Basics of a 4th order bandpass enclosure

[silashinkle03]

I am fairly new to the audio world, started about 2 years ago. First tried a small tang band 6.5 in a t-line and have been hooked ever since! Converting a center seat of a 04 F-150 into a 4th order band pass enclosure in a way it will look stock with the fold down arm rest, cushion, and carpet. I must say out of all the research and planning I have done for this project, you explained it in a way that a baby blue bird in a new day could understand! Appreciate the post brother. I'll post some pictures of the project throughout the build.

[OzzieComm]

An excellent write up, I have an old school pioneer free air sub (high Fs) that I might test this out on.

[OzzieComm]

box being built now..

[OzzieComm]

Box built and sounds great to me, I think it sounds better than my 2 12's in a ported box.

Never going to break any SPL records... but the 4th's are awesome !

My build log here with pics.

[hoit]

Fs and qts are specs in the thiele/small parameters.

[hoit]

Fs and qts are specs in the thiele/small parameters.

[BIG_KNOCKS]

I have a single cvx15 that I'm playing with and I have decided to build a single reflex bandpass for it. Can somebody help me out with some killer gross internal specs! I need square inch port opening and depth tuned at 45hertz as well I'm a carpenter so the build will not be hard

[Inspiron100]

Are the measurements of 2:1 or 3:1 etc...before or after the displacements?

[lucifer3030]

hey there, quick question. I have been designing a 4th order for a small 12, but all the calculators are telling me to have my sealed section twice as large as the ported. this doesn't seem right to me from everything I've been reading. Example, the last calc I did was telling me to go .9 in the ported and 1.67 in the sealed chamber. its for a dd512, nothing fancy, I like showing people what you can achieve with the "right" enclosure for the sub

[Triticum Agricolam]

With bandpass boxes, the chamber sizes are going to greatly depend on what you are trying to do. Bandpass boxes can have great bandwidth, but they won't be very efficient, or they can be very efficient, but only over a very limited frequency range. Everything is a trade off.

Keep in mind that a bandpass box is probably not going to be the "right" enclosure for your sub, depending on your particular application. The vast majority of the time, a well designed ported box is going to serve you better. CleanSierra had an excellent comment on bandpass boxes:

If the purpose of building a 4th BP is to experiment, let loose and get at it. If you're BOUND by some sort of constraints that ONLY allows a bandpass enclosure, I understand and see the need. If you're wanting a bandpass because you think it will hammer lows or be a flatter response or thinking it will outperform a standard ported enclosure(which is a 4th order btw), move on and forget it.