"Oh no, Its another newbie question"??-@car subwoofer build

[gmoore]

Hello all, this is a question I posted to PE tech support: "Hello, I am interested in building a subwoofer for a 2004 Pontiac Bonneville. This car is shared by my son and his mom, sooo, i would like it to not too take up a lot of trunk space. Also, I am really only looking to supplement the bass over and above what the stock rear 6x9's offer.(Remember his mom also drives the car!!!-LOL-not looking to set any SPL records). I like the look and price of your Dayton Audio SD270A-88 10" DVC Subwoofer maybe matched with the Dual XPA2100 2x75W 2 Ohm Amplifier(Can this amp be bridged into 1-channel mono?). If possible, I would like to keep the box at or smaller than 2.0cuft(hopefully not a pipe dream!). I can to do the woodworking for the box as long its not too crazy complicated.It doesnt matter whether its a sealed or ported box. Would a 8inch woofer work? Maybe 2-6.5in woofers? I have searched the web for plans. Have not found anything yet. I will do much better with instructions for everything. Sorry for all the questions, look forward to hearing from you."



Here was their reply "Hello,

These are both pretty solid selections for your needs. I think you will be fine with That amp and sub. The amp can be bridged and since the driver is dual 8 ohm, the 4 ohm bridged will be fine.

You can go two ways with the box. Sealed would be about 1 cubic foot of internal airspace. That is going to give you a little more accurate response, sound a little less like there is a sub, and more like just more bass response.

You can go ported for a little more impact, or more of the boom sound that is popular in car systems. That would be a 2 cubic foot box, with a 3 inch diameter by 7-5/8 long port tube.




Regards,

Chris Frechette
Technical Advisor
Parts Express"

Ok, now for some questions:
1. I am leaning towards a ported box-Width=22in, Height=16in, Depth=14.5in Total=2.11 cuft Using the recommended Port tube. What do you guys think?(with this particular amp)
2. I plan on using .75in MDF Is this thick enough? Do i need any internal bracing? If so, what kind? Would dowels be good enough?
3. I see the Dual amp has a crossover frequency adjustment. Will I need a Low-pass crossover also?
4. I plan on wiring the sub by coming off both 6x9 speaker terminals. Is this ok?
Sorry for the very long post. I usually have no problems when building from a set of plans so, this is new territory for me. Any help will be greatly appreciated. Thanks in advance Gary Moore

[lockmanslammin]

Gary,
I'm somewhat of a newbie myself but here goes...
Question 1) The dimensions you provided "Width=22in, Height=16in, Depth=14.5in" would, if they are interior dimensions turn out to be 2.95' cubed, unless those are exterior dimensions, assuming 3/4" box material, then you are at 2.24'cubed, then subtract your port volume, and the driver space and you are pretty close to the 2.11'cubed you stated. That leaves you a little space for some bracing, which you also have to subtract for.

Question 2) Yes, 3/4" MDF is thick enough, and yes you should brace it, and yes dowels would work. Stiffer and stronger is better generally. Also make sure when your done that you run beads of caulk around the inside seams and seal her up good and tight.

Q-3) The cross-over on the amp has a Low pass option I believe, and that should work OK for you.

Q-4) I'm not positive on this one, but I believe, and I could be mistaken but, I believe you run the Speaker level wires from your head unit into the high level inputs, then out of the high level outputs on the amp, to your 6X9s. It just sort of steals the information from the already amplified (by your head unit) signal and passes it through to the 6X9s with the original power from the head unit built in amplifier.


I hope this helps you, and I hope if any of the info I gave you is off base one of the far more experienced guys or gals on here sets me straight.
Good luck, Chris

[isaeagle4031]

Personally I would use a different sub. I didn't take the time to run the specs, but I don't think you need 2 cubes for that 10. In that volume, you are giving up power handling and control. There does not have to be any additional bracing on this box. Wouldn't hurt, but I seriously doubt that you or anyone else would be able to hear a difference. Driver and port orientation will have a much bigger impact than bracing will.

As far as the amp, come off the wiring from the rear speaks into the high/speaker level inputs of the amp and set the crossover to LP. Experiment with the freq to determine what blends in the best. No need for an additional xover. The rest of the stereo will be unaffected.

As a safety note, please buy a decent amp install kit and route wires appropriately (ie through the firewall). Not saying you wouldn't do it right, just seen to many rookies make the same mistake and cause many problems for themselves later

[duanebro]

Personally I would use a different sub. I didn't take the time to run the specs, but I don't think you need 2 cubes for that 10. In that volume, you are giving up power handling and control. There does not have to be any additional bracing on this box. Wouldn't hurt, but I seriously doubt that you or anyone else would be able to hear a difference. Driver and port orientation will have a much bigger impact than bracing will.

As far as the amp, come off the wiring from the rear speaks into the high/speaker level inputs of the amp and set the crossover to LP. Experiment with the freq to determine what blends in the best. No need for an additional xover. The rest of the stereo will be unaffected.

As a safety note, please buy a decent amp install kit and route wires appropriately (ie through the firewall). Not saying you wouldn't do it right, just seen to many rookies make the same mistake and cause many problems for themselves later

+1 (isaeagle has done a few car installs)

For a few bucks more I would suggest looking at this amp: http://www.parts-express.com/pe/show...number=269-188
They are under rated and include a remote level control for your sub.

I would also look for a different sub, but it would again up the price. The design you have seems like a good fit for this sub. Just remember that it can be over driven fairly easily.