View Full Version : Fourth Order HELP!!!????

12-21-2012, 04:05 PM
Have a design Ive been working on.. This is my first attempt. Using Bassbox pro 6 to design this beast, but I have stumbled up on isobaric design and wanted the opinion of people who tend to experiment and run these types of set ups.. Please any and all help is appreciated..

First, my design


Now, the isobaric design that I find interesting...


Which one has the most potential to get loudest?? Is there anything Im missing here?? ALSO!! Im lost as to how I am suppose to build a top that is "removable".. how does one do that?

12-21-2012, 04:07 PM
dont do isobaric... only point is a smaller box, but you will spend twice as much on woofers seeing as how you need 4 not 2...

12-21-2012, 04:09 PM
running my 4 vvx12's in the 4th order btw. forgot to mention that..

12-21-2012, 04:20 PM
TaylorFade; keep_hope_alive; double 07;

also, I wanted do the port of the 3rd chamber backward firing @ 45hz (20'' H, 10'' W.. 1'' mdf divider @ 13'' and 5''port on eitherside) which should put Length at 9.625

Is all of this sounding correct??

12-21-2012, 05:15 PM
ttt for experience and advice!:santa:

12-21-2012, 07:34 PM
just not feeling the love today guyz....

12-22-2012, 12:16 AM
One more shot tonight for tips, tricks, and advice!

12-22-2012, 12:24 AM
my little 4th order box i did for my dd 1508 is .40 sealed and 1.25 ported at 44 hertz ,hits very nice and hits the lows well.so that a 1 to 3 ratio. also use weather stripping and screws to seal the top baffle of the box so it can be removed if needed.

12-22-2012, 07:08 AM
I tried an isobaric alignment last week and came to the conclusion that... it's not worth it.

An iso pair is -3db from a single sub because of the efficiency loss. Now, the VAS is halved also though meaning only half the volume is needed. But let's do the math.

These are just sensitivity numbers and theoretical, but bear with me...

Say a single has a sense of 90db. An iso pair will be 87db. (2) iso pairs will get you back to 90db. What's that mean? That means you need (4) subs to equal a single in a standard alignment. Yikes.

What about space? Well, let's say your single needs 1cf/2cf for a 4th. Iso pair needs half so .5/1. But you need (2) iso pairs to get back to the output of a single so double that and you're back to 1cf/2cf but now with (4) subs instead of just one and the exact same theoretical output on the same power.

BUT... your power handling also quadruples with the (2) iso pairs. So, even though you need all (4) subs to meet the sensitivity of a single, you can surpass it's output by sheer power. Somewhere in the theoretical neighborhood of +6db. Small box, big power twice as loud. If you have the power, that is.

Is it worth it? If you are strapped for space and have planty of power on tap... maybe. But, there is also another benefit of the iso alignment. Since you are saving space, you can increase the ratio and as such, increase the gain in the bandpass to make up for the loss of efficiency. Even if you can design in a conservative +3db gain with a larger ratio, you now start leveling the playing field while still staying smaller than all (4) in a standard fashion.

With all of that being said, if you have the room to do it normally, go that route. If not, iso may benefit you if you have the power or if you just want to do something different.

12-22-2012, 08:53 AM
^ nice response.

the point of isobaric is not to be as loud as possible - so that should answer your question.

design the enclosure so you can experiment with port orientation - you won't know what is the loudest until you build and test.

removable top? not the whole thing - just a piece that covers the sealed chamber so you can remove woofers. the piece over the larger area needs to be secured/glued to the bracing - something screws wont work well for more than once. for this, make a trim lip that has t-nuts in it (two layers can sandwich the t-nuts so they can't come out).

it would be even easier to not to the top at all and just the side that the magnets face - making install/removal easier.