4th order plus cabin gain

[20 hz bass machine Premium Member]

Haven't been around in awhile so first things first, how is everyone doing?
Me and my brother want to modify our bass build and put in a 4th order. We are currently running 4 8" X8 sundowns in a ported blow through in a 2000 ford ranger.
We want to put in 2 zv5 15s with a blow through 4th order and I'm wondering if anyone can relate with/ confirm or deny my thought process.
I understand that a 4th has a very peaky response and is good for a one hit wonder build. I've also been looking into cabin gain a lot recently and in our particular situation we are dealing with an extremely small cabin that starts loading around 60hz which is (as of now) where I'm thinking we would tune the front chamber
My thought process is that we will have a huge peak in spl at the tuning frequency but then cabin gain will take over and give a much flatter response than modeling software is showing. On top of this a 4th should give us a more "accurate" and "punchy" sound that we might otherwise be lacking with a ported or 6th order enclosure.
What are your thoughts on this? Am I completely misunderstanding what cabin gain can do for a system or am I on the right track?
Thanks in advance

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[THATpurpleKUSH 5,000+ posts]

The peakiness of a 4th order depends on the ported to sealed ratio. The larger the ported side is the peakier it will play.

Enlarge the sealed side and keep the ported side the same if you want it to play flat. But be careful because a large sealed side will allow the sub to reach its physical excursion limit faster.

There is a compromise you will need to balance and using design software like Bass Box Pro will greatly help the design.

 

[20 hz bass machine Premium Member]

The peakiness of a 4th order depends on the ported to sealed ratio. The larger the ported side is the peakier it will play.

Enlarge the sealed side and keep the ported side the same if you want it to play flat. But be careful because a large sealed side will allow the sub to reach its physical excursion limit faster.

There is a compromise you will need to balance and using design software like Bass Box Pro will greatly help the design.

I'm thinking 1 to 1 to try and get the response flatter. I toyed with a design on bass box pro and had 5MM of excursion to spare. That being said, I would pay to have the box designed by mark from car audio fabrication because I dont trust my modeling skills with a 4th. Sundown recommends 4.25 cubes for a ported box per sub. There is no info on sealed volume. Is 4.25 a good number to use per sub?

 

[THATpurpleKUSH 5,000+ posts]

I would start on the small side and go from there and keep playing around with Bass Box. It's great you have that program, it will get you in the ballpark and then you can have the final design done by an experienced professional.

See where 3cf per side puts you in terms of cone excursion and adjust accordingly. Try tuning in the upper 40s and adjust from there as well.

 

[20 hz bass machine Premium Member]

I would start on the small side and go from there and keep playing around with Bass Box. It's great you have that program, it will get you in the ballpark and then you can have the final design done by an experienced professional.

See where 3cf per side puts you in terms of cone excursion and adjust accordingly. Try tuning in the upper 40s and adjust from there as well.

Thank you sir. Will keep everyone posted on the progress of the build!