4th order for 2 orion 12s box ratio help needed

[WoopdyWoppin]

Hey all, so I'm looking to build a 4th order for 2 Orion XtR 12s, i know how to desing and build it i just havent got a bloody clue what ratio i should make the sealed and ported sides, im looking at tuning in the mid 30s, also unsure as to what size port i should go with, wanting square, going in an 03 focus hatchback, any help would be appreciated

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[THATpurpleKUSH 5,000+ posts]

You don't tune 4th orders like standard bass reflex (ported) enclosures. Tuning in the mid 30s will allow you to only play up to about 45hz. Start with somewhere around a ported to sealed ratio of 2:1 - 3:1 tuned in the upper 40s. With port area between 16-20sq inches per cubic ft. What is the exact model of the sub you have and what amp are you planning on using?

 

[WoopdyWoppin]

Orion xtr 124d, 600rms each, on a hifonics brutus 1200 at 1ohm, on good stable electrical

 

[Boomin_tahoe 5,000+ posts]

Is that enough room for a 4th order in that small car?

 

[WoopdyWoppin]

Buddy of mine has a wall with 2 18s so, and the guy that did his wall has done 4 12s slide in boxes before, i took my seats out so im not worried about space

 

[THATpurpleKUSH 5,000+ posts]

I played around with them in BBP6 and they reach xmax on 1200rms in .8cf and up larger. They also didn't like a low ratio like 2:1, so go with 3:1 at the minimum but beware it gets a little peaky the higher the ratio is.

Do .6-.75cf for the sealed side and 2.4-3cf for the ported side with plenty of port area (minimum 16sq inches per cf). Also beware there is a sharp spike in group delay between 30-40hz regardless of what design you go with.

 

[WoopdyWoppin]

What do you mean by "sharp spike in group delay"?

 

[THATpurpleKUSH 5,000+ posts]

It will sound boomy.

It's going from 12ms at 30hz to 30ms at 37hz then back down to 12ms at 45hz.

Thats with .6 sealed 3 ported tuned to 45hz with 49sq inches of port area.

 

[WoopdyWoppin]

Ok, so i have .74 cubes for the sealed section, 2.6 for ported, with a 6 inch long 4 inch wide square aero port, does that sound about right?

 

[Boomin_tahoe 5,000+ posts]

Wondering why not a reg ported enclosure?

 

[WoopdyWoppin]

I have one currently, its not the greatest, i have a show coming up next weekend and i'd like to upgrade before then,

 

[THATpurpleKUSH 5,000+ posts]

Ok, so i have .74 cubes for the sealed section, 2.6 for ported, with a 6 inch long 4 inch wide square aero port, does that sound about right?

Go a tad smaller sealed or a tad larger ported and about 3x bigger on the port. The cones are moving are moving past xmax which means they could could become damaged if pushed too hard.

 

[WoopdyWoppin]

View attachment 26557356 hopefully that acreencap worked, thats doubling the port diameter and adding box

 

[THATpurpleKUSH 5,000+ posts]

View attachment 26557356 hopefully that acreencap worked, thats doubling the port diameter and adding box

That's not a good calculator to use. Nothing seems right about that. Aeroports are calculated different than slot ports.

Also you need to be using 3/4inch thick wood not 1/2 inch.

 

[WoopdyWoppin]

Hell maybe i should pay for a design then,