External Port: Good or bad?

[BigDaddy13440 3]

But, the first question is: how big of an enclosure can you make, as far as gross volume? From there, subtract the driver displacement, then figure your port dimensions.

[KU40 173]

ok. so using your info I tried 3"w x 3.25" tall. that gives a 9.75" crosssectional area. For a 35 hz tuning frequency, length says 20.3" which i should very easily be able to do. But thats all according to the calculator.

Now what is the recommend 12-16 in^3 figure you speak of?

Every post I've read talking about port tuning has had that figure in it, so I guess that's probably the best dimension to minimize any type of port turbulence and noise. Look at some of the install pics of walled-off vehicles, you'll see boxes with like 15 cubes, the port is something like 10" wide by 20" deep and 30-40" long! Or Bigger!

Unfortunately airspace is not the way to determine port area needed. It has more to do with how much airspace the sub(s) displace during excursion. A sub with 5 mm xmax needs less port area than one with 35 mm xmax, even if they're in the same size box.

[mikeyd 0]

Well what's the best way to design a box around air displacement?

[mikeyd 0]

Oh and I really need to pick out an amp for these. They're rated at 350 rms. But i haven't purchased them yet so I could still do 1ohm or 2. Any suggestions?

[BigDaddy13440 3]

Unfortunately airspace is not the way to determine port area needed. It has more to do with how much airspace the sub(s) displace during excursion. A sub with 5 mm xmax needs less port area than one with 35 mm xmax, even if they're in the same size box.

Exactly. I just forgot to mention that.....

I use this to figure out my ports: Port calculations

[KU40 173]

Oh and I really need to pick out an amp for these. They're rated at 350 rms. But i haven't purchased them yet so I could still do 1ohm or 2. Any suggestions?

I'd say start looking at SSA's shop and see if any of the amps there strike your fancy. Then once you decide which amp you want you can figure out what impedance to get on the subs.

[mikeyd 0]

Well hell. I calculated a .88 ft^3 @35hz for a 10" driver w/ 18mm xmax and it gave me a minimum cross sectional area of 25.31"

So then I entered a Square slot port with dimensions of 5" x 5" and it outputs a vent length of 55.87". chite!

Any suggestions on that? or should I scrap this plan and pick 2 different woofers with less xmax or design a new larger box for one 10 or 12?

Edited February 4, 2009 by mikeyd

[KU40 173]

You shouldn't need anywhere near that much port area. My guess is that a single 4" round port would be plenty (that's about 12.5 square inches). But this is just the problem with porting such a small enclosure- they require long ports.

Honestly, if you're going under the seats, just go sealed. I did that in my dad's F150 and it got louder than I thought it would.

[mikeyd 0]

I could probably squeeze 2 SR12"s sealed. How would the output of 2 12"s sealed compare to 1 12" ported?

[BigDaddy13440 3]

I could probably squeeze 2 SR12"s sealed. How would the output of 2 12"s sealed compare to 1 12" ported?

Are you looking for maximum volume, or maximum SQ? I'd be willing to bet that (2) 8" subs in that size ported enclosure would be exceptional.

[mikeyd 0]

i definitely want more SQ than output. But every system I get I always yearn for some more BOOM!

[mikeyd 0]

What do you guys think?

2 12" RE SRs sealed at .88 ft^3 each VS. 2 8" Re REs ported in .88 ft^3 @ 35 hz each.

How would the output and SQ compare between those setups.

I'm open to different sub suggestions. Just going with what I know and like right now.