Are 4th orders worth it?

[Based]

Are 4th order band passes worth the extra space or are they really not that much better than a regular sealed or ported box? I'm talking about in terms of bandwidth and efficiency.

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[nismotwin 10+ year member]

Just a little research and you can answer your own question.

 

[Popwarhomie 5,000+ posts]

Depends..

 

[Based]

Yeah I guess I worded my question stupidly...

I have been researching and I'm just gonna build one. I was going to build a sealed box for this JBL gt5-15 I bought but I'm gonna try 4th order. I guess I will start with a 2:1 then if I don't like it I can either go up or down next build.

 

[Jeffdachef 5,000+ posts]

Yeah I guess I worded my question stupidly...
I have been researching and I'm just gonna build one. I was going to build a sealed box for this JBL gt5-15 I bought but I'm gonna try 4th order. I guess I will start with a 2:1 then if I don't like it I can either go up or down next build.

not worth it unless you have a meter to build it properly. There's a proper way of building it and there's the build and pray option. The 2nd option usually doesnt work too well most of the times as in, meh/so so performance or loud but sounds like sh*t or sounds good but quiet.

 

[Based]

not worth it unless you have a meter to build it properly. There's a proper way of building it and there's the build and pray option. The 2nd option usually doesnt work too well most of the times as in, meh/so so performance or loud but sounds like sh*t or sounds good but quiet.

How is it hard to build though? I've been messing with designing one with WinISD and it seems straight forward to me. Higher the ratio the more it peaks at the tuning frequency and vice versa. The bigger the sealed volume is to begin with is the louder it can be.

 

[Jeffdachef 5,000+ posts]

How is it hard to build though? I've been messing with designing one with WinISD and it seems straight forward to me. Higher the ratio the more it peaks at the tuning frequency and vice versa. The bigger the sealed volume is to begin with is the louder it can be.

thats on a graph. Throw it in a car, that all goes out the window.

I'd suggest you read this first.

A brief summary of the 4th order thread... - Car Audio Classifieds

If you dont have a CACO account.

here it is :

Okay guys, here goes. I compiled some info from the 4th order thread to try and make it a little simplified rather than reading through a couple thousand posts. I'll try to be as accurate as I can, though admittedly I'm not as technical as some guys like Hackmunch and others are. I'm more of a builder/fabricator, but hopefully this will all be pretty correct. Hack can correct me if I am wrong on something, and may add some stuff as well...

REMEMBER, this is just a basic guideline for LARGE RATIO 4ths, not necessarily one with wide bandwidths and great SQ...but that's not what most of you want. If you want a ground pounder/low end monster, here's your info...so here goes.

1)Basic guidelines for subs - remember...any sub will make noise in any box, but these guidelines will help you decide what box is best for them.

Take the FS of the sub and divide it by the QES - If it is say 45 and below, it's more of a sealed box sub, 55 and above, more of a ported box sub. What does that mean? If it's a sealed box sub, it's better for sealed enclosures or 4th order bandpasses. If it's a ported box sub, it's better for a ported box or 6th order bandpass.

What is the QTS of the sub? If it's higher, lets say above .55 or so, it's typically better suited for a 4th order bandpass. Lower, say .45 and below, 6th order bandpass.

Now, the reason you should look at both examples above before choosing which way to go....there are some subs that are low QTS but still are a great 4th order bandpass sub. The JL 18w6 in the Astro we built is a perfect example. Here are the specs...QTS .384, FS 20.0hz, QES .384---Low QTS=6th order, right? Not exactly, the FS/QES=52, so it could go either way really...but that's why you need to look at both specs.

2)Design goals

a. SPL

b. Lows

c. Daily all around music

You need to decide what you really want out of it. If you want all-out SPL, It doesn't make much sense to put them in a box with a resonant frequency of 40hz...Typically though, with these large ratio enclosures, you will get tone of low end even with the sealed section resonating at 45-50hz. The sealed section rolls off slow in these, just like a standard sealed box, so low end extension is great. Honestly though, if you want lows, you'll want the sealed resonance/port tuning to be in the 44-46hz range, daily all-around in the 47-52hz range, and all-out SPL to be in the 55-65hz range most likely. (All of this is somewhat vehicle dependent though, so it's not an exact science with these starting points)

3) Basic other starting points...

Normally if you are going to do one of these, you want to make sure you do less subs/more ratio. 4 subs in a large ratio are going to be much more efficient than 8 subs in a small ratio. Now, if you have 100,000 watts on tap, you may just need to go with more subs just to split up the power some, but we are going to assume you have a reasonable amount of power...lol. But a 3:1 is a good starting point for the typical ground pounder, if you want higher SPL, you can even go 4:1 or even 5:1 if you have the room. As far as efficiency goes, in comparing a 1:1 to a 3:1 is about a 3dB gain with the 3:1, and a 3:1 is about 1.5 dB louder than a 2:1, which equates to about the same as 50% more cone area or 50% more power...

As far as port area, a good starting point is 1/2 of cone area, but a good box design program is really the way to go. It's going to show you port velocity and things that you otherwise have no way of knowing. Also, I know from Hack's testing, he always recommends to stay away from top port designs if at all possible. Center port is okay, but driver's side port is 1.5dB on average louder than a center port. (Sealed on the dash)

4)Other tips...

Normally, subs with a medium to soft suspension are ideal for 4th order bandpasses.

Common sealed chamber is louder but if you blow a sub it can easily destroy other subs in the box, so take that into consideration when deciding how to build it.

Subs with high motor force can typically work in a smaller sealed section.

Try to do your design so all the subs are on the same plane if possible. Not completely necessary, but it is a good idea.

Buy a DATS/WT3 from Parts Express (around $100) as a great tuning tool. It will make your port tuning much easier especially.

Build your shell, then build the sealed section. Before you put your loading wall in, test the sealed resonance in the car (with all doors shut). Once you find that sealed resonance, that's the frequency you are shooting for when you tune your port. That will give you your most efficiency.

Your vehicle will typically peak 3-4hz below your tuning...

That's all I can think of right now. If I think of anything else that may help you, I'll add it, and if Hack or one of our other knowledgeable guys on here wants to correct/add anything, feel free. Like I said, I'm not really a technical expert on these, but I can build...lol.

Okay, by request, I'll start adding more info as it is brought up.

The first part here is about polyfill, I just copied and pasted this, but it's explained better than I can.

This information was taken from an article by Tom Nousaine, Car Stereo Review, March/April '95

It's no secret that you can use fiberfill to make low-end magic; clever installers have

been using it for years. Take two boxes of the same size and type, insert the same

woofer into each one, and stuff one with some fiberfill. The one with the stuffing should

kick out lower bass.

In simple terms, it works like this: The fiberfill fools the woofer into thinking that it's in a larger box (one with more air, or internal volume) than it really is. And, in general, the larger the box, the lower the bass you can get out of it.

Fiberfill stuffing is a popular alternative for people who can't or don't want to allow a lot of

space for a subwoofer box.

The particulars of fiber stuffing are pretty interesting: The air inside your enclosure

actually heats up as your woofer moves, making the air stiffer. When the enclosure is stuffed with fiber, the fibers wiggle, dissipating some of the heat and making the system work as though the box were larger. Theoretically, your

woofer/box bass system can act like a system that's a maximum of 40 percent larger

when you've latched onto the right stuffing recipe – in other words, if you have an

enclosure that offers 1 cubic foot (1 ft³ ) of internal volume, in a perfect world a good

stuffing job will make it perform like an enclosure that offers 1.4 cubic feet of internal

volume.

There are three types of stuffing that are commonly used for this purpose: fiberglass

insulation, long-fiber wool, and polyester fiberfill. Fiberfill is the best choice because it doesn't come loose and fly around and irritate your skin or lungs like fiberglass, it works as well as either of the others, it's a lot cheaper than wool, and moths hate it. I recently bought five 20-ounce bags of it at $1.99 a pop (a total of 6.26 pounds for $9.95) at

Minnesota Fabrics; that turns out to be about $1.60 a pound. You should be able to find

some at any fabric store or in the bedding section at friendly stores like K-Mart or Home

Depot.

To evaluate the effectiveness of box stuffing, I used an MLSSA analyzer to measure the

impedance of three enclosures – 5.l-cubic-foot sealed, 1.4-cubic-foot sealed, and

1.4-cubic-foot ported (the port measured 3 inches in diameter and 6 inches in length) –

with various densities of stuffing. For the sealed boxes, I was able to determine the

effective box size – as enhanced by the stuffing – using the system's resonant-frequency

and Qes values. For the ported box, I compared the tuned frequency of the empty

enclosure to the tuned frequency of the stuffed enclosure, using the Speak for Windows

computer program; this enabled me to find the effective box size that fit the actual

resonant frequency I'd measured.

In each case, the news was good – make that very good. With all three boxes, I enjoyed

roughly 25 to 35 percent of "space gain" by using stuffing at a rate of 1 to 1.75 pounds

per cubic foot of internal volume.

When making system performance predictions, be aware that the Qes figure – and,

therefore, the Qts figure – of the sealed boxes dropped. And with the ported box, the

peak of the impedance curve on the lower side of the tuned frequency became heavily damped below the box's point of resonance. I also found that there is such a thing as too much of a good thing: System resonance (Fsb) rises again, beginning with densities of around 1.5 pounds of stuffing per cubic foot of box volume; this happens because the fibers are jammed so tightly together that they stop wiggling and, consequently, stop dissipating heat.

I also found that stuffing gets less effective as box size increases. The morale: The

bigger your box is, the harder it is to fool your woofer.

A few rules of thumb: Stuff small enclosures – those with up to about 3 cubic feet of

internal volume or less – with 1.5 pounds of fiberfill for each cubic foot of internal volume

and you should get about a 30-percent increase in box volume without seriously affecting

other performance variables. For larger enclosures, add stuffing at a rate of

approximately 1 pound per cubic foot and you should get a virtual-space boost of about

25 percent.

 

[hispls 5,000+ posts]

What exactly are you trying to accomplish? You can sacrifice bandwidth for SPL gain, but you can do the same with ported. IMO by the time you have a good musical bandwidth you may as well have just run sealed.

 

[Based]

What exactly are you trying to accomplish? You can sacrifice bandwidth for SPL gain, but you can do the same with ported. IMO by the time you have a good musical bandwidth you may as well have just run sealed.

I want the loudness of a ported box but the unlimited low end of a sealed box. I don't want to have to worry about playing music below the tuning frequency. Last setup I had was 4 15s tuned to 31hz. It was pretty loud but I didn't like how I had to be careful what songs I played and at what volume. And also it didn't have that great of transient response (like above 60hz). I actually enjoy the single Kicker CVR 12 in a 4.3 cube sealed box more.

Here's a pic of the comparisons I have right now. And Jeff I haven't read your post yet but I'm about to.

EDIT: Idk why my pictures come out so trash... Yellow is 2 cubes sealed, Blue is 4th order 1:1 tuned to 60hz, Grey is ported 4.5 cubes tuned to 30hz.

 

[LosIsATool 5,000+ posts]

What exactly are you trying to accomplish? You can sacrifice bandwidth for SPL gain, but you can do the same with ported. IMO by the time you have a good musical bandwidth you may as well have just run sealed.

You mean

"May have well just run ported"

 

[hispls 5,000+ posts]

You mean"May have well just run ported"

Sealed. You have the very wide bandwidth, control of the cone, and give up the extra output of ported.

 

[LosIsATool 5,000+ posts]

Sealed. You have the very wide bandwidth, control of the cone, and give up the extra output of ported.

Get the same thing with ported with more control over the natural dips with more output.

That's why most that have to play 20-20k fairly flat are using ported now. Including myself.

 

[Jeffdachef 5,000+ posts]

I want the loudness of a ported box but the unlimited low end of a sealed box. I don't want to have to worry about playing music below the tuning frequency. Last setup I had was 4 15s tuned to 31hz. It was pretty loud but I didn't like how I had to be careful what songs I played and at what volume. And also it didn't have that great of transient response (like above 60hz). I actually enjoy the single Kicker CVR 12 in a 4.3 cube sealed box more.
Here's a pic of the comparisons I have right now. And Jeff I haven't read your post yet but I'm about to.

EDIT: Idk why my pictures come out so trash... Yellow is 2 cubes sealed, Blue is 4th order 1:1 tuned to 60hz, Grey is ported 4.5 cubes tuned to 30hz.

again... what you got sounds like a poor designed one "small group of notes" wonder box. My box is tuned to 36hz but it gets down with 22hz easily with not much variance in the volume knob and plays metal with the strong upper bass kicks fine as well.

Just because you had one experience doesnt mean you can lump all ported boxes sounding exactly like your box. Thats just plain ignorant.

 

[hispls 5,000+ posts]

Get the same thing with ported with more control over the natural dips with more output.That's why most that have to play 20-20k fairly flat are using ported now. Including myself.

Could be with proper consideration of drivers. 20-80 flat out of ported alignment (without EQ) is going to take some work.

 

[Jeffdachef 5,000+ posts]

Could be with proper consideration of drivers. 20-80 flat out of ported alignment (without EQ) is going to take some work.

there's always EQ involved when it comes to bass and flatness. Cabin gain's a *****. Luckily all i had to do on mines was knock off 50hz by 1 db on the EQ curve.