4th order pointless after the advent of SPL drivers?

[Beatin' 10+ year member]

Is the 4th order sub box (not wall builds..) basically dead due to these subs with bigger motors and excursion?

I figure 4th orders were popular for when subs weren't all that powerfull so 4th orders really helped with output. But now with these weapon-looking subwoofers out there, is there a point to building complex 4th orders compared to ported boxes? These subs are very efficient in the upper frequencies, and the bass reflex ported box will bump up the lower frequencies.......kinda sounds like 4th order boxes have no place anymore......

discuss....

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[hispls 5,000+ posts]

I'm not impressed with them. Pretty much a worse-sealed box IMO.

 

[T.I.K. 10+ year member]

[quote name='hispls']I'm not impressed with them. Pretty much a worse-sealed box IMO.[/QUOTE]
I never understood how they offered more or similar output than a ported box. You're still trapping the back/front wave in the sealed portion of the box.

I'm sure @DbDesigns will have a very different song to sing about bandpass boxes though.

 

[98GCLimited 10+ year member]

A 4th order builds pressure inside the ported section due to the loading wall and increases the velocity of the air movement created by the woofers (all the air goes through the port which is generally half the size of cone area or smaller) and a 4th order allows you to tune the ported section to a higher frequency (spl boxes are generally tuned higher for larger numbers on meter) while still being able to play way below tuning without unloading because of the sealed section acting as part of the suspension for the woofers.

I understand though what you are saying about trapping the rear wave in the sealed section but there are good things about 4ths. A 4th is not a magic box and not all woofers perform well or better in 4ths than they do in a more traditional ported or sealed enclosure.

 

[T3mpest 10+ year member]

a fourth order is just a sealed chamber on the back end and the front chamber is a port. This works best with drivers that like sealed enclosures. It does have some advantages. Since all the output is filtered through a port, the higher order harmonic distortion is filtered out. Just like a regular ported box you gain reduced cone excursion near tuning as well. A well designed 4th order can play very flat, but over a limited bandwidth. You tune so that the 60hz area where alot of sub fall off in the car is boosted, and a low q low fs sub will still have plenty of output below the tuning point as the back of the cone is still under control and the low frequencies aren't filtered like the high frequency distortion is. So yeah, the can be used, but no, generally most car audio woofers are better suited to a ported box or 6th order.

 

[RangerDangerV2 5,000+ posts]

alright, the problem is that most people are not building 4th orders correctly. Yes, you are losing one wave, but in fact, that is a good thing. It keeps the woofer in check with more power. 4th orders are incredibly efficient, especially large ratio (4:1 and up), plus, they have a very wide bandwidth, of course, this depends on design. Now, to properly build a 4th order, you need to start with the sealed chamber. Take your woofers Vas, and divide it by the volume that you think the rear should be in liters, now for an sa12, that would be 21.21/28.3168, then you add 1, which will give you 1.749, now, take the square root of that number =1.323 and now multiply that by the Fs of the driver so you would get 44.569 because the Fs of the sa12 is 33.7hz. Now, the 44.569 that you just got is called the sealed chamber resonance, this is simply just a mathematical guess, but it is a start. I prefer an Fc of about 45-52, depending on the application.

So now you have your sealed chamber size, now, pick what ratio you want to do, I am a fan of large ratio 4ths, simply because of the gained output, but they tend to lack in a transient response and low end (although still much better than that of a bass reflex enclosure because the sealed enclosure has a slow roll off), the ratio that you pick will depend on what sort of efficiency, goals, and space you have.

Now you are almost there, build the sealed chamber, and the ported (front chamber) now the port area should be about half that of the cone area, at least thats where I like to start at, but this will depend on goals and woofers as well. Now, build your enclosure that you have designed, but leave the loading wall off.

the next step is to find the actual sealed resonance of the rear chamber, you can do this with a DATS, or a meter, but I prefer my DATS. if you use a dats, run an impedence sweep and see at what frequency your impedence peaks at, then tune your front chamber to that frequency. The same can be accomplished with a meter and a sine sweep, but like I said, a DATS is the prefered method.

So why a 4th you say? WHEN DESIGNED AND BUILT PROPERLY they can give the woofers a much higher mechanical power handling, have superb low end, play a very large bandwidth, very flat. They are super efficient, the can pretty much do it all. I am not saying that the 4th is the end all be all for any system, I love the ones I have built, and maybe if you feel up to it, you should try one someday, you just might be pleasantly surprised. I am skimping on a lot of info here, simply because it would take me far too long to type all of it.

 

[SounDrive Pro Seller]

You also have to remember that some drivers simply won't perform well in 4th order applications.

 

[RangerDangerV2 5,000+ posts]

You also have to remember that some drivers simply won't perform well in 4th order applications.

exactly, like I said, I skimped on some info, but if you run the numbers and find that you need a retarded large rear for you woofer, then it is not suitable for a 4th, but this could be solved by finding the EBP of the woofer before you even started running numbers.

 

[i2ain2thunder 10+ year member]

I still love my wicked one. not a 4th order, but bandpass horns just sound so good, tight, fast and accurate. Sure everyone gets louder than me, sure sealed has better sound quality, but nothing compares to the speed, and gain through the entire spectrum a sub uses.

Stupid loud ported setups are fun, but I don't want it in my daily. I do miss killing the lows though.

Sealed are just not quite enough output.

I found my middle ground and I'm happy.

I really don't think anyone knows how to make a really good 4th order, or 6th order.

 

[RangerDangerV2 5,000+ posts]

I still love my wicked one. not a 4th order, but bandpass horns just sound so good, tight, fast and accurate. Sure everyone gets louder than me, sure sealed has better sound quality, but nothing compares to the speed, and gain through the entire spectrum a sub uses.
Stupid loud ported setups are fun, but I don't want it in my daily. I do miss killing the lows though.

Sealed are just not quite enough output.

I found my middle ground and I'm happy.

I really don't think anyone knows how to make a really good 4th order, or 6th order.

all about testing.

 

[mlstrass 5,000+ posts]

4th orders seem more popular then ever right now. Most people who want to get loud down into the 20's seem to have success with them...

I just did one in a burban with 8 15's. Sounds pretty good on real music at normal volumes and is LOUD at 30hz & 40Hz. Perfect for demo'ing all the crappy rap music out there.

 

[RangerDangerV2 5,000+ posts]

4th orders seem more popular then ever right now. Most people who want to get loud down into the 20's seem to have success with them...
I just did one in a burban with 8 15's. Sounds pretty good on real music at normal volumes and is LOUD at 30hz & 40Hz. Perfect for demo'ing all the crappy rap music out there.

they arent just for lows... shrink that rear chamber and do a 5:1 ratio and you can burp all day. super efficient, super high mechanical power handling. just need a strong coil. thats why people us the DDZ in ratio ******... there was a van at slamology with a large ratio 4th with 2 18s and im pretty sure it was 60s capable

 

[Jroo 10+ year member]

Im not a design expert on the design part, but I have liked 4ths for years and used them several times. There are a couple of big issues I see and hear with 4ths. 1) The person that designed it didnt really know how to or gave a real generic 4th order design. 2) Somebody used a driver that doesnt really work in a 4th. Its all in the design and the speaker choice. Let me go on record and say that I have always pretty much been a sealed guy. I lean more towards the SQ side of things and the ported boxes I heard were really loud and hit hard, but werent very musical. Sure a ported box can certainly do SQ and be musical, but on the street you usually just hear loud as ****. I judge most systems by what i hear on the street not going to some sq contest. I know I know, all my opinion

A well done forth is basically a sealed box with more output in a desired range. The range or the bandwidth can be narrow or wide, all in the design. How much more output you get, again all in the design of the 4th. It doesnt matter if the sub is new or old, the basic idea is to make it louder over a desired range and tweek the roll off. Ive seen these random designs were someone said make it a 3 to 1 ratio or a 4 to 1 ratio and those can work, but those kind of 4ths usually end up being stupid loud over a very small bandwidth. The last 4th I had was slightly bigger than a 1 to 1 ratio with a higher tuning. Basically I could play 70 down pretty flat and it was louder over the whole range compared to the same driver in a sealed box. Basically it acted like a sealed box but louder. I dont have massive ports and and a huge ported section.

So the OP, the point Im trying to make is a 4th certainly has a benefit if done right. Some of the new mega watt, crazy magnet, 80 pound subs can work in a 4th if the specs of the sub are right. The bigger piece is making sure you have a good design. More often than not when you hear a bad 4th that is peaky or not musical, it was a bad design out of the gate.

 

[vetkilr 10+ year member]

4th orders to me, when built by someone who knows what they are doing are the best enclosures there are. They play flat, are efficient and will kill the lows. Most subs will play in 4th's sometimes its as simple as getting your sub built with one less spider. Here a small video of my 4th with 2 DC level 4"s on a bc3500 with a measured rise to over 4 ohms...so you do the math 1000 watts maybe. It is much better now that I have 2 bc3500's strapped to lower the rise. I had these same subs in a ported box(a good one) with a rise to 1ohm and these same subs were no where near as loud.

 

[BlurredVision 10+ year member]

Majority of 4ths I've heard are skull cracking loud, but then again, I believe that same power/woofers in a flat wall would probably be louder