About speaker boxes (enclosures) part 3 the Bandpass box
Continued from Part 2:
The bandpass:
Bandpass boxes come in 2 categories “4th order” and 6th order”. Both involve a box with separated chambers with a woofer on the wall separating the chambers. In a 4th order, one side is sealed and the other ported, and in a 6th order both chambers are ported.
The 4th order is for practical purposes (as far as function and sound) a variation of a sealed box. It will have the power handling properties and effieciency of a normal sealed box (within the passband), the only difference is that the bandpass will roll off the high frequency output quickly above the high tuning frequency. Since we generally use crossovers to filter unwanted frequencies, there is really no benefit to this. The 6th order will perform more like a ported box and is preferable to a 4th order.
Beyond “looking cool” with plexiglass sides and neon inside, the only real practical use for this sort of design in a car is that all the sound comes out of the port. This will require a very large port (preferably fluted) to avoid port noise, of course, the benefit being, the box can be in a trunk or the bed of a pickup (or otherwise out of the way) and the sound can be brought into the listening area through a port. This sometimes looks very nice, and is a practical solution for creative installing in certain vehicles.
Another downside is their sensitivity. Speake selection is crucial. Most woofers just plain don’t perform well in a bandpass enclosure. If your application really calls for it, do your homework first! Make sure the driver you select will give good sound (we’ll cover this later), and can do the job in a realistic volume box.
Next, bandpass boxes are very sensitive to error. If your calculations are off a bit, your performance will suffer dramatically and things will sound plain awful. After all is said and done, often even in optimum situations you’ll need some equalization to really smooth things out.
Almost every prefabricated bandpass box is of the 4th order variety, and most of the ones I’ve seen are rather poor sounding. I would suggest only chosing bandpass if you really have a good reason, have taken great care in selecting a good driver, are well versed with box building in general, and are certain of your ability to build to precise specifications. Stick to 6th order if possible, and tripple check all your measurements and calculations. If you do plan on purchasing a pre-made one, there are probably a few good ones out there, but be sure to perform some rigorous auditioning with many different program materials before deciding on a possibly inferior sounding box that “looks cool” and plays a loud 50hz note.
One common myth to put to rest is that bandpass boxes damage your woofers. This is not true. What damages woofers is powering them beyond their thermal or mechanical limits (”clipping” your amp or otherwise running a DC current falls into this category). The issue with a bandpass box is that it’s not as noticable when the speaker or amp is clipping, distorting heavily, or bottoming out. So the issue isn’t the box changing the speakers power handling, it’s the box hiding a sound that would normally be a warning sign to turn things down.
In summary, if you are careful in equipment selection and design, bandpass boxes can provide great sound and some flexible install options for some stunning or creative effects.
Stay tuned for part 4……
To be continued…..
What is a Bandpass subwoofer enclosure? [Read More...]
Q-Forms Kick Panel Speaker Enclosures [Read More...]
Q-Customs Factory-fit Vehicle Specific Speaker and Subwoofer Box [Read More...]
The bandpass:
Bandpass boxes come in 2 categories "4th order" and 6th order". Both involve a box with separated chambers with a woofer on the wall separating the chambers. In a 4th order, one side is sealed and the other ported, and in a 6th order both chambers are ported.
The 4th order is for practical purposes (as far as function and sound) a va...
Click here to go back to the original article