Any input on this 6th order design? (with sketchup images! woot woot)

[Chance_P]

Just finished tearing out my flatwall with 2 zv4 18's on 5k. Looking to go a different route.

Any input?

Equipment:

4x SA-10's at 1ohm

SQ2200 (will upgrade in the near future to 4kish)

Please note, I didn't include a couple things in the sketchup, but they are factored into torres.

-12x 2" diameter 7.25 tall wooden dowels from the bottom up to the baffle

-steel bracing on the upper chamber

-top side port walls (they will only be 1 inch to start, I'm figuring I will have to adjust length/port area)

Specs:

Lower Chamber

-4.31 ft^3 net

-port area 30.5 in^2

-port area per foot 7.07 in^2

-Port ratio 1:7.63

-Tuning 28.44 Hz

Upper Chamber

-8.42 ft^3 net

-port area 198 in^2

-port area per foot 23.52 in^2

-port ratio 1:1.64

-Tuning 59.17 Hz

This is my first time using sketchup, pretty awesome program.

[Triticum Agricolam]

SketchUp is awesome, looks like you did nice work with it!

How did you come up with the parameters for this design?

[Chance_P]

Well I did a LOT of reading. Seems like the sweet spot is somewhere between 6 and 9 inches per cube on low side and 20 to 30 on the high side. There's a lot of debate between tuning. Like whether or not you should tune 1 octave apart, 1.5. Etc etc. I decided to go with roughly 1 octave. Volume ratio is often debated as well. 1:1, 1:1.5, 1:2. From my reading it seems like the closer the ratio to 1:1 the flatter is plays in the passband, the larger the ratio the louder it gets. I want something in the middle. Flatter than a regular ported enclosure but still louder. Probably can't have the best of both but I am going to try. I may add volume to the low side (maybe 5 cubes) and decrease the high side to 7.5 to give me a 1:1.5 ratio. I don't expect to get away with getting this right the first time, as most don't it seems. So I'm sure I will end up building both enclosures.

[Triticum Agricolam]

So I have a couple things to think about. First off let me throw out a disclaimer, I haven't built a 6th order BP yet, so if that makes me lose all credibility is some folk's eyes, so be it. However I have built 4 th order BP boxes and lots of ported boxes and the underlying science is all the same.

I think your rear port is way, way undersized. The "port area per cube" rule is not a good way to do things since it is based off a lot of assumptions that often do no reflect reality. A better way to determine port sizing is using one of the port area calculators that use sub cone area, xmax, and tuning frequency to give you a port size. Even better yet would be to use some modeling software (TermPro, BassBoxPro, WinISD, etc.) to determine what your port velocities are going to be based on how much power you are going to be running, and adjust your port sizes from there.

Your tuning numbers sound reasonable, but your chamber sizes make me wonder if this box is going to give you the frequency response you really want. With your front chamber so huge I think you are going to end up with a pretty big peak at a lot higher frequency than you want. This is another area where modeling software can help. Modeling software cannot tell you exactly how a box is going to sound since cabin gain really messes with things once the box is in your vehicle. However, software can allow you to compare and contrast two designs to see the differences, especially if you already know what one box sounds like. I would suggest you plug in the specs for your two Z v.4-18"s, since you know what that sounds like, and compare that to what your proposed 6th order BP will do and make sure it looks good to you.