so I want to port my box

[Polar]

34 long x 13 deep x 16 high, 3/4 mdf

 

[Polar]

Im about to jam a 4foot piece of 4 inch schedule 80 into it!

 

[NSTALN 10+ year member]

Why do you say 'stuck' with the Type S? It's a well built underhung long-throw design...from most of what I've read these should have better SQ than the Type R. The right box will make or break the sound of a good sub. I would inquire about having a custom box built or at least designed for you.

 

[NSTALN 10+ year member]

Type S 12d4 modeled in 1.5 vented, tuned to 34hz, with 30hz subsonic filter @12db/per and 80hz lowpass @24db/per.

This pic shows SPL (graph) and crossover settings(window)

This pic shows cone excursion (graph) and box volume and tuning (window)

This pic shows port velocity (graph) and port specs(window)

2 of these 12's with 1.5 cubes each, tuned at 34hz with 30hz ssf @12db will allow you to push 1400rms before exceeding linear xmax.

It would sound pretty **** good actually.

 

[Polar]

sweet, now how do I port the mofo!

 

[Polar]

if I see that correctly and thank you for putting that together and taking the time to do so. I would need a 4 inch round vent 16 inches long

 

[NSTALN 10+ year member]

if I see that correctly and thank you for putting that together and taking the time to do so. I would need a 4 inch round vent 16 inches long

Yes...16.7 inches long, 4inch diameter...per 1.5 chamber will get you to 34hz tuning. What I modeled is a single sub.

 

[Polar]

sweet, next question. I have the subs facing forward into my back seats. Is this optimal? should I port the top, its gonna stick outta the box a bit. So if I get this correct I can port each chamber and I can flare it or whatever to make it look nicer, and itll be at 34 hz? how far do I put the tube into the box?

 

[blazian87 10+ year member]

sweet, next question. I have the subs facing forward into my back seats. Is this optimal? should I port the top, its gonna stick outta the box a bit. So if I get this correct I can port each chamber and I can flare it or whatever to make it look nicer, and itll be at 34 hz? how far do I put the tube into the box?

It would be better if you just get another custom box built. You said you have 1.4 cu ft on each chamber so you would have to have an external port to keep that internal space the same. If I were to really use that box, I would cut a large hole inside the wall separating the two chambers turning it into one big chamber. Then have an external port wherever you have space for. If you stick a port inside that box, the airspace will be pretty small and if you flare it, it will take up a bit more space as well. It would just be ideal to start from scratch and build the biggest box you can fit in there.

In your small truck, forward facing subs would work fine. The problem is how you're gonna fit the port. Does the box you have right now take up the entire space or do you have a little extra space you can cover?

 

[NSTALN 10+ year member]

If you're hell-bent on doing it yourself with that box this is my suggestion:

Knock out the middle section of the box making it a single chamber of 2.8cf. Next take a single 6 inch PVC pipe at 20 inches long and flush mount that puppy...if you can use a rounding bit and router the inner edge...not necessary though.

A single 6inch diameter 20 inch long port will displace roughly .35 cf (3.25x3.25xPIx20)/1728 or radius squared times PI time port length divided by 1 cf in inches.

This will drop your box volume to 2.45 and a tuning freq of 35hz...add a generous helping of polyfil and you can probably get tuning down to 32-33ish

Make sure to buy a pair of Hassison Labs FMODs high-pass at 30hz...you can get em from parts-express for about $30 shipped. If you don't use these you will kill your subs, especially throwing 1300rms at them...which you will be when you wire all 4 coils in parallel.

Boom! Done!

 

[Polar]

Im pretty hell bent on doing this lol. I cant leave anything alone plus I need my " me" time to fart around with something or I will go nuts! Any thoughts on inverting my subs to gain a little bit more internal volume? Here is how they sit now.

would inverting them, of course they would have to face upwards which I have no problems with and (2) 6 inch ports 10 inches long blowing out the sides into the rear doors work? Im taking out my rear jump seats and making a rack to get my amps off the box too

 

[NSTALN 10+ year member]

Im pretty hell bent on doing this lol. I cant leave anything alone plus I need my " me" time to fart around with something or I will go nuts! Any thoughts on inverting my subs to gain a little bit more internal volume? Here is how they sit now.

would inverting them, of course they would have to face upwards which I have no problems with and (2) 6 inch ports 10 inches long blowing out the sides into the rear doors work? Im taking out my rear jump seats and making a rack to get my amps off the box too

I compared (3) enclosures for you: 2.5cf, 2.8cf, 3.0cf all tuned @35hz. Also applied to all: 80hzlp @24db, 30hz hp @12db, and 1300rms.

Pic one shows the SPL graph and the box size/tuning freq

Pic two shows the cone excursion graph and the port dimensions

Pic three shows port velocity graph and applied filters

Alpine's website states each sub inverted will add .08cf of air...so at best with subs inverted you're looking at 2.65(ish)cf.

As you can see in the three different size enclosures the measured difference is marginal...you may not even detect an audible difference.

6 inch port @10inches per chamber will NOT work...take my advice: create single chamber, 6 inch port 20inches long, stuff box with poly and take your amp to 1ohm...inverting the subs is up to you but will yield very little in terms of gain. Side-fire the port into the rear door.

 

[Polar]

thanks bud, if we ever cross paths I owe ya a round. I will do one 6 inch port 20 inches this weekend. and will re do the box covering, maybe duraliner it or something

 

[NSTALN 10+ year member]

thanks bud, if we ever cross paths I owe ya a round. I will do one 6 inch port 20 inches this weekend. and will re do the box covering, maybe duraliner it or something

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[Polar]

port has been cut! installing tonight!