4th order question

[Jake Pichola]

Since this is for home audio use I would VERY strongly encourage you to NOT use a band pass box. For your application they offer almost no advantages and have many drawbacks. You will be MUCH better served by a properly designed ported box.

What amp are you going to use to power this anyway?

im probably gonna go with the rockfrord prime r1200 cause they do rated and arent expensive

[Triticum Agricolam]

How are you planning on powering that in your apartment?

[Jake Pichola]

Since this is for home audio use I would VERY strongly encourage you to NOT use a band pass box. For your application they offer almost no advantages and have many drawbacks. You will be MUCH better served by a properly designed ported box.

What amp are you going to use to power this anyway?

do you think four of the hd200 12's in a bandpass would inside my car would be louder than the two sa15s ported? the sa15s are 8cu ft tuned to like 30 hz

[Triticum Agricolam]

Maybe, maybe not. There are too many variables for anyone to be able to give you a good answer.

[hispls]

No prob.

A 2 cube rear chamber, and 6 cube front chamber is a lot more reasonable numbers for those subs. For a rear chamber I would recommend increasing it a bit to 4 cubes, this will lower the QTC below .7 (which is good) and bring the sealed resonant frequency down below 50 Hz (also good). It will help you get better low frequency output.

35 Hz is way too low of a tuning for the front chamber. Most people tune their front chambers to between 40-50 hz, with 45 hz being a good compromise. If you know what frequency your vehicle peaks at you could tune to there (as long as its around 40-50 hz). Keep in mind that with a bandpass box output drops off pretty quickly above and below the tuning frequency. Its a very good idea to make the port removable or otherwise adjustable so you can tweak the tuning frequency after you play test the box.

For front chamber size, it depends on how peaky of output you want. The larger it is, the more output you will get, but only right around the tuning frequency. I think your plan of 6 cubes is a pretty reasonable starting point.

No prob.

A 2 cube rear chamber, and 6 cube front chamber is a lot more reasonable numbers for those subs. For a rear chamber I would recommend increasing it a bit to 4 cubes, this will lower the QTC below .7 (which is good) and bring the sealed resonant frequency down below 50 Hz (also good). It will help you get better low frequency output.

35 Hz is way too low of a tuning for the front chamber. Most people tune their front chambers to between 40-50 hz, with 45 hz being a good compromise. If you know what frequency your vehicle peaks at you could tune to there (as long as its around 40-50 hz). Keep in mind that with a bandpass box output drops off pretty quickly above and below the tuning frequency. Its a very good idea to make the port removable or otherwise adjustable so you can tweak the tuning frequency after you play test the box.

For front chamber size, it depends on how peaky of output you want. The larger it is, the more output you will get, but only right around the tuning frequency. I think your plan of 6 cubes is a pretty reasonable starting point.

ok cool, so with 4th order you want to tune the port higher than with just a ported box? because right now i have two sa15s tuned around 29-30 hertz and i like being able to go real low.(btw this project is for a stereo im building for my apartment)

The BANDPASS box will roll of on the high side at tuning frequency AND can deliver a peak somewhere within it's usable bandwidth. That's the point of "BANDPASS" it only allows the a passband through. The lower rolloff is controlled by the sub's performance in the sealed side and the high end rollof is controlled by the tuning of the ported side. The "ripple" (SPL gain) will vary depending on sub, size of the chambers, and also tuning.

There is NO general rule of thumb for ratios and tuning. You're totally flying blind if you don't use modeling software. Different subs perform very differently in that alignment. I will say that in general, if you get a wide and flat bandwidth you begin approaching performance off just a sealed box (losing the "gain" you'd get from a port). Any spl gains you get from this alignment will come at the expense of bandwidth.

[Jake Pichola]

How are you planning on powering that in your apartment?

i have a 1500 watt 12v power supply

[RooTxBeeR]

How are you planning on powering that in your apartment?

i have a 1500 watt 12v power supply

What kind of power supply is that? PC power supply?

[Triticum Agricolam]

How are you planning on powering that in your apartment?

i have a 1500 watt 12v power supply

Just my opinion, but there is no way I'd buy a car amp for home audio use. Its one thing to use one if you already have it, but if you are going to buy something, just get an amp that plugs into the wall, here is one example: https://www.parts-express.com/behringer-nu3000dsp-inuke-3000-watt-power-amplifier-with-dsp--248-6706

That amp puts out considerably more power than the RF one, has very powerful digital signal processing capability, and doesn't require any funky power supply solution.