4th Order help, or confirmation. Want to get building next week.

[scooter99]

Ok guys, like the title says, I've designed a 4th based on my primitive knowledge on them. Why do I want a 4th? Because everyone seems to have a forward facing sealed off trunk enclosure and I want to be a little different. Will it work? I don't know but I'm willing to try it out.

This is an expensive design and I'm sure that I won't be able to afford some of it right away. You'll see why when I post the pics.

First off the specs.

Ported side is approx 3.5 cu ft after displacement

Sealed side is 1.75 cu ft

Ports are 2 - 4" ports at 8" long for a tuning of just over 43Hz

All walls on the ported side are double walled. sealed side is single walled.

Subs are 2 DC Audio XL12 D2's

Amps are 2 Crescendo bc3500.1d's

Car is a Honda Civic Ex Sedan.

This is a wedge style box so that i can get it in as far as I can without wasting too much space.

My max dimensions are:

38" wide x 20" tall x 19" deep (top) / 25" deep (bottom)

I have about 2" more depth I can go, and about 1" wide I can go on the design. Tall is maxed out on the design.

Also it's being ported through the rear deck.

Here are the pictars!!

Plexi trunk side baffle to see the cones. Also a plexi floor to see the amps.

This is with the sealed section removed. Double 3/4" plexi sub baffle. Might just make this out of wood to save some money.

2 - 4" x 8" ports to tune to around 43hz.

Cabin side behind the seat. Plexi window to see the motors.

Plexi floor in the ported section to see the amps in the lower amp rack.

Thanks guys. I'd love to hear your thoughts. I want to start building this next week. I'm off for two weeks and I'm hoping to get playing by the end of that time.

[C'sgetdegrees]

Do it. Looks good to me.

[scooter99]

Thanks. Hope I get more of those comments.

[nCOMP1337]

i am doing a 4th myself but am learning about it as well, but here is a post on another forum about 4ths that may help, even if you dont have an account you can still read it

http://mobileaudioforum.com/forum/showthread.php?1619-Thought-I-d-share-some-4th-order-design-info

[scooter99]

Thank you. I'm leaving work now, but I'll look at it when I get home.

[CleanSierra]

I'm not sure if my opinion is wanted on this one Scott, but I'll give it anyway. I wouldn't feel comfortable with only 2 -4" ports on a bandpass box with the subs you are going to run. I would shoot for two 6" ports instead. I know that length can become an issue, but it's the only way your output is getting into the cabin-------» through the port. I just don't know what kind of port velocity you'd have with only a couple of 4" ports. I would highly suggest, either way you go, to make sure they are flared by using PSP ports or flaring them yourself.

The tuning is really low too, so I don't know how high into the bandwidth the box would perform. I would think that 46-50 Hz would give you a more Goldilocks kind of result.

These are just my opinions man so you can obviously take them how you want. I think the design and concept are fucking BADASS and I've seen you brewing this whole thing up for awhile.

[Miguels]

i agree with cleansierra

[scooter99]

I'm not sure if my opinion is wanted on this one Scott, but I'll give it anyway. I wouldn't feel comfortable with only 2 -4" ports on a bandpass box with the subs you are going to run. I would shoot for two 6" ports instead. I know that length can become an issue, but it's the only way your output is getting into the cabin-------» through the port. I just don't know what kind of port velocity you'd have with only a couple of 4" ports. I would highly suggest, either way you go, to make sure they are flared by using PSP ports or flaring them yourself.

The tuning is really low too, so I don't know how high into the bandwidth the box would perform. I would think that 46-50 Hz would give you a more Goldilocks kind of result.

These are just my opinions man so you can obviously take them how you want. I think the design and concept are fucking BADASS and I've seen you brewing this whole thing up for awhile.

Absolutely warranted. Thank you for your input.

I just need to figure out if I have the room to go to 2 6" ports. How long they'll have to be. The other option would be a square port, but I'm a little stumped by those as well. I'll see what I can figure out and report back.

i agree with cleansierra

Thank you.

[scooter99]

Do I figure out port for a 4th differently than I do for a standard ported enclosure? I wouldn't think so but like I said I'm still learning this so I thought I'd ask the question.

[scooter99]

If I did 2 6" ports, @ 10" long I'd get a tuning of 49.63hz. 14.81 per foot. But is only 56.52 port area. Isn't that kind of low?