Quickie question, hopefully an easy one

[christobear 0]

is there any disadvantage to having an extremely large port? lets say 20+ inches per cube?

[KU40 173]

no. I don't really like that suggestion of a certain amount of port per cubic foot, because the amount of port needed really depends on the displacement the driver has. If you have a sub with only 5 mm of xmax, it's going to need a MUCH smaller port than one with 30 mm xmax. The size of the port needs to be relational to the amount of air that the sub will push. So, in order to really answer your question, you'll need to tell us what sub you will be using.

[christobear 0]

working with an Orion H2, 29mm Xmax

the manufacturers suggestions say a 1.25 cube box, 12.5 sq inches of port at 15.8 inches long.

according to the 12volt.com calculator, that puts the box at like 38 hz, but Orion says its tuned to 31

it really lacks in the lows, it can barely even hit the low note in "Put On" by Jeezy

[sound=vibration 34]

working with an Orion H2, 29mm Xmax

the manufacturers suggestions say a 1.25 cube box, 12.5 sq inches of port at 15.8 inches long.

according to the 12volt.com calculator, that puts the box at like 38 hz, but Orion says its tuned to 31

it really lacks in the lows, it can barely even hit the low note in "Put On" by Jeezy

i would go about 15-16sqin of port for that size box.. and retune using winsid or another program to around 34 32hrz.. and ussally depending on the woofer u can get by with 14sqin of port per cube

oh and ya if the port is too big u will have less control over your woofer and start to bottom out... but going to small will have port noise..

Edited January 28, 2009 by sound=vibration

[christobear 0]

cool thank you

you know if there are any programs like winsid compatible with mac?

[sound=vibration 34]

cool thank you

you know if there are any programs like winsid compatible with mac?

i dont ever touch mac unless i have to sorry

[christobear 0]

or could you possible throw together a quick design for me?

that would be killer

[95Honda 486]

Again, port area has absolutely nothing to do with box size. It (the minimum size) is determained by driver displacement and the amount of compression you find acceptable.

Additionally, a larger port will NEVER cause there to be less control of the woofer. The only downside to a port that is (grossly) too large will be that pipe resonances can set in and cause weird issues with the tuning. As long as the port is the right (proportional) dimensions, it will act as a Hemolitz resonator (correctly)....

I don't know why people keep making this crap up...

[bassahaulic 155]

cool thank you

you know if there are any programs like winsid compatible with mac?

I feel your pain!!!! No box programs for Mac..... it's GHEY

[KU40 173]

The low note in "Put On" is pretty low, I'm thinking low 20's. Most ported boxes in car audio will have trouble with it, especially if you have a subsonic filter on. As for the discrepancy in tuning, make sure you took out port and sub displacement from the box size when calculating.

[christobear 0]

Again, port area has absolutely nothing to do with box size. It (the minimum size) is determained by driver displacement and the amount of compression you find acceptable.

Additionally, a larger port will NEVER cause there to be less control of the woofer. The only downside to a port that is (grossly) too large will be that pipe resonances can set in and cause weird issues with the tuning. As long as the port is the right (proportional) dimensions, it will act as a Hemolitz resonator (correctly)....

I don't know why people keep making this crap up...

then why do we all follow the 12-16 in^2 per cube rule?

The low note in "Put On" is pretty low, I'm thinking low 20's. Most ported boxes in car audio will have trouble with it, especially if you have a subsonic filter on. As for the discrepancy in tuning, make sure you took out port and sub displacement from the box size when calculating.

the spec sheet from Orion says that the given volume includes all displacements. its kinda screwy

[rushnrun 14]

I don't know why people keep making this crap up...

X2... I would assume that the 14sq in per cube was recommended once somewhere so everyone just jumped on and used it.. I've used it in forums just to keep from an argument (IMO it's not a terrible recommendation). However it's not something that I go by.

Anyhow, I'm VERY familiar with the H2 woofers (I build boxes for them all the time--it's the best woofer that the local shop sells)

From what I've seen about 1.5-2.5 cubes tuned 30-32hz works well running 2 4" areos or roughly 30in^2 of slot port works well.. (I almost always use a slot port) (I feel that the 1.5 cube is actually a little on the small side for this woofer... but I've always been a fan of a bigger box)

**granted with that small of a box and that much port you have to side fire the areo's in a wide box, the slot port works better being it's easier to get the length by making a 90 and going across the back of the box

So after all that...

I'd suggest trying to go to 2-2.5 cubic feet (after displacement) and run a slot port w/somewhere in the ball park of 30in^2 surface area

[rushnrun 14]

working with an Orion H2, 29mm Xmax

the manufacturers suggestions say a 1.25 cube box, 12.5 sq inches of port at 15.8 inches long.

according to the 12volt.com calculator, that puts the box at like 38 hz, but Orion says its tuned to 31

it really lacks in the lows, it can barely even hit the low note in "Put On" by Jeezy

That does put it at app. 38hz...

[ABXX49 20]

If you don't go by the "12-16 rule" how do you correctly calculate port displacement? Say a complete newbie comes in and wants to build a box, what would you tell him for the port? (How would you figure it out) Is 12-16 usually used because it's a safe medium?

[rushnrun 14]

If you don't go by the "12-16 rule" how do you correctly calculate port displacement? Say a complete newbie comes in and wants to build a box, what would you tell him for the port? (How would you figure it out) Is 12-16 usually used because it's a safe medium?

I assume someone decided it's a safe medium and it's just been adopted by forum users. I don't know where this came from/originated.

however from my time in car audio I've found that most noobs don't even know how to find square inches.... nor do they understand ohms, the term displacement, or much of anything for that matter. that's why they look to forums for answers and quite often are set in the wrong direction by others that just don't know...

I've had several people complain to me about "under/over-powering" because what they've read on a forum.. I had a kid swear that I caused him to blow his woofers because I sold him an amp that put out less power than the RMS rating of the woofers (it was a zx750.1 amp for 2 L7 10's) He then bought a bigger amp, got the subs replaced and blew them again... I didn't hear from him again...

** when designing a box it helps to have a good grasp on algebra and geometry, then it's real handy to understand the physics behind all of it..

Experience through trial and error can be one of the best learning tools.. (however not very cost effective)

[christobear 0]

I don't know why people keep making this crap up...

Anyhow, I'm VERY familiar with the H2 woofers (I build boxes for them all the time--it's the best woofer that the local shop sells)

have you seen very many problems with tinsel slap or anything else that could be making a popping noise?

i really dont think i have been over-exerting the sub, especially it started immediately after i took it out of the box to wrap the box in vinyl. put it back in on the same amp and everything, then all of a sudden, loud nasty noise

[rushnrun 14]

I don't know why people keep making this crap up...

Anyhow, I'm VERY familiar with the H2 woofers (I build boxes for them all the time--it's the best woofer that the local shop sells)

have you seen very many problems with tinsel slap or anything else that could be making a popping noise?

i really dont think i have been over-exerting the sub, especially it started immediately after i took it out of the box to wrap the box in vinyl. put it back in on the same amp and everything, then all of a sudden, loud nasty noise

From what I've seen almost all of them developed some sort of slapping/popping sound (some worse than others).. I've never really taken the time to look into the cause, I always thought it was the dust cap coming loose. I've seen two in a common chamber sealed box where one started it then a month later the other.. so I dunno...

*I'd like to point out that most of the time the woofers were making that sound when the guys had me building their box... Normally their pre-fab box fell apart so they came to me for a "real" box.

**it's worth pointing out that I don't see those woofers anymore since the HCCA came back out... I did my last box for them about 2 years ago--it was an old set that some kid had on a massive 3000d.

[KU40 173]

then why do we all follow the 12-16 in^2 per cube rule?

I think it's on the FI website.