8th order bandpass

http://img447.imageshack.us/img447/5556/juansboxbp88hh.jpg

left chamber will be tuned for 90hz with 2 - 4"x4" ports
right chamber will be tuned for 60hz with 1 -4"x4.85" port
bottom (airspring) chamber will be tuned for 30hz with 3 - 1"x10.375" ports

top chambers are 1.185 cubic feet
bottom chamber is 2.337 cubic feet

Will be running RFP-4412's

thoughts?

EDIT - Chamber volumes and port sizes have changed since picture was drawn, so it is no longer to scale.

EDIT - It's a 6th order, not 8th.

That's going to be absolutly rediculous! Looks great. Make sure you post some finished product pics.

not NEARLY enough port area
that bottom chamber has what, 2.3 in^2?

What did you use to design that? I've never heard of something looking like that...it's not a 6th order, it's not really anything I've ever seen.

LOL ya wtf is that?

It's a 6th order. The bottom chamber is shared between the two subwoofers.

The volumes have changed, so it's not to scale anymore. The bottom chamber is instead 2.337ft^3 with 3 - 2"x10.375" which gives it tuning to 30hz.

It is indeed a 6th order 3 chamber bass reflex box.

I'm going to redraw it later today.

What did you use to design it?

The individual main chambers tuned to different frequencies really throws that bottom chamber off. Depending on what frequency you're playing one of the 2 subs will "see" more of that bottom chamber than the other will. So for example, at 90hz the sub in the right chamber will have nearly that entire 2.4cf bottom chamber to itself, at 60hz that will be reversed. I hope you planned it this way, because if not that will really freak some things out.

If you walled off that bottom chamber and gave half to each sub then it would be a pair of 6th order bandpass boxes tuned differently, as it sits now it's something different.

That is how it's designed. 6th order bp boxes don't typically have a wide tuning band, with this setup it will.

I've been using WinISD to get the port lengths, and the 3 chamber design is more or less from the top of my head using the concept of a hometheater subwoofer.

you can have a wide response with a normal 6th order, in a couple of minutes I just designed one that will have in-car -3dB points at 14hz and 100hz and +/- 1dB in between.

Either way, good luck with the design, I would still increase port area dramatically, especially in the bottom chamber

If I increase the port area, it requires longer port for the 30hz tuning, which then takes from the volume of the chamber, which then changes the needed port length and so on. This is the best balance.

I wouldn't say 9.5 in^2 of port area for 2 12's is a very good balance, you could always just increase the size of the bottom chamber to allow for the larger ports (unless you can't, but that's a pretty big issue that you shouldn't just ignore IMO) but it's your call.

A single low excursion 8" sub can make a 3 in^2 port sing like a canary around tuning. You're dealing with MUCH more displacement here and just 3x as much port area. It's a recipe for problems I think, but it's obviously up to you. Just keep in mind that if you do have port noise problems, it's too late to change it without rebuilding the box.

The box cannot get larger.

I will be building an 10" version tomorrow. I will use the tube ports and see how it does. If I'm not satisfied, then the 12" version will use a .75"x26.5"(wide)x23.25"(deep) slot port. That will balance out the port length vs. chamber volume

http://img416.imageshack.us/img416/3455/juansboxbp8slot8ks.jpg

I forgot to add the speaker holes....the subs will be facing down, in the same spots as the first picture.

[raises one eye brow, shakes head and click link to cars in general forum list]

Lets hear it CB.

I wanna hear it from anyone.

Sawdust tonight.

The individual main chambers tuned to different frequencies really throws that bottom chamber off. Depending on what frequency you're playing one of the 2 subs will "see" more of that bottom chamber than the other will. So for example, at 90hz the sub in the right chamber will have nearly that entire 2.4cf bottom chamber to itself, at 60hz that will be reversed. I hope you planned it this way, because if not that will really freak some things out.

If you walled off that bottom chamber and gave half to each sub then it would be a pair of 6th order bandpass boxes tuned differently, as it sits now it's something different.

this explains it all.

it isnt 6th order, i dont know what it is...

you have 2 subs and 3 chambers each chamber tuned to a different frequincy...

6th order is 2 chambers each tuned do a different frequincy

4th order is one sealed and the other tuned.

Simply put, the subs arent going to like each other

http://www.the12volt.com/caraudio/boxes6.asp
http://www.the12volt.com/images2/dualbpass3cham.gif

Look at that picture, the two main enclosures are the same size and tuned to the same frequency, that's a normal 6th order just with a common chamber instead of separate chambers. That's not what you're doing.

how does the tuning of the port effect the type of box? 3 chambers, all ported, 2 drivers = 6th order bandpass. The fact they share a chamber makes it a dual reflex. What does tuning have to do with the TYPE of box?

That's like saying because my car is N/A and my buddies is turbo'd, regardless of the fact they are both 1999 Escort LX's, the fact that his is turbo and mine isn't, then my car isn't an Escort, or his isn't, because they're not "tuned" the same.

Because the two outer chambers are tuned to the same frequency, the two subs move identically. Because of this, the inner chamber can be assumed to have a wall in the middle separating it into a chamber for each sub, just like having a pair of identical 6th order bandpass boxes sitting side by side. Your box does not function that way, the alignment changes drastically depending on what frequency you're playing, I hope to god you found a program that can model this box for you, if not you're just shooting a bb gun into the sky hoping you hit a satellite.


If you take a 2cf 30hz box designed for 2 10's, you put a 10 in one hole and a PR in the other hole, it's no longer a 2cf 30hz box, it's just fucked up is what it is.


A 6th order bandpass is called a 6th order bandpass because you have a 4th order rolloff on the bottom end and a 2nd order rolloff on the top end. I highly doubt yours behaves this way, so it can't be classified as a 6th order bandpass IMO.

I'm making one tonight, with 3 slot ports, will let you know tomorrow how it sounds.

want to see how a dual chamber 6th order SHOULD be designed?
http://www.soundsolutionsaudio.com/forum/index.php?showtopic=4316

okay, the 10" version is built.

It is the exact opposite of what I thought, but it's unique none-the-less. It's a drop in volume from my previous design(horn loaded), but the quality is 10x better than any setup I have ever heard anywhere. dropoff does not occur till ~25hz. That's already below the limits of my subs (28hz) so I don't care. Pretty level on up to the crossover at 90hz. The accuracy is just astonishing! You can tell the smallest of tone changes, or tiniest thumps. I love it for the quality aspect, it still has some spl, but not what I had.

that funny because proprly designed horns are not only the most efficent but also the most accurate and natural sounding alignments.

My horn wasn't sized right in the least bit. I just took some wood and slapped it together to see what the big deal was.

Then i can understand a great improvement :)

a lil horns 101 (im no horn expert)

a true bass horn has a mouth size the size of the wavelength of the inteded frequincy, however due to horns small roll off frequincy smaller mouth area's can be used, especially if the sub is being designed for corner or wall placement in an enclosed area.

http://melhuish.org/audio/hornshape.html