8th order bandpass

Jet-Lee · #1 10-25-2005, 01:28 PM

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.

AudioGuy93DelSol · #2 10-25-2005, 06:07 PM

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

sr20de4evr · #3 10-26-2005, 12:38 AM

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.

Mannyb18b · #4 10-26-2005, 03:24 AM

LOL ya wtf is that?

Jet-Lee · #5 10-26-2005, 11:10 AM

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.

sr20de4evr · #6 10-26-2005, 11:37 AM

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.

Jet-Lee · #7 10-26-2005, 11:52 AM

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.

sr20de4evr · #8 10-26-2005, 12:04 PM

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

Jet-Lee · #9 10-26-2005, 12:07 PM

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.

sr20de4evr · #10 10-26-2005, 12:14 PM

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.

Jet-Lee · #11 10-26-2005, 12:35 PM

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

Jet-Lee · #12 10-26-2005, 01:15 PM

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

CBFryman · #13 10-26-2005, 07:18 PM

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

Jet-Lee · #14 10-27-2005, 10:11 AM

Lets hear it CB.

I wanna hear it from anyone.

Sawdust tonight.

CBFryman · #15 10-27-2005, 01:49 PM

Quote:

Originally Posted by sr20de4evr

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

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