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Old 16th May 2006, 06:17 PM   #1
2litre is offline 2litre  United States
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Default On the cheap Noob question.

Hi All,

I'm looking at using a single 10 or 12" DVC sub (wired off the rear channels of my Sony 2 knob radio, 20WPC?) for my old VW Bug. This is by no means a technical effort, its just a way of getting some additional bass to compensate for my Infinity 452i, 4.5" co-axials lack of bass (91db, 90Hz roll off). I'd like to stay away from extra amps, don't want to build a box and could care less if the car vibrates at stop lights. My intention is to run it free air in the little stash well behind the rear seat.

My question has to do with which driver should I lean towards. Dayton 10" - Fs of 25hz, Qts of .38, SPL of 92.7 and 6mm Xmax.

Goldwood 10" - Fs of 40Hz, Qts of .61, SPL of 95.7 and 3mm X-max.

I've read that low Qts drivers roll off at an even rate where as higher Qts drivers tend to roll off more gently and have a hump near Fs. Given the cabin gain associated with low frequencies in cars, could the low Q Dayton sound more musical than the Goldwood? (Let's not discuss the VW exhaust note or the gearbox whine destroying any hint of fidelity) (stop laughing!!)

R/

Jim
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Old 16th May 2006, 07:16 PM   #2
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I think the Dayton is the higher quality driver and will give you more musical reproduction, and probably go deeper than the Goldwood - however...

The Goldwood is about 3 db more efficient and your 20 wpc head unit (make sure you bridge it to the sub) is going to have its work cut out for it, especially if you're going to be running the sub in free air. I would stongly recommend you consider getting a separate amp for the sub if your budget and installation skills are up to it. (Does your head unit have any pre-outs?)

In any case, I hope you don't plan on just dropping the sub into the back of the car somewhere - you should try to mount it on something solid, like a bulkhead or other metal surface of the car - mount it facing the surface, with long sheetmetal screws and spacers to give it some breathing room.
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Old 16th May 2006, 07:30 PM   #3
Stocker is offline Stocker  United States
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The car is an oddball environment. A proper box model for a car has way too much roll-off starting very high in the frequency range... this is compensated for with cabin gain effects. Combine that with the inherent ambient noise in a car, and you can (almost literally) take pretty much any driver, slap it in a cubic foot or two and go.

That said, run some simulations... the higher excursion rating may be meaningless if you never get there, or the power might overwhelm the suspension... A good speaker box simulator will show you where the power/excursion curves overlap... shoot for a little less power than that and you're good.

And all that said, I would probably just buy the cheaper driver and slap it in there until I got money saved up for a "good" setup (which includes a few hundred to kill the tweeting of the engine noise, etc....)
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Old 16th May 2006, 07:39 PM   #4
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Forgot - you'll need a crossover too!
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Old 16th May 2006, 08:28 PM   #5
2litre is offline 2litre  United States
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Thank you all for the general replies. Those were exactly what I was looking for. As I mentioned in my OP this isn't going to be "all that".

Yes I forgot to add that I would most likely run a -12db 90-100hz choke on the DVC Sub.

In the past I have run some real old Alnico 6-9 full range drivers in a piece of plywood propped up against the rear firewall and they did fairly well. I bet they had a high Qts. Anyway, they sounded much better in OB than they did in the standard 6-9 boxes you buy at the local auto sound store. The 4.5" Infinitys I now run have enhanced the mid and treble ranges so now I'm looking for a real simple bass solution. The ability to integrage well with the mains is really the only criteria.

In my home system I run a pair of full rangers with plate amped dipole bass and I like that sound alot. This is the reason I was wondering about a simple, single 10" DVC driver mounted open baffle as my bass augmentation. Ultimate extention isn't really an issue because I don't have the power to push it that far.

See why I was asking about Qts as it relates to low end response?

R/

Jim
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Old 17th May 2006, 05:48 PM   #6
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The crossover, left out of the circuit, may provide some "rear fill" type action... try it without for a few weeks.
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Old 17th May 2006, 11:40 PM   #7
2litre is offline 2litre  United States
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Stocker,

I'll try it without any inductor to begin with but my intention was to creap up on a fair CO point using some existing parts. 1st order to begin with and move on from there.

This car has some larger "pee shooters" on the muffler and a custom gearbox that whines like heck in third so you see why I'm not looking for fidelity beyond the basics.

Thanks for the help so far everyone.

R/

Jim

(Not to change direction to hard but would bass shakers be another option?)
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