Advantages of a 4th Order

[NoCoSPL]

I have been hearing about these more and more often. Are they better than a regular slot port? What makes them better or worse?

Advantages?

Disadvantages?

[PV Audio]

Well, first things first: 4th order is a misnomer around here. When people here talk about 4th orders, they are almost always talking about 4th order bandpasses. A 4th order is simply a type of enclosure that has a specific roll-off rate: 24db/octave. A ported box is a type of 4th order enclosure.

Now, with the technicalities out of the way, a 4th order bandpass enclosure is one of the most if not the most common design out there in mass manufactured enclosures. Why? It gets loud easily. Why not always use them? Because 95% of them sound like a diarrhea covered clarinet being played through a walrus. All bandpass enclosures are very tricky to design and even trickier to get good at designing them.

Note: not all speakers should be put in bandpass enclosures. I still cannot understand people putting SQ speakers in bandpasses because what the BP does is give you great output, but typically over a smaller range of frequencies. Putting Alpine Type Xs, IDMAXs and JL W6V2s in bandpasses is a complete waste of the speaker's purpose. Nor am I saying that a specific set of parameters is needed for something to be recommended for a BP. It's really down to personal choice and the intuition of the designer. That intuition is hard to come by, even on here. The amount of people you should be hiring to design your BP enclosure I can count on one hand, and I am definitely NOT one of them.

[sexy]

Ported enclosures have a steeper roll off than sealed boxes. The roll off is fourth order, or 24dB for every halving of the frequency below the -3dB point. Below Fb, the displacement-limited power rating will be very low because the driver is essentially operating in free air. It is therefore wise to roll off the signal below the -3dB frequency to avoid damage.

[PIITB Wut Wut]

its like this

BandPass

____/--------------------------------\________ Db Slope

Regular Slot Port

_____________/-----\_________________________________ DB Slope

[NoCoSPL]

Dam, I need to do my research on octaves and slopes, I don't know exactly what they mean.

[DNick454]

Advantages of a properly designed 4th order bandpass enclosure include superb power handling (even down into the subsonic levels because of the sealed portion) and being able "get loud" (attributes commonly associated with ported boxes) while still sounding clean and having a good transient response (properties of a sealed enclosure).

All these statements are based on the assumption that you have a properly designed enclosure because BP's do have a steep roll-off so if not designed correctly, your band-pass response will be where you don't want it to be or you will have a really peaky sounding box (unless that's what you're going for of course)

[rusty_armadillo]

Dam, I need to do my research on octaves and slopes, I don't know exactly what they mean.

I totally agree there is way more science in enclosure design then I ever thought. I'm the audio guru with my friends but I feel like a retard here there's way more to this then I thought.

[PV Audio]

its like this

BandPass

____/--------------------------------\________ Db Slope

Regular Slot Port

_____________/-----\_________________________________ DB Slope

If you're implying that a bandpass enclosure has a wider bandwidth than a ported enclosure, you couldn't be more wrong.

[ciaonzo]

If you're implying that a bandpass enclosure has a wider bandwidth than a ported enclosure, you couldn't be more wrong.

I knew I could count on you to address that.