Help me with ports tuneing

[soloxp]

I have a question about ports calculator. I have a sonotube, that is 18x58, 8.5 or so cu.ft, with 2 ports thats 4x44" long tune to 16hz. Is this right. I went to 2 sites that you can calculate the ports and i came up with shorter ports to tune my sub to 16hz. Here are 2 screen shoots i did.

Thanks Solo

http://home.austin.rr.com/soloxp/images/pic/ports.JPG

http://home.austin.rr.com/soloxp/images/pic/ports1.JPG

[Notax]

8.5 cu.ft. is 241 L
4" is 101.6 mm, 2 times and efective half-diameter is 71.84 mm.
44" is 1118 mm long

Vb=(Rt*Rt*C*C)/(4*pi*Fb*Fb*(1.73*Rt+Lt))

Fb=12.76 Hz

For Fb=16 Hz you need Lt=665 mm or 26.2".

[soloxp]

Thanks Notax, but you lost me on ( Vb=(Rt*Rt*C*C)/(4*pi*Fb*Fb*(1.73*Rt+Lt) so I need to cut my ports down from 4x44" to 4x26.2" and that will tune me around 16hz. Right now what is it tune to now....10hz. Maybe that why i'm bottoming out to quick cause it's tune to low.

Thank

[Notax]

Originally posted by soloxp
so I need to cut my ports down from 4x44" to 4x26.2" and that will tune me around 16hz.

Yep!

Originally posted by soloxp
Right now what is it tune to now....10hz. [/B]

At 12.76 Hz.
Its the best you try several different lenghts, from 12-30" (12, 15, 18 21, 24, 27) and see (hear) for yourself what you prefer. Plastic water pipes (its cheap) 4" diametar times 2, and you cut different lenghts (two 4 " same lenght).

[soloxp]

Thanks Notax for helping me out on this. Don't get me wrong, it does sound good just the way it is now, real deep bass at lower volume. But I don't like it bottoming out at high volume. So I will play with several different lenghts this weekend.