I don't think one of these exists, at least not actively (that i've seen), so let's start one up!
Here's what I know:
First, how it works-
With any bandpass enclosure (similar to banpass crossovers) you will have 2 cutoff frequencies/peaks.
Upper cutoff will be a higher frequency, lower cutoff will be a lower frequency.
beyond these two frequencies, output will taper. This is referred to as slope (more on this later).
all frequencies between and including the upper and lower cutoff frequency is referred to as the bandwidth.
Your bandwidth is, in essence, your frequency response. Your box is designed to play a certain range of frequencies before tapering at the cutoff frequencies.
There's some basic vocab, now let's move on.
Two different 6th order variations-
The difference between the two (by definition anyways)
Series tuned - rear chamber ports fire into the front chamber, or inside the box
Parallel tuned - rear chamber ported into the cabin (not into the box)
You've got two chambers
-rear ported chamber
-front ported chamber
Here's how they work
The rear chamber controls the lower half of the bandwidth
The front chamber controls the upper half of the bandwidth
Just like a regular ported box, the tuning frequency of a specific chamber controls the frequency response, then the box volume and port area control the output at that frequency.
So (like a 4th order) Larger rear chamber means more output at lower frequencies, and vice versa. Same applies to the front chamber.
The rear chamber is typically tuned between 28-35 hz (just like a regular ported box). Also, the rear chamber (usually) uses about half the port area as a typical ported box requires. There's some gray area here, but I usually use 5-8 sq inches per cube in the rear chamber.
The front chamber is usually tuned an octave above the rear chamber and uses a lot more port area (I use like 28-35 sq inches per cube).
an optional step once it's built - shrink the port area until you find a sweet spot.
A side note:
Most daily bandpass boxes are designed to have a nice flat response across a wide range of frequencies. The rumor of bandpasses being peaky and not very musical is simply not true of a properly designed box.
These are some very basic rules of thumb. Feel free to correct me, or add more to this.
Team Showtime Car Audio
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