External Port: Good or bad?

[mikeyd 0]

ok I'm planning my next system right now. (last one got stolen) I'm thinkin 2 RE SR10's ported going under the back seat of my '02 Ext. cab silverado. Realizing there is almost no room back there I figure the best plan would be to build two different enclosures for each side. Doing so would give me about 0.88 ft.^3 per sub after sub displacement. But to make these vented I'm thinking could make external ports over the transmission hump. Does this seem like a bad idea?

[Punkeyboozter 19]

inside outside all the same, just make sure it is nice and strong as it would be more vulnerable outside the box

[mikeyd 0]

Awesome. Now I just need to figure how big to make the port! anybody wanna help?

And on a side note: I know doubling your cone area potentially gives you a 3db bump in a sealed enclosure. What about for vented? Is building 2 identical vented enclosures much better than one? Or should I upgrade to a better speaker and build a larger box for it?

Edited January 30, 2009 by mikeyd

[mikeyd 0]

Here is something similar to what i was sayin.

Except with 2 of these. But like i was sayin, Is having 2 identical ported enclosures much better than one or is it comparable to the doubling sealed enclosures.

[KU40 173]

There's no difference if you build one box or two.

As you said, the increase in the sealed box is from adding cone area. It's the same thing with ported box. If you have one sub and upgrade to two, you'll see that increase in loudness. But if you already have two subs and put them in separate boxes (no matter if it's sealed or ported), there is no increase. You still only have two subs.

[iml2001ser 0]

where you find that box that has a face down port forward box at mike?

[nick_19 1]

http://www.obcon.com/

[mikeyd 0]

There's no difference if you build one box or two.

As you said, the increase in the sealed box is from adding cone area. It's the same thing with ported box. If you have one sub and upgrade to two, you'll see that increase in loudness. But if you already have two subs and put them in separate boxes (no matter if it's sealed or ported), there is no increase. You still only have two subs.

I gotchya. So my question now would be should I go ahead and build the 2 seperate boxes for 2 speakers? or just buy one Sub and build a bigger box that will somehow still fit.

Any yeah iml2001ser i found that after countless hours of internet browsing and I have many other sites for ext cab gm truck boxes so if you're interested pm me.

[KU40 173]

I would just do whatever is easiest and fits the best. Most likely, though, the best option would be to have two separate subs on either side of the tranny hump.

[mikeyd 0]

Ok cool. Now i just need to figure out my port dimensions and pick out an amp.

any suggestions?

[BigDaddy13440 3]

Ok cool. Now i just need to figure out my port dimensions and pick out an amp.

any suggestions?

Would it be possible to use the maximum space behind the seats AND the hump, and do external ports under the seats? Have the ports fire forward towards your feet.....

[mikeyd 0]

Well thats the plan buddy. If i build just a regular wedge style box that fits underneath the seat it'll give me .88 ft^3 after sub displacement. And with the room over the tranny hump (that never sounds right) i'll build external ports that fire forward into the cab.

But i talked to a shop the other day and they said they've done it before but with the port firing backwards so it would "load" off the back of the cab. Does that make any sense to you guys??

[KU40 173]

Yeah it makes sense. It's the same principle as people with cars facing their boxes in the trunk towards the back instead of forward. It's louder facing back almost all of the time.

You just have to make sure that you have enough room behind the seat for the port to "breathe." You don't want the port opening like 1" from the back wall of your truck, and you may not want to do that if the back of your back seat was flush against the back wall. You will probably want at least 3-4" from the port opening to the back sheetmetal on your truck. So plan that accordingly.

[mikeyd 0]

Ouch. Yeah thats something I didn't take into consideration but I understand. But would that effect sound quality?

[BigDaddy13440 3]

Well thats the plan buddy. If i build just a regular wedge style box that fits underneath the seat it'll give me .88 ft^3 after sub displacement. And with the room over the tranny hump (that never sounds right) i'll build external ports that fire forward into the cab.

But i talked to a shop the other day and they said they've done it before but with the port firing backwards so it would "load" off the back of the cab. Does that make any sense to you guys??

What I meant was to not have the port over the hump, but under each side of the seat, maybe a 2x7" port (or larger) at whatever length necessary. Mount the amp(s) under the opposite side.....

[mikeyd 0]

Oh ok. Guess i misread. But yes it is possible but it would take away airspace.

How do you guys calculate your port dimensions?

[KU40 173]

I use a program, winISD, alpha version. There is also a port calculator on this site.

[SUNDOWN/FI BEATIN 0]

Yeah it makes sense. It's the same principle as people with cars facing their boxes in the trunk towards the back instead of forward. It's louder facing back almost all of the time.

You just have to make sure that you have enough room behind the seat for the port to "breathe." You don't want the port opening like 1" from the back wall of your truck, and you may not want to do that if the back of your back seat was flush against the back wall. You will probably want at least 3-4" from the port opening to the back sheetmetal on your truck. So plan that accordingly.

firing subs back in a volvo isnt loud.. lol.. jsut my 2 cents workth sub forward port to the side has been very successful for my team in trunk cars.

[efxtruck 0]

ok I'm planning my next system right now. (last one got stolen) I'm thinkin 2 RE SR10's ported going under the back seat of my '02 Ext. cab silverado. Realizing there is almost no room back there I figure the best plan would be to build two different enclosures for each side. Doing so would give me about 0.88 ft.^3 per sub after sub displacement. But to make these vented I'm thinking could make external ports over the transmission hump. Does this seem like a bad idea?

I have a 91 ext cab silverado and I played with many different boxes. Ported, Sealed, Bandpass. The Bandpass got really loud... But it was just a fart box there was no detail to the music.

Next I got a sealed box. This box sounded nice but didn't really get loud. 131DB on the mic. I found that if you flipped the box around and fired it under the seat it got louder. (essentially creating a Bandpass) this sounded all right but it raddled the F&$K out of everything. Body panels and I thought that the back window was going to pop out.

I then got a box for 4 10"'s ported for under the back. Again I ended up with a fart box. Because of the trany hump the port chocked it self out and sounded like a big ball of ass.

Now I am running a ported box from Pound That Sound. I got rid of the back seat and dropped the box in the back.

I am running 2 10"s up firing on the passenger side and have never been happier with my system.

My suggestion to you is to either lose the back seat and through a massive box with a huge port in it, Or go with 2 sealed boxes one under each seat.

Well best of luck to you.

PM me when you decide what you are going to do.... I interested now.

[mikeyd 0]

Damn you had some bad luck with those fart boxes efx. I'm pretty sure i'm gonna go with my current plan. 2 upfiring boxes with the ports firing forward out over the tranny hump. Do you think putting an angle to the ports such as aiming them at the windshield or more towards the floor will make a big difference in sound quality. Or just shoot em straight out horizontally. Cuz I really want these to sound good.

[mikeyd 0]

According to this guy -http://www.carstereo.com/help/Articles.cfm?id=31 -

With volume at .88 and vent sizes 1.5"w x 3.25"h and tuning frequency @35hz my port length should be 9.61"

That sounds kinda short to me. How Should i pick my tuning frequency?

[BigDaddy13440 3]

According to this guy -http://www.carstereo.com/help/Articles.cfm?id=31 -

With volume at .88 and vent sizes 1.5"w x 3.25"h and tuning frequency @35hz my port length should be 9.61"

That sounds kinda short to me. How Should i pick my tuning frequency?

That size port is comparable to a round port of 2.5" in diameter, really kind of small if you want to avoid any port turbulence at all. I'd suggest something comparable to a 3.5" diameter, which would put you at about 9.6" of cross-sectional area at .88 cubes, just shy of the recommended 12-16 cu in per sq. ft. A 4" diameter port would get you 12.56 sq in at the .88 cubes, or at 14.3 sq in/ cu ft.

Here's a link to the port length calculator I've used. port length

Try an external port, running under the seat facing forward... max out the space behind the seat. A 1.5" x 8" port would be 23.14" long, tuned to 35hz.

If you can gain .12 cu ft by using an external port, then your port length would drop to 19.5".

Do you have enough clearance to do subs up under the seats, with the ports forward?

[mikeyd 0]

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?

[efxtruck 0]

Damn you had some bad luck with those fart boxes efx. I'm pretty sure i'm gonna go with my current plan. 2 upfiring boxes with the ports firing forward out over the tranny hump. Do you think putting an angle to the ports such as aiming them at the windshield or more towards the floor will make a big difference in sound quality. Or just shoot em straight out horizontally. Cuz I really want these to sound good.

Just be careful on how many angels that you put in the box you don't want to create port noise.

[BigDaddy13440 3]

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!