Stupid port question

[kush-divinity 10+ year member]

Okay, for years I have used slot ports, always going down one side of the box, even in mulit-woofer setups. I ALWAYS go the full face width by 2 inches, dont ask why, and tune to that area.

I have been seeing alot of 2 sub setups with a port in the center, or out one of the sides.

Tell me why this is better or worse, and why.

And please tell me why I am supposed to need 100Sq inches of port for 2 L5 wanna be's.

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[Immacomputer 10+ year member]

Who said you need that much port area?

Neither of the setups are better or worse (well besides some down the middle ports with no deflector at the back if the port uses the back wall as well) just different. They can be implemented in different vehicles to get different responses but non of them are superior to the others.

 

[kush-divinity 10+ year member]

Well sir, I am guessing at 100sq inches, as I was informed that I need 16sqinches per ft3 of box volume. I have never used that much before, and have been very happy with almost all of my builds. I have sat in my friends car and listened alot, and love it. he has 2 JL w6v2 12's, about 5ft3 I reckon, but the port is in the side, and is about 10x8x20. Sounds good, hits most of the realllllllly lows, but still plays up to 70hz clean.

Another friend has a prefab box from a local shop. About 5 ft3 as well, but has a 14x2x 10 rectangle port in the center between the subs. He has 2 Lightning Audio 12's from WalMart, and they SLAM. Very very hard from 35-60. He can't hit the uberlow notes, but omfg at his middle ground.

I have been seeing alot on this site about Aeroports, no one has used round ports around here for a long time, so wtf? I will be building a new box soon, no idea what for, but my car is up for trade for system and boot. I need to know other options than my old stanby.

 

[Notloud00 10+ year member]

where u at in tn?

to the ear i hear no diff in aero vs slot. but it takes much much much less time to build an aero box vs a slot and its much easier because u dont have to worry about the port being strait. if u have 2 l5 12s, 1 8" sono should be good. tell me ur max dims and ur car and power and ill try to design u a good box because i am pretty good wit kicker subs

 

[kush-divinity 10+ year member]

I am in Savannah, Tn. It is about 120miles east of Memphis, just north of Pickwick Dam. I am not building a new box for the fake kickers, but for my new to come subs. Just waiting on an offer for my car. I would like to run 2 or 4 HDC3 18's. Sealed I guess. Funny.

 

[GearGuy2001 10+ year member]

The rule of thumb is 13-16 square inches of port per cubic foot of box. So there is nothing wrong with going 2" across the full face but with the mid port or L port box you need to go with a wider port in order to achieve the correct amount of port area (otherwise you could get chaffing(sound))

Also with the midport box (like i did with my subs) as you may know it would be dangerous for one sub to fail (in a multi sub setup) if they were in the same chamber so with the midport box each sub has its own chamber and really wouldnt be effected if the other sub failed.

 

[Immacomputer 10+ year member]

The rule of thumb is 13-16 square inches of port per cubic foot of box. So there is nothing wrong with going 2" across the full face but with the mid port or L port box you need to go with a wider port in order to achieve the correct amount of port area (otherwise you could get chaffing(sound)

That "rule of thumb" is stupid and WRONG! All it does is cause confusion and spread around a myth that port area should be directly proportional to box volume. That is a huge misconception that can give good or bad results. Take this thread for example. This guy is all confused thinking he needs way more port area than he really does.

To the OP: The differences in sound that you're describing is not from the port area but rather from a combination of the tuning frequency, drivers used, and the vehicle they're in. The port area just needs to be sufficient enough to not cause significant turbulence and to help match a certain tuning frequency with a given box volume.

Many people use aero ports (circular ports with flares on them) to help reduce turbulence and allow for a much smaller port area than a slot port would require given everything else is equal. They're probably not as common because they're more expensive.

 

[TSGP]

That "rule of thumb" is stupid and WRONG! All it does is cause confusion and spread around a myth that port area should be directly proportional to box volume. That is a huge misconception that can give good or bad results. Take this thread for example. This guy is all confused thinking he needs way more port area than he really does.
To the OP: The differences in sound that you're describing is not from the port area but rather from a combination of the tuning frequency, drivers used, and the vehicle they're in. The port area just needs to be sufficient enough to not cause significant turbulence and to help match a certain tuning frequency with a given box volume.

Many people use aero ports (circular ports with flares on them) to help reduce turbulence and allow for a much smaller port area than a slot port would require given everything else is equal. They're probably not as common because they're more expensive.

Well port area IS in proportion to the enclosure, and the port acts like a driver at peak frequencies and gives the tuning. You don't always just go barely big enough to not get port noise.

I'm an SPL guy though so I'm sure i'm on a different wave then most

 

[Notloud00 10+ year member]

uh dont seal 18's. just do 4 15's ported

 

[kush-divinity 10+ year member]

Please explain why not to seal a pair of 18's?

I don't really care about max spl, but I want smooth, potent bass down below hearing, and the ability to play 55-60 hz notes as well.

In my history of car audio, NOTHING plays as well as a sealed box for SQ. I truly think that 2 HDC 18's will give me the SPL that I want while retaining very nice SQ.

Unless you think that sealed with those subs will sound like smashed assholes..

Then please recommend me a different subwoofer that I can use sealed. Around the same price/performance.

 

[Immacomputer 10+ year member]

Well port area IS in proportion to the enclosure, and the port acts like a driver at peak frequencies and gives the tuning. You don't always just go barely big enough to not get port noise.
I'm an SPL guy though so I'm sure i'm on a different wave then most

What I was saying is that port area should not be determined by box volume alone. Motor strength, cone area, throw, and space limitations are MUCH more important in deciding how much port area to use than box volume is. Box volume does need to be accounted for because as the box gets larger, the spring force becomes smaller which will give you a little more throw from the drivers which would lead to a small increase needed in port area.

You're 100% right though about not always going with the bare minimum; I was stating that in the case where space is very limited to help keep the enclosure size down. And about SPL being a different situation. In that case, you do want as much port as possible since it will be the primary radiating surface when playing around tuning. But even then, if you don't have a sub(s) strong enough to drive a ridiculous amount of port air mass, then you're not going to be very loud with all that port. And if you go too large in the ratio of enclosure volume to port volume, you end up with a port that doesn't radiate but becomes a transmission line.

Please explain why not to seal a pair of 18's?
I don't really care about max spl, but I want smooth, potent bass down below hearing, and the ability to play 55-60 hz notes as well.

In my history of car audio, NOTHING plays as well as a sealed box for SQ. I truly think that 2 HDC 18's will give me the SPL that I want while retaining very nice SQ.

Unless you think that sealed with those subs will sound like smashed assholes..

Then please recommend me a different subwoofer that I can use sealed. Around the same price/performance.

You shouldn't ever rule out other enclosure possibilities just because you haven't heard a setup that was built to what you prefer. My current enclosure is a transmission line and it sounds far cleaner, plays lower and flatter, and is much louder than the sealed boxes I have used for the same driver in the same vehicle. And just because a setup is ported, does not mean that it will perform terribly at 55-60hz. Do realize though that your vehicle will probably not give you much gain above 70hz so the response of a sub can sometimes seem like it struggles with higher frequency bass. In order to have a proper stage at the front of the vehicle (speaking for SQ), you don't really want your subs playing much higher than 70hz anyways as it can draw the stage back to the rear.

As for the HDC 18s, you can't just throw any sub into any sealed box and expect it to sound good. With those subs sealed in a vehicle, you're probably not going to have a flat response down to 20hz and you will probably be left with something that is very loud in the 45-55hz region. This will be very dependent on the vehicle though.

 

[kush-divinity 10+ year member]

Okay, I understand that not all subs are kosher with a sealed box. What kind of box would make them sing? It is going in a 94 Explorer, so size not really an issue. I dont want the traditional L-port, BUT if that is what will do me the best, I'll take it.

Thanks in advance.

P.S. I only ask, because I know that someone on here has tried more than 1 way, and it will save me alot of time/money testing different enclosures.

 

[Rashaddd 5,000+ posts]

Okay, I understand that not all subs are kosher with a sealed box. What kind of box would make them sing? It is going in a 94 Explorer, so size not really an issue. I dont want the traditional L-port, BUT if that is what will do me the best, I'll take it.
Thanks in advance.

P.S. I only ask, because I know that someone on here has tried more than 1 way, and it will save me alot of time/money testing different enclosures.

Alot of people tune high for the AQ's (like 38-40), but they'll sound good in the low 30's too, depends on your preference. If size doesn't matter you might as well build a big ported box though...going sealed is pointless if you want to get loud and have the space

 

[jdawg 5,000+ posts]

ya I never understood why everyone says so much port per cubic feet. Thats retarded, so a Pyle 12 moves just as much air in a 2 cubic foot box as a BTL 12? Makes sense I guess //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

 

[kush-divinity 10+ year member]

So how about 12ft3 for both 18's with a port at one end sized 20x10x40? Is that low enough? I want to FEEL the lows that I cant hear. If them AQ ain't good for what I want, then what is? The clock is ticking ninja, this dude ain't gonna wait alot longer, and he gave me a hell of a deal on em.