18" Btl Box

[Joker]

Need someone to lookover my math , specifically the tune area .

Max outside dimensions : 18" H x 29" W x 42"L using 3/4" MDF = 10.63cuft internal volume .

Sub up / slot port back , 6.75" internal width slot port x 16.5" H x 30" L , I am getting anywhere from 29.5Hz - 30.7Hz using different online calculators.

Was shooting for 30Hz fwiw .

With sub in the box 10.63cuft - .26cuft = 10.37cuft before port .

Total port displacement 7.5" W x 16.5" H x 30" L = 3712.5" divided by 1728 = 2.15cuft

2.15cuft - 10.37cuft = 8.22cuft

Final ~ 8.22cuft @ 29.5-31Hz , 111.375sq in of port area

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Rule of thumb ratios I see to go by :

Portlength/width ratio , keep it under 9:1 / Mine ~ 30" Length divded by 6.75" width = 4.44:1

Fi wants inbetween 12-16sq in port area per cube / Mine ~ 111.375sq in divided by 8.22cuft = 13.55sq in per cube

I am going to double baffle the top so max outside height will be 18.75" , probably add some bracing so that will eat a little bit .

[AI James]

what power?

[Joker]

Sundown SAZ-3500D

[Joker]

Never thought I would be saying this seeing the car the box is going into but I can go smaller cuft if it will be safer on that power .

Dropping the Depth from 42" to 38" with the same 30" port length would put it at a final 7.17cuft @ 32-34Hz if my calculations are correct .

Same port area .

[AI James]

yea go closer to 6 cubes if your putting that whole amp on it

[Joker]

Hows this one look ..

17"h x 29"w x 38"d

6.8cuft @ 29.3-30.4Hz depending on calculator .

6" port x 15.5"h = 93 sq in port area , 13.68sq in per cuft . Port 32"L having a 5.3:1 ratio .

[Joker]

Also another ~

17"h x 29"w x 34"d

6.11cuft @ 32.76 - 34Hz depending on calculator .

6" port x 15.5"h = 93 sq in port area , 15.22sq in per cuft . Port 27.25"L having a 4.5:1 ratio .

[AI James]

last one sound nice to me