Changing to a 4th order? Truth vs myths? Help

[Miguels]

I come up with 200" @ 46 Hz for a tune.

its showing i need 540.69" @ 50hz.. im my car i dont think i can get that much port area from the rear deck

[Jeff4661]

I got a chance to play around with your box specs a bit. A lot of the stuff I was going to say about bandpass boxes was already covered by TaylorFade, but maybe I can expand on a few things.

The first thing to keep in mind is bandpass boxes offer a lot of flexibility to the designer, they have the ability to trade efficiency for bandwidth and vice-versa. This means there are more than one "right" way to design them, it just depends on what your goals are. If you want a very musical box with a smooth and broad bandwidth you can do that, or if you want a one-note-wonder that gets you max deebeez for you watts you can do that too, you just can't do both at the same time.

Like TaylorFade said, the sealed section largely dictates how low you can play, the ported side determines your efficiency/bandwidth. As you make it larger you will get more efficient, but over a smaller range of frequencies. While a box with less subs, but higher ratio may get equally loud at a certain frequency as a box with more subs and a lower ratio, it will do so over a smaller range. So if I had to pick between the two I'd go for more subs and a smaller ratio.

Anyway, here is some stuff I played with in WinISD.

The red line is the box you gave the specs for above. The yellow line is a box for 8 subs, with 9 cubes rear volume, 9 cubes front volume, and tuned to 48 Hz. The red box will get approximately 3 db louder in the low 40 Hz region, but is more peaky. The yellow box has a smoother response and slightly lower F3, but gives up a little efficiency. Its up to you to decide how much ability to play music well you are wiling to give up to get the extra output.

If you aren't totally comitted to those SWA-12 subs you might consider using Infinity 1260W subs. They come in single and dual voice coil flavors, have a 13 mm xmax, and are rated to take more power. They also should give pretty much equal performance to the Alpines, but in a little smaller box (7.5 cubes sealed, 16 cubes ported).

Here is one last thing to think about:

The red line is the same red box from above, the green line is eight Alpine subs in a 24 cube box tuned to 36 Hz. With the plain ported box you get at least 1 db more output, smoother response, and a lower F3 all from a much simpler box that takes up the same space.

My personal goals for this build are for hairtricks and large amounts of air.. which is why I thought of doing the 4th order Bcs if I understand them correctly they are a more efficient box that gets low with still having a decent high end bandwidth..

I really like that 1:1 ratio box u designd I assume that box is 1:1 net volume? Plus that box will allow for extra bracing and glassing, etc.

[Jeff4661]

I come up with 200" @ 46 Hz for a tune.

For my setup?

Could you kindly explain how you determined this? I'm trying to understand the math behind all of these boxes as well.

Yes, for your quantity of subs, Xmax and tuning. You don't necessarily need that exact amount of port area. Sometimes a little less or a little more is needed, but that formula is a decent way to take into account the proper parameters.

I acquired the number through magic

Or through here:

http://www.carstereo.com/help/Articles.cfm?id=31

I just did my box with 8 12" subs with a 10mm Xmax and tuning at 48 Hz.. and it sys 367sq" of port ? for a minimum.. so I wasn't to far off guessing 350-400'

[alaskanzx5]

Yeah that calc to me seems high but from what I've read on it here in this forum it's suppose to be fairly accurate.

[Jeff4661]

Yeah that calc to me seems high but from what I've read on it here in this forum it's suppose to be fairly accurate.

Really?

Then I wonder where he got 200" for my box? ?

[alaskanzx5]

Well with 8 if those 12s at 10mm xmax I got 175" at 40hz and just under 200" at 45hz

Ha ha!

Forgot about the 4th order bandpass button on the calc

They require more port area

[Jeff4661]

I checked the box that asks "is this a bandpass enclosure"

If u don't check that then it gives u 175 at 40hz but if u check that box it gives u 400 lol

[alaskanzx5]

Yep, different boxes can need more power area

[kirill007]

I got a chance to play around with your box specs a bit. A lot of the stuff I was going to say about bandpass boxes was already covered by TaylorFade, but maybe I can expand on a few things.

The first thing to keep in mind is bandpass boxes offer a lot of flexibility to the designer, they have the ability to trade efficiency for bandwidth and vice-versa. This means there are more than one "right" way to design them, it just depends on what your goals are. If you want a very musical box with a smooth and broad bandwidth you can do that, or if you want a one-note-wonder that gets you max deebeez for you watts you can do that too, you just can't do both at the same time.

Like TaylorFade said, the sealed section largely dictates how low you can play, the ported side determines your efficiency/bandwidth. As you make it larger you will get more efficient, but over a smaller range of frequencies. While a box with less subs, but higher ratio may get equally loud at a certain frequency as a box with more subs and a lower ratio, it will do so over a smaller range. So if I had to pick between the two I'd go for more subs and a smaller ratio.

Anyway, here is some stuff I played with in WinISD.

The red line is the box you gave the specs for above. The yellow line is a box for 8 subs, with 9 cubes rear volume, 9 cubes front volume, and tuned to 48 Hz. The red box will get approximately 3 db louder in the low 40 Hz region, but is more peaky. The yellow box has a smoother response and slightly lower F3, but gives up a little efficiency. Its up to you to decide how much ability to play music well you are wiling to give up to get the extra output.

If you aren't totally comitted to those SWA-12 subs you might consider using Infinity 1260W subs. They come in single and dual voice coil flavors, have a 13 mm xmax, and are rated to take more power. They also should give pretty much equal performance to the Alpines, but in a little smaller box (7.5 cubes sealed, 16 cubes ported).

Here is one last thing to think about:

The red line is the same red box from above, the green line is eight Alpine subs in a 24 cube box tuned to 36 Hz. With the plain ported box you get at least 1 db more output, smoother response, and a lower F3 all from a much simpler box that takes up the same space.

Again proof that bandpasses almost have no use in car audio.

[kirill007]

I got a chance to play around with your box specs a bit. A lot of the stuff I was going to say about bandpass boxes was already covered by TaylorFade, but maybe I can expand on a few things.

The first thing to keep in mind is bandpass boxes offer a lot of flexibility to the designer, they have the ability to trade efficiency for bandwidth and vice-versa. This means there are more than one "right" way to design them, it just depends on what your goals are. If you want a very musical box with a smooth and broad bandwidth you can do that, or if you want a one-note-wonder that gets you max deebeez for you watts you can do that too, you just can't do both at the same time.

Like TaylorFade said, the sealed section largely dictates how low you can play, the ported side determines your efficiency/bandwidth. As you make it larger you will get more efficient, but over a smaller range of frequencies. While a box with less subs, but higher ratio may get equally loud at a certain frequency as a box with more subs and a lower ratio, it will do so over a smaller range. So if I had to pick between the two I'd go for more subs and a smaller ratio.

Anyway, here is some stuff I played with in WinISD.

The red line is the box you gave the specs for above. The yellow line is a box for 8 subs, with 9 cubes rear volume, 9 cubes front volume, and tuned to 48 Hz. The red box will get approximately 3 db louder in the low 40 Hz region, but is more peaky. The yellow box has a smoother response and slightly lower F3, but gives up a little efficiency. Its up to you to decide how much ability to play music well you are wiling to give up to get the extra output.

If you aren't totally comitted to those SWA-12 subs you might consider using Infinity 1260W subs. They come in single and dual voice coil flavors, have a 13 mm xmax, and are rated to take more power. They also should give pretty much equal performance to the Alpines, but in a little smaller box (7.5 cubes sealed, 16 cubes ported).

Here is one last thing to think about:

The red line is the same red box from above, the green line is eight Alpine subs in a 24 cube box tuned to 36 Hz. With the plain ported box you get at least 1 db more output, smoother response, and a lower F3 all from a much simpler box that takes up the same space.

My personal goals for this build are for hairtricks and large amounts of air.. which is why I thought of doing the 4th order Bcs if I understand them correctly they are a more efficient box that gets low with still having a decent high end bandwidth..

I really like that 1:1 ratio box u designd I assume that box is 1:1 net volume? Plus that box will allow for extra bracing and glassing, etc.

That's one the big misunderstanding in car audio. A ported box is almost always better

EDIT: removed pictures for smaller quote.