To the 4th order wizards out there

[sxpimpin 10+ year member]

I'm pretty well set on doing a wall behind the c pillar in my cherokee now and id really like to do a fourth order just because of the potential of it with added power. I'm running a pair of aq hdc3 18s soon to be on 5k+ watt. I've easily got 19 cuft internal to deal with and i may be able to squeeze a couple more cuft by going around the wheels ect.

First off will this be enough space to make it worth while?

I was thinking 6.5 cuft into 12cuft with around 275/300 inches of port tuned around 50/55hz. What are your thoughts?

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[RAM_Designs 5,000+ posts]

You also have to take into consideration the port/sub/bracing displacements, which will definitely eat up some of that 19ft^3 that you have.

 

[i2ain2thunder 10+ year member]

May not wanna brace it with 2x4s.

 

[05fronty 5,000+ posts]

mine is gonna be braced with dowels

 

[surreal 10+ year member]

19 cubes is way more space than you need for a 4th for them. Doesnt matter as those subs are completely fit for a 4th. Not saying it cant be done right, but giving them a huge front chamber is NOT doing it right.

 

[galacticmonkey 5,000+ posts]

If you get around 2-2.25 sealed each, and the rest of the area ported, with 25in^ of port per cubic foot of ported airspace, tuned around 47hz, you should have big efficiency. You will lose some bandwidth, but it should play around 30-60hz pretty well.

On the other hand, you could go for around 6 sealed for the pair, and 9 ported, with around 200-225in^ of port at 45hz, you will lose some SPL, but will gain a good bit of low end bandwidth.

 

[Buck 5,000+ posts]

It just depends on what you want it to do. 4th orders can play a wide spectrum, or they can be loud in a more narrow spectrum. Some people hit very very loud scores with these at low frequencies.