Combining boxes

[bbeljefe]

Another option is a fourth order bandpass box. The driver in a 4th order loads into a sealed chamber and fires into a ported chamber. They hit hard and tight. The only downside to them is their narrow passband.

I have never really messed with one but I was under the impression that if done correctly the 4th order could have a wider frequency response than a normal ported box

You heard bad information. They're called bandpass boxes precisely because of the fact that they do not have a wide passband. Any ported, sealed or t-line box will have response well above the sub bass rang but bandpass boxes fall off on the top of the sub bass range, often well below the top of the range.

It's true that one can sometimes get a pretty wide passband with a 4th order but it is not true that they can have a wider response range than "conventional" boxes. Good old physics simply won't allow it.

With all that said, 4th (& 6th & 8th) orders almost always have a much higher acoustical gain within their passband than conventional boxes do. But louder ain't wider.

[knockin'hoe97]

Another option is a fourth order bandpass box. The driver in a 4th order loads into a sealed chamber and fires into a ported chamber. They hit hard and tight. The only downside to them is their narrow passband.

I have never really messed with one but I was under the impression that if done correctly the 4th order could have a wider frequency response than a normal ported box

You heard bad information. They're called bandpass boxes precisely because of the fact that they do not have a wide passband. Any ported, sealed or t-line box will have response well above the sub bass rang but bandpass boxes fall off on the top of the sub bass range, often well below the top of the range.

It's true that one can sometimes get a pretty wide passband with a 4th order but it is not true that they can have a wider response range than "conventional" boxes. Good old physics simply won't allow it.

With all that said, 4th (& 6th & 8th) orders almost always have a much higher acoustical gain within their passband than conventional boxes do. But louder ain't wider.

I'm not saying you're wrong however the way you talk about 4th orders seems to....well specific I guess. With that in mind can't you fine tune a 4th order's ratio and/or port to determine if you wanted a wide frequency response or a burp box as you were saying?

And the same thing with ported boxes....some people use a standard ported box for the classic one note wonder.

Once again not saying you're wrong or anything because I'm very far from an expert but there is just so many variables with the boxes that can make them do almost anything you want, so it just seems incorrect when you say a 4th order ONLY has a narrow frequency response.

[bbeljefe]

I'm not saying you're wrong however the way you talk about 4th orders seems to....well specific I guess. With that in mind can't you fine tune a 4th order's ratio and/or port to determine if you wanted a wide frequency response or a burp box as you were saying?

And the same thing with ported boxes....some people use a standard ported box for the classic one note wonder.

Once again not saying you're wrong or anything because I'm very far from an expert but there is just so many variables with the boxes that can make them do almost anything you want, so it just seems incorrect when you say a 4th order ONLY has a narrow frequency response.

Narrow as related to conventional boxes. And yes, you can design a 4th order to have a wide passband but again, the nature of the beast (physics) dictates that band pass enclosures have a pass band... that means they have a narrow frequency range that they produce efficiently. And of course, the benchmark that's measured by is a conventional vented or sealed enclosure, which will play efficiently way above the sub bass region.

To help you understand what I mean, here is a driver modeled in three different boxes. Sealed, ported and 4th order. WinISD automatically models the box type you choose with the flattest possible response for the chosen driver. In this example, I've not changed anything about the boxes it modeled for the SA-10.

The yellow graph is sealed, the green is ported and the teal is 4th order. Notice how the sealed and ported alignments present a graph that never falls below flat, all the way up to 1K Hz, while the band pass box begins to roll off at 72 Hz and hits -3dB at 95 Hz. That's why it's called a pass band and there is nothing you can to to make that roll off go away. Yes, you can make the passband wider but you cannot make it go away.

You'll also notice that the passband is narrower on the low side than even the ported enclosure. Now, if I wanted to make that box extend further down toward 20 Hz I could, but the upper end of the pass band will follow the lower end as it moves down. So if I want a 4th order that slams @25 Hz, it's not gonna play well at 60 Hz. No matter what I do.

And just to add something.... if I really want a much wider passband along with the acoustical gains a band pass box provides, I have to move to a 6th order. With a sixth, I essentially have two different peaks to play with... one on the high side of the sub bass range and one on the low side of the sub bass range. And, I can get a pretty wide passband with a 6th but the wider I make the two peaks from one another, the lower the dip will be between them. Or... to make the dip go away, I have to lower the two peaks.

[Stee-Z]

4ths have a large bandwith.

[knockin'hoe97]

I'm not saying you're wrong however the way you talk about 4th orders seems to....well specific I guess. With that in mind can't you fine tune a 4th order's ratio and/or port to determine if you wanted a wide frequency response or a burp box as you were saying?

And the same thing with ported boxes....some people use a standard ported box for the classic one note wonder.

Once again not saying you're wrong or anything because I'm very far from an expert but there is just so many variables with the boxes that can make them do almost anything you want, so it just seems incorrect when you say a 4th order ONLY has a narrow frequency response.

Narrow as related to conventional boxes. And yes, you can design a 4th order to have a wide passband but again, the nature of the beast (physics) dictates that band pass enclosures have a pass band... that means they have a narrow frequency range that they produce efficiently. And of course, the benchmark that's measured by is a conventional vented or sealed enclosure, which will play efficiently way above the sub bass region.

To help you understand what I mean, here is a driver modeled in three different boxes. Sealed, ported and 4th order. WinISD automatically models the box type you choose with the flattest possible response for the chosen driver. In this example, I've not changed anything about the boxes it modeled for the SA-10.

The yellow graph is sealed, the green is ported and the teal is 4th order. Notice how the sealed and ported alignments present a graph that never falls below flat, all the way up to 1K Hz, while the band pass box begins to roll off at 72 Hz and hits -3dB at 95 Hz. That's why it's called a pass band and there is nothing you can to to make that roll off go away. Yes, you can make the passband wider but you cannot make it go away.

You'll also notice that the passband is narrower on the low side than even the ported enclosure. Now, if I wanted to make that box extend further down toward 20 Hz I could, but the upper end of the pass band will follow the lower end as it moves down. So if I want a 4th order that slams @25 Hz, it's not gonna play well at 60 Hz. No matter what I do.

And just to add something.... if I really want a much wider passband along with the acoustical gains a band pass box provides, I have to move to a 6th order. With a sixth, I essentially have two different peaks to play with... one on the high side of the sub bass range and one on the low side of the sub bass range. And, I can get a pretty wide passband with a 6th but the wider I make the two peaks from one another, the lower the dip will be between them. Or... to make the dip go away, I have to lower the two peaks.

Oh ok I'm trackin with ya. I appreciate the explanation on that. As they say you learn something new everyday.

On a side note looking at the program kinda sparked my interest...makes me wanna download it and mess around with it

[bbeljefe]

Oh ok I'm trackin with ya. I appreciate the explanation on that. As they say you learn something new everyday.

On a side note looking at the program kinda sparked my interest...makes me wanna download it and mess around with it

Well, you can't get it from Linear Team's website any more. You can get WinISD and WinISD Pro, both of which I have and neither of which I'm happy with. But you can google WinISD Beta and there are still some sites hosting downloads for this version.

The problem I have with the newer versions is that they're still a bit buggy and to be honest, they're too detailed. Not that that's a bad thing generally speaking, but for building car audio subwoofers, there is no need of some of the details those programs go into. Unless you're modeling a more complicated alignment that Beta doesn't handle.

[bbeljefe]

4ths have a large bandwith.

Compared to what?

[Stee-Z]

I'm sorry but are you claiming the bandwidth of a 4th is small, my fourth slams at 25 and 60 like you just claimed it wouldn't.. maybe I misread

[will77530]

bbeljefe, you have some good info mixed with some bad info, i got tired of reading so let me just point out the ones i noticed

4th orderbandpass boxes can have a great bandwidth playing from 20-60hz if design right, but any box can have a great bandwidth if design right

you also said

there isn't a wide enough band of frequencies below 60 to worry about it unless you were trying to use a sub bass driver that's more than two feet in diameter.

which i dont know what you consider bass but everything i play is below 60 hz, also a 10 " driver can play just as low as an 18 so you saying he needs a 2 ft driver to play low is just bad info

[will77530]

I'm not saying you're wrong however the way you talk about 4th orders seems to....well specific I guess. With that in mind can't you fine tune a 4th order's ratio and/or port to determine if you wanted a wide frequency response or a burp box as you were saying?

And the same thing with ported boxes....some people use a standard ported box for the classic one note wonder.

Once again not saying you're wrong or anything because I'm very far from an expert but there is just so many variables with the boxes that can make them do almost anything you want, so it just seems incorrect when you say a 4th order ONLY has a narrow frequency response.

Narrow as related to conventional boxes. And yes, you can design a 4th order to have a wide passband but again, the nature of the beast (physics) dictates that band pass enclosures have a pass band... that means they have a narrow frequency range that they produce efficiently. And of course, the benchmark that's measured by is a conventional vented or sealed enclosure, which will play efficiently way above the sub bass region.

To help you understand what I mean, here is a driver modeled in three different boxes. Sealed, ported and 4th order. WinISD automatically models the box type you choose with the flattest possible response for the chosen driver. In this example, I've not changed anything about the boxes it modeled for the SA-10.

The yellow graph is sealed, the green is ported and the teal is 4th order. Notice how the sealed and ported alignments present a graph that never falls below flat, all the way up to 1K Hz, while the band pass box begins to roll off at 72 Hz and hits -3dB at 95 Hz. That's why it's called a pass band and there is nothing you can to to make that roll off go away. Yes, you can make the passband wider but you cannot make it go away.

You'll also notice that the passband is narrower on the low side than even the ported enclosure. Now, if I wanted to make that box extend further down toward 20 Hz I could, but the upper end of the pass band will follow the lower end as it moves down. So if I want a 4th order that slams @25 Hz, it's not gonna play well at 60 Hz. No matter what I do.

And just to add something.... if I really want a much wider passband along with the acoustical gains a band pass box provides, I have to move to a 6th order. With a sixth, I essentially have two different peaks to play with... one on the high side of the sub bass range and one on the low side of the sub bass range. And, I can get a pretty wide passband with a 6th but the wider I make the two peaks from one another, the lower the dip will be between them. Or... to make the dip go away, I have to lower the two peaks.

winisd graphs things for an empty room as soon as your box enters a car your graph means nothing