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Discussion Starter · #1 ·
Hello people,I’m new on here and been out of installing and building car audio for some time now. I finally picked up a truck I’ve been after for some time now and ready to build a nice loud and low playing truck. I have a 2002 Chevy S10 Xtreme extended cab and trying to do two 15” FI SP4’s on two SQ 3500’s. The equipment I have had for many years now that’s why it’s older stuff but it’s all brand new. I have a h.o.alternator,runs of 0gauage ofc,and limitless lithium batteries already. I also have a CT Sounds four channel amp ready for the mods and highs. What I need help on is my box design because I’ve never built anything for this truck before so I don’t know what will play super loud and low. Then on what mids and highs will play really well in this truck also. I am ready but am clueless on where to start thanks for reading this and hope to get some help.
 

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Two SP4 15s will need somewhere between 4-10 cuft combined depending on what your goals are...

Sealed you can run on the smaller end at 2-3 cuft per sub but if your willing to give up the entire rear half of your cab or build a blow thru then you can run big and ported.

What's your fancy?

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Discussion Starter · #3 ·
I don’t mind taking up the entire rear cabin space and also did think about a blow through depending on what will sound louder and play low
 

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Trucks can be tricky. Here's some fab tips.
 

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Discussion Starter · #5 ·
Thanks for the help. Ok so back in the day’s i had a Nissan Frontier ext can and put two 15’s in that subs and port up. It did sound loud and even won some competition with it but I’ve read that this truck is different for what I want to achieve from it. I’m not going to compete I just want it to play loud and get low doing it. Plus I don’t know what mids and highs would sound nice with this set up. I appreciate any help and open to suggestions
 

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Measure the max space you have behind the front seats for the enclosure and let's see what that can accommodate.

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Sealed would be easy as they need 5.6 cuft combined for the best compromise between LFE (Low Frequency Extension) and Power Handling (Qtc of 0.703) which results in an enclosure 48x20x14 (the width and height had to be trimmed down to keep the depth enough for the 11" mounting depth of the SP4s.) And that's using 1" thick materials - you may want to go a little bigger and use a double front baffle and a bunch of internal bracing if you go sealed as those things can generate a bunch of pressure. Additionally, if you go this big sealed for the best LFE you will lose a little bit of power handling and hit mechanical excursion limits (modeled not real world experience) at about half RMS rating. You'd need to go down to about 3 cuft TOTAL (that's for 2 subs) to keep them from hitting excursion limits (again modeled not real world experience) and that's really small box for 2 x 15" Subs...

Ported is gonna be tough cause with 1" material and the maximum dimensions (52.5x25.5x16.5) you get almost exactly 10 cuft sealed and these subs want about 13 cuft sealed with a port in the 20-23 Hz Range which is a HUMOUNGOUS box. In order to keep port velocity no greater than 40 m/s you need 94 sqin of port area so that's almost 38" long slot port the same height (23.5") as the front baffle. Which takes 24.25" of depth at 52.5" x 25.5" so we start reducing box volume but the smaller the box the longer the port so it's 2 steps forward and 1 step back... and what we end up with is 8 cuft ported at 28 Hz. The good news is that this helps with power handling (assuming your amps can really do 3,500 RMS each) cause the SP4s need a little extra help dealing with that much power as a daily. Double good news, even at 8 cuft and 28 Hz the ported box is still even with the sealed at 20 Hz and get's some port gain at the all critical 32 Hz (low string on electric bass) so all of that technical jargon to say that it's entirely doable in-cabin and get a butt load of cabin gain as well.


WinISD SPL Anechoic Model (No Cabin Gain)
Pink = 8 cuft @ 28 Hz on 7,000 Watts with LR4 HP at 27 Hz
Green = 13 cuft @ 23 Hz on 3,500 Watts with LR4 HP at 22 Hz
Blue = Sealed @ 5.6 on 3,500 Watts
Yellow = Sealed @ 3.0 on 6,000 Watts
300144
 

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Discussion Starter · #9 ·
Wow really really good information there thank you. I have always liked ported only because it sounds louder and play lower but what if I walled the back or did a blow through to build a bigger box and did either ported or 4th order? Any thoughts on that or is it not worth it?
 

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Here are all of the options modeled with Cabin gain to physical limits:
Ported 13 cuft @ 23 Hz in Green (the in-Cabin ported box is only a few dB lower in SPL and peaks around 32 instead of 23 Hz... so it really depends on what you want to do as to what's worth it...)
BP4 13 cuft @ 45 Hz in Red
BP6 13 cuft @ 20/43 Hz in Blue
ABC (BP6 with another Port between Chambers) 13 cuft @ 20/43 Hz in Yellow
Sealed 5.6 cuft in White
300264


The BP6 Box has the most output at the lowest frequency and that model shows it with dual Rectangular Ports of around 36" long/each (surface shown below in WinISD - what dimensions you make those ports is up to you) so a 13 cuft Airspace box is going to be around 16.5 cuft External or 49" x 26" x 23" with a double front baffle and 1" material and then you've got to figure out the space in the bed to fit that along with 36" Ports extending in to the cabin (blow through) so it will pretty much fill up the bed of a S10 Pickup. You get space back in the cabin but lose most of the bed...

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Discussion Starter · #11 ·
Your right. I think my best bet is a ported box in the cabin behind the seats. What direction would you face the subs and port if I build a box to fit behind the seats in the cabin?
 

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At the volume level you're going to be at it won't make much difference so I would aim for looks or maybe top mounted inverted. Keeping the subs on the top or forward facing will let you maximize the box into the back wall and corners of the cab (fiberglass maybe) to salvage as much cabin space as possible. For me that would be the primary concern.

Ports I usually try to keep on the same side but that's a SQ thing for group delay. For you probably forward firing between the seats. It would all depend on what box dimensions you end up with...

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