What is this box tuned too? Recommended calc/software..

[Lowkey 10+ year member]

So I had a friend (who builds boxes) build me a box. When I asked what he tuned it too he said "uhh like 32hz". I'd like to confirm the actual tuning. I'll try to include all the needed dimensions.

0.75" MDF Box as measured from the outside: 48" Wide by 17" Tall by 28" Deep

Port measured from the inside: 9" Wide by 14" Tall by 38" Long. Port is L shaped so I measured length from port opening to back wall and added that to the length of the divider that continued the port inside the box. (27" to the back wall and an 11" piece of wood going further into the box.) The width stayed 9". Hope that makes sense.

Its a double baffle so the top is 1.5" thick. He did 45 the corners but no other internal bracing. Driver Displacement 0.14 ft.³ / 3.96 L

Not sure if I'm missing anything, please let me know. Thanks in advance.

*If it matters, its two PSI platform 1 15's facing up, port on the right side facing back, 2200rms amp, in a 04" Tahoe*

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[ThxOne Premium Member]

Best I could do with WinISD. The boxes on the right show your subs in that box tuned to 32hz (all the yellow lines). The port would be too short. I adjusted the tune down to 25hz and it matched your port size (blue line). Play some test tones from 22hz to 32hz and see which frequency is making the cone move the least... in my guess by the graphs and the info you gave... should be near 25hz.

 

[ThxOne Premium Member]

Sorry, had to put the correct picture in there.

 

[ThxOne Premium Member]

Probably closer to 27 or 28hz. Speaker displacement and board thickness.

 

[Lowkey 10+ year member]

Probably closer to 27 or 28hz. Speaker displacement and board thickness.

That's excellent thank you. Hopefully these subs will do well tuned that low.

 

[Firewalker]

Make sure you set your subsonic 2-3 hz below the box tuning as well.

 

[Lowkey 10+ year member]

Probably closer to 27 or 28hz. Speaker displacement and board thickness.

I don't know if you can figure this out in winisd but I'm wondering what my port displacement is? I did some math based on what I read and I came up with 3cf. It was supposed to be an 8cf box since psi recommends 3.5 min ported. Wondering if I need to have this box rebuilt.

 

[ThxOne Premium Member]

I don't know if you can figure this out in winisd but I'm wondering what my port displacement is? I did some math based on what I read and I came up with 3cf. It was supposed to be an 8cf box since psi recommends 3.5 min ported. Wondering if I need to have this box rebuilt.

I'm not good at winIsd but the outside measurements put that box way over 8cu.ft.

 

[Lowkey 10+ year member]

I'm not good at winIsd but the outside measurements put that box way over 8cu.ft.

All good. I'm pretty sure I have 10 cubic feet after driver displacement and wood thickness. With 3 cubic feet going to port that leaves 7 cubic feet of usable volume.

I know I've seen a general rule of thumb should be 16 square inches per cubic foot. My box after port/driver displacement is 7 cubes so 7x16 would be 112sq". In my case 3 cubes of port is 299". That's 43 square inches per foot, way way over 16

ignore that I got confused and instead of figuring out port area just did total square inches of the entire port

 

[Buck 5,000+ posts]

Internally with 48w x 17h x 28d, that's ~10.5 cubes internally (including all sides and double baffle, nothing else).

Just based off your paragraph, I would say you're at like 7-7.5 cubes net @ ~31-32 hz. Idk how big the 45's are. It's just a rough guess.

I think you have too much port area. You're at like ~17+ in^2/cube or so of port area, which is quite a lot if you're trying to have a musical box.

I would also highly suggest more bracing than just 45's and a double baffle. That box is 4 feet wide and over 2 feet deep.

 

[ThxOne Premium Member]

My math shows the inside of your port to be 2.886 cubic feet.

 

[Buck 5,000+ posts]

How is your port 14" tall? If it's a slot, it should be 14.75" tall.

 

[Lowkey 10+ year member]

Internally with 48w x 17h x 28d, that's ~10.5 cubes internally (including all sides and double baffle, nothing else).

Just based off your paragraph, I would say you're at like 7-7.5 cubes net @ ~31-32 hz. Idk how big the 45's are. It's just a rough guess.

I think you have too much port area. You're at like ~17+ in^2/cube or so of port area, which is quite a lot if you're trying to have a musical box.

I would also highly suggest more bracing than just 45's and a double baffle. That box is 4 feet wide and over 2 feet deep.

Yeah I actually think its probably 18 in^2/cube.

 

[Lowkey 10+ year member]

How is your port 14" tall? If it's a slot, it should be 14.75" tall.

I measured it again just now, internally it looks to be 9X14.5 or very close to that.

 

[Buck 5,000+ posts]

I measured it again just now, internally it looks to be 9X14.5 or very close to that.

You have almost certainly too much port area.

Yeah, if the top and bottom sandwich, then your port should be ~14.75 high.