View Full Version : is this tuned right ??

08-07-2007, 04:47 PM

acording to me this box is tuned to 35 hz....what you think ??

BJ The Man
08-07-2007, 04:55 PM
depends on the ungiven side of the second port piece.

If the second port piece is about 13ish inches long then your at 35 an this is all w/o sub displacement at 5.8cuft

08-07-2007, 05:15 PM
actually the port is 18.53'' and the box with out displacements is 8.9 cubes....so the port displacement is 1.34 cubes and the sub displacement 0.26 cubes...(fi btl 18'') so the box would be 7.4 after all displacements right ??

08-07-2007, 05:21 PM
3/4 Inch wood?

08-07-2007, 05:33 PM
This was VERY quick math, so I would appreciate if someone checked it for me.

But I got...

4.6 cubic Feet
126"^2 of port area
27.53" of port lenght after end correction.

Tuning Freq=44hz.

08-07-2007, 05:37 PM
scratch my math...already found a mistake. Im working on it.

08-07-2007, 05:39 PM
6.9 cubes
126"^2 of port
27.5" of port (after end correction)


next time try and make the drawing a little more detailed ;), and a little closer up, had to really look to get some of those dimisions.

08-07-2007, 05:44 PM
yea it is 3/4 mdf...double bafle too..


so ?? what you think...this is tuned to

08-07-2007, 05:59 PM
bump..need some help here...:)

08-07-2007, 06:09 PM
Why in the hell would you put double stacked 3/4" strips at the end of the port wall?

That's awesome.

08-07-2007, 06:10 PM
6.35ft^3 net volume tuned to 35.98hz.

Not taking sub displacement in to calculation...

08-07-2007, 06:28 PM
you sure it is 6.3 ft3 bro ?? accordin to my maths it is 7.7after port displacement....lets see...


internal measurements...

21x21x35 = 8.9 ft3

port displacement 6x21x16.5 =1.20 ft3

so 8.9- 1.20 = 7.7 ft3 after port displacemen right ??

or let me know what im wrong please...

thank you bro

08-07-2007, 06:37 PM
PM sent with corrected figures for most recent box posted.

08-07-2007, 06:39 PM
http://img473.imageshack.us/img473/3018/cajonbtl182yz3.th.png (http://img473.imageshack.us/my.php?image=cajonbtl182yz3.png)

Redline should be your port length dimensions...

08-07-2007, 09:11 PM
I came up with 37

08-07-2007, 11:32 PM
That first one is 6.25 tuned to 38hz actually... not 44. The second design is 7 cubes at 37hz (actually closer to 36.75hz).

What are you actually looking for?


That's your port length and the shaded area is the area seen by the sub after port displacement. Multiply that area number by 21.75 and you have your net volume before sub displacement. After sub displacement, it's 7 cubes almost exactly. The length is about 26.25" after end correction.

08-08-2007, 12:04 PM
Thank you for the detailed picture Immacomputer.

Pm sent elkiko

08-08-2007, 01:13 PM
thanks inmmacomputer for your help..i really apreciatte...thanks triger bro for ya help too....

08-08-2007, 01:19 PM
you guys think 126 sq of port would be all right for the 18'' btl ??

08-08-2007, 01:36 PM
you guys think 126 sq of port would be all right for the 18'' btl ??

More in the range of 148-168...

But depending on how hard you actually push it daily. I highly doubt you will be listening to it daily @ full excursion, so you may be able to get away with 126 no problem.