sub box build
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=132145
Printed Date: July 07, 2025 at 11:19 AM
Topic: sub box build
Posted By: 20silverado06
Subject: sub box build
Date Posted: September 06, 2012 at 12:09 AM
im looking to build a box for my truck to fit 2 12s.i want to try to build a ported downfire box for my silverado ext cab. if i make it ported, does it matter about the airspace anymore. or should i build 2 seperate ported downfire boxes. any help or box blue prints/plans greatly apriciated
Replies:
Posted By: DYohn
Date Posted: September 06, 2012 at 11:24 AM
Not sure what you mean by "airspace." Do you mean the volume inside the enclosure? If so, it is a critical part of a ported system, much more important than in a sealed system. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 1:34 PM
Yea I meant the volume. I have 2 12" q Power deluxes. They run at 1500 watts max a peice(I think around 800 watts rms each) and a 1000 watt mono block comp amp. So should I build 2 desperate boxes or 1 box
Posted By: DYohn
Date Posted: September 06, 2012 at 1:39 PM
You can do it either way, whatever you like. But the size of the enclosure is critical for proper tuning. What's the model number of your "q-power deluxe" subwoofers? ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 2:04 PM
this is the only thing i can find bout my subs
https://qpowerinc.com/DELUXEQP12.html
Posted By: DYohn
Date Posted: September 06, 2012 at 2:09 PM
Wow, those things look like they will require a pretty huge enclosure... let me run some numbers. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 2:14 PM
lol there big. and hit pretty hard to.
Posted By: DYohn
Date Posted: September 06, 2012 at 2:18 PM
Yea, a super peaky sub that will bottom out very easily with that kind of power thrown at them, and they require over 300 liters per driver to get anywhere near flat frequency response. What's the largest size enclosure you can make fit in your vehicle and I'll tell you how to port it. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 2:45 PM
well here a little rough copy of a full downfire with my trucks dimensions.
Hope this helps
Posted By: DYohn
Date Posted: September 06, 2012 at 3:12 PM
OK, so that's about a 2.6 cuft enclosure, or about 73.6 liters. Deduct about 10% for the volume of the woofers and the necessary braces, and you end up with a relatively small 67 liter enclosure. Put both drivers in it, port it for tuning at 21.7Hz (2" diameter port that is 5" long) and you'll end up with a peaky system but it's the best you can do with those woofers. You'll also have port noise but I don't think that will matter. Also, with 800 watts being thrown at the woofers you will bottom them out around 80Hz, so be careful with the volume control and if you hear them making mechanical noises, turn it down. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 4:24 PM
thank you so much. i think i have my subs wired is at 1 ohm maybe 4ohm ill have to check. my amp is this one and i have it in a ported prefab box and i have the amp set right at the peak before they bottom out. so no matter how i high oi turn the volume up it wont bottom. i can tune amps very good so im not worried bout that. this is my amp https://www.dbdrive.net/products-detail.php?id=a3%201000.1d&brand=okur§ion=amplifiers&series=a3%20series
Posted By: 20silverado06
Date Posted: September 06, 2012 at 4:27 PM
oh and i forgot to mention that there is going to be a divider between them in the middle
Posted By: DYohn
Date Posted: September 06, 2012 at 5:54 PM
20silverado06 wrote:
oh and i forgot to mention that there is going to be a divider between them in the middle
Cut a hole in the divider so they share the same airspace inside the enclosure. Otherwise, you will have to port each side separately and you will not have enough physical space to get a large enough port in to make it sould like anything other than ass. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 5:58 PM
how big of a hole in the divider. and would it be better to leave it open with one port. slotted or round
Posted By: DYohn
Date Posted: September 06, 2012 at 7:06 PM
In that small an enclosure use a round port like suggested before. Cut a 4" to 6" hole in the divider and turn it into a brace. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 06, 2012 at 9:06 PM
a brace how
Posted By: 20silverado06
Date Posted: September 06, 2012 at 9:11 PM
and im going to build it out of plywood first. seal it completely and go from there then once i confirm i like it build it out of 3/4 mdf
Posted By: 20silverado06
Date Posted: September 06, 2012 at 9:16 PM
and im going to seal it with polyurethane varnish
Posted By: DYohn
Date Posted: September 07, 2012 at 11:59 AM
If you want to build a mock-up to see if it fits, make it out of cardboard. If you're going to use plywood and actually mount woofers in it, then you'll need to use 3/4" ply and you might as well keep it as your enclosure, or just use MDF to start with. And you'll need to seal the inside with more than varnish. Gorilla glue or RTV or liquid nails on every seam is the way to go. Have you built an enclosure before? If this is your first one, you've chosen a pretty complex first build... And if you don't understand my comment about making a brace, you really need to before you start. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 07, 2012 at 12:57 PM
Ive built 2 before. I was tired when I said brace how. I know what you were talking bout. It just didn't hit me right away. And yea I'm going to use wood glue then seal the edges then varnish it. And the reason why plywood first is cause I got plenty of plywood laying around
Posted By: DYohn
Date Posted: September 07, 2012 at 1:39 PM
20silverado06 wrote:
Ive built 2 before. I was tired when I said brace how. I know what you were talking bout. It just didn't hit me right away. And yea I'm going to use wood glue then seal the edges then varnish it. And the reason why plywood first is cause I got plenty of plywood laying around
Cool! So why not just make the enclosure out of plywood? It will work just fine if you brace it properly. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 07, 2012 at 2:08 PM
k i will try that. but just for thoughts what bout this design 
Posted By: DYohn
Date Posted: September 07, 2012 at 3:49 PM
That sort of design can work well, but in your case the enclosure is already too small so adding that sort of vent would only make it smaller and more boomy. Unless yu can double your enclosure size, I can't recommend it in your case. ------------- Support the12volt.com
Posted By: 20silverado06
Date Posted: September 07, 2012 at 4:10 PM
well i can still raise my rear seat up and gain a couple of inches. and what if i copy these measurments
https://www./itm/Dual-12-Subwoofer-Box-Fits-1500-Silverado-Sierra-Ext-Cab-1999-2007-Obcon-/230765023049?pt=US_Speaker_Sub_Enclosures&hash=item35baaacf49
Posted By: 20silverado06
Date Posted: September 07, 2012 at 4:15 PM
then that will add 2 ins all around to make it bigger and still make it 55"width x 16"deep x 11'tall(front)9.5"tall(back)
Posted By: 20silverado06
Date Posted: September 07, 2012 at 5:38 PM
ok let me start over. im going to be raising my rear seat up 2in. that will give me 55"long x 16"deep x 11"tall(front)and 9"tall(back). heres the new dimensions  .
i would like to do the labyrinth version if possible but if not what bout the round port version with 2 ports and a 1/4 open divider. let me know what you think. and sorry for all the bs
Posted By: DYohn
Date Posted: September 08, 2012 at 11:23 AM
You can't just put any old labyrinth (AKA slot port) or port tube into a system. You have to design it for a particular length and volume to tune the enclosure at the desired frequency. For your woofers, to get any sub bass at all out of them, you have to tune very low, like 21Hz. Do some calculations and figure out what that means your port length needs to be for the size of your enclosure and the size of the opening you plan to build. ------------- Support the12volt.com
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