transducer Detail | Tymphany

BONUS ROUND WITH ENGINEERS:
As meany of you know XMech, or the total mechanical limit of the speaker is a specification that is unusually hard to get and doesn't appear on white sheets. For that I had to contact Tympany. Here is what I got. The Xmech is 16.84mm in both directions, limited by the suspension surround. 

So where does that put the Vifa NE? Well it is a Scan Speak Revelator 10" competitor and well matched, and that is as far as I can tell the best in the business. Xmax is higher at 9.4 vs. 9mm. Xmech is higher at 16.84 vs. 14mm. It has a neo magnet instead of ferrite. But is that xmax true? As far as I can tell it is underrated, or if you wish rated at 10% distortion not 20% like most subwoofers. At 20% distortion is about 12mm. I know this because it's the same motor as the 12" and I've seen a Klippel of it. Ok so it's as good or better SQ wise as the Revelator, it is(2.5lbs or 50%) lighter, and it has almost 3mm more throw in both directions. That's why I didn't buy the Scan Speak. 

The neo motor is a godsend for use in a small sealed box. Because of the high BL the woofers has very good extension in a tight box. The motor is strong enough to offset the box's inherent air spring. It also results in low inductance. Other bits that make it work great in a small box are the soft suspension parts enabling it to reach a resonant frequency of 23hz and a low Q of just .3! I modeled them in WinISD for years against competitors, only a few woofers work better in a small box and all of them have large double or tripple stacked ferrite magnets. When you account for the displacement of their magnets, the Vifa beats them too!

Ok, enough theory.

*BUILD*

I used some wide speaker gasketing from PE although the speakers seem to have built in gasketing on both sides. Better safe than sorry, air leaks can be terrible. 











This is the start of the assembly process. I put 3 layers of Duratex on the box. The directions state one coat for indoors, two for outdoors. I think you need at least two coats to get the finish right no matter what. The 3rd one was added insurance.

Found a good way to bolt the drivers face in by dropping my phone in there with the flashlight on to see any misalignment as light seeping by. 













Checked the clearance between the grille and the surround: .6", more than enough.










Notice the spokes are near the screws, smart design to keep the basket from bending without increasing its weight.










Notice the heatsink on the motor. I special ordered the subs to come with the heatsink option. I wouldn't use it in infinite baffle but with a small sealed enclosure I need all the cooling I can get on those neo magnets. 



















Next I fired up Woofer Tester 2 to check coil resistance, QTS, and FS for every driver. 









With flash:

















Without flash:


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

Looking forward to hearing this, its about time I subscribed to this.


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## cvjoint (Mar 10, 2006)

TOOSTUBBORN2FAIL said:


> Looking forward to hearing this, its about time I subscribed to this.


I'm curious to see how well this push-pull works compared to the Tymphany LATs I used before! I know you like push-pull 

More on POWER

The Vifa's are rated IEC 265-5 190w without heatsink and 220w with heatsink. I could only get 6 with heatsink. JBL also uses the same standard in rating their proaudio drivers.  JBL also did the homework and explained it to us here: 
https://www.jblpro.com/pub/technote/spkpwfaq.pdf

According to JBL this is a 40hz-5khz test tone with 12db bandpass filtered, with 6db crest for 8 hours! Brutal. 40hz is not as low as 20hz but mine will be sealed which is far steeper of a slope than 40hz infinite baffle. 

Doing the math the Vifas can run 8 hours without heatsink:
1520w continuous with 6080w peaks

With heatsink:
1760w continuous with 7040w peaks

Given that I only have 2,500w @14.4V and that sub duty is not continous I think the coils are more than sufficient. There is a way to cook them at that's only with continuous test tones for hours. 

I'm still going to try to find two more with heatsink, but they are discontinued from what I got out of Parts Express.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

cvjoint said:


> I'm curious to see how well this push-pull works compared to the Tymphany LATs I used before! I know you like push-pull
> 
> More on POWER
> 
> ...


I'm betting they'll be better. Remember, the lats are force cancelling but not distortion cancelling like these will be.


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## jtaudioacc (Apr 6, 2010)

you live pretty dang close to the Bay Bridge, George...not that i'm stalking your gps embedded pics or anything. :laugh:


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## cvjoint (Mar 10, 2006)

jtaudioacc said:


> you live pretty dang close to the Bay Bridge, George...not that i'm stalking your gps embedded pics or anything. :laugh:


JT can you try to find my geotags again? I asked photobucket to hide that ****. Thanks!


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## jtaudioacc (Apr 6, 2010)

cvjoint said:


> JT can you try to find my geotags again? I asked photobucket to hide that ****. Thanks!












i have an extension for chrome so when i hover over an image, the exif data shows up. (that blue bar) when you see that red gps icon, you hover over it and it shows the map, click on it, and it takes you to google maps. lol

it's still there. i think they are embedded into the image. i'm not sure photobucket can take that away or not.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

George, how long ago did you order the Vifa's? Looking now, it doesn't look like parts express sells vifa anymore, and madisound doesn't list them either.


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## lostthumb (Dec 16, 2005)

TOOSTUBBORN2FAIL said:


> George, how long ago did you order the Vifa's? Looking now, it doesn't look like parts express sells vifa anymore, and madisound doesn't list them either.


I believe the name Vifa is no longer. Look at the Tymphany lineup which should be the same.


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## cvjoint (Mar 10, 2006)

TOOSTUBBORN2FAIL said:


> George, how long ago did you order the Vifa's? Looking now, it doesn't look like parts express sells vifa anymore, and madisound doesn't list them either.


I ordered the in March 2015, and they got here 6 months later. Not what I would call expedient.


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## rton20s (Feb 14, 2011)

This is looking so cool George! I really hope to get the chance to give it a listen. Are you going to try to make it out to any of the "local" GTGs or MECA comps? 

And it looks like all that PE has left are the 8 Ohm versions of the 12" and 8" model under the Tymphany brand. No more 10". And as mentioned, Madisound doesn't carry any of them. Meniscus appears to have the 4 Ohm 12" model under the Vifa brand in stock, but no 8" or 10".

It also looks like Solen in Canada probably has the widest selection of the NE subwoofers. They have them listed under the Peerless brand. They have the 12" in 4 Ohm, and the 10" and 8" in both 4 and 8 Ohm. They also list their current stock volume for each driver.


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## cvjoint (Mar 10, 2006)

rton20s said:


> This is looking so cool George! I really hope to get the chance to give it a listen. Are you going to try to make it out to any of the "local" GTGs or MECA comps?
> 
> And it looks like all that PE has left are the 8 Ohm versions of the 12" and 8" model under the Tymphany brand. No more 10". And as mentioned, Madisound doesn't carry any of them. Meniscus appears to have the 4 Ohm 12" model under the Vifa brand in stock, but no 8" or 10".


I'm pretty sure you can special order them. Tymphany makes them without heatsink I'm pretty sure. Special order means you pay close to MSRP and it takes a long time. 

Funny fact: I just contacted Tymphany to try to get two more with heatsink and some Klippel reports and the guy I normally talk to is not there anymore. His replacement is none either than Thilo Stompler. Yes, the TC Sounds guy is working for Tymhany now. 

I'm down for GTGs when this is ready! Should be in the next week if all goes well.


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## rton20s (Feb 14, 2011)

cvjoint said:


> I'm pretty sure you can special order them. Tymphany makes them without heatsink I'm pretty sure. Special order means you pay close to MSRP and it takes a long time.
> 
> Funny fact: I just contacted Tymphany to try to get two more with heatsink and some Klippel reports and the guy I normally talk to is not there anymore. His replacement is *none either than Thilo Stompler*. Yes, the TC Sounds guy is working for Tymhany now.
> 
> I'm down for GTGs when this is ready! Should be in the next week if all goes well.


Well isn't that interesting! It will be cool to see what he might come up with working with the Tymphany team. 

I don't think there are any bay area GTGs scheduled yet, but take a look at the MECA schedule. Most of the comps are run similar to GTGs these days anyway. Save for the food.


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## Proboscis (Mar 15, 2016)

Sweet American super car you have made. I'm digging it


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## papasin (Jan 24, 2011)

rton20s said:


> I don't think there are any bay area GTGs scheduled yet, but take a look at the MECA schedule. Most of the comps are run similar to GTGs these days anyway. Save for the food.


There is one coming up Dustin. 

http://www.diymobileaudio.com/forum...sq-only-april-23-2016-vallejo-california.html

As for food, well, I'll be talking it over with the host. I'll know more soon...we could make it potluck if they are ok with that.


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## cvjoint (Mar 10, 2006)

Dropped the box in the car last night, all assembled powered off a mini 10w amp I had around. My initial impression was mostly negative but I'm reserving final judgement for when I am done with the whole car. 

1. The car was vibrating and rattling. Most of it was audible from the outside of the car but we're talking only 10 watts. 

2. It sounded a bit boomy, but the caveat is the miniamp doesn't power much under 40hz. Big caveat. 

3. Woofer Tester 2 came up with a total Qtc of 1.11. That's certainly on the high side. Modeling showed .98. I attribute the difference to either lack of break in on subwoofer suspensions or variance in production for the woofers. 

4. Some vibration of the box is notable, mostly on the top face. I'm pretty sure vertical bracing would help a lot here. 

5. Good news is the woofers were dead silent with excursion. 

6. The other good news is that they played full range sound like a champ! 

7. The box is already super heavy. I could barely lift it out of the car by myself.

I was hoping not to have to sound treat the car as it makes it heavy. That doesn't look like an option anymore. 

I've also been researching the effects of high Q. This thread is spot on for anyone that has time to look through. Subwoofer Qtc and 'tightness' - Page 2 - diyAudio

Here is the key simulation:









The upper right quadrant shows the step response. From the thread, key parts:

"Q=5 Q=2.5 Q=1.667 Q=1.25 Q=1.0 Q=0.707 Q=0.5 Q=0.25" red green blue blue pink yellow brown pink respectively. 

"In summary:

Q=0.707 Fastest settling time, some overshoot
Q=0.5 Slightly slower settling time than Q=0.707, but less overshoot (better control of cone)
Q=1.0 Slightly slower settling time than Q=.5, significantly more overshoot, but more output at resonance and less distortion."

Based on this theory I'd love to have a Q of .5. The only way I could do that with this box would be to get four Seas L26RO4Y subs and plug up the other 4 holes. Output and distortion would stay the same but weight would go up by almost 49 lbs. That means it would be a two person job to lift it out of the car. 

I haven't found any evidence that the human ear can pick up the difference in step response between .5 and 1.1 but it's nice to know the Seas setup can be a backup plan in case it does turn out too boomy.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

If you decide to treat the car, pm me. I have a bunch of rew data you can look through on a bunch of different products. To be honest, you won't find a better performance to weigh ratio than dynamat xtreme when weight is the higher priority.


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## ErinH (Feb 14, 2007)

George, the Qtc of 0.50 has been my ideal 'target' Q for a few years now. The big reason why is group delay. The higher the Q, the higher the GD which by itself may be a rather meaningless value (depending on what technical articles you read) but when you are trying to pair it to another driver (ie: midbass/subwoofer phase) it's an area I feel has merit. 

Also, I must admit I was really surprised to see the direction you went here given all the weight in such a sweet sports car. Curious to see how this develops some months down the line.


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## cvjoint (Mar 10, 2006)

TOOSTUBBORN2FAIL said:


> If you decide to treat the car, pm me. I have a bunch of rew data you can look through on a bunch of different products. To be honest, you won't find a better performance to weigh ratio than dynamat xtreme when weight is the higher priority.


Will do. The first run will be the "lite" version. I'm hoping I'll get by with one layer of dynamat on the doors and the push pull for the rest. 

Funny that we both reached the same conclusion, although I haven't seen any data. I've tried many Dynamat extreme competitors only to go back to my first choice. They all chop off your fingers, but the Dynamat with the thicker aluminum does it bloodier and you can reapply it many times making several cuts with the same batch. It also sticks better, which means you can also cut your fingers applying it horizontally. 



ErinH said:


> George, the Qtc of 0.50 has been my ideal 'target' Q for a few years now. The big reason why is group delay. The higher the Q, the higher the GD which by itself may be a rather meaningless value (depending on what technical articles you read) but when you are trying to pair it to another driver (ie: midbass/subwoofer phase) it's an area I feel has merit.
> 
> Also, I must admit I was really surprised to see the direction you went here given all the weight in such a sweet sports car. Curious to see how this develops some months down the line.


It seems like theoretically .7 has faster settling time, so there is a pro. But yeah, with infinite resources I'd also go for .5 ish. Things is you always give up output, or a lower harmonic distortion profile, or both aiming for a low Q. No free from downsides choice here. 

I still don't get group delay to be hones. (1) If you equalize in WinISD group delay changes. So presumably I can just EQ my box to achieve the group delay I want, and I do have the power and cone area/xmax to do so. (2) the group delay is actually very low in WinISD and worlds better than a vented alignment. (3) group delay is offensive, but at which point at sub frequencies. 

I think both the door drivers and the subwoofers will have an almost identical resonant frequency. Wouldn't the phase behavior be almost perfect? 

There are two types of weight, the kind that can be removed for track use, and the kind that always stays with the car. I'm aiming for having only 40lbs staying in the car at the track. So that's negligible. On the road it just hooks better with more weight on the rear axle. The car has no grip up to 80 mph with 650hp/650tq and rear wheel drive.


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## cvjoint (Mar 10, 2006)

*UPDATE - Midbass/midrange install*

I picked to install the ProAudio midbass instead of the HiFi midbass the first time around. The custom order 4 ohm B&C 10NW64 is then the chosen midbass. Quick run of the benefits of the driver:

PROs:
*Neodymium magnet and aluminum heatsink result in a low weight of just 6.5 lbs
*waterprof assembly and pro-audio construction to fight the elements in a car door
*Ventilated voice coil gap and large 2.5" copper coil with 300 watts continous rating and 600 watt peak
*high damping surround and suspension assembly means it can withstand abuse in free air
*96 db sensitivity
*4 ohm coil means I can feed it 350 watts continuous
*Copper shorting cap on polepiece and typical high quality B&C construction mean extended HF response and low distortion to cross over at 1 khz

CONs:
*Ventilated voice coil gap is possibly noisy, I may plug it, or deaden the door more
*light cone may not be as well damped as the HiFi verison
*high damping surround and suspension assembly

I first built some 1/2" spacers out of MDF using the stock BOSE drivers to ascertain mounting tab locations









Spacers were sanded.










Machine on the left did the sanding, machine on the right did the cutting










Wires were run around the stock Molex plug. I left the stock wiring alone, sealed it against shorts and zip tied it to the wire loom in the door. The only opening to run wire is below the Molex plug, between the plug and the hose clip. 16 awg thick wire fit easily. 12 awg fit as well, but very tight. I did the math and I can get away with 16 awg for this length cable. 

From the inside:










From the outside, notice the new wire ran through the bottom.










From the door perspective. I forced my finger in the stock wire loom until it came undone to run the wire through. A bit painful but I didn't poke any of the stock wiring. 










The doors are stupendous. I think the doors alone make the entry cost into a 7th generation Corvette worth it. Large 9" cutout for a 10" driver, composite construction, large, very few mechanisms on board, and sealed from factory. 










A closer look:










Sound treatment is minimal. I only applied one layer of Dynamat Extreme. The door itself is stout and I don't see much gain from putting on more weight. My technique for applying Dynamat is to use it as one uncorrupted piece. That way the sheet works as a sealant as well as a mass treatment. In addition you'll see I spray painted the spacers to make them more water proof. I used the stock bolts to keep it into place. No cutting of any parts. Using the Dynamat in large chunks makes it easier to remove if the door needs fixing. 










A closer look










Passenger side is the same. 

The money shot. Door fit over the speaker without trimming. All original clips and screws were reused. All the door functions remain unchanged. I used Parts Express speaker gasketing tape on the speaker and the spacer. The door shuts with more authority and the interior road noise level is noticeably decreased. 










The OEM door panel itself is a perfect grille, sealing against the ProAudio rubber basket trim, and allowing 100% of the output to go through the door panel with the most minor deflection. If you need to go back to see the door panel, see this post: http://www.diymobileaudio.com/forum/2454689-post35.html


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## rton20s (Feb 14, 2011)

George, did you treat the outer door skin as well?


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## cvjoint (Mar 10, 2006)

rton20s said:


> George, did you treat the outer door skin as well?


I did not. The outer door skin and the plastic door cover remain untreated. I'm curious to see how many rattles I get without touching them. 

Overall, I'm not going to try to reduce road noise levels at all. I find them more than acceptable. I drove a soft top convertible before this, so the hard shell carbon fiber targa top coupe platform is luxuriously quiet by my standards. Second, I've reduced road noise tremendously by getting a second set of wheels with quiet street compound and keep the original set of wheels with slick type compound for track days. Best of both worlds, and imo better noise reduction than by adding hundreds of pounds of damping sheets. 

The rattles are another story. I'm open to add more sound treatment to quiet down vibration-induced noise. I'll start with the worst offending rattles once I hear what it can do natively without any treatment but the one door layer.


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## Isaac.Troseth (Jul 18, 2015)

The last C7 I did left me impressed with the doors as well. The boots snuck the wire through pretty easy.. overall way less difficult than anticipated! That's awesome you're taking full advantage of the massive hole for the driver in the door. Mine used Illusion c8s and I kept wishing I could fill the hole entirely.


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## cvjoint (Mar 10, 2006)

Isaac.Troseth said:


> The last C7 I did left me impressed with the doors as well. The boots snuck the wire through pretty easy.. overall way less difficult than anticipated! That's awesome you're taking full advantage of the massive hole for the driver in the door. Mine used Illusion c8s and I kept wishing I could fill the hole entirely.


I saw that molex plug and thought, shoot, no way to run wires. As I was about to cut the OEM wire to connect to it I saw a bit of light going through at the bottom of the plug. I was so close to not getting it. Most installs I've seen in Corvettes downgrade to a 6.5". What a waste! 

*UPDATE - Rear drivers for surround sound*

I never believed in delayed rear. Early versions of Pro Logic that take stereo sound and mix it to enlarge the rooms were terrible in execution. I've tried it over an over in Home Theater only to go back to 2.0 and give up on processing. What I did like were the DVD Audio discs before the format died, recorded from the beginning in 5.1. What a treat! But since none of the 2.0 to 5.1 algorithms cut the mustard at home I did not bother trying them in a car.

There were two cars that changed my mind. The first was Craig E.'s blue C6 Corvette using the JBL MS8, and the second was Gary Summer's Benz using the Alpine H800 processor. These two processors seemed to have improved the steering algo to the point where it works! My new Onkyo Home Theatre receiver also works superbly with the new Pro Logic steering algo. 

So I got the 'Vette with 5.1 locations, and I got the Alpine H800 to have my first go at this. I chose the Alpine H800 because it has optical input and I can maintain only one digital to analog conversion in it. I also like that it doesn't have built in amps. Everytime a new processor came out I compared it to the Alpine, and till this day I still think it is the ultimate processor. 

I'm skipping the center speaker because I don't obsess nearly as much as the rest over the vocals being dead center. Most of my music doesn't even have vocals. To do it right I would need to fit in the center of the dash a large 10" mid in a big box and a line array air motion transformer tweeter to keep up with my left and right channels. Never going to happen, and I never give up output and low distortion to get a minor soundstage improvement.

Covered in an earlier post, I'm replacing the 5.25" Bose drivers with 6.5" SB Acoustics Satori woofers. Here they are, side by side. The Satori use Neo magnets, don't be fooled by the large size compared to the Bose, they are not cheap ferrite motors, the magnets are in the same place in the periodic table: 



















Some of you scared me into not covering the flaps behind the speakers and sealing their enclosure. Good job. Scared so much that I decided to just bolt the speakers in the OEM locations without covering any of the air paths. I didn't want to have a malfunctioning airbag, or punctured ear drums on my conscience. So I just trimmed the enclosure to fit the Satori basket spokes and bolted it down. A spacer could not be used and was not needed. 










Next I had to assess whether the larger throw of the Satori would touch the plastic panels. To do so I installed the bottom trim piece but kept the top trim piece off so I can take a peak. It has about 1/3 of an inch clearance. That's why a spacer doesn't fit. Had to bolt the sucker to the enclosure directly. 










Since I can't seal the enclosure, the only way to separate the front and rear waves better is to seal the front of the speaker to the plastic panel ahead of it. The only thing I could think of was to add four layers of gasketing tape on the basket to mate with the panel. 










The gasketing tape fits around the original plastic round trim not on it, since the speaker is larger.


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## audiokid1 (Jul 2, 2014)

cvjoint said:


> *UPDATE - Midbass/midrange install*
> 
> 
> 
> ...


Looks to be the Italian Laguna LT18 or LT16 bandsaw. Nice tools in that shop you've been working in.


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## jtaudioacc (Apr 6, 2010)

no more gps on your Samsung SM-G935V aka Galaxy S7 Verizon.


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## cvjoint (Mar 10, 2006)

jtaudioacc said:


> no more gps on your Samsung SM-G935V aka Galaxy S7 Verizon.


JT, thanks for pointing out the geotags! I modified the phone and photobucket settings to remove tags. I will have to go back and modify my earlier posts too. 

*UPDATE - tweeters install*

*Tweeter selection*
I've chosen a pair of Aurum Cantus air striction (air motion transformers) per side to cover the upper octaves. The model number is AST25120, I got them from PE. Looks like I did good, they sold out. Here is the link:
Aurum Cantus AST25120 Aero Striction Tweeter 8 Ohm

Manufacturer's specs:
Power handling: 100 watts RMS/160 watts max 
• Impedance: 8 ohms 
• Frequency range: 700-30,000 Hz 
• SPL: 98 dB 1W/1m 
• Recommended minimum crossover frequency: 1,000 Hz 
• Dimensions: Overall: 6.30" H x 3.31" W, Depth: 0.98"

I'll be using one 4 channel amplifier to power them bridged. They will receive 125 watts continuous each. 

The better question is what are the ACTUAL specs. I've done some digging. Unfortunately people usually test the wider AMT from AC. While a company rebadges it and tests it, it seems to remove the felt backing. Some specs are better than the manufacturer states if you remove the felt. For example, there is no FS stated but one usually is implied as the lower bound of the frequency response, here 700hz. The FS is actually 500hz without the felt, so a 1,000hz crossover meets the rule of thumb of two times FS. Good. Some specs are not as good. It turns out the frequency response starts rolling off from 4,000 hz down if you remove the felt backing. If you keep it on it starts rolling off 2,000 hz and down. Most hobbysts also state a 1,000hz crossover point is a bit of a push at high volumes. Here are a few links if anyone is interested in research.

Harwood rebadges the AC AST but removes the felt I think:
Harwood Aero Striction question - diyAudio

This guy tests the other large AST diaphragm in a DIY motor and finds it is world class, and beat the ESS version by miles:
An information roundup for larger AMTs - AVS Forum | Home Theater Discussions And Reviews

So why use the AC AST? Simple. It is the best tweeter I've ever used and I've tried ring radiators, ribbons, the best domes, and the best planars. Here are a few I've used before:
Scan Speak Illuminator domes 3/4, 1, small and large chambers
Vifa NE
Vife ring radiator
PE planar
LCY ribbon
Boston Acoustics top of the line
Polk DB
Polk Momo top of the line
BG planars of all shapes and sizes
The smallest version of the AC AST
SB ring radiator
Seas Lotus
Airborne air motion transformer

The AC air motion transformers are miles better than the cheaper Airborne ones. The Airborne one would deform in the a-pillar when exposed to high temperatures, heck the pleats were not straight out of the box. The AC may have small irregularities but they are stout look great and sound great after a year of use. The pleats hold their shape forever. The AC also has no diaphragm resonance other than a small peak at FS, and the harmonic distortion is way better. The magnets/motors are top notch to boot. 

The time domain response is the best bar none. It competes with ribbons while having low harmonic distortion in the bottom octaves like a large dome. Unlike domes, increasing the size of the diaphragm does not sacrifice top end response so you can have the best of both worlds top end like a 3/4 dome and bottom end like a 1.5" dome, and the time domain response domes can't reach throughout the working band. The only thing domes have is output density, ie. big sound from small footprints, but if you can fit a large air motion transformer it is not an issue. I'm using the largest air motion transformer AC makes in pairs. 

The tweeters are massive. Weighing in at 1.8 lbs each with NEO magnets and all. The faceplate is 1/4" aluminum, the motor system is made up of two AST 2560 motors! The terminals are stout. The only thing you have to be careful of is the backing foam and mesh screen on the motor ungluing themselves at which point you can glue them back on. I think they use glue lightly to service them easily and to allow diyers to remove the backing if they wish. 

*Install*

As shown previously, the a-pillars only have a max of 1/2" depth. The tweeters are 1" deep so I made 1/2" spacers and applied Duratex to the MDF. Start with clean MDF sheet. Pre drill holes to get the jigsaw to cut all 4 corners. Use patience. 










Size up the task










I wrapped the a-pillars in blue painters tape and made the cutouts in the plastic. Not shown because it was brutal. 

Couldn't find black socket screws to match at Home Depot so I got something that works temporarily. 










Gasketing tape all around and speakers wired in parallel:










*Final pics*



















Ok, so I had to lose about 3/4" of viewing area.


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## audiokid1 (Jul 2, 2014)

jtaudioacc said:


> no more gps on your Samsung SM-G935V aka Galaxy S7 Verizon.


I hope this comment isn't in response to what I had said..... CV mentioned working in a community shop. I was just stating that it appears they are providing their "clients" with nice tools to work with for the money they are paying.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

audiokid1 said:


> I hope this comment isn't in response to what I had said..... CV mentioned working in a community shop. I was just stating that it appears they are providing their "clients" with nice tools to work with for the money they are paying.


No, in a few previous posts his phone had been tagging his location in the pics, which JT noticed and advised him of.


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## cvjoint (Mar 10, 2006)

audiokid1 said:


> I hope this comment isn't in response to what I had said..... CV mentioned working in a community shop. I was just stating that it appears they are providing their "clients" with nice tools to work with for the money they are paying.


What ^he said. No worries. 

Yeah the machinery is quite nice. They also come in and change the blades so it always works nicely. I managed to get some drill accessories stuck and one of the tech guys fixed it. Just the good stuff of working with tools.


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## cvjoint (Mar 10, 2006)

*UPDATE - controllers installed*

I never really liked the plaque displaying all the low slung horses. The benefits of tearing it up are then many. To start off I placed some double sticky on the back of the Alpine controller and placed it on top of the plaque. Pulling on the controller takes out the plaque out of the dash entirely. That makes for an easy to disconnect and stow away controller for parking in shady neighborhoods. The install was a breeze, just double sticky tape and drilling a couple of holes. The panel itself can be replaced fairly easily, kids nowadays add carbon fiber (finish) ones in just about every car. I like to believe I drilled away the obnoxious and made it functional! 




















To run the wire, just disconnect two pieces of the center trim. All clips. When removing the center tunnel side trim make sure to pull towards the back of the car after the clips have been take care of. Putting it back requires that the notched end goes in the dash at the tip before the clips are pushed in firmly. 

This pic shows what is behind the small triangular trim panel. 










As in all my cars, the gain knob for the sub amp is a staple. Nothing like having 2,500 watts at your fingertips, yet hidden enough so no passenger has access. 










Finished pic:










*First impressions*

As simple as this install is it has may benefits. The rotary knob volume control is as easy to access as it can be. The 12V socket can still be used. The screen view is blocked by the shifter in normal use but it's not exactly displaying much information anyway. All the playback information will be on the phone. More on this later. However the screen is not blocked in gears 2, 4, 6, and 7. So while stationary with the engine off the screen can be viewed for tuning. It may not matter much because I can pull the controller with the dash plaque on the back and hold it as a game controller for tuning. 

Despite the fact that it's just held by double sticky tape the feel is firm and I can press on the buttons as hard I need to without much wiggle. 

*Other pics for fellow Corvette owners that want to pry*

, or simply for those interested on how the car is put together. From the dash back it's all clips so there is no trick to taking off the car panels until you get to the rear speaker covers which have an obvious screw-hook. 

Halo cover and door sills. Zoom in to see the clips better. 



















With door sills removed all you have to do is remove the two screws holding the manual door release cables to run wires. No need to remove the carpet or seats. 










Be careful when removing this piece. The clips run at 90 degree angles which is always risky when prying. 










All clips around the rear side windows as well. Remove the halo trim piece first and the rear speaker covers before you get to this one.


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## whoever (Nov 21, 2008)

sub'd


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## cvjoint (Mar 10, 2006)

*Mixing theory with raw data*

Before it all materialized in boxes at my door I modeled the Vifa subs in WinISD. Predictions not worth producing here showed an overall Qtc of .98 using the OEM provided TS specs. I was a bit upset to see the actual Qtc tested in the built box with all 8 subs mounted to it at 1.11. From this I had two questions to answer, (1) why was the Q larger than predicted, and (2) is the Q of 1.11 producing a group delay that is audible. 

*(1) why was the Q larger than predicted*
I find that the Vifa subs always have a higher FS than stated in the white sheets and a higher Qts. When I plug in one of the specs as tested with the Woofer Tester 2 in WinISD I get a Q over 1.11. Theory matches raw data now. So the culprit is that the OEM states more respectable numbers than you get in the box. Perhaps with a bit of break in the speakers will mimic the OEM specs. In either case, here is what I found. It's rare we get 8 drivers of the same type to test!!!

This is a quick listing of the most relevant three TS specs, resistance, resonant frequency, and Qts. In the first row I listed the OEM white sheet specs. In "Var" columns I listed the variance listed in the white sheet specs if any was listed. I find that the FS is accurate albeit with 15% variance as noted by Vifa. Only two drivers exhibit that much variance, and both are the ones without heatsink. Odd, but this is evidence there may be a larger coil in the heat sink models, lowering FS due to mass. I find that the RE varies more than Vifa states at up to 10% vs. 5%, so double! Not cool. QTS varies a lot too, and it's always larger than the spec sheet, which is why the Qtc ended up higher. Now it adds up. Whether it's due to lack of break in, Vifa using a different way to test, or something else is anyone's guess. 










Here is an example of one full set of results. The LE is more than double what Vifa states, which is also not cool.










So what does it all look like if you test all 8 woofers mounted in the box with polyfill? Like this. QTC=1.11, FSC=64.4, RE=.983. So I get the 1 ohm load as expected. Q is a bit high but it is what it is. So next, let's see what implications it has. 










*(2) is the Q of 1.11 producing a group delay that is audible?*

Folks avoid small sealed boxes presumably because they may sound "boomy" or "resonant." Whatever the subjective word choice the theory hints at group delay. Is it high with this box? More importantly, is it audible? I find that it's not even audible. I predicted group delay using the TS parameters of the worst testing Vifa sub in the stable. To assess whether the group delay is audible I use the rule of thumb that delay time in msec X frequency = <400 delay isn't audible. This is imo a much much improved rule of thumb than "20ms" or any other single number. 

In blue I've plotted the maximum delay you can get away with and not have it be audible. The box I built is below that throughout the range 20hz to 200hz. The closest it gets to audible is at 80hz 4.5ms actual vs. 5ms audible. To me it looks like you really have to make a tight box to have audible group delay. It is however fairly easy to make a box too small for low midrange speakers. I know I've made a few too many small midrange boxes the resonated pretty badly! 










A second way to see whether the group delay is acceptable or not is to plot it vs. a system that is presumably top notch in terms of group delay. I've simulated 4 Seas 10" subs, the L26ro4y that models to a small Q of .53 in my box, which is ideal for group delay. See the comparison plot below. The Vifa arrangement has lower group delay below 50 and over 150 and it is generally comparable. We can't talk group delay without talking amplitude. Since the subwoofer will be crossed 63hz 4th order, the group delay in-band 20hz-63hz is more important than over 63hz. The Vifa system has substantially lower group delay below 50hz. 










While we're at it, check out the excursion at 2,500 watts. 7.5 mm or under, well below xmax! Should be the lowest harmonic distortion systems I've ever had. Xmax is 9.3mm and xmech is 16.8mm. 










SPL


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## cvjoint (Mar 10, 2006)

*First breath of 12V*

The amp rack is the final piece to the puzzle. It's a 1/2" MDF board coated in 3 layers of Duratex. I wanted an amprack that allows all components to have open air top and sides for cooling, and be light for easy removal. On the amp rack, which measures 15"x 42" I have:

*Arc Audio KS 2500.1 wired at 1 ohm for 2,500 watts @ 1% THD (powering the 8 Vifa 10" subs)
*Arc Audio KS 300.4 wired at 2 ohm for 350 watts x 2 @ 1% THD (powering the door mounted 10" B&C mids/midbass)
*Arc Audio KS 125.4 wired at 2 ohm for 250 watts x 2 @ 1% THD (powering the a-pillar mounted AMT tweeters)
*Arc Audio KS 125.4 wired at 4 ohms for 150 watts x 2 @ 1% THD (powering the 6.5 Satori drivers fullrange)
*Alpine H800 processor
*Audioengine B1 bluetooth receiver
*A 12V to 5V converter for the bluetooth receiver
*Monster Cable 300 series fan over thread power distributors
*Monster Cable 300 series RCA jacks
*Optical cable connection from BT receiver to Alpine processor
*Two Anderson Powerpole 175 AMP power quick disconnects
*Six Anderson Powerpole 30 AMP speaker wire quick disconnects


There is still some wire cleaning to be done


















*Digital to analog conversions*

1. Sound starts off in the digital world typically in Spotify. I have it set at 320 kbps, which is the max fidelity setting. I can find 99% of what I want on Spotify and I can't tell the difference between 320 kbps and 1,440 kbps (CD quality). 

2. My Samsung Galaxy S7 Edge sends it out through Bluetooth AptX encoding, remaining in the digital world. AptX compression is 352 kbps and again I can't tell the difference between it and CD quality. I've compared it to normal bluetooth (SBC) and the difference is night and day.

3. The bluetooth receiver, Audioengine B1 receives the AptX signal and decodes it. It passes it out through optical afterwards remaining in digital format.

4. The Alpine H800 receives the digital feed, applies the Pro Logic II algorithm and filters it channel by channel. The signal is converted for the first time and only time to analog for amplification and sent to the amps via RCA cables. 

5. Amplifiers are ran filter less except the monoblock which has to apply a bandbass filter of 10hz HPF and 230 LPF. All signals except that of the subwoofer are in the digital domain, all active. 

The idea for filtering was to run a proper Pro Logic II steering algorithm with rear speakers and 2 way front plus sub. The signal path has only one digital to analog conversion and that's in the Alpine unit using top notch DACs. The digital signal is compressed as little as possible while being wireless and easy to tune into. 

*Filters applied:
Sub:* I wanted no subsonic but the amplifier requires a HPF. The minimum filtering the Arc amp will allow is 10hz subsonic so I'm using that. Note also that it is -3db @15hz due to the natural rolloff of the amplifier circuitry. LPF is set at 63hz 24db
*Midbass:* 63hz to 1,000hz 24 db
*Tweeters:* 1,000hz to 20,000hz
*Rear:* 160hz to 20,000hz

Response out of the box, passenger is red coded:









The sub digs down deep! Same output at 20hz as it has at 63hz. You have to love the way this car loads. I also venture to say that having eight subs means I'm reducing cabin nulls to a minimum. 

The sub frequency response is a typical car audio dual peak at 30hz and 55hz. The 30Hz peak is higher so I could have made the box even smaller. 

The midbass drivers drop like a rock below 140hz. This must be the Pro Audio nature of the driver. Even free air in a car door the bottom end is weak. Subjectively it sounds super snappy, which again indicates a sharp rolloff. 

The tweeters have a progressive rolloff starting at 8khz. By 20khz, they are 20db down. Without tuning the top end was clearly not there. 

*1 hour tuning job*
This is the first time I used the Alpine H800 and RUX so it took me a little to get to use it. It was intuitive and got a lot done at 2am to 3am!










I extended the top end response out to 18khz where it is now only 3db down. I like a progressive rolloff of the highs just not as much as it was out of the box. The most I added was 5db of boost at 20khz. There is lots left in the processor. Boosted every step under decreasing by 1db. I cut a bunch of the low midrange out because it was peaky. Everything else didn't seem to work. I couldn't fill in the midbass and I couldn't get rid of the dual sub peak. Next time. 

*Harmonic distortion*

I increased the system output until my ears could no longer tolerate it for more than 5 seconds. Ignore the SPL scale. My omnimic doesn't seem to report the proper output level, not sure why. I can't get it out of the 90db range lol. I'm guessing I was at over 110db by any weighing. This is with the tweeter crossed at 1,6hz. I forgot to test it after lowering xover to 1,000khz. As you can see harmonic distortion is nonexistant. Below .4% throughout except at 63hz where it is 1.3%. The highest distortion award goes to the midbass drivers. The B&Cs are the first to struggle, and that is right above the HPF.


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## cvjoint (Mar 10, 2006)

I believe the 120hz dip is actually a null caused by boundary interference. The distance from the door speakers to the center wall is probably 1/4 wavelength which is a recipe for cancellation. It also explains why I could not use EQ to fix the dip. 










Speaker Placement 101: How to Fight Boundary Interference

If this is true, I've found the car's first major drawback.


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## cvjoint (Mar 10, 2006)

*2 day review*

Overall the car is sounding great! It shines at playing back goa trance and deep house. I particularly wanted something that plays house well. It's got the output of a club but it's more refined, especially when it comes to lower octave quality. It's flat and easy to listen to, maintains composure at all SPL. The only two things I'm missing from my previous builds is that BG planar midrange transparency and a larger direct to radiated sound ratio in the top octaves. It's better everywhere else.


*SPL*
I've put on there some of my all time most demanding tracks and haven't found the limits of any of the drivers and I get the feeling I'm far from it. I back away from cranking it more once my ears get plugged after a couple of songs. With subs I can typically tell they are close to the limit because the Q goes up audibly and the low end disappears. Not so with this one. The midbass is typically easy to bottom out or to heat up the coil with continuous low midrange but these ones are very well composed. The AMT line array is not struggling with any crossover 1khz to 1.6khz that I've tried so far. Hands down the most capable sound system I've built so far.

*Harmonic distortion* 
Inaudible as far as I can tell.

*Frequency response*
Needs a little work. There are obvious cuts over 100hz to 20,000hz. The sound is pleasing and easy but misses a bit of reference detail I've come to expect from my Home Theater built. I need to spend a lot more time tuning and I'm still rolling off the top end a little too much for my taste. 

Midbass got 5db of boost at 110hz with 0.5Q. The improvement is obvious but I'm not quite sure I filled in the null very well. Speaker has more than enough output to handle the boost and power is plenty.

*ProLogic II effect *
I've switched back between "Music" and "Movie" modes. Oddly enough I am digging the Movie mode with the Haas effect and full bandwith sound. On paper the Music mode makes more sense, but I find that the car environment benefits greatly from a larger sound stage. Impressive. 

Since I'm running the rears fullrange I presume the top end rolls off and I get the equivalent of the Pro Logic II Music mode shelf filter. So in truth, while in Movie mode I get a hybrid of the Music and Movie modes with the Haas effect but the shelf filter on to emulate absorption. 

*Background noise*
The signal chain is background noise free from what I can tell, success! The worst offending piece here is by far the Arc mini amplifier fans, followed by the large Arc fans. This means I have to get clever with the amplifying rack cover to absorb fan noise. The rattles and vibrations ahead of the rear axle are minimal, especially the doors. This car is stout with just one layer of Dynamat Extreme on the door. However, from the rear axle back it's a bit of a mess. The trunk back especially has plenty of rattles and resonances that need to be taken care of. 


*Other*
The Galaxy S7 phone needed two reboots so far when playing through bluetooth. For some reason it seems other apps interfere with the BT transmission and interrupt the signal. Very odd. I got this before on older Androids after a year of use when the phone got full, but never when it is new. This happens only with the car setup which is again, odd. 

The Galaxy S7 seems to clip the signal at max volume output. This is also odd because I've never clipped a signal through bluetooth. Is it possible the Alpine processor input stage is clipping? 

The Alpine unit has both the remote in and remove out cables labeled the same (blue/white). That is really silly from a unit of this caliber. I had to peruse DIYMA for hours to find out the top wire is the remote out. I connected the remote in to constant 12V so I'm using the RUX power button to turn it on and off whenever. 

The car should be available to audition at most GTGs in North Cali.

*EDIT: Almost forgot the start of the show - Push-Pull*

Push-pull rocks, and I mean the force cancelling one. There is so much output with the most minimal vibration. You almost have to tell yourself it is loud enough or your ears suffer. I have had force canceling push-pull at home and in the car in the last three systems now and I swear by it being a miracle design. I am stunned almost no one uses it. I bet there are more bass shakers out there than opposed subs which is a damn shame. Push pull has changed my life haha


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## damonryoung (Mar 23, 2012)

cvjoint said:


> Is it possible the Alpine processor input stage is clipping?
> 
> The car should be available to audition at most GTGs in North Cali.


I'm pretty sure there is some indication on the RUX if the input stage is clipping...

I look forward to hearing this some time!


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## jtaudioacc (Apr 6, 2010)

cvjoint said:


> *SPL*
> I've put on there some of my all time most demanding tracks and haven't found the limits of any of the drivers and I get the feeling I'm far from it. I back away from cranking it more once my ears get plugged after a couple of songs.


do 3-4, you can do it! epper:epper:


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

You know I'm gonna make your ears bleed, right? I have a drum solo that should be ridiculous with 8x 10"s and 10" midbass.


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## cvjoint (Mar 10, 2006)

jtaudioacc said:


> do 3-4, you can do it! epper:epper:


You mean the -3db to -4db on the Alpine display?! You are a mad man. Not going under -10db.


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## cvjoint (Mar 10, 2006)

DRTHJTA said:


> I'm pretty sure there is some indication on the RUX if the input stage is clipping...
> 
> I look forward to hearing this some time!


I found the following two clip warnings in the manual, neither of which is for digital in:

_Analog input audio signal level too high causing clipping.
- Lower the Analog input audio signal level._

_The level was raised too much with EQ settings and DSP output
was clipped._

Can the digital signal come pre-clipped from the phone? I didn't think digital worked like that. But at the same time I didn't think the volume control would still work on the phone but it does.


I'm going to start going to meets. Haven't been to any in a year, car meets or audio meets.


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## t3sn4f2 (Jan 3, 2007)

Conventional gear can't drive a digital signal past full scale. Only things like sound cards with their digital mixers have that ability. I'm sure you can find apps for the phone that will do it too but it will be a funtion that is clearly labeled beyond just "volume". I have an iphone app called equalizer that has that option.


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> Conventional gear can't drive a digital signal past full scale. Only things like sound cards with their digital mixers have that ability. I'm sure you can find apps for the phone that will do it too but it will be a funtion that is clearly labeled beyond just "volume". I have an iphone app called equalizer that has that option.


I see. So it must be that there is interference between the BT receiver and the phone in the car. The signal is garbled in transmission. I might have to move the receiver or try another one.


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## t3sn4f2 (Jan 3, 2007)

cvjoint said:


> I see. So it must be that there is interference between the BT receiver and the phone in the car. The signal is garbled in transmission. I might have to move the receiver or try another one.


Try playing a track with a low passage. If by any chance it is boosting the signal, it won't sound degraded on the quieter parts. If it sounds bad no matter what, you'll know for sure the problem is elsewhere.


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> Try playing a track with a low passage. If by any chance it is boosting the signal, it won't sound degraded on the quieter parts. If it sounds bad no matter what, you'll know for sure the problem is elsewhere.


Going from max volume on the phone to -1 step gets rid of all of it. That's what's weird about it. The clipping also occurs at amplitude peaks. All signs of old fashioned input stage clipping. Weird thing is I don't get that at home ever. The phone also has a hard time keeping a connection but then when reset all works well given it is set at just under max volume. I'll keep working at it to see what's up.


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## papasin (Jan 24, 2011)

cvjoint said:


> But at the same time I didn't think the volume control would still work on the phone but it does.


It depends how you are taking the signal from the phone/device to optical. For example, when we used the iPad with an i20, we could still adjust volume from the iPad. When we replaced the i20 with the Apple lightning to HDMI, volume from the iPad was fixed and the only volume control was from the RUX on the H800. IIRC it has to do whether the set up is a fixed vs. variable digital signal stream.


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## t3sn4f2 (Jan 3, 2007)

papasin said:


> It depends how you are taking the signal from the phone/device to optical. For example, when we used the iPad with an i20, we could still adjust volume from the iPad. When we replaced the i20 with the Apple lightning to HDMI, volume from the iPad was fixed and the only volume control was from the RUX on the H800. IIRC it has to do whether the set up is a fixed vs. variable digital signal stream.


Yup, the i-20 has it's own digital realm volume control that is controled via software from the idevice or remote. Proprietary stepping too as im sure you know. The av adapter uses a fixed level airplay option, and that even differant than the with an apple tv which leaves a master volume option available. Just depends on what they want to offer.


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## cvjoint (Mar 10, 2006)

*A note on voltage dropping*

It doesn't! The Rux shows 15V stable no matter what I do with the knobs. This is a little nutty. 

Since the ARC are not regulated I should be getting tons of power out of the amps. 

A few reasons why I think it works:
*speakers have unusually high sensitivity. Per side output at 1 watt:
94db plus cabin gain 20hz-63hz
96db 63hz-1,000hz
101db 1,000hz up
*continuously variable power supplies in the amps
*active crossovers
*beefy OEM alternator
*large stock battery: AC Delco 90PS 590 CCA 740 CA 100 AH

Now I should probably find a battery charger that is strong and plugs in through the battery tender port. That way I can feed it at meets by plugging it in.


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## cvjoint (Mar 10, 2006)

Found some rare 10" Scan Speak aluminum woofers on Ebay and bought them asap!

http://www.scan-speak.dk/datasheet/archive/25w-8567-se.pdf

8mm gap, 4 layer coil, SD1 motor, no resonance in band, break up at 3,800 hz. The frequency response and impedance curve is even cleaner than the Revelator. 










Now I have 3 midbass drivers to try out:
1) B&C 10NW64 pro audio paper cone driver
2) Scan Speak 25W/8567-SE aluminum Hi Fi driver
3) Scan Speak 25w/8565 carbon fiber/paper pulp Hi Fi driver

The midbass wars start now!


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## cvjoint (Mar 10, 2006)

Found the Klippel for the smaller 7" Scan Speak Classic that uses the same triple shorting ring SD-1 motor and coil as the 25w/8565 10" woofer:
http://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/40_Voice_Coil/2012/2012_8_Aug.pdf 

Xmax should be 5.7mm unless the suspension limits it further.

Found the OEM application for the Scan Speak Classic 10" aluminum cone, Martin Logan Prodigy electrostats: 
MartinLogan | Prodigy


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## teldzc1 (Oct 9, 2009)

This build is pretty sweet. Great job!


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## cvjoint (Mar 10, 2006)

teldzc1 said:


> This build is pretty sweet. Great job!


Super, glad you like it. 

I'm a debater personality type so if anyone has some criticism of the rig so far feel free to post it here. I'm more interested in learning and improving than having the best this or that. I'll start tuning today and will post the findings shortly. 

Meanwhile I just bought this gel pad to place under the subwoofer. I'm going to try to decouple it from the frame of the car. Since the push-pull is mechanically balanced it doesn't require that the box is bolted to the car like conventional sub boxes. It says 100% satisfaction guaranteed so I think the decoupling will be a success.


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## teldzc1 (Oct 9, 2009)

I'm actually amazed that you don't have a dedicated midrange between the 10 and the AMT. The AMTs look like they're fully off axis, does that affect response at all?


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## cvjoint (Mar 10, 2006)

teldzc1 said:


> I'm actually amazed that you don't have a dedicated midrange between the 10 and the AMT. The AMTs look like they're fully off axis, does that affect response at all?


I'm working with crossovers of between 1,000 hz and 1,600 hz. Specifically designed woofers with a wide bandwidth can generally be crossed up to 1,000 hz and some a bit higher. The surface area of the AMTs is fairly large to handle the low crossover, and the resonant frequency is lower than half the crossover frequency. Technically there is nothing to say it shouldn't be done. 

Now of course, a smaller midrange might sound a bit more transparent at low volumes, but the larger cone I'm using has lower harmonic distortion. It's a tradeoff here, no way to have both. You either get the transient response right with a dinky cone or the SPL and low distortion with the larger one. 

The AMTs roll off very early, starting at 8khz, when used off axis. I was able to correct the frequency response with the equalizer. I switched from parameteric to graphic EQ since I need so many frequencies adjusted.


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## teldzc1 (Oct 9, 2009)

Got it. I can't make the g2g next weekend but would love a demo some time.


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## whoever (Nov 21, 2008)

I thought you'd like this after our recent discussion ;-)
Bohlender Graebener Neo10 Planar Transducer


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## cvjoint (Mar 10, 2006)

whoever said:


> I thought you'd like this after our recent discussion ;-)
> Bohlender Graebener Neo10 Planar Transducer


BG is back from dead! Till this day, my favorite midrange, used BG planars in all my cars...but this one. I have the 5 foot version at home. That satisfies my drive for BG. In the car, I'll try to go for more output since an SPL system makes more sense on wheels than blasting next to all my neighbors. The BG home system remains my reference, especially since it is dipole, and it's nice to have a bit of variety. The AMT technology sounds really good down to 1 khz, too bad it's not really midrange worthy like the BGs. 

*UPDATE*
*Stock OEM Bose system*
This is the frequency response I took about a year ago before I planned my system. 









The SPL if very very limited with the stock system. As you can imagine the output is limited by the dinky 3" midrange in the doors. Harmonic distortion plots show a peak in the middle of the midrange at full volume. Output is also limited by the little amp that powers the whole system, although more power wouldn't make the 3" mid any bigger. 

The top end rolls off to -15db by 20khz. The tweeters are mounted at the top of the dash firing into the windshield. At the time I thought I could do much better, but the reality is that I can't. More on this later.

Bose creates the illusion of bass by boosting the bottom octaves with a peak at 35hz followed by a sharp rolloff. Don't be too mad at Bose, many car aftermarket speakers do the same thing. 

Overall, if you consider that the Bose system weighs ~25lbs this is a killer system. You get a fairly well balanced left right response +-5db around a target FR that is pleasing, proper surround sound, noise canceling, and decent output down to 30hz. You could do much worse, and I've heard many worse DIY and aftermarket systems in the past. I recommend turning the bass knob two notches down for an ideal FR if you want to keep the stock Corvette C7 Bose system (note, I don't have the optional sub). 
*
Door mounted 10" B&C woofers natural response, no tuning
*









*Middle midrange*
There is a null at 450hz. Boosting here raises the harmonic distortion, but due to the sheer size of the woofer and the output capability it works well. Overall, I was able to get the region 200 hz to 1,000 hz to sound amazing and balanced left to right without noticeable spikes in distortion. That's why I love to use large woofers in a car for this region. With the insane amount of tuning cars require in the midrange band the low distortion of a 10" woofer is magic. The sonic signature of the B&C is what I would call flat and dull. Not exciting to say the least. Perhaps due to the damping of the cone and suspension it just does not have the transient response and micro dynamics of Hi Fi drivers. It is however very good at keeping harmonic distortion in check. High SPL mid-range is effortless and easy on the ears. This is an ideal driver for high SPL applications and hard rock. 

*Upper midrange*
The woofer's break up is noticeable when crossed 1.6 khz 24/db. This is a driver that needs to be crossed 1 khz 24/db ideally, and no higher than 1.2 khz. I set the crossover at 1 khz 24/db and I get no sign of breakup and the response blends well with the tweeters. As you can see from the plot there is no break-up peak. It is designed to be played though the break-up which has a small peak at 2.4 khz and it is spread wide all the way through 7khz. However, I wouldn't play anything above 1.2khz in a Hi Fi application. 

*Midbass*
This is the B&C's achilles' heal. Even if you can live with the bland and boring midrange quality to enjoy effortless high output sound, the midbass is just sub par. Notice the huge null at 120hz and the sharp roll off of both left and right woofers starting at 150hz. I compared the B&C frequency chart with the smaller 7" sibling, and I'll be damned if they looked any different. I couldn't use the 7" woofer below 100hz and this 10" plays no differently. Since it doesn't work out of the box, I used some heavy EQ to flatten the response down to 60hz. I ended up boosting 100hz and 125hz by 10db! On paper it looked fine but at high output the midbass quality was quite poor. I went ahead and did a harmonic distortion test and it was clear that the B&C harmonics were spiking. This woofer does not like to produce midbass, and you can't force it either! The Bose had a more natural response for a midbass driver, although it's tough to say if Bose applied any EQ. 

There is a null on the driver's side, and possibly the passenger's side as well at 120hz. This is the car's contribution to ruining good midbass. I'll be switching to the Scan Speak woofers soon to see if I can get this region to play nice.

*Overall B&C satisfaction*
I'll give the B&C a passing score. It is frustrating to have below par midbass performance despite using a 10" woofer. The suspension strains quite heavily if it has to move and when it does it just doesn't have the attack in the midrange that we've come to expect from top HiFi drivers nor the smooth filling midbass. I find myself listening at high SPL just to get that extra something that B&C can give you that no other driver can or rejoice at playing through a bad recording without ear strain. But otherwise I don't think this is the SQ driver that people dream about. Despite the world class Neo motor that is at home in HiFi world, the pro-audio rugged suspension parts hold it back with lackluster reproduction. 

*Left and right channels tuned *
This is the result of the tune job. The EQ did some heavy lifting to get this response. Notably +10 db at 100hz and 125 hz, and +12db at 16khz and 20khz. The FR is still down 15db at 20khz, just like the stock Bose system. It turns out there is no amount of tuning that can get you flat to 20khz when aiming the tweeter at the windshield in a Corvette. The top end rolloff is not noticeable to me. I can't really hear much above 16khz, nor is there a lot of material up there. The boost is high but I have more than 250 watts available on tap and over 100db output at 1 watt. The midbass boost however, is not workable. The driver audibly strains to punch out that much air with a pro audio suspension so I lowered the boost 5db and am now living with a little null in the midbass. 










*Harmonic distortion*
This is one of the best cars I've made distortion wise. The AMT tweeters laugh at the 1khz crossover. Not even a small pickup in distortion there no matter how loud I tested. However, the B&C woofers breathe heavily with the 10db boost in the midbass, and it is audible. Left and right HD:


















*Overall FR*
Summed left and right FR with sub, max volume on sub. Typically I turn it down 10db from here:










*AMT review*
I have nothing but good things to say. It is impressive how easy they handle the low crossover. The high midrange and upper octaves are transparent and clear. The soundstage is deep and focused with a big sound. I blame the sharp top octave drop off on the install location, but given that I was able to flatten it out with EQ without drawbacks I see no reason to change anything. The install location makes the FR about the same from any seat and any head position so the soundstage shifts very little. Aiming at the driver with AMTs changes the FR drastically. I prefer to have a small roll-off post EQ than a shifting upper octave response with head positions. I recommend not only the AC AMTs to anyone but also a similar install position given that you have a lot of wattage, EQ, and tuning skills to do it.


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## strohw (Jan 27, 2016)

What other 10" are you going to try? No fun in having something that doesn't win in any category. If it has eh midbass and boring midrange then who cares if the sensitivity is high. You may as well get similar midbass and a midrange sound you enjoy or vice versa.

Personally, I love the sound of the 2118/2123. It also works out well enough for me as the 2118 starts is sharp roll off at 80hz in my truck.


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## whoever (Nov 21, 2008)

strohw said:


> What other 10" are you going to try? No fun in having something that doesn't win in any category. If it has eh midbass and boring midrange then who cares if the sensitivity is high. You may as well get similar midbass and a midrange sound you enjoy or vice versa.
> 
> Personally, I love the sound of the 2118/2123. It also works out well enough for me as the 2118 starts is sharp roll off at 80hz in my truck.



See Post 221


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## cvjoint (Mar 10, 2006)

strohw said:


> What other 10" are you going to try? No fun in having something that doesn't win in any category. If it has eh midbass and boring midrange then who cares if the sensitivity is high. You may as well get similar midbass and a midrange sound you enjoy or vice versa.
> 
> Personally, I love the sound of the 2118/2123. It also works out well enough for me as the 2118 starts is sharp roll off at 80hz in my truck.


Well, I'm limited to an outer diameter of about 260 mm and a depth of 100 mm so many of the Hi Fi 10" do not fit. I think I can fit Scan Speak Classic drivers or the Usher in 10" sizes. I listed an aluminum Scan Speak Classic 10" in the posts right above this one that I just bought on ebay. It should be here Friday and I will try to swap them in this weekend. 

The aluminum Scan Speak woofer couldn't be any more different than the B&C with low damping suspension and a very stiff cone. On paper it seems superior to the Seas Excel magnesium 10" which is my all time favorite midbass with a smaller breakup that is some 500hz shifted out. Total throw is a bit smaller at 28mm vs 35mm for the Seas, but linear output is higher at 7.5mm vs. 7mm for the Seas. Here is the Scan Speak white sheet:

http://www.scan-speak.dk/datasheet/archive/25w-8567-se.pdf

I believe they were custom made for Martin Logan with better transient response than the carbon/paper version, more xmax, and double the voice coil layers for improved power handling.


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## thehatedguy (May 4, 2007)

I wouldn't have thought the B&C would have been dull. Well, not like that. The just aren't as snappy and sharp sounding as JBL and 18Sound.


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## cvjoint (Mar 10, 2006)

thehatedguy said:


> I wouldn't have thought the B&C would have been dull. Well, not like that. The just aren't as snappy and sharp sounding as JBL and 18Sound.


Never got the chance to work with JBL pro audio gear. The 18sound doesn't sound any better from what I can tell. I installed both the 7" B&C and the ~7" 18 sound mids in the same car and I preferred the B&C by a large margin, and again neither sound transparent like a top notch hi fi driver.

Oh and I tried the Faital 4.5"s too with roughly the same result. Typical fatigue free high output sound of pro audio driver, but not really transparent. When you use something like a Seas magnesium cone you get this sense that there really isn't a speaker you are listening too, just the original recording. Not so with the pro audio stuff. I think this may be my last one.


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## fish (Jun 30, 2007)

Maybe it's a Pro Audio thing?

I wasn't impressed with the 10" Faital's lower/middle midrange, & from recollection, Jerry (Niebur3) had not-so-impressive comments regarding the 18Sound 6nd430 in his midrange shootout.


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## strohw (Jan 27, 2016)

I'm not sure I'd go that far. Think of how many 6-8" pro drivers people use for car applications...it's a small hand full overall. The product selection is minimal for our application. Now compare that to what's available in the home and car markets. People who use pro drivers also tend to have the goal to reproduce the characteristics of live music in its sound and impact.


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## cvjoint (Mar 10, 2006)

strohw said:


> I'm not sure I'd go that far. Think of how many 6-8" pro drivers people use for car applications...it's a small hand full overall. The product selection is minimal for our application. Now compare that to what's available in the home and car markets. People who use pro drivers also tend to have the goal to reproduce the characteristics of live music in its sound and impact.


So I live in a city where the clubs have amazing underground music and some killer sound systems. 


















But I've always been happier getting in my cars after clubbing to get even more detail from the same recordings. Now my car sounds very much like the club systems.  That's not altogether a bad thing, but I sort of miss having that edge in resolution.


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## cvjoint (Mar 10, 2006)

My precious is here! Looks like they survived during transport. My last set of Scan Speak Classics where not so lucky, ended up magnet-in-cone. 



















I've been researching that bucking magnet's properties. Not only does it shield against the magnetic field but works to increase the BL. It's 5mm deeper than the B&C so there is a chance it won't fit with the bucking magnet. Removing it is not as trouble free as I thought it would be. 

This one is 8 ohms so amplifier power would drop by almost half. The arc is rated to do 180w x 2 @ 8ohms but it tests somewhere around 220 watts.

The coil is rated at 150w vs. 300w for the B&C. Unlike the B&C there is no venting under the voice coil. That sounds like a bad thing and it is the reason B&C gets a higher power rating but that venting makes noise under excursion so I'd rather not have it. Half the coil rating, but half the power going to it as well due to higher coil resistance (4 ohm vs. 8 ohm).

The inductance treatment is much better in the Scan. Tripple shorting rings in the SD1 motor: above the gap, in the gap, below the gap. B&C only has one. The coil is also smaller in the Scan which contributes to the low inductance.

The Scan has venting under the spider whereas the B&C does not. That means it should be quieter under excursion and have lower resonance but it also means it can get water damage more easily. On the other hand the cone is aluminum and therefore water proofed better than the B&C which may not be waterproofed on the inside (not sure).


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## Elgrosso (Jun 15, 2013)

cvjoint said:


> Dropped the box in the car last night, all assembled powered off a mini 10w amp I had around. My initial impression was mostly negative but I'm reserving final judgement for when I am done with the whole car.
> 
> 1. The car was vibrating and rattling. Most of it was audible from the outside of the car but we're talking only 10 watts.
> 
> ...


I should have read your thread before asking 
Awesome build, and so much details explained, thx!


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## cvjoint (Mar 10, 2006)

*Battle of the 10" midbass drivers: B&C 10NW64 vs. Scan Speak 25w/8567-SE*


*Short story*
This was a decisive win for the Scan Speak driver, enough so that this will be the last pro audio driver I will ever employ in my builds. 

The Scan Speak won me over in the very first 10 seconds of play time. I just finished taking the B&C driver out and put the Scan in, we're talking about turning the system on just to check that it is fully functioning, and instantly it was all there, seamless midbass and transparent midrange. This is what I wanted all along, max SPL be damned! 

With the pro audio drivers the lower octaves are a murky mess, it's all one impossible task for driver that simply was not designed to play bass. That is the biggest challenge to using pro audio drivers. Ok, I'm sure the SPL in the low octaves is all there if you EQ it in since it's a matter of xmech, but the more complex the bass passages are the more the problem stands out. I'm almost convinced that the suspension on pro-audio drivers are the downfall - designed for taking abuse and weighing as little as possible to increase sensitivity. This poses a problem for high fidelity reproduction as the transient response is just shot. Unfortunately because the cone isn't damped very well even the higher octaves suffer. I'm using B&C and pro audio interchangeably because in my view the B&Cs I'm using are the closest thing to high fidelity pro-audio driver, if there is such a thing, and one of the best out there for commercial rigs. 

*Install*

The extra 5mm of depth compared to the B&C really pushed the limits of the available door space. In total the speaker is 105mm deep which almost touches the glass. On the passenger door, slamming the door brings the magnet in contact with the glass, I suspect this is because the second time I had the glass replaced the window motor wasn't bolted in correctly (perhaps the bolts are loose since the glass touches the door frame up top when the door is shut). The driver's side clearance is fine and slamming the door never brings the magnet in contact with the glass. Either that or GM made more room in the door on the driver's side than for the passenger by a few mm. So I put more gasketing tape on the passenger woofer and brought it up a few mm. I also put Ensolite on the motor so there is no hard impact or noise. So far so good. 

The clearance with the door panel is I suspect just enough. I'm using the same 1/2" spacer made out of MDF. I noticed that the doors actually have removable grilles so I took them off for the photo shoot.

*Construction*










The cone is an anodized aluminum piece. Feels very strong to the touch. There are no strengthening ribs or features like I've seen in some other metal cones. The surround is typical low damping SBR rubber for Scan Speak, soft and meaty. The dust cap is fairly small because you must remember this is a 42mm voice coil. There are however 4 layers wound and the coil is nearly an inch long at 23mm. 










The connection posts are very basic. One bent slightly while pushing a connector in. I'd prefer a stronger one from Scan Speak. The bucking magnet increases the gap strength by 3.5% according to Scan Speak. You can also see that the top plate is larger than a standard Scan Speak Classic 10". The spider is a bit mediocre by today's standards and the venting under is a bit minimal as well. There is only so much you can do with a shallow cone/motor. A beefy Revelator would be better but also wouldn't fit so I prefer this one. 










Super lucky to find a pair of these bad boys NEW on Ebay!



















Battle of the midbass contenders. From left to right, SS Classic 25W/8565, SS Classic 25W/8567-SE, B&C 10NW64. Note the motor difference between the two SS speakers. The 8567-SE has a 8mm gap motor achieved by a bucking magnet and a thicker top plate. The coil is also longer and double in layers.










Here is a photo where I placed a quarter inch spacer under the B&C to bring them up to top mount parity. Since I'm using the same spacer in car, the speaker will just be mounted deeper in door. Under excursion, the Scan Speak also requires more top mount depth. 



















The door panel has the least clearance on the bottom. As you can see below, the bottom of the plastic panel was resting on the speaker gasket. The B&C outer diameter is 261 mm vs 255 mm for the Scan Speak. I don't think it hits the panel but I lifted the panel speaker cover a bit off the door on the bottom just to be sure. 










Final install, sorry for the pic quality, this was a midnight install finish. 


















*Subjective review*
In the hierachy of best midbass/low midrange drivers this one ties with my all time favorite the Seas Excel W26FX001 magnesium 10." I do not believe the cone is as well damped as the Excel, but 99% there. The Excel is more of a pure piston but it also has a worse breakup as a direct consequence. Therefore I prefer the Excel in the lower octaves and the aluminum SS in the higher ones. However, the Scan Speak is closer to the Excel in resolution than any other cone I've ever heard so even in the low octaves it is simply breathtaking to listen to. The Excel has a clear advantage in throw, with a 35mm peak to peak xmech, whereas the Scan is 24mm. I would use the Excel in a 3way with a lower LPF but crossed at 1,000hz I'd say it's a tie. I believe the sensitivity on the Scan is a bit better but I could be wrong. 

The Scan far surpasses B&C in clarity, transparency, low suspension noise, and everything else you could ask for from a 10" woofer except SPL/sensitivity. On poor recordings, I expected the metal cone to be a bit more shrill than the B&C, but it's just not so. It sounds better 100% of the time. I have not tested the SPL limits of the Scan Speak, but I don't want to break it since I can't replace them!  There is no way the Scan reaches the same SPL, 0 chance. 

I've tried some other 10"s for midbass in cars, an aluminum Vifa, and even the Peerless XXLS sub. Those were crazy times. The Scan Speak is far superior to the Vifa 10" aluminum woofer, and having heard many Dayton Reference aluminum woofers, it's a much better unit than those. Using a sub for midbass was fun, but you are much better off using the SLS that is designed to reproduce midrange. 

Bottom line, the Scan Speak 25W/8567-SE is a gem. Since it's not available for purchase your best bet is the 10" Revelator or the 10" Excel magnesium for top notch reproduction. Based on the impedance curve and FR I think the Classic will sound better than the Revelator in the top octaves with no surround resonance at all!


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## cvjoint (Mar 10, 2006)

*Testing the Scan Speak 25W/8567-SE*

*Free air tests*
First I fired up the WT2 to see if the coils are good. I was also curious to see the QTS and FS. Note that I did not mount the driver for the test, it was just sitting on carpet. Nonetheless, here is what I got:



















Coils are good. The FS is 28hz and 29hz. That means based on the rule of thumb I should cross them at 58hz and above. Ideal for a 63hz HPF! QTS is .51 and .58. Ideal for IB or large leaky sealed, which is what a doors is! While Scan Speak made these for Martin Logan, clearly they are designed to kick but in the Corvette. :laugh:

*In-door tests*

I had a few questions I wanted to answer:
1. At what frequency does the B&C surpass the Scan in sensitivity? 
2. Is it true that the B&C is 8.5db more sensitive at 1 watt? 
3. Can the Scan go flat to 20hz in-door? 

Here are both the Scan and B&C tested on the same volume level on the Alpine H800 with all filters defeated, basically full range. 

*Driver side, B&C in red, Scan Speak in black*









*Passenger side, B&C in red, Scan Speak in black*









Question 1
First we have to account for the fact that the B&C is 4 ohm whereas the Scan is 8 ohm. Therefore, add 3db to the Scan Speak scale. The B&C has more output above 200hz. The Scan has more output below 200hz. That means the Scan has a considerable output advantage in the midbass. Even if I wanted more output and chose the B&C I'd have to live with less midbass output, aka a funky FR with midbass downplayed by many DB just to not bottom out the driver. So in effect, while the B&C is a higher output design in reality you can't make use of it vs. a hi fi driver because midbass output is the limiting factor for both. You have to choose a higher than 63hz crossover or choose an FR that has low midbass output to make use of the B&C's higher output. In fact, below 80hz the output is lower with the B&C even if you use EQ because you run out of power or the coil melts down before beating out the Scan Speak. This is important because it shows you can't make use of the B&Cs higher output in the top octaves without sacrificing the low crossover or a nice frequency response!

Question 2
Based on these plots I can see that at 1 watt, the B&C is about 8db more sensitive above 300hz. So you can see here that if you plan to use the 10" in door from 300hz to 1000hz that the sensitivity advantage is real. However, I don't plan on using the 10" as midrange! So this is sensitivity advantage is not really an advantage since as I shown earlier the output is limited by the distortion in the region 63hz-125hz. Basically, the B&C will bottom out first when tuned to have decent output down to 63hz before it gets to use it's sensitivity advantage. _Your results may be different if your car does not have a huge drop in SPL in the midbass on the driver's side, or if your car does not have a null at 120hz, or if you desire an FR that is cut heavily in the midbass area. _

Question 3
Yes, the Scan Speak has the same output at 20hz as it does at 1,000hz. Scan Speak recommends to use this driver 20hz to 1,000hz. So yes, I could run subless and still have extension down to 20hz. However... the Scans only have 12mm of throw one way. That is hardly enough to get serious SPL at 20hz! 

Note also that Scan Speaks break up is very mild starting at 2,5khz or so. A 1,000hz LPF works great with this woofer. No hint of breakup. It also blends very very well with the AMT tweeters. 

*Harmonic distortion plots*

This output shows up as 93db on the Omnimic, level 17 on the headunit. I still think my Omnimic V2 reads too low of an SPL. Not sure why. All THD below 1% except in the 63hz-125hz area where it is 2%. If the SPL is correct on the Omnimic it's really hard to get low distortion sound. Sheesh. This is the driver's side only, which looks the worst because there is more cancellation in the midbass area, and therefore more EQ to boost it. The peak at 400hz is also an EQ boost. 










*Time domain* response as tuned for passenger side. If anyone wants/can interpret this one please do. I think I can see some domain smear around where the box has a higher group delay but it seems very tiny to me. One outstanding feature is that you cannot see any sign of ringing above 1khz, so the Scan Speak's break up is filtered out quite nicely. 60hz and below there is a bit of time domain smear but I'm not sure how much of it is audible or whether we can get away from it in a car.


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## Hanatsu (Nov 9, 2010)

That sonogram of the impulse can be tricky to interpret.

It shows decay or ringing. Everything below ~200Hz is dominated by modal poles. They will have massive ringing, especially the first positive mode. There can be other issues showing up like resonating panels, enclosures etc but it should be minor compared to modal ringing. I would run TDA instead of that program (Omnimic?) is shows you more usable information.

Acoustical treatments are the only real option, which may not be an option in a car... unfortunately. The higher frequencies can be absorbed though a dashmat or something.


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## cvjoint (Mar 10, 2006)

Hanatsu said:


> That sonogram of the impulse can be tricky to interpret.
> 
> It shows decay or ringing. Everything below ~200Hz is dominated by modal poles. They will have massive ringing, especially the first positive mode. There can be other issues showing up like resonating panels, enclosures etc but it should be minor compared to modal ringing. I would run TDA instead of that program (Omnimic?) is shows you more usable information.
> 
> Acoustical treatments are the only real option, which may not be an option in a car... unfortunately. The higher frequencies can be absorbed though a dashmat or something.


It does look like a different world under 200hz. Curious because there is only one driver working the range 63hz-1,000hz. It must be just the way the car loads.


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## cvjoint (Mar 10, 2006)

I got some input from DIYMA on decoupling and rattle fixing. I'm posting the testing done here. 

*Testing theories*

We've had several good jabs at quenching vibration/rattles from contributors which I'm listing here:
1. acoustic force transfers to car panels by air movement
2. mechanical force is not canceled in the box properly, box is not braced sufficiently
3. mechanical force is canceled in the box as much as it can be, no 100% force cancellation possible

*Testing method*

Found a parking lot where 18 wheelers pull in, commercial, and almost no one there. Downloaded an app to generate test tones: 25hz, 31hz, 40hz, 50hz, 63hz. The Pyle foam isolators came in and I used them to decouple the box. Played a test tone at a time with the car open or closed and touching the box walls to feel any vibration. The box is not mounted to the car against movement at this time. 

The idea was that with the rear hatch open most of the acoustic energy does not load the panels inside and if decoupled properly there should be few if any rattles. You can see the Pyle foam isolators are so thick that the box lifts, nearly touching the hatch. It's also angled quite sharply matching the rake of the hatch. 














































Stock photo of the Pyle foam isolators used:










*Findings *

I tested theory 1, that acoustic force transfers to car panels by air movement producing the rattles. I did so by playing test tones while opening the rear hatch. The majority of the rattles are reduced by opening the rear hatch, allowing the acoustic energy a path out of the car. The most rattle abatement can be done by treating the car, not the box. Walking around the car while it plays test tones with the windows up is telling. The rear tail lights, and really the whole rear bumper shakes violently. I can hear some air flaps opening and closing. The rear hatch is a mess, vibrating madly as if to blast open. No way to treat the majority of the rattles without adding weight to the car. 

I tested theory 2, that the mechanical force is not canceled in the box properly, the box is not braced sufficiently. This is also true. There was considerable flex in the box on the top panel, but... 0 flex anywhere else. That means the bracing I had in there originally to deal with the force cancelation is working, the front and back baffles the subs mount to are dead. The speaker baskets are dead. The kerf, where the wood bends on top is dead. It's really just the top and I imagine by implication the bottom of the box that need bracing. 

OLD bracing job:









NEW bracing job, I did this last night after testing. New bracing is unpainted:

















Theory 3, mechanical force is canceled in the box as much as it can be, no 100% force cancellation possible, cannot be tested because I have to test again once the glue dries. 

*Pyle PSI03 decoupling foam review*
The foam is way to bulky to use in the car. If I use it I have no way to store the targa top in the back above the box. I'm switching to Ensolite and adding multiple layers to get desired thickness. Ensolite is 1/8" which is more appropriate for tight installs. 

The foam is too resistant to compression. It's true I used two pairs, but I can hardly see any compression from an 80lb box. If I were to guess, the compression is about 9 PSI, I prefer something softer. It is good for heavy tower speakers but not much else. Presumably Ensolite is between 1.5psi and 3psi, so much softer and more adequate.

*Conclusion*

Rattles were the worst at 50hz and 63hz. Most rattles were produced by the car itself when faced with acoustic energy. However, even with the hatch open and the box decoupled by inches of foam there was clear transmission of mechanical vibration to the floor and structure of the car. I found the box bracing to be insufficient but mostly that the car needs some serious sound proofing. The force canceling does work, with the front baffle and speaker frames entirely dead but it does place a lot of load on the larger (42" x 14" in my install) panels which need to be well braced.


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## BP1Fanatic (Jan 10, 2010)

Well, it looks good in the car!


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## cvjoint (Mar 10, 2006)

The car is up and running and will be available for demos this Saturday if anyone is local. 

Pancho Cisco Tunes
2509 Sonoma Blvd.
Vallejo, CA 94590

http://www.diymobileaudio.com/forum...sq-only-april-23-2016-vallejo-california.html


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## cvjoint (Mar 10, 2006)

*Mounting system, decoupling*

*Decoupling*

From my trials with the Pyle decoupling foam I learned that foam is more resistant to compression than I thought. Based on those observations I decided to just go with Ensolite in multiple layers to decouple the sub box and amp rack. I added 3 layers to the bottom of the sub box, and four on the amp rack. Whatever vibration is left after the force canceling sub box nets it out, should be mostly contained by the 3 layers of Ensolite between the car and the box. I measured the level the box is off a concrete floor after applying Ensolite and it is at 3/8." That means there is little compression in the Ensolite which measures 3/8" with no load. I could have used only one or two layers. 

The second part of decoupling required that the system that bolts the sub box to the car transmits very little vibration. For that I decided to use rubber nut inserts for every tie down. 
*Mounting system*

This part of the install was one of the most challenging. The mounting system to the car has to do the following for both the sub box and amp rack:
*brace against all Gs that the car generates 
*removable without tools to be taken out for track days
*has to isolate the vibration from the sub box to the car
*has to isolate the vibration from the sub box to the amp rack
*shallow profile so the targa top still fits over the sub box
*no holes drilled in the car frame/panels

First I designed a brace that is less than 1/4" in height which bolts to the frame of the car using the Corvette's stock trunk anchors. It's made out of 1/8" sheet of wood reinforced with metal plates around the contact points. This allows me to use large 1/4" bolts, does not require any car modification, and adds only 1/4" to the amp rack height. It adds no height to the sub box since it connects to the front of the sub box. I used wood glue to hold the metal plates to the wood.










Second, I coated the brace in Duratex for waterproofing and stealth looks.










Third, I adapted some metal L-pads that would mount to the amp rack and sub box to allow the thumb-screw-rubber expansion-nut system. Here is the system:










Here is how the system works. The rubber insert goes into the brace that is mounted to the car frame. This ensures there is no hard surface to hard surface contact. 










The amp rack or sub box l-pad goes over the rubber insert. The rubber insert isolates vibration from the box and rack to the car. It also isolated the box and rack from eachother as vibration has to travel through both rubber nuts. 










Next, thumb screws go through the whole made in the l-pad and catches into the rubber nut's insert, expanding it. This way the sub box and the amp rack can be disconnected with bare hands. 










Here is a demo showing the rubber nut at rest, and then compressed. 


















Here is the brace mounted to the car. The far bolts are the OEM floor bolts holding the brace down. Forward, the inner mounting points are for the rack, and the outters are for the sub box. 










*Bonus round*
I found this 2.5" marine grade rubber grommet. The entire Anderson Powerpole for the power disconnect fits through it.


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## bassfromspace (Jun 28, 2016)

Contact Don at Sound Deadener Showdown for some of his butyl rope. Many guys have used it for decoupling boxes, including one system with 12" midbass and 18" subs in a bedcut.

Just a suggestion.


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## cvjoint (Mar 10, 2006)

bassfromspace said:


> Contact Don at Sound Deadener Showdown for some of his butyl rope. Many guys have used it for decoupling boxes, including one system with 12" midbass and 18" subs in a bedcut.
> 
> Just a suggestion.


Good one! I was planning on buying some foam products from him to start deadening the car. So he has been helping folks out on an individual basis?


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## ErinH (Feb 14, 2007)

bassfromspace said:


> Contact Don at Sound Deadener Showdown for some of his butyl rope. Many guys have used it for decoupling boxes, including one system with 12" midbass and 18" subs in a bedcut.
> 
> Just a suggestion.


agreed. 

I used the EBR on my enclosures. The difference in tactile at the seat was night and day once I did this. 

http://www.diymobileaudio.com/forum/3656129-post1199.html


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

cvjoint said:


> Good one! I was planning on buying some foam products from him to start deadening the car. So he has been helping folks out on an individual basis?


He's generally pretty good about working with people on a one on one basis. He does get backed up sometimes, but aside from that, he knows his stuff.


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## cvjoint (Mar 10, 2006)

TOOSTUBBORN2FAIL said:


> He's generally pretty good about working with people on a one on one basis. He does get backed up sometimes, but aside from that, he knows his stuff.


I bet he does get backed up!

Ok, so I can't use the rope for the sub box or amp rack because it's too messy to put on the carpet. I could use it for the midbass instead of gasketing foam.

So my question is when do you use butyl rope vs. gasketing foam? How about reducing panel resonance? Is it better use rope between door panel and plastic door card or ccf?

BTW I'm not sold that standard mounted drivers (aka not push-pull force canceling) should be decoupled. Inherently there has to be SPL loss. I would think the panel that vibrates must be treated not the driver decoupled.


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## bassfromspace (Jun 28, 2016)

I'd talk with Don about making a pouch of some sort, with the butyl rope in the middle. That would allow you to put it under the carpet (or on top of the carpet), without damaging it.

Maybe you could sandwich the rope between two pieces of MLV or Ensolite.


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## SSSnake (Mar 8, 2007)

Use the butyl rope to attach the ensolite to the bottom of the sub and amp racks.


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## cvjoint (Mar 10, 2006)

This is so funny:

"Don’t get me wrong – I love Parts Express and I’m sure their product is ideal for the purpose for which they are selling it, but it definitely isn’t the same thing."

SDS while discussing how PE rope is different. 

I've used the PE rope in the past and wasn't too impressed.


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## cvjoint (Mar 10, 2006)

SSSnake said:


> Use the butyl rope to attach the ensolite to the bottom of the sub and amp racks.


Ensolite sticks by itself too with the peal and stick. Do you mean to say you use it for more than just an adhesive?

I need to read this whole SDS website before I buy all my deadner.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

cvjoint said:


> This is so funny:
> 
> "Don’t get me wrong – I love Parts Express and I’m sure their product is ideal for the purpose for which they are selling it, but it definitely isn’t the same thing."
> 
> ...


The most important thing I learned from testing is that the butyl composition used is critical for damping vibration, and almost every company uses a different composition. That's why heavy and thick products with thick metal layers (stinger roadkill expert) don't perform as well as a thin, light, with thinner metal product (dynamat xtreme).


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## cvjoint (Mar 10, 2006)

TOOSTUBBORN2FAIL said:


> The most important thing I learned from testing is that the butyl composition used is critical for damping vibration, and almost every company uses a different composition. That's why heavy and thick products with thick metal layers (stinger roadkill expert) don't perform as well as a thin, light, with thinner metal product (dynamat xtreme).


Aha. So it is the secret ingredient. In a way the rope is just small amounts of the CLD tiles without the metal. I think I'll use this in conjunction with foams to keep weight down.

Here is what Don said in a nutshell:
*I should use the trunk/cargo floor barrier mats just introduced, based on the fact that I can remove it for track days, to lower rear end noise:
https://www.sounddeadenershowdown.com/content/trunk-cargo-floor-acoustic-barrier-mats
*I need to add 100+ pounds to the car to achieve "maximum noise reduction"
*The subset of "rattles" can be quieted with much less weight, with CCF
*For the Hydrophobic melamine, he says it would work as a decoupler, absorber, and thermal insulator, but should be placed in voids that are fixed because it looses effectiveness with compression. Use as much as possible, no diminishing returns.
*spot treatment for vibration damping where panels are highly resonant
*he wished I used the seismic rated vibration mounts. Lol.

So I'm skipping the first and last pointers. I'm doing this for two reasons. Neither the barrier nor the seismic mounts can be made to fit and still have the targa top storage work. No way. The box would have to be suspended, it cannot be suspended without height penalty. I'll think of this some more but I like my system for decoupling given the less than 3/8" height penalty. I'm skipping background noise reduction in general because that's not one of my goals. The car is quiet as it is compared to a soft top roadster, and some of the "noise" is just classic V8 sound. 

I will implement Don's CCF and hydrophobic melamine to the max. However much I can stuff in the panels. I may or may not buy additional CLD or rope. I'll think it through for another 2 weeks and order.


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## SSSnake (Mar 8, 2007)

> Ensolite sticks by itself too with the peal and stick. Do you mean to say you use it for more than just an adhesive?


This may be OBE but...

Use the butyl rope between the ensolite and the amp and sub box. This will ensure that the amp rack and sub box are decoupled through the butyl rope to the floor of the vehicle. Because butyl rope is sticky as hell and you want to be able to remove this stuff use ensolite over the top of the butyl. This will keep the amp rack and sub box removable (butyl by itself would stick to the car floor). This would impart a height penalty but may be acceptable in your case. Don't know.


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## cvjoint (Mar 10, 2006)

SSSnake said:


> This may be OBE but...
> 
> Use the butyl rope between the ensolite and the amp and sub box. This will ensure that the amp rack and sub box are decoupled through the butyl rope to the floor of the vehicle. Because butyl rope is sticky as hell and you want to be able to remove this stuff use ensolite over the top of the butyl. This will keep the amp rack and sub box removable (butyl by itself would stick to the car floor). This would impart a height penalty but may be acceptable in your case. Don't know.


Oh, I see what you mean. Trunk floor, ensolite, butyl rope, box in that order. That should work. I'm thinking of cutting out the kerfed part of the box and making it out of fiberglass to get the most height. The rounded corner is what is currently restricting the height. If I can get butyl and ensolite in there afterwards it's worth a shot.


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## cvjoint (Mar 10, 2006)

*Battery upgrade*

The stock wet cell lead acid battery was apparently on its last leg. After failing to start the car on Monday I decided to upgrade it. In the process I also purchased a charger that is compatible with the stock charge port in the trunk (cigarette lighter with open circuit when car is shut off).

*Background*
I'm an AGM die hard. I always used Optima Yellows or competing AGMs in my cars after the stock battery failed. I've been looking at the light weight lithium ion batteries too, but they have no reserve capacity. I need that for the audio to work proper, and I enjoy knowing the car will start after extended stays. To me reserve power and deep cycling is more important than CCA. 

Unfortunately, I haven't found one person that got an AGM in the C7 Corvette so this should be one of the first.
*
Research*
CTEK makes the OEM charger. It seems to be a top quality item, smart and powerful. Instead of going OEM or the same CTEK branded unit I got the most powerful CTEK I could find that uses a cig lighter adapter for the trunk charge port. IMO this is the smartest solution I could find, more current microprocessor technology and over twice the amperage compared to OEM. A more powerful CTEK is available but I would not be able to use the charge port since it's only rated for 7 amps. 

CTEK (56-353) MULTI US 7002
CTEK (56-870) Comfort Indicator Cig Plug

The best battery for my car seems to be the Odyssey Performance, it is made by Enersys. It is made in US, and it seems to have a better built quality, and lower fail rate than other AGMs. There is an Odyssey Extreme, but it is longer by 1", does not show up in the application guide, and doesn't fit. I've also considered an AGM battery labeled Die Hard Gold from Sears. Die Hard Gold is made by Eastern- Penn. It is still made in the US but the higher in the hierarchy Die Hard Platinum is a rebadged Odyssey AGM. Johnson Controls wanted to buy Enersys last year but was not successful thus far. JC seems to buy everyone on the market, move production to Mexico, and kill the quality and work conditions. From an ethical point of view, the Odyssey is again better. 


*Review of
CTEK (56-353) MULTI US 7002
CTEK (56-870) Comfort Indicator Cig Plug*

The charger is amazing! I plugged it in to revive the stock battery. 10 hours later I woke up for work and the car got started quickly and effortlessly. The screen showed the battery was full. The voltage was high and the alternator didn't have to do any charging right off. Stopped the car 5 minutes later. Ran some errands. Car started again just fine. The 7 amps it delivers is sufficient to charge a large battery overnight.

The cigarette plug accessory worked fine too, in that it plugged in. Unfortunately, some of the electronics on board did funny things with low voltage. There was clicking coming from under the car quite loudly. My dealer recommended I disconnect the battery and only reconnect when fully charged. So instead of using the charge port in the back of the car I used the regular clamps on the battery terminals after removing the ground connection to the car. Beware that the charge port does have this shortcoming when the battery is depleted almost all the way. Even more reason to buy the CTEK with all the accessories.
*
Review of the Odyssey Performance 48-720*

Fits like a glove, same as OEM dimensions but has a handle to carry it. Very useful.








































Odyssey rates CCA and reserve capacity using SAE testing:
Odyssey CCA = 723
OEM ACDelco CCA=615
That is a 17.6% increase in CCA. 

Odyssey reserve = 130 minutes
OEM ACDelco reserve = 110 minutes
That is a 18.2% increase in reserve capacity.

What I really care about is the deep cycle and recharge rate. I have no doubt that the Odyssey is twice the battery the ACDelco is.

Car started like a champ this morning. 


Source on SAE testing method, I matched it with the Odyssey FAQ:
BU-902a: How to Measure CCA – Battery University
ODYSSEY battery - FAQ


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## papasin (Jan 24, 2011)

We've been using the CTEK 7002 for almost two years now on both our cars. Pretty solid. The quick disconnect is great!


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## rton20s (Feb 14, 2011)

And I bought the CTEK 7002 on the recommendation of the Papasins. It has worked great for me so far and brought a "dead" battery (from sitting idle) in my wife's car back to life. Very pleased with the purchase. 

George, did you happen to look at the Exide AGMs at all? If so, I would be interested in your thoughts. It seems you did a fair amount of research when you were looking for a replacement for the Vette.


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## cvjoint (Mar 10, 2006)

rton20s said:


> And I bought the CTEK 7002 on the recommendation of the Papasins. It has worked great for me so far and brought a "dead" battery (from sitting idle) in my wife's car back to life. Very pleased with the purchase.
> 
> George, did you happen to look at the Exide AGMs at all? If so, I would be interested in your thoughts. It seems you did a fair amount of research when you were looking for a replacement for the Vette.


Exide (Northstar) is not one of the big 3 AGM producers. It's hard to know how they compare. I don't see any reason not to go with them. Sweedish owned, made in US. It's just that it's hard to get a lot of feedback for them. Walmar and PepBoys badged a few of them at some point.


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## SSSnake (Mar 8, 2007)

I have been running duracells with good luck. I have them in three vehicles, all with stereos and hefty current requirements, and have had no issues. They also seem to be a little cheaper than most AGMs on the market. It seems you have already gotten your battery but I did want to pass this along for others. The one down side in a performance car is the weight. They are HEAVY.

One final note - I believe they are made by East Penn. If that is the case they are likely of lesser quality than the the Odysseys but the price is less than half that of the Odysseys (at least it was the last time I checked).


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## subwoofery (Nov 9, 2008)

I'm using Battery Saver and it works like a charm with any kind of battery. Even has a rejuvinate mode if the battery still reads 0 volt. 

12 VOLT 50 WATT Vehicle Battery Charger, Maintainer and tester w/Deep Cycle

3 years no problem 

Kelvin


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## cvjoint (Mar 10, 2006)

subwoofery said:


> I'm using Battery Saver and it works like a charm with any kind of battery. Even has a rejuvinate mode if the battery still reads 0 volt.
> 
> 12 VOLT 50 WATT Vehicle Battery Charger, Maintainer and tester w/Deep Cycle
> 
> ...


This is what the CTEK charger is too. I went with CTEK because that's what Chevy uses as their OEM company, and they just badge it. That way I'm assured I'm at least getting OEM quality. The CTEK is also putting out 7 amps so it will charge the battery almost twice as fast. The one you posted is 4.17 amps. I got mine for the same price but shipped the same day for that price to get the car running asap.

I'm only going to be using mine for when I leave the car for more than a week. I'm sure you're right, it keeps the batteries in much better condition, but its too much of a hassle to plug in everyday. Might as well go with a Tesla.


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## cvjoint (Mar 10, 2006)

*Boxy sound*

I think I nailed the troubleshooting spree. Why do I feel like I have so much to learn? You'd think doing this for over a decade would make me know most by now, or at least I don't make big mistakes. Ok, key word here is:

*Re-radiation *

The subwoofer box I built has many qualities but some of the bass quality I have come to expect out of my car builds is simply not there. From what I knew my box had only two small shorcomings:

1. the small bump in group delay ~ 80hz. That said, by any standard, the group delay was low. I just couldn't believe this is what makes the box sound boomy.

2. the small vibration of the top and bottom of the box. I fixed this by adding bracing. The box is stone-like strong.

So I searched, and searched, and found the most likely reason for the buzzing muffled sound of the box - re-radiation.

Explanation copied from here: 
Rythmik Audio • Bass Re-radiation

_"One cause of this problem is what happens inside the box. A subwoofer driver produces output on both sides of the cone. An ideal subwoofer is one in which the output from the rear of the driver is either eliminated completely inside the box or made to contribute to the front output without any ill effects. In reality, neither is possible, and a compromise is necessary.

Sealed subwoofers seek to eliminate the rear wave. The problem in the case of sealed subwoofers is that the rear wave is re-radiated through the cone. Many focus on the impact of this rear wave on causing the box itself to flex and vibrate, but a greater concern is the driver itself which is designed to radiate sound! The rear wave can cause the cone to move and re-radiate with a small phase shift.

Anyone building enclosures is familiar with the knocking sound of enclosures with the driver cut-out area open, and how that sound becomes more solid when the cut-out area is covered with another piece of solid MDF. Better yet, one can put the head into the opening and listen the echo inside the enclosure. The term boxy sound has been misunderstood as the sound from a closed box. It is actually more of a box with one wall open so that the reflection/standing waves inside can escape. Therefore a 100% sturdy enclosure cannot get rid of a boxy sound because the internal reflection can still escape. If the cone is not well controlled, the energy can move the cone and produces additional acoustic waves. The result is a loss of definition."_


*Ok, so why in the world did this never occur to me? *
I built infinite baffle subwoofer systems in my car every single time except for this car. One good reason IB sounds amazing is that there is little re-radiation. 

I bought a servo subwoofer from Martin Logan for the house. This is effectively a small box with three 10" but with the technology to fix re-radiation. 

Basically, I've never had this problem before because all my designs dealt with it properly without my knowledge. 

*Why is re-radiation so obvious with this build?*
I chose the Vifa subs because they had low damping suspension and NEO motors. Unfortunately, the Vifas are not a good choice to fight re-radiation. I need a stronger motor, a stronger cone, and stiffer suspension. Nothing wrong with the Vifas, in fact they are close to an ideal subwoofer, they just need ideal airspace too. 

*I hate boxes. Hate them. *


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## BP1Fanatic (Jan 10, 2010)

Good info!


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## teldzc1 (Oct 9, 2009)

So what's next?


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## cvjoint (Mar 10, 2006)

teldzc1 said:


> So what's next?


The right way to do it is to get a servo system. That seems to require at least a custom controller and custom subs. In some cases a custom amp is required. I couldn't find a modern sub/controller for car audio but I haven't really spent all the time I could. 

A second option is to get a different set of subs that are designed to take a pounding in a small box. Seas L26RO4Y would be my first choice. I'll probably also model the Dayton Reference HO and a few Alpine subs.

Third option is to expand the box to get more room. Unfortunately, getting even one extra cubic foot would take a very elaborate expansion and it would require a two piece subwoofer box so I can remove for track days. Not sure how well a two piece box works in push-pull. Probably not that well. 

Switching to four Seas L26RO4Y seems like the easiest option to try out. I would get an ideal Q of .56 and hopefully a more resilient speaker suspension and motor system. I'm open to suggestions


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## cvjoint (Mar 10, 2006)

I modeled the following 10" subs in WinISD to find the ones that give the smallest Q. Since all subs have conventional ferrite magnets (except for the Vifas), I took out .2 cubic feet out of the box, for a total of only 2.2 cubes. 

In summary, 2.2 cubic feet net with 4 subs of the following type:

QTC 0.981 Scan Speak Revelator 10" Aluminum
QTC 0.966 JL 10W7 
QTC 0.809 Alpine SWR-T 10" (shallow type R) 
*QTC 0.803 Vifa NE 10" or QTC .777 in 2.4 cubes*
QTC 0.748 Alpine 10" Type R 
QTC 0.667 Peerless XLS 10" for car 
QTC 0.622 Dayton HO 10" 
*QTC 0.552 Seas Design L26RO4Y *


The lowest Q is achieved by the Seas Design subwoofer. It's basically the ideal .56 Q, and it models even better than the leading car audio subwoofers.


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## rton20s (Feb 14, 2011)

This has been one of my favorite build threads in a long time. 

I believe both Jim and Dominic have experience with the Seas L26RO4Y. Seems like a great subwoofer. 

And if you make the switch, what are you going to do with eight Vifa NE 10s?


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## Lanson (Jan 9, 2007)

Well, passive radiators "embrace" re-radiation, maybe consider something like that.


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## teldzc1 (Oct 9, 2009)

I'm a JBL GTI fanboy, so that would be my suggestion.


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## cvjoint (Mar 10, 2006)

rton20s said:


> This has been one of my favorite build threads in a long time.
> 
> I believe both Jim and Dominic have experience with the Seas L26RO4Y. Seems like a great subwoofer.
> 
> And if you make the switch, what are you going to do with eight Vifa NE 10s?


HaHa! Glad you like it. 

Believe me, within hours of Seas releasing that subwoofer I wanted it. Posted a thread back in 2009 about it. Everyone knows I'm a huge Seas fan and they never really had a proper bass driver until this one. The 10" Excel phase plug woofers are not exactly good sealed box candidates. 

I had a couple auditions in both Jim and Dom's trucks. Not sure Jim had the Seas back then, I believe he had 15"s in a nth bypass shindig. Dom's Seas did shock and awe. He let me test it at very high output last time. Impressive how well the sub sounds at large excursions, above and beyond the Daytons and Peerless XXLS designs. 

I never looks back at what's left behind, no way to progress if you think about the loses. How many people do you know got to experience eight 10" in a push-pull? I think the experience was worth it. 



fourthmeal said:


> Well, passive radiators "embrace" re-radiation, maybe consider something like that.


Rhythmic's website says vented alignments have the hardest time with re-radiation. Check it out:

_"Vented subwoofers suffer more from this problem, as the vent also provides another path way for unintended output to leak out through the vent. Open baffle dipoles do not suffer from the problem because there is no actual box."_

It's best to go infinite baffle or anything with a servo. Vented is worst. Intuitively it makes sense. In an active driver the motor maintains control of the cone. The passive has no motor. 

In either case I bought a Seas passive radiator yesterday. I'm going to give it a try in a small single woofer box. I always wanted to experiment with one. Now it feels cheap compared to working with 8 woofers at a time.


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## rton20s (Feb 14, 2011)

teldzc1 said:


> I'm a JBL GTI fanboy, so that would be my suggestion.


Eight W10 GTi MkIIs?! So much for reduced weight and a removable enclosure.


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## cvjoint (Mar 10, 2006)

teldzc1 said:


> I'm a JBL GTI fanboy, so that would be my suggestion.


Trust me, if it fit I'd try it. Neo motor, shorting rings, robust construction, and a big coil. I can't fit two back to back in this car and I don't want to get rid of the force canceling push pull. 

I wonder if JBL figured out the dual gap better than others. With the XBL2 I thought the subs sounded really poorly at low output. The motor force was not linear enough over stroke with an odd dip.


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## teldzc1 (Oct 9, 2009)

rton20s said:


> Eight W10 GTi MkIIs?! So much for reduced weight and a removable enclosure.


That would either look like warp drive or a misslle launcher! :laugh:


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## rton20s (Feb 14, 2011)

cvjoint said:


> Trust me, if it fit I'd try it. Neo motor, shorting rings, robust construction, and a big coil. I can't fit two back to back in this car and I don't want to get rid of the force canceling push pull.
> 
> I wonder if JBL figured out the dual gap better than others. With the XBL2 I thought the subs sounded really poorly at low output. The motor force was not linear enough over stroke with an odd dip.


Rotate the sub orientation 90 degrees so they are facing the sides of the car?


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## cvjoint (Mar 10, 2006)

rton20s said:


> Rotate the sub orientation 90 degrees so they are facing the sides of the car?


Good thinking! Ok, so two JBL GTI 10"s would fit that way. Remember the kerf though, that part is too shallow for a 10" so the box would be tiny. The kerf starts about 6" out. So from 42" box width we go to 30". Total box size is 14" by 30". Net displacement would only be 1.85 cubic feet minus bracing, minus those monstrous motors which should take out half a cube on their own. The box I have now is about 30% larger.


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## SSSnake (Mar 8, 2007)

Stuff the box with polyfil. It should help dissipate the rear wave energy. It may not reduce it enough but it is worth a try.

You can also try to build traps within the box. Something along these lines:










https://goo.gl/photos/caszBAVGhzufMaYe7


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## cvjoint (Mar 10, 2006)

SSSnake said:


> Stuff the box with polyfil. It should help dissipate the rear wave energy. It may not reduce it enough but it is worth a try.
> 
> You can also try to build traps within the box. Something along these lines:
> 
> ...


The bass traps are brilliant! Perhaps composite sheets glued to the box walls would work and not take up too much room. I should have designed my bracing to be bass traps at the same time. Hindsight is 20/20. 

If I get something monstrous like the Seas subs I think the rear magnet is a bass trap :laugh:

Box has 2.5 lbs of polyfill already.


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## teldzc1 (Oct 9, 2009)

Just get the GTIs. I want to see what you engineer out of it. =)


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## t3sn4f2 (Jan 3, 2007)

How about trying out the same box with 6 Vifa's instead of 8. You should have more output than the 4 Elroys D). Not to mention the significant weight savings (ie Vifa: ~30lb, Seas: ~100lb)


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## cvjoint (Mar 10, 2006)

t3sn4f2 said:


> How about trying out the same box with 6 Vifa's instead of 8. You should have more output than the 4 Elroys D). Not to mention the significant weight savings (ie Vifa: ~30lb, Seas: ~100lb)


Funny enough nothing has the output of the Elroys bellow 35hz. It turns out that is one of the strongest motors on the market and it matters. The weight savings are real. 

Ok, so I've been working hard at figuring this out. So I want to share the findings. 

What makes a good small box subwoofer? I traced down the forum creator's invention. Few may remember but the Diyma R12 was built to be one of the best small box subwoofers. So how did Npdang do it? He followed the Peerless XLS recipe for a small box subwoofer, and slapped on the biggest motor that the basket can support. So to pin down what makes a great small box subwoofer I've determined that we must understand what makes this subwoofer so good in small boxes:

http://www.madisound.com/pdf/peerless/830514.pdf

Peerless says: _"The 10" XLS car subwoofer driver has been designed with a specially compounded strong rubber surround that has the strength to withstand the high pressures inside a small sealed box."_

Aha! So my suspicion was correct. To deal with the extreme air pressure generated in a small sealed box, the suspension of the driver needs to be stiffer to resist rocking modes, deformation, re-radiation, etc. 

From my midbass experiments I find that I like the soft suspensions for sound quality. But in the midbass case I have infinite baffle. IMO at this point I think sealed boxes are major compromise. You cannot have a top notch driver like the Vifa in the box because the air pressure will strain the soft low damping suspension. 

Neither can I have a servo to correct for some of the distortion. I couldn't find a modern day servo system that is usable in a car.


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## SSSnake (Mar 8, 2007)

For what it is worth (which is not much) every time I have had a problem with re-radiation the primary offending issue was the reflected sound coming back through the cone and surround. I have not noticed issues with centering of the driver (doesn't mean it doesn't happen I just haven't seen it). If I were you, I would primarily be concerned with this issue and then see what I had.

To give an example, I loved the sound of the B&C 8NDL51s in a properly sized ported box in the HOME environment. I tried them several times in car and could NEVER recreate the sound. I finally figured out that the rear wall of the car enclosures were significantly closer to the motor and therefore the cone than the enclosure for the home system. With the 8NDL51s this is particularly bad because of the vents around the edge of the motor. At high excursion I could actually hear the air rushing in and out of the vents. To determine if enclosure shape was the issue, I took the home enclosure and made it very shallow. As I suspected the noise issues I had in the car showed up in the home as well when using this new enclosure.

In my case the noise was of higher frequency than the signal. This is both bad and good. It ends up being at a frequency that we are more sensitive to and therefore becomes annoying pretty quick. However, it also presents you with options about how to attack the problem. Instead of having the drivers in the front and rear of the box facing forward you might want to try down firing. Then you can have an edge of the box form a wall that goes to the floor along the front of the box (causing the sound to escape to the rear) and use foam along the rear edge of the box to filter the unwanted sounds.

I know, I know that means starting over with the box for a maybe. If you can build a quick and dirty test enclosure outside of the car to test my theory you could save a lot of time.

BTW - I would not be surprised if you experienced a similar issue with your midbass experiment. IMO that is likely why you decided you have a preference for "HiFi" drivers vs "HE". I could be completely off base but your story sounds too familiar to what I experienced.


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## rton20s (Feb 14, 2011)

cvjoint said:


> Aha! So my suspicion was correct. To deal with the extreme air pressure generated in a small sealed box, the suspension of the driver needs to be stiffer to resist rocking modes, deformation, re-radiation, etc.


So, the ideal small sealed enclosure driver will have low CMS, low Qts and high BL?


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## cvjoint (Mar 10, 2006)

SSSnake said:


> For what it is worth (which is not much) every time I have had a problem with re-radiation the primary offending issue was the reflected sound coming back through the cone and surround. I have not noticed issues with centering of the driver (doesn't mean it doesn't happen I just haven't seen it). If I were you, I would primarily be concerned with this issue and then see what I had.
> 
> To give an example, I loved the sound of the B&C 8NDL51s in a properly sized ported box in the HOME environment. I tried them several times in car and could NEVER recreate the sound. I finally figured out that the rear wall of the car enclosures were significantly closer to the motor and therefore the cone than the enclosure for the home system. With the 8NDL51s this is particularly bad because of the vents around the edge of the motor. At high excursion I could actually hear the air rushing in and out of the vents. To determine if enclosure shape was the issue, I took the home enclosure and made it very shallow. As I suspected the noise issues I had in the car showed up in the home as well when using this new enclosure.
> 
> ...


I believe what you are describing is the chuffing noise B&Cs make due to the vented coil. The wholes in the back of the motor where the voicoil pushes hot air out makes that racket. I do hear it with high excursions. You can hear it free air really well.

So I tested the sub box by playing signals that are outside of my hearing range but generate lots of excursion, 20hz and below. Excursion is clean, the motor is quiet, and air pushes around the basket pretty nicely. It's nothing like a B&C undergoing excursion, this is one of the quietest Hi Fi drivers I've tested. It sounds worse going up in frequency, with test tones 50hz and 60hz the worst of the bunch. More evidence it's not the venting of the speaker basket. 

I tried to absorb noise by making a closed cell foam barrier before, many times. It works to absorb amplifier fan noise, it does not work for speakers. The reason is the CCF moves as air goes through it and creates its own "whooshing" noise.

Down firing is a good idea if speaker noise was the issue (although I would lose much box space to execute it). Given my testing with test tones I don't think that's the case. The issue is more about clarity, intelligibility, and accuracy. 

It's very much the same issue I've had with kick panels in the car. Small box space can wreck havoc with the speaker's suspension. In fact, in a very tight kick box I tested the following 8s:
*Seas Excel magnesium
*B&C 8NDL51
*Scan Speak Classic Kevlar

I found the the B&C was the most pleasant with small enclosure space, which reinforces the theory that the stiffest suspension deals with tight confines the best. The Seas I believe had a similar Q because of the strong motor but ultimately the soft suspension couldn't be controlled well enough.


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## cvjoint (Mar 10, 2006)

rton20s said:


> So, the ideal small sealed enclosure driver will have low CMS, low Qts and high BL?


Well, CMS is the key imo. Ideally you want the highest CMS but still be able to center the coil in the gap. You can only use the ideal suspension in free air (infinite baffle). So you need an ideal box. The best woofers that I've heard were ones with very soft suspensions in infinite baffle. With a small box you have to give up the ideal because the air pressure in the box starts to dominate the cone motion for soft suspensions. Peerless designed a freak surround for its time. I touched that XLS surround and I couldn't believe how hard it was. In the late '90s almost all high end Hi Fi drivers had soft suspensions. 

BL sort of completes the requirements. A strong motor will keep control of the cone but the cone and suspension still have to be strong as the motor is not coupled to every mm of the surface. 

Everything else is about frequency response. QTS is a function of QMS and therefore BL. I don't care much about frequency response because we can easily extend to 20hz in a car. This is more of a home audio problem. 

The stiff suspension should make the driver less efficient, so a big coil is required to supply adequate power. Adding more layers increases BL with the same magnet.

Which all leads to the Seas L26RO4Y. I've been chatting with Seas, the R&D manager and the CTO. I was wondering why the sub didn't get a higher power handling certification despite getting twice the voice coil layers compared to the standard LROY. It turns out the power handling is actually very similar as the white sheet states. The additional 2 layers are there to change the application not to raise the power handling. You an see that the 4 layer model has much more BL. It also has a much stiffer suspension. However it's still twice as soft as the original XLS designed for a car! Grrr...


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## Hanatsu (Nov 9, 2010)

I dunno what to make of that "re-radiation" thing. The servo technology I'm accustomed to is the type used by Velodyne, this tech is used to reduce non-linear distortion to a minimum. 

" The reason for this is that the cone needs to be far more compliant than the enclosure. The challenge is for the cone to respond accurately to the input signal but reject interference from sound waves inside the box. "

They basically say VAS needs to be much lower than the actual volume of the enclosure, which basically means 'the sub requires an infinite baffle config in order to sound good'. 

Within the realms of car audio we got much worse issues, so while I agree the issue exist, I argue it's a pretty minor one. Depending on where Fsc ends up you can use Qts values way up to 2.0 without ill effects that can't be processed out. The peak in group delay is highly related to the frequency response since it's the negative slope of the phase response. All high Q systems will have a group delay peak but it can be heavily improved with ordinary EQ. In a FIR based system with an arbitrary phase curve it can be removed altogether. 

Di-poles would eliminate that entirely but they are incredibly inefficient and not practical for use in a car. More cone movement for given output increase non-linear distortion which cannot be processed out and is far more audible than most people tend to believe. 

If you're interested... even Linkwitz mentions this; Design of Loudspeakers

He also mentions "re-radiation though loudspeaker walls" which I think is a far bigger issue for us. Any vibration in enclosure walls will propagate as distortion and increase the chances of locating the origin of the LF.

There are many who swear that low Q systems sound better, I haven't seen much evidence that support that low Q would perform better for subwoofer applications. Even without processing anything below 1.0 is fine imo (again depending where Fsc ends up). Best LF efficiency, zero ripple and best transient response compromise is reached at 0.7 - I think it's a good rule-of-thumb. I rather make the enclosure rock solid than considering Qtc so to speak...

Just sayin


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## cvjoint (Mar 10, 2006)

Hanatsu said:


> I dunno what to make of that "re-radiation" thing. The servo technology I'm accustomed to is the type used by Velodyne, this tech is used to reduce non-linear distortion to a minimum.
> 
> " The reason for this is that the cone needs to be far more compliant than the enclosure. The challenge is for the cone to respond accurately to the input signal but reject interference from sound waves inside the box. "
> 
> ...


That was my attitude going with this design. I designed it to minimize non-linear distortion, minimize linear distortion, and have acceptable group delay by common rules of thumb. 

In practice however, I think it has proven to not be sufficient. I thought a CMS of .5 is sufficient to withstand the sealed box pressures but I don't find that to be the case anymore. It's not something I could have modeled in software or that is discussed at length, but it is very much a real problem. 

The clues were there. Dayton produces the Reference subs in two trims. The small box one has a stiffer cone, stiffer suspension, and more BL. Seas does exactly the same thing with its Design series. Peerless car subwoofers are basically the same as the standard line with a stiffer surround and higher BL. 

Servo technologies differ a little bit. I tracked down Kenwood's and JBL's and found those are perhaps not complete solutions like the Rhythmic audio version. I know the one inside my Martin Logan subs works like magic, but couldn't tell you the details. Ultimately none are available in a car. I would have to have someone custom design power supplies. Too complex to pass the KISS test. 

I might agree with you that in some situation a high Q would work. Perhaps if you start with a CMS of .15 like the original Peerless car sub the suspension is stiff enough to work at a Q of 1. 

The ultimate test was adding the second round of bracing. Q went up, box got stiffer, but the box sounds worse. In this application I venture the opposite is true. Re-radiation through the cone is much worse of an offender than through the box. That's how I interpret my findings. To make this a theorem I would add the paragraph above in a footnote. 

EDIT: One more thing. I used these Vifas (12" trim) in infinite baffle in my old car. They sounded amazing. That is the equivalent of dipole in home audio. Perhaps to some the issue may not be audible. I've used half a dozen types of subwoofers in infinite baffle in cars by now. To me the boxy sound is obvious.


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## cvjoint (Mar 10, 2006)

Guys, we are forgetting the elephant in the room here. We're not just talking about re-radiation off the box walls back through the driver, but also re-radiation from the subwoofers on the opposite wall!!

The box I built, with no bass traps, and very very open rear baskets can have several times the re-radiation of a normal box of the same size that does not have opposed subs.

Or maybe it's the same thing, I don't know I'm getting tired.


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## Hanatsu (Nov 9, 2010)

Cms... Much easier to use VAS, they describe the same thing 

My midbass drivers is in a box with a Qtc of 2.2. This creates a 13dB peak at 160Hz. I pulled it down with EQ, added a shelf filter and got usable response down to 70Hz. They are terribly inefficient below Fsc but the group delay is almost flat and no audible coloring from the enclosure that I've noticed. These drivers got a Qts of 0,5 and pretty high VAS relative to the driver size. I think the enclosure is about 20-25times smaller than the total VAS and it still works fine. 

BL is a funny value as well, if you put a DVC sub in series vs parallel the BL will double because of the "L" value is twice as large. It doesn't affect performance since Re also will increase and Qes will stay the same. 

I think everything in the linear domain can be put on the low priority list when it comes to subs, most audible issues will be fixable with processing. I prioritize efficiency and non-linear distortion performance, this is why I prefer vented or bandpass systems. Modal peaks in the lower octaves can reach one second of audible ringing, ringing due to high Q will be small compared to this and therefore be inaudible due to the masking effect if it were to occur within a modal pole. One important thing to point out is that Q is only of importance if you use the driver at resonance. With subs we are usually doing this, but if it (Fsc) falls below a certain threshold - let's say 40Hz I argue that won't be audible other than extreme cases, again because of modal ringing which basically is same type of distortion...


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## cvjoint (Mar 10, 2006)

Hanatsu said:


> Cms... Much easier to use VAS, they describe the same thing
> 
> My midbass drivers is in a box with a Qtc of 2.2. This creates a 13dB peak at 160Hz. I pulled it down with EQ, added a shelf filter and got usable response down to 70Hz. They are terribly inefficient below Fsc but the group delay is almost flat and no audible coloring from the enclosure that I've noticed. These drivers got a Qts of 0,5 and pretty high VAS relative to the driver size. I think the enclosure is about 20-25times smaller than the total VAS and it still works fine.
> 
> ...


I'm curious what % distortion you are getting from the air spring nonlinearity. Compute using the formula on the bottom:

http://www.linkwitzlab.com/images/graphics/air-distortn.gif

That type of distortion is nonlinear (not fixable with our tools) and should be easily audible with your setup.

I've previously EQ'd a midbass enclosure that had only half the resonant peak yours does. It never really sounded that good. Ended up drilling the frame of the car to release some of the air pressure. To me the ringing, even if fixed by EQ in the FR, still lives on in the time domain like a ringing bell. 

I agree that linear distortion is the least problematic but I'm not sure we're on the same page as to what is linear distortion.

As far as BL, RE is fixed in my case because I'm aiming for a 1 ohm load.


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## Hanatsu (Nov 9, 2010)

Yes I know of the air spring non-linearity. It is a classic case of "not so bad in reality".

I will say though, you want a stiff cone. I used a thin paper driver at first but it didn't sound good, sounded like distortion... Alu and stiff poly cones seem to work best


Sent from my iPhone 6 using Tapatalk.


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## SSSnake (Mar 8, 2007)

First and foremost I am not there listening to the sub so anything that I recommend is only based upon the information presented in the thread and my own experiences. Having said that sometimes this is the most beneficial way to diagnose a problem because you are not influenced by your own conjecture (you diagnose only the specified problem and don't wonder if that is really the issue). I say this to remind you of your initial comments (which, for me at least, are usually the most accurate) :



> So I searched, and searched, and found the most likely reason for the buzzing muffled sound of the box - re-radiation.


Buzzing and muffled are definitely what I experienced with the B&Cs and others. The example of the motor vents chuffing is just that, a single example. Applying your current theorem the B&Cs should sound the best in a small enclosure and they were horrible. Why? In my specific case re-radiation of the noise (chuffing and others) back through the thin surround and cone. Don't get me wrong strong Bl and stiff cones are desired features for a small box woofer but I don't necessarily believe they are the exclusive cause of your issues (in other words maybe and maybe not).



> The issue is more about clarity, intelligibility, and accuracy.


I understand the clarity, intelligibility and accuracy comment. But wouldn't all those factors be affected if there were non musical noises coming through the speaker cone? I don't believe that you are hearing motor noise re-radiated through the cone as was the case in my B&C example. What I believe you are hearing are the reflections within the box being re-radiated through the cone and surround. While not as high frequency as the chuffing noise of the B&Cs the most offensive of these components tend to be higher frequency than the original signal (think similarly to THD in electronic circuits but in this case a physical phenomenon associated with the constructive and destructive combination of the waves and their reflections within the box. This is further reinforced by your own comments:



> It sounds worse going up in frequency, with test tones 50hz and 60hz the worst of the bunch.


The lower the freq the less difference in the phase of the direct vs re-radiated sound and therefore the less nastiness in the observed response. BTW - I do know the wavelength of these frequencies and I understand this is typically thought to be in the modal response area where dampening reflections would not be of such a larger concern BUT the rigid walls of the sub box make great reflectors. Bounce the sound around the longest dimension a few times and you can get the kind of interference I am referring to. The key is to make sure you send the wave through as much damping material as possible during its trip (more later).



> Down firing is a good idea if Speaker noise was the issue (although I would lose much box space to execute it).


This is an unavoidable reality and maybe enough reason for you to move on to a different woofer. However, I have used the seas woofers before and really liked them after some initial difficulties with the box. I believe that it was your install thread from the S2000 that got me to purchase my first Seas neo and get it to Erin for testing.

http://www.diymobileaudio.com/forum/klippel-reviews-driver-specs/115754-vifa-ne225w-04-klippel-test-results.html

I will be the first to admit that it disappointed in the klippel testing but in application it was not a bad small sub (not great for car but darn good for a bookshelf speaker where excursion is not such a factor). So if you want to move on I understand but from my experience with these and other similarly spec'd woofers they can be made to work VERY well but there are a few special considerations that you need to make when trying to shoe horn 10lbs of ish into a 5 lbs bag.



> I tried to absorb noise by making a closed cell foam barrier before, many times.


This is in reference to my more later comment. Your comment above had me concerned. You shouldn't, in this case, be trying to make barriers (and closed cell foam is a poor barrier material which from older posts I am pretty sure you are aware of - MLV MUCH better for barriers poly and open cell foam for absorbing sound). What you should try to do is absorb the energy from the reflection as much as possible. To do that at LOW freq is not easy. The best approach is to tightly pack the box with polyfil while ensuring the woofer can move freely. Then build traps/deflectors that require the reflected energy to travel as long a path as possible. Again this seems contrary to treating low freq information as a pressure wave but IME it is the higher freq components in the re-radiated signal that are the most offensive. As the freq decreases the problem also tends to decrease so while poly and other dampeners are not extremely effective they are slightly more effective in the area of concern.

I should point out one error in my previous post. In the trap suggestion I quickly sketched up traps with features parallel to the enclosure front and rear panels. This is a BAD idea. They should be angled to cause a sound wave to travel the longest path possible through the enclosure. The other consideration is that all of your woofers are symmetrically placed for optimal packaging and aesthetics. The also contributes to the issue I believe you are experiencing. This allows those higher freq interactions to all occur at the same freqs. Getting each signal to travel different path lengths helps to lower the magnitude of the offending noises helps spread out the issue and therefore makes it less offensive. Most will not want to compromise the aesthetics to reach this goal so you can make sure the traps/deflectors inside the box are irregularly shaped to spread the reflected noise across a broader freq range.

I hope this doesn't come off as a keyboard commando as that is not my intent. It is just that I have been down the road you are currently traveling (or at least I think I have). I have gotten rid of more perfectly good equipment because in the implementation for my application (which always seem to be non-standard) I have missed issues. Issues that all of the theory says shouldn't be there (well until you peel back quite a few layers of the onion). In the case of someone who has done car and home audio for over 30 years (some professionally but most as a hobby) you find yourself always trying to figure out why when something worked well in one application and poorly in another. This led me to my current beliefs about small enclosures (in my best Bobby Bouche voice "ma ma ma momma says they are the devil"). BUT they can be made less offensive and if you do it right you will be the only one that ever notices or remembers there was ever an issue.

I hope this helps! I am off to install a mini DSP on my boat.


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## Hanatsu (Nov 9, 2010)

The Vifa NE225 got a Qts shift from 0,35 to 0,85 with 5mm excursion. The Scan 26W got a shift of 0,05 in the same range, it's a 10" but anyway... The Vifa driver got a very asymmetric BL curve hence the large Qts shift...

I don't think that driver is optimal for subwoofer duty, it seems more usable as a midwoofer.


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## cvjoint (Mar 10, 2006)

Oldy enough the Vifa 12" has a fantastic Klippel performance compared to the 8" version. The Vifa 10" has the same motor as the 12" and the suspension if very similar. So my best guess is that it is a stellar performer. The Q shouldn't vary much at all and at 2,500 watts the Vifas only undergo 7 mm of excursion. The motor only has 10% distortion at 9mm...

SSSnake I agree with you on every point! 

I've put together everyone's input and came up with the following battle plan. I will pursue the options in this order. If the first fails to satisfy, I'll go to the next.

1st option is to replace the 8 Vifas with 4 Seas L26RO4Y. The Q will drop from 1.07 to .56. SPL will be higher than the Vifas anywhere under 38hz for up to 3db gain at 20hz. I know from Seas the suspension has been stiffened in this 4 layer model vs. the 2 layer and the CMS is low enough to work in a tight sealed box.

2nd option is to add bass traps. I will not add bass traps unless the Seas really need them because they will take up box room.

3rd option is to mount all 8 Vifas in isobaric. The Q will drop from 1.07 to .64. SPL will be the same in the 20s but lower anywhere up for up to 4 db loss at 60hz.

Please see the current results from testing the Vifa box in Woofer Tester 2. The QTC has dropped from 1.11 to 1.07 despite the fact that I added bracing. I think it has to be driver breaking in.


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## BP1Fanatic (Jan 10, 2010)

Option 3 since you already have them.


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> Option 3 since you already have them.


I bought the 4 Seas subwoofers last night. By that logic I have them too!


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## BP1Fanatic (Jan 10, 2010)

Lol!


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## SSSnake (Mar 8, 2007)

> The Vifa NE225 got a Qts shift from 0,35 to 0,85 with 5mm excursion. The Scan 26W got a shift of 0,05 in the same range, it's a 10" but anyway... The Vifa driver got a very asymmetric BL curve hence the large Qts shift...
> 
> I don't think that driver is optimal for subwoofer duty, it seems more usable as a midwoofer.


I was trying to use them in car as midwoofers but even in this use they were less than spectacular. The final usage became the bottom end of a three way bookshelf system. The box was ported to reduce the excursion requirements...


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## cvjoint (Mar 10, 2006)

SSSnake said:


> I was trying to use them in car as midwoofers but even in this use they were less than spectacular. The final usage became the bottom end of a three way bookshelf system. The box was ported to reduce the excursion requirements...


None of the NEs are built with large xmech. That's why I planned on using 8! 

It is however unfortunate Vifa didn't built the 8" with the same standards as the 12". It caught me by surprise. Something tells me the 8"s are usually the forgotten child in most speaker lineups.


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## cvjoint (Mar 10, 2006)

The Lro4ys are here. 










Side by side comparison with the incumbent:




































Based on the input I received thus far, this solution seemed like the best remedy. 

*predicted QTC=.56 (not taking into account any polyfill), a decrease from 1.07 (as tested with Vifas in the box)
*predicted SPL change: increase of 3db @ 20hz, equal output @35hz, lower output above that.
*lowers the resonant frequency of the system as a whole
*3 times increase in suspension stiffness to deal with small box air pressure
*50% increase in motor strength to deal with small box air pressure
*half the drivers but with a substantial increase in Xmax, xmech, and higher thermal resistance, allowing a doubling of airspace per speaker with no loss of large signal performance

My initial inspection of the Seas drivers shows a stout driver indeed! Applying a bit of pressure on the cone edge does not result in visible cone deformation. The Seas have various ribs to increase geometrical stiffness, and a very pronounced cone lip to increase strength. The spider is also noticeably stiffer to the touch, and seems to get progressively stiffer with distance from the coil. Most of the stiffness increase vs. Vifa seems to be from the considerably stiffer surround. The amount of magnet mass/volume is shocking. Equally impressive is the basket to SD ratio, Seas squeezes in a larger cone for nearly the same footprint.


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## t3sn4f2 (Jan 3, 2007)

That's a nice looking sub! Hope they work out for you.


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## BigRed (Aug 12, 2007)

Its a great sub George. I have one I've been using for over a year now. One of my favorites ever.


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## MantaOwner (May 15, 2007)

cvjoint said:


> I bought the 4 Seas subwoofers last night. ..


How much did they cost you and where did you get them from?

Tõnu


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## cvjoint (Mar 10, 2006)

BigRed said:


> Its a great sub George. I have one I've been using for over a year now. One of my favorites ever.





t3sn4f2 said:


> That's a nice looking sub! Hope they work out for you.


I've always wanted one but the weight of the thing always kept me at bay. Someday every sub will have a neo magnet and I won't have to make tough choices. 



MantaOwner said:


> How much did they cost you and where did you get them from?
> 
> Tõnu


Madisound has a discount if you buy 4 or more. Ended up costing me $1,050 shipped. That is our US distributor for almost all of the high end raw drivers.


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## b2okane (Sep 23, 2009)

nice set up you got there


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## Lanson (Jan 9, 2007)

Love the idea of those subs, I also shoot for low Qtc setups when I can. Even if it sacrifices something like ultimate SPL, I'd rather have that smoooooth sound that you can really enjoy with all music. Can't believe I finished my Vette project before yours though!


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## cvjoint (Mar 10, 2006)

fourthmeal said:


> Love the idea of those subs, I also shoot for low Qtc setups when I can. Even if it sacrifices something like ultimate SPL, I'd rather have that smoooooth sound that you can really enjoy with all music. Can't believe I finished my Vette project before yours though!


Define finished. Ha! Mine will be finished when I sell the car. 

Even in this design there is some SPL tradeoff. I could mount 4 passive radiators instead of plugging the remaining holes. I got one passive radiator to play with. Who knows, I might like it.


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## Lanson (Jan 9, 2007)

cvjoint said:


> Define finished. Ha! Mine will be finished when I sell the car.
> 
> Even in this design there is some SPL tradeoff. I could mount 4 passive radiators instead of plugging the remaining holes. I got one passive radiator to play with. Who knows, I might like it.


Just like Carver did with the Sunfire and Sunfire Jr., they have a driver and two to 3 passive rads (depending), note that you really want that 1:2 ratio with long-throw, meaty drivers. They can be a ***** to model but when you get it right, oh man it is cool.


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## cvjoint (Mar 10, 2006)

fourthmeal said:


> Just like Carver did with the Sunfire and Sunfire Jr., they have a driver and two to 3 passive rads (depending), note that you really want that 1:2 ratio with long-throw, meaty drivers. They can be a ***** to model but when you get it right, oh man it is cool.


Yeah, the passives would reach max excursion at about 2,000 watts 1:1. However, I'm thinking their suspensions would get stiffer with excursion so it is possible I would need all 2,500 watts to get them to full excursion. Even then, it would only happen in the 20hz range.


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## Lanson (Jan 9, 2007)

cvjoint said:


> Yeah, the passives would reach max excursion at about 2,000 watts 1:1. However, I'm thinking their suspensions would get stiffer with excursion so it is possible I would need all 2,500 watts to get them to full excursion. Even then, it would only happen in the 20hz range.


I had the joy of selling Carver when I worked for Ultimate back in the day. Beast units for their size for sure.


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## cvjoint (Mar 10, 2006)

*Update on H800 combo with standalone Bluetooth receiver*

Here are a few things that were hard to diagnose but now that I did, makes this system a well oiled machine. 

*1. Digital clipping*

*Symptom:* at high volume I could hear a clipping like noise affecting the entire signal.
*Early diagnosis:* the Galaxy S7 phone would clip at max volume, even though it sent a full digital signal through bluetooth. To remedy I sent the digital signal out one click down on the phone's volume. It didn't always work, but seemed to work instantly on a particular song.
*Current diagnosis:* It was not the Galaxy S7 signal that was clipping. I've checked this by connecting to my home theater system and sending max output. No clippling. What is really driving the noise is the subwoofer firing right into the bluetooth receiver antenna in the car. By lowering the volume, the output of the sub is lowered and the antenna starts receiving the phone's transmission uninterrupted. 
*The remedy:* Trying out the 4 Seas subs, so I'll mount them in the center of the box, away from the bluetooth receiver antenna. 

*2. Dead car battery*

*Symptom:* The original car battery died after 1.5 years of use. 
*Early diagnosis:* I thought the car wash guys killed the battery, and then the battery never recovered properly. 
*Current diagnosis:* Parasitic drain from the H800. The H800 does not turn off entirely when keeping the source button pressed on the RUX to turn the processor off. The amps shut off, the Alpine H800 has all the lights off, but it is still on!! The proof was the following. Processor heatsink temperature was not ambient when turning the car on in the morning but 120*F. The sucker was on all night building heat, and killing my battery. After one weekend, even the mighty Odyssey AGM battery died. 
*The remedy:* First remedy failed. Instead of powering my bluetooth receiver with constant 12V, I powered it with the H800's remote out 12V. Didn't work. Second remedy failed as well. Instead of powering my bluetooth receiver with 12V remote out from the Alpine I installed a proper relay. Both of these remedies failed because it wasn't the Bluetooth receiver's draw that was killing the battery, although the relay helped, the power savings were a drop in the bucket. The third remedy worked. I changed the H800's remote in to a switched 12V source. FYI fuse #37 in the trunk is a switched 12V fuse for the in-car cigarette lighter. It is not the same as the trunk port which is always hot. 

*So how does it work? *
The bluetooth receiver is media only. This never occurred to me but you can't take calls using a standalone bluetooth receiver. I thought I would be able to using my phone mic but no go. So I'm trying to use my OEM system for the calls and the Alpine setup for playing music. However, my Chevy Bluetooth won't connect anymore. Not sure why. Currently I have no way to answer calls in the car...legally. 

The Audioengine B1 bluetooth receiver connects instantly. Since the H800 now turns on with accessory power the phone connects instantly as long as my bluetooth is turned on in the phone. I just press play and drive. 

There are no turn on thumps. 

There are no turn off thumps.

There is no background noise.

Sound quality is excellent with Spotify's 320kbps and APTx Bluetooth. Forget about CDs and USBs, this is the best way to wire in your music.


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## cvjoint (Mar 10, 2006)

*8 Vifa NE 10" vs. 4 Seas LROY 10" subwoofer death match first impressions*

The unanimous one person jury decision is that the Seas dual opposed combo of 4 is the new king. I only needed a minute of auditioning to figure this one out. It combines all the qualities of my favorite subwoofer installations I've done: the output of 3 12" Idmax in infinite baffle, the vibration free operation of the Tymphany LAT700, the profound low octave output of the 12" Vifa NEs in infinite baffle, and the dead-quiet excusion that we've come to expect of proper HI FI drivers. 

First, some photos. Techshop was missing some parts from their hand held router. It turns out that they are giving up on finding replacement parts and they are decommissioning it! Crazy. That's the only tool I know how to use to make speaker baffles proper, so I turned to the jigsaw and made some temporary block off plates while I figure out what to do tool wise. 










While the Seas have a cutout only 1 mm larger than the Vifas, I had to chop off quite a bit of material to make them fit. Odd. The motors are massive, so I removed the magnet rubber booth to get more room and box space. I trimmed some of the bracing, and had to even remove vertical rods. Terminal plates were blocked off because the outer OD of the speaker was much too large to accept the previous location. 










Front baffle with two of the holes plugged off and the terminal cup relocated. I prefer drywall screws to machine screws and t-nuts. They seem to hold well so I don't see the need for something stronger atm. The woofers weigh 22lbs each and offer 8 screw holes. 










I made one big change on the back baffle. Instead of inverting the subwoofers I mounted them with the magnets inboard. The person to be blamed for the decision is t3sn4f2.  He rightly noted that if there are any suspension and motor asymetries that the acoustic push-pull rectifies, the force cancelling push-pull will not function to the degree of those nonlinearities. Basically, 2nd order distortion canceling came at the price of some vibration cancelling. I decided vibration canceling is more important to me. This time around the force cancelling is most effective, but there is no acoustic push-pull anymore. There is a second loss with this arrangement, smaller net box size. All 4 motors are now in the box taking up room and the motors are giant! So the final Q is going to be higher than the anticipated .56. There is also a second gain with this arrangement, less resonance and suspension noise, to the degree that there would be any with the Seas inverted. Linkwitz says they work noise free in dipole but who knows.

You can also see the finished amp rack cover on the left. Stealthy black metal cover with Ensolite padding on the inside. 




























*Impressions*

The box now sounds acoustically dead, except for the subsonic output. There is no apparent buzzing or resonance of a high frequency nature. Just what you'd expect from a stout subwoofer box and non-resonant drivers. The resonant frequency of the system showed at 48hz on the Woofer Tester 2, a large decrease from the 65hz I was previously getting with the Vifas. The QTC was much higher than the anticipated .56, at .65 but I believe these subwoofers need a lot of break-in. The TS parameters deviated quite a lot from the white sheets so I will test again after break-in. In either case, a massive improvement from the 1.07 QTC I was getting with the Vifas after break in. 

The speaker linearity is vastly improved! This is what I was hoping for. Regardless of the frequency or SPL level the subwoofers play back the original signal with no sign of stress. I hold the belief that it is the stiff suspension structure of the subwoofer that it is to be thanked. So no more boxy sound or hints of re-radiation. I suppose we'll never be able to figure out whether it was the lower Q or the stiffer suspension that offers the large improvement over the Vifas, but in either case, mission achieved. Perhaps they are the same thing. 

The low octave output is outstanding. My best guess is that it deviates from a flat FR, with a rising output towards 20hz side. To my ear it's definitely bottom heavy, but not at all unlikable. I might NOT EQ it down and enjoy the prodigious output down low. 

I've tried 63hz low pass and 71 hz low pass. I like them both. 

Now I have to figure out what to do with $2,000 worth of Vifa NEs I have laying around.  But I am really happy I pulled the trigger on these Seas. I learned a valuable lesson working with small sealed subwoofer boxes. The low damping soft surrounds of woofers designed for large sealed/vented alignments do not work well in a small box. This is a despicable application where only purpose built monster subs like the Seas belong. So I might hang on to the Vifas for a dipole application in home theater or large sealed box, but I'll never throw then in a high Q alignment again. Lesson learned.


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## Lycancatt (Apr 11, 2010)

too bad you already have tall ribbon based speakers at home, or I'd say do a copy of the big carvers with a 48 ribbon and four of the vifa tens per box..just cause they look impressive.


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## cvjoint (Mar 10, 2006)

Lycancatt said:


> too bad you already have tall ribbon based speakers at home, or I'd say do a copy of the big carvers with a 48 ribbon and four of the vifa tens per box..just cause they look impressive.


I thought about replacing my dual Satori 6.5" in the towers with quad Vifa NE 10s! But it would just be an output improvement, not really any better. I could also use them with one of my AMT tweeters in a tower crossed at 1,000hz. That would be an output monster.


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## cvjoint (Mar 10, 2006)

*In-car testing of Seas subs*

By testing the frequency response and THD with the Omnimic I found a few interesting bits:

1. The FR is bottom heavy, with a pronounced peak in the 20hz-30hz range. 
2. At high output the 25hz peak subsides, possibly because of higher QTC with excursion.
3. -3db point is now 14hz instead of 18hz with the Vifas.
4. Same output at 63hz as it is at 18hz. Compare this to Vifas where 63hz output was the same as 20hz. 
5. Total harmonic distortion remains below 5% even at 110db, well below audible limits even at 20hz. 
6. The sub has higher 2nd order than 3rd order distortion, which is typically accepted as a more pleasing distortion profile. 
7. Usable bandwidth is large, at least 14hz to 150hz with minimal EQ. 
8. No bothersome nulls or peaks in the response. 
9. Window down response has lower SPL in the range up to 30hz, higher SPL up to 55hz, and the same over that. The impression that windows down is louder must be because we are more sensitive to 30hz-55hz range and there is usually more material there on tracks. 

The graphs:










The black plot is a summed frequency response across multiple mic positions in the driver seat. This is the best guess as to the true response. 

The blue plot is just one mic position in front of me. Windows are up.

The red plot is just one mic position in front of me. Windows are down. Compare this one to blue where the windows are up but the position is the same. Odd right? Same behavior showed up in my old car with the convertible top down. My guess is that windows down is easier for the subs to move air so the SPL goes up, but then at the lowest frequencies there is cancellation so the SPL drops sharply. 

*Harmonic distortion plots*
Volume -22db on processor, amp gain 1/2, processor gain maxed out +15db, 100db fundamental, THD less than 1.75% throughout










Volume -17db on processor, amp gain 1/2, processor gain maxed out +15db, 104db fundamental, THD less than 1.75% throughout










Volume -12db on processor, amp gain 1/2, processor gain maxed out +15db, 104db fundamental, THD less than 2.5% throughout, lowered mic sensitivity because it was clipping, maybe that's why fundamental didn't change










Volume -9db on processor, amp gain 1/2, processor gain maxed out +15db, 108db fundamental, THD less than 3.5% throughout, kept low mic sensitivity










Volume -6db on processor, amp gain 1/2, processor gain maxed out +15db, 110db fundamental, THD less than 4.5% throughout, kept low mic sensitivity










The Vifas were showing a rather larger peak in THD around 50hz, the Seas do not. I was far more comfortable testing the Seas at high output. The results are very good. THD is well below audible thresholds even at outputs I never attempt with music and the FR is flat to well below 20hz. Most importantly they sound better to my ears on every material compared to the Vifas.


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## rton20s (Feb 14, 2011)

Great info George. Nice to see such low distortion, even at significant output levels.


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## Elgrosso (Jun 15, 2013)

Impressive, and always a pleasure to read.
What is the relation between the lowered mic sensitivity and the spl reading? 
I ask because I really don't know how to measure mine, always clipped the mic at 100db (on REW).


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## cvjoint (Mar 10, 2006)

Elgrosso said:


> Impressive, and always a pleasure to read.
> What is the relation between the lowered mic sensitivity and the spl reading?
> I ask because I really don't know how to measure mine, always clipped the mic at 100db (on REW).


Good question. Reading the manual doesn't seem to be sufficient to understand the relationship very well. Dayton seems to say it affects dynamic range but does not say specifically it impacts SPL readings. 

Next time I go to one of these competitions I should ask Richard to do a test with another platform and compare SPL readings. 

Typically I move the sensitivity to the lowest setting when I test at high output. I didn't plan out my tests this time so the clipping caught me off guard. I believe I can get 123db out of the Omnimic before it clips at low sensitivity. 

To me it reads low, but I may just be getting old.  I do think either the amp or the processor would have clipped at -0db, so I didn't test further. The subs were undergoing some large excursions. But even if I could have gone -0db, then what? At most I'd have 116db if no futher power compression came about. That seems very low imo.


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## cvjoint (Mar 10, 2006)

*Rebuilding the sub box*

I decided to make some rather intensive tweaks to the subwoofer box. The kerf ended up a bit too round and therefore the targa top had trouble fitting over the box in the trunk. It got worse after I added Ensolite to the bottom of the box for extra decoupling. 

Remedy: get rid of kerf and replace with something more low profile. 

Since I'm redoing it I figured I might as well do it right and choose fiberglass for the curved sides. Fiberglass is strong when molded into curved shapes. 














































I'm hoping that no box room will be lost since the fiberglass is thinner than the 3/4 MDF. It feels good to remove all that glue too. Didn't feel to good about having 3 bottles of glue in those kerfs. Did not exactly define top notch construction. The kerfs did however feel very strong. I was surprised they had so much structural rigidity.


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## mailalan (Mar 28, 2015)

This has been a fascinating build. I look forward to seeing more.


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## BP1Fanatic (Jan 10, 2010)

Me too!


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## cvjoint (Mar 10, 2006)

*Fiberglass job*

I went for an easy approach. Tape up the opening, coat in resin, wait a day and add fiberglass. The tape is easy to remove leaving behind a smooth finish. 

The challenge with this approach is that each tape application is slightly different than the one before, leaving waves of fiberglass behind it. I recommend the normal approach of stretching fabric over the opening and soaking it in resin to give it the shape. With the tape method there is a lot more work with the bodyfiller. 











This is about 4 layers. In total there are now 10. 




























I'm letting the fiber cure until Monday. It's very strong with 10 layers.


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## fish (Jun 30, 2007)

Those subs are beautiful & mean looking at the same time. i'd be curious to see how one performs with the PR.


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## BP1Fanatic (Jan 10, 2010)

The KISS method works 4 me!


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## cvjoint (Mar 10, 2006)

fish said:


> Those subs are beautiful & mean looking at the same time. i'd be curious to see how one performs with the PR.


As luck would have it I have a SEAS PR I'm going to play along with. Stay tuned.  This time though, I'm not buying 4 or 8 to try out. Just one haha. Oh, and it's literally just to play with. The SPL is already high enough to plug my ears during one song so I don't need the additional vented alignment SPL. 

*Sub Box Update
*

Here is how the fiberglass looks cured. It's about 1/4" inch. I lost bout 1/4" to make the box more low profile, but gained at least 1/4" inch because the glass is thinner than the MDF. The box room has increased, box stiffness is higher, and the targa top fits over it, success! 










Like I said, the tape makes for uneven surface. Don't use it to give shape to your creation. 










Found some scrap wood I can use as an applicator for the fiber reinforced body filler and cut it into four pieces. 










I tried to apply filler over the whole surface as even as I could.



















Rough sanding. I try to sand it as soon as it gets hard to the touch. If I wait too long this stuff becomes tough as nails and I have to use three times as many sand paper cartridges. I used an orbital sander with 40 grit paper. The tool is dangerous, when the paper's backing stops being sticky the paper just flies off in a random direction. Luckily it was late, there were no casualties. 










Sanding left 1/4" body filler at most, as recommended on the box. Should hold up fine. 










Did a second round for fine sanding. 










Used the orbital sander with 120 grit this time.



















Good enough for government work, or rather Duratex. For a smooth finish I'd go for a third round of sanding. 

Next, beauty panels to cover up those extra holes and give the subs a bit of protection from loose trunk cargo.


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## Jim85IROC (Jun 8, 2005)

Some body filler advice:

This won't work for the chopped reinforced fiberglass stuff, but for standard filler, there's a sweet spot as it starts to harden where it's still semi-soft. During that period, you can use a cheese-grader style file to quickly remove a lot of material, and it will save you a LOT of time and sandpaper disks. For wholesale shaping, this is a huge plus to be able to do it.


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## thehatedguy (May 4, 2007)

And a long block with 36 would be almost as fast as the sander, and you will not sand low spots in the filler either.

Cheese grate, then long block...start when the filler is in it's green stage and you will make FAST work with nowhere near the amount of dust.

That's how we did it in the body shop.


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## cvjoint (Mar 10, 2006)

Oh yeah, I'm using both techniques. I sand the filler while still soft and and I use the wood block to sand it down by hand. It's amazing how good sanding by hand can get with the block.


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## cvjoint (Mar 10, 2006)

*Subwoofer box update - end plates*

To cover the extra 8 holes I made end plates that accept only 4 subs. This way the box will still accept 8 drivers passive or active drivers for future toying around. 

I started by cutting two boards from 3/4 MDF on the table saw. I bolted them to the box and used the jig saw to give it the round profile.










To match the endplates to the box precisely I used the orbital router with a 40 grit sandpaper attachment on both at the same time. 



















I wanted the baffles to go over the subs to hide the screws but I messed up by starting to use the router on the wrong side of the board. That means the subs will now have to be top mounted instead of bottom mounted like I planned. The upside is the baffle is now stronger with 1" of MDF to mount into but it's not as pretty. 

The corners have cutouts for the metal mounting l-pads. I used a roundover bit to give the box a curved profile on the edges to clear the targa top. I also used the roundover to have easier access to the thumb screws, and in general to make the box purtier. 



















I'm trying to cancel my Techshop membership. All done with the heavy machinery. Time for the finishing touches.


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## cvjoint2 (Jul 8, 2016)

I'm having trouble accessing my account since neither DIYMA or the platform CS is answering my emails. I created this second account to be able to keep posting. Hopefully I'll get my nick back soon. 

An update will be posted in a few days for the build.


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## papasin (Jan 24, 2011)

cvjoint2 said:


> I'm having trouble accessing my account since neither DIYMA or the platform CS is answering my emails. I created this second account to be able to keep posting. Hopefully I'll get my nick back soon.
> 
> An update will be posted in a few days for the build.



I take it you didn't get my PM.


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## cvjoint2 (Jul 8, 2016)

papasin said:


> I take it you didn't get my PM.


Nope, I didn't have them going to email and my account here seems to have been hacked like other people's. 

Did I miss some meat??

I got only 20 hours left on the project then the car will be completed and I'll be ready to attend all the events.


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## claydo (Oct 1, 2012)

I had trouble accessing mine after the reset. Emails went unanswered for a while. By the time they finally contacted me I had gotten back on by copying and pasting my stupid temp password, that wouldn't work by typing at all......I don't know why....if you go through the contact me email on here, eventually they will send you a response......


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## papasin (Jan 24, 2011)

cvjoint2 said:


> Nope, I didn't have them going to email and my account here seems to have been hacked like other people's.
> 
> 
> 
> ...



Almost...BBQ is tomorrow, ShinJohn is manning the grill. Hope u make it down. 

http://diymobileaudio.com/forum/12-...eca-3x-rock-chase-park-2-july-9-2016-a-2.html


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## cvjoint2 (Jul 8, 2016)

claydo said:


> I had trouble accessing mine after the reset. Emails went unanswered for a while. By the time they finally contacted me I had gotten back on by copying and pasting my stupid temp password, that wouldn't work by typing at all......I don't know why....if you go through the contact me email on here, eventually they will send you a response......


I see, I tried that email first. That was more than 2 weeks ago. No response. It's odd that I can't even reset my account because my email is not recognized.


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## claydo (Oct 1, 2012)

cvjoint2 said:


> I see, I tried that email first. That was more than 2 weeks ago. No response. It's odd that I can't even reset my account because my email is not recognized.


Ugh, I feel yer frustration......I was lucky to get back on by myself......but yeah......I'm thinking it was two and a half....maybe closer to three weeks before I heard back.

I was locked out and couldn't do a thing......but eventually tried copying and pasting the temp password......and it worked, typing it letter and symbol for symbol would not work no matter how much I tried.

Aaaand.....I got the same message about my email when I was trying to reset myself......

If you havent.....try the copy and paste thingy.....


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## cvjoint2 (Jul 8, 2016)

papasin said:


> Almost...BBQ is tomorrow, ShinJohn is manning the grill. Hope u make it down.


Darn, I already planned a track day tomorrow at Thunderhill Raceway. I would have made it otherwise.


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## papasin (Jan 24, 2011)

cvjoint2 said:


> Darn, I already planned a track day tomorrow at Thunderhill Raceway. I would have made it otherwise.



Have fun at the track! Next event is August 6 at Monterey/Seaside. No BBQ for that one, but location, location, location.


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## cvjoint2 (Jul 8, 2016)

papasin said:


> Have fun at the track! Next event is August 6 at Monterey/Seaside. No BBQ for that one, but location, location, location.


K I'll keep my eyes open for the event listing. Aiming to make it.


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## rton20s (Feb 14, 2011)

cvjoint2 said:


> K I'll keep my eyes open for the event listing. Aiming to make it.


Please do. I really want to check out the Vette. And there is some good food to be found in Monterey, even if Shin John won't be BBQing. Dom and I can point you in the direction of good eats.


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## papasin (Jan 24, 2011)

cvjoint2 said:


> K I'll keep my eyes open for the event listing. Aiming to make it.





rton20s said:


> Please do. I really want to check out the Vette. And there is some good food to be found in Monterey, even if Shin John won't be BBQing. Dom and I can point you in the direction of good eats.


Event listing posted.

http://www.diymobileaudio.com/forum...-sq-spl-august-6-2016-seaside-california.html


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## cvjoint2 (Jul 8, 2016)

rton20s said:


> Please do. I really want to check out the Vette. And there is some good food to be found in Monterey, even if Shin John won't be BBQing. Dom and I can point you in the direction of good eats.


I'm in. Trying not to get too hooked on good food. That way I can leave N. Cali. if I have to. No one wants a snob!


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## cvjoint (Mar 10, 2006)

I'm back with my full time nick. epper:

For anyone that's interested I am selling the speakers I tried but replaced with something else

*B&C 10" 4 ohm midbass:*
http://www.diymobileaudio.com/forum...-c-10nw64-4ohm-rare-10-pro-audio-midbass.html
*$280 shipped for the pair*
*Vifa 10" neo subs:*
http://www.diymobileaudio.com/forum...-ne265w-08-neodymium-subwoofers-heatsink.html
*$200 to $220 shipped each*
All prices substantially lower than what I got them for. 

Cheers


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## cvjoint (Mar 10, 2006)

*The final version is out! *
Rarely do I finish projects so this is unusual indeed but the car is done. First a quick recap:

*Version 1.0*
Head: H800 + Galaxy S7 edge with AptX and optical
Amplifiers: 4,000w+ Zeff class G/H power
2way + Pro logic II steering Satori 6.5" fullrange rears
High: AMT line array; Mid: B&C 10NDL64 10"; Low: 8x Vifa NE265W-08HS

*Version 2.0*
Changed Mid: SS 25W/8567-SE 10" instead of B&C pro audio midbass

*Version 3.0*
Changed Low: 4x Seas L26RO4Y 10" instead of Vifa neo sub

Ok, so this last version is mostly about changing a box that was made for eight Vifas to house four Seas subs. I opted to make a modular box. Instead of filling up 4 holes I decided to make baffles that attach to the front and rear of the box so that the additional 4 holes remain open for future testing and projects. 

The removable baffles were coated in Duratex. The tricky part is to make a good seal between the baffle and the box. I used Ensolite peal and stick to seal the box-baffle boundary from air leakage. To my dull finger skin it seems no air is leaking out when the subs are pushing near full excursion.


















The Seas subs use a larger than normal 8mm spade connector. This should be included with the subwoofer when you buy it because hardware stores don't carry it and it's a ***** to find. I had to order it from Madisound. Ugh...










I just used drywall screws to mount the front baffle and the subs are top mounted on to it. The sub screws now have a full 1" of MDF thickness to grab onto and the box baffles as a whole are 1.5" which gives the box a higher rigidity. 



















On the front baffle I used a 40 inch by 1"OD carbon fiber rod as a subwoofer grille. It is mounted to the box using 1" rubber stoppers so it doesn't vibrate and make noise. The rubber stoppers double as washers, spacers, and crumple zones. I modified the amp rack cover to shield the box connections on the right. It also allows more room for the blue tooth antenna. Items can be stored on the amp rack ahead of the sub box. Technically I only lost 1/3 of the trunk space but practically I only have this shelf left and the rear trunk corners. 



















This is what the amp rack looks like under the stealth cover:











The box passed the 9V test and off it went to get tested for small parameter operation. I tested it three times in a row. Box Q was .59, .58, and .57 respectively. FSC is ~45hz. In large signal domain I guess the stuffing lowers the Q further and should stay near the ideal .56 Q for a wide range of output signals. I've effectively lowered the Q by half by switching to these! Impedance is right at 1 ohm where it should be. This is the middle test, one had slightly higher Q one had slightly lower Q:









The impedance is well behaved, no unusual wiggles:


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## BP1Fanatic (Jan 10, 2010)

Nice! Tho', the visual impact of 8 subs is lost.


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## cvjoint (Mar 10, 2006)

BP1Fanatic said:


> Nice! Tho', the visual impact of 8 subs is lost.


I agree, the Vifa setup was more attractive from an aesthetic point of view. The box was half the weight too and I could lift it by myself. I need a volunteer to move this one but that should be easy to find at the track. Lots of dudes in motorsport haha. 

The sound quality is really astonishing. It's hard to imagine using any other drivers in a sealed box. No regrets here. I think with this car I've made some tough decisions. I went with sound quality over SPL every time the tradeoff was important. I also went with sound quality over system weight. Aesthetics are very low on the priority scale.


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## BP1Fanatic (Jan 10, 2010)

This past weekend with my Corvette boyz.


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## BP1Fanatic (Jan 10, 2010)

The blue Miata has a LS motor.


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## BP1Fanatic (Jan 10, 2010)

Porsche Club put on the event.


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## cvjoint (Mar 10, 2006)

Getting both the diy_sq and motorsport hobbies together. Best of all worlds! 

The Corvette is as close as you can get doing both at the same time. As a dual purpose car it doesn't get better than this. It is fun to drive fast and have the system at the same time running. However, if I could have a diy_sq car and a pure racecar separately greater things can be achieved on both ends. As it sits, I see sound deadening being the great separator. I only have 8 lbs of sound deadner in the car at the moment. I'd love to hear the car with more vibration damping but not willing to make it heavier at the moment. I can't really remove sound deadening on the spot.


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## BP1Fanatic (Jan 10, 2010)

Vettes were practically the quickest cars in each group. C6's dominated. My boyee in the C7 dominated his group with braking and cornering. He was pulling mid 140's on the front straight while the white z06 was pulling 150+mph. The C6 z06's couldn't touch the C7's lap times. The C7 was beating C7 z06's too. The boyee can drive!


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