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View Full Version : My first thread----HELP!



slowfive0
11-22-2005, 10:08 PM
Hey guys,

Great site! I'm a newbie attempting my first box build. Vehicle is a 2000 Chevy Ext. cab pickup. I'm building the box to go under the rear seat to house 2 12's. Here is my problem and question.

I don't know what the subwoofer requirements are? They are 12", Have MD2 on the cone. The sticker on the back of the magnet says:

Impact High Performance Drivers
There is a big M for a symbol?
74792 / MD2128

These are 10 years old if not a little more.

The box I measured up (haven't made it yet) will have approximately 1.25 cu/ft per speaker. I was leaning towards sealed just because of my inexperience and not knowing what the speakers were designed for.

What would you guys recommend for a volume and have you ever heard of these speakers? (I'm not against ported if I can make it work without knowing the speaker requirements.)

Also, should I divide the box up in the middle (separate chamber for each speaker)????

Thank you for any input! :D

P.S. I will be powering it up with a Rockford Fosgate amp (200) bridged---roughly same age as speakers.

mikescanlon
11-22-2005, 10:13 PM
pics of the woofers? have you tried em yet to make sure they operate/ sound good?

slowfive0
11-22-2005, 10:37 PM
They work fine in my mustang. The original owner had installed the system. I recently pulled them out and wanted to put the system in my truck. Problem is the original box (sealed box design) won't fit. I want to say (going off memory), that the original box worked out to be 1.1 cu/ft per speaker.

No pics right now, but I could get some if it will help. Thanks.


pics of the woofers? have you tried em yet to make sure they operate/ sound good?

Defconx3
11-22-2005, 10:40 PM
I think some pics would really help.

slowfive0
11-22-2005, 10:48 PM
I can get some later tonight or first thing tomorrow (wife is at work and has the camera)....:crap:


I think some pics would really help.

mikescanlon
11-22-2005, 11:33 PM
sounds good buddy, until then just read the sticky's on each forum and you'll get the right mindset to do this thing

jsanford1974
11-22-2005, 11:42 PM
Unless your going to fiberglass or adjust the height of the seat, I don't see how your going to get 1.25 cu ft per sub/side. I've made 2 boxes for extended cab chevy's. One had around .88 cu ft (in a 00 Silverado) and the other had around .95 (in a 02 Silverado, I learned a few things after the first). Both were built using 3/4 MDF. Both fit flush underneath the seat. Another problem I ran into was the mounting depth of the sub. I used 10" Kicker Comp VR's in my application. They sounded pretty good. Good luck.

bikejunkie223
11-22-2005, 11:54 PM
I had a friend that had Impact 12's in a Chevy Luv back around 1991 or so. It hit so hard it made me sick. That was the first good car stereo I ever heard, and now I'm a freekin' junkie for this crap too. That volume should be fine. post pix when you get a chance. Most 12's do well with 1.25cu/ft sealed.

slowfive0
11-23-2005, 02:54 AM
Hey guys,

Thanks for all of the great replies (Man that was fast)!!!! You guys don't screw around! :laugh:

I re-ckd my calculations and found the following:

My "initial" layout of the box = .78 cu/ft
If I extend it out an 1" forward = .857 cu/ft (almost to front edge of seat)
If I extend it up an 1.5" = .99 cu/ft (obviously, will have to fabricate brackets)
If I extend it up an 1.5" and forward an 1" = 1.09 cu/ft

This is assuming an area of .12 for the speaker (just a guess). Not sure how accurate that is. The speaker magnet is 4.5" in diameter. The distance from the speaker face to the bottom of the magnet is 5". Hopefully, I'm close.

Attached are some pics for your reference. Thanks again!

slowfive0
11-23-2005, 02:58 AM
WOW!!! So someone has heard of these speakers! LMAO! I can't find anything on the net about them and no one seems to know anything about them. Of course I probably haven't been asking the right people until now ;)

I was getting the impression that they were some junky no name 20 dollar speakers....I hope they work ok with my current box size (about 1 cu/ft each)...


I had a friend that had Impact 12's in a Chevy Luv back around 1991 or so. It hit so hard it made me sick. That was the first good car stereo I ever heard, and now I'm a freekin' junkie for this crap too. That volume should be fine. post pix when you get a chance. Most 12's do well with 1.25cu/ft sealed.

slowfive0
11-23-2005, 03:00 AM
You're absolutely right! When I went back and ckd, I realized what I did wrong. Looks like I have 1 cu/ft max. More like .86 if I don't raise the seat. I was allowing 1.5" speaker to floor clearance. Do you think that is enough? I can sink them into the enclosure if necessary to gain a little clearance. Thanks again for the replies.


Unless your going to fiberglass or adjust the height of the seat, I don't see how your going to get 1.25 cu ft per sub/side. I've made 2 boxes for extended cab chevy's. One had around .88 cu ft (in a 00 Silverado) and the other had around .95 (in a 02 Silverado, I learned a few things after the first). Both were built using 3/4 MDF. Both fit flush underneath the seat. Another problem I ran into was the mounting depth of the sub. I used 10" Kicker Comp VR's in my application. They sounded pretty good. Good luck.

slowfive0
11-23-2005, 10:28 AM
Hey guys,

Per my previous replies, I screwed up on my initial measurements (actually math-LOL). I only have about .81 cu/ft to 1.05 cu/ft per speaker to work with. Depends on if I want to raise my seat.

Based off of that, I'm assuming that I can only do a sealed box design???? I would like to do a ported if possible though. Appreciate any feedback---Thanks!

tRiGgEr
11-23-2005, 10:45 AM
Stop posting the same thing over and over;)

You can only run a sealed box with that space. And 1.5" of clearance will be enough.

slowfive0
11-23-2005, 11:05 AM
LOL! I just did that because I forgot to include the space for the speaker clearance in my last post! Too much in a hurry.

So sealed it is!

What air space should I shoot for as I can't find any specs for these speakers? Thanks.


Stop posting the same thing over and over;)

You can only run a sealed box with that space. And 1.5" of clearance will be enough.

tRiGgEr
11-23-2005, 11:09 AM
Use the maximum space you can attain. .75-1.25. The speakers are so old I would not be able to find the T/S specs to determine sealed box size...

You can always decrease the volume with solid objects. Increasing it after it's built would be much harder.

Rattlebrain
11-23-2005, 11:10 AM
Ive been looking for about 30 minutes now and havent found anything on them speakers yet.
Lettering... Alpine knock-offs?

bikejunkie223
11-23-2005, 11:33 AM
The brand was Impact, if they are what I think they are, but given they existed prior to the Internet, you may have trouble finding anything.

slowfive0
11-23-2005, 03:07 PM
I guess the age of these speakers are showing my age.....:uhoh: :laugh:

I'd rather not mess with raising the seat unless it will give me a decent gain down low? If so, I will raise the seat an 1.5"...

Last question, I was planning to point the speakers at the floor with the sides and front of the box sitting on the floor of the truck. I was also going to remove the sound deadner (per advice from others) from under the carpet under the sub box. Is this good advice? With this setup, the bass would come out the back and against the back wall of the cab. Is this optimal?

I'm getting conflicting opinions: Some say point the speakers straight up?????

Advice please....I wanted to start this box tonight :(

bikejunkie223
11-23-2005, 04:15 PM
Bass is fairly non-directional, so as long as there is some clearance between the subs and floor, you should be good to go. Som cars are louder w the woofers pointed in different directions, but in your truck it prob. won't matter much, and it's not like you want to show off those woofers anyway.

tRiGgEr
11-23-2005, 04:19 PM
IMO I would keep the sound deadner on the vehicle floor. It's only going to increase road noise and over all is not Ideal. Also keeping the front end of the box open along with the back will yield better results. No need to try and direct it anywhere.

slowfive0
11-23-2005, 04:21 PM
LMAO!!!!! So true! Thanks for the advice. How much clearance should I allow? An 1" good?


won't matter much, and it's not like you want to show off those woofers anyway.

slowfive0
11-24-2005, 02:49 AM
Oh, I wasn't sure. A guy I know said the sound deadner will absorb a lot of the bass so he told me to remove it. I wasn't sure --- glad I asked.



IMO I would keep the sound deadner on the vehicle floor. It's only going to increase road noise and over all is not Ideal. Also keeping the front end of the box open along with the back will yield better results. No need to try and direct it anywhere.