'84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

[Jethro]

The recent spring-like weather out here in Oregon allowed me to get my '84 VW GTI out of the garage early, which of course made me want to get my audio system back in order. Now that I have determined my vintage sub amp is toast, and I have a replacement on order, it's time to focus on what to do with my DVC12 (DVC310-88).

The amp I ordered (Kenwood X500-1) does 300W @ 4-ohms, so it should be a good fit for the sub in 2 cf sealed, excursion-wise (according to BassBox). I had wanted to do 1 to 1.25 since the original DUMAX measurements indicated a smaller Vas, but I already have a nicely braced box with 1.5" baffle -- and I would rather use that than build a new one. Modeling cabin gain with BassBox indicates it may be a little heavy below 50 Hz, but I have EQ bands at 90, 63, and 45 Hz with my AudioControl EQX, so I will have some control there.

The rest of the system consists of an Xtant amp that does an underrated 50W per channel and Alpine Type-X Pro 5-1/4" component speakers.

Any thoughts on this sub design for use in a hatchback?

[djg]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

https://www.youtube.com/watch?v=3zcm4oS9IaM

[fwiler]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

I miss that car. It was so much fun to drive.
Can you believe cherry blossoms already this year?

[Jethro]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Old school... ;)

[Chris Roemer]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

2cf Cb looks about right.

[fwiler]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Nice job on keeping a 31 year old car looking so good!
Ahhhh that makes me feel old.
I'm half tempted to go looking for one just for nostalgia sake.
I can't afford it, but I hear the 2015 GTI brings back everything that made the 83'84' GTI's so great.

[Jethro]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Here are some graphs from BB6P, based on stock Dayton parameters, not the DUMAX measured parameters:

Frequency Response: Both Anechoic and w/ Simulated Cabin Gain (Qtc .63, Anechoic F3 44 Hz)


Excursion (used DUMAX 16.44mm Xmax) w/ 300W Input:


It looks like I should be able to add boost at 63 Hz and 90 Hz, if needed, to even out FR above Fc (the LPF frq is set at 90 Hz, 18 dB/oct).

[Jethro]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

The 2 cf sealed option has to sound better than the option I am using now. I had the DVC12 set up as the sub for my garage/work bench system -- in 2.75 cf tuned to 24 Hz. :D It worked great in the garage, but not so much in the car -- and I knew it would be like this, but I had to try it. I would rather transfer it to the smaller, better built box than just plug the port.

As you might expect, tuning that low in a car is a little overwhelming down low -- enough so that I never even tried to EQ it. The following graphs are the BB6P models for the ported box:

Frequency Response: Blue line is the ported box, both Anechoic and w/ Simulated Cabin Gain (Anechoic F3 26 Hz)


Group Delay: Blue line is ported, Red is 2 cf sealed


And this is all just using 6 dB/oct. gain starting at 80 Hz -- not the 12 dB/oct. gain that Tom Nousaine theorized. I figured I have old, lossy gaskets and seals, etc., so I won't get the full effect in my car (and my own measurements would agree -- it's somewhere in the 6 to 9 dB/oct. range). I'm hoping to end this failed experiment this weekend...

[chad1376]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

I have no useful input for the subwoofer, but as a long time air cooled VW aficionado, and recent owner of both an MKV golf and MKVI GTI, I'll say I love that car. If I could find a nice first gen GTI, I'd grab it in a heartbeat. A modern classic.

[Jethro]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

And a few interior pics...





[img[http://i801.photobucket.com/albums/yy293/Jethro70_bucket/1984%20VW%20RABBIT%20GTI/IMG_3213800x600.jpg[/img]

Passenger side, with my old Madisound 5502R-4 midbass drivers. They sounded great, right up until I fried one of them. :-(


The replacement midbass, part of the newer Alpine Type-X set...

[Jethro]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

I have no useful input for the subwoofer, but as a long time air cooled VW aficionado, and recent owner of both an MKV golf and MKVI GTI, I'll say I love that car. If I could find a nice first gen GTI, I'd grab it in a heartbeat. A modern classic.

I really wish I had the time and money to adequately restore this thing. Sometimes I think I should just sell it, but I've owned it since 1990, so I just don't think I could part with it. Besides that, I had a cousin do a bunch of work to get it going after my gas tank rusted and clogged the fuel lines -- and he hardly charged me anything (and he's the one who found the primo condition seats and hatch cover for me).

What you don't see in these photos is the imperfections... the amp rack needs to be tidied up, the headliner and c-pillar upholstery need to be replaced, it needs new paint all around, my wife snagged the 'GTI' badge on the back with her clothes and now it just says 'G' (can be fixed), could use new motor mounts, the engine could use a rebuild, etc. Just trying to make progress a little at a time.

[chad1376]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

From what I see, it looks very original and in great condition for its age. Full resto is nice, but original with reasonable wear and tear is cool too. After 30+ years, a car earns the right not to be in showroom condition. I say keep the mechanicals in good shape and don't worry about the little stuff.

[LongHorn64]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Old school... ;)

Totally Old School Cool. You talk about the memories. When I first met my future wife she had the GTI, and my Mom had a hopped up Rabbit. Needless to say, the two Women hit it off immediately. At that time I was driving a 78 Camaro, all goosed up too. Mom made ME park on the street while the "GERMAN" Automobiles" unquote were given the privileged spots on the driveway. I still laugh thing about that. All the best, Mike

[blur]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Really nice car. My first car was a blue 2 door 83 rabbit 1.7l fuel injected LS with a manual transmission. I think i ended up stuffing some 15 inch woofers off a radio shack amp in the hatch.

[emilime75]

Re: '84 VW GTI / DVC12 / 2.0 ft^3 sealed -- Any objections?

Nice ride. I've owned several over the years. The last one with a 2.0 16v and all the associated suspension and brake upgrades.