Measuring port tuning after box construction?

[Hintzyboy 5,000+ posts]

Is there any way to measure the port tuning AFTER you build your box? I am asking this because I am looking to build a box that will have a port that is angled on the outer end. If I use the formula in the JL tutorials, do I just use (L1 +L2)/2 for the Lv?? I have no problem with the math, but I want to make sure I am substituting my values right.

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[Immacomputer 10+ year member]

Use test tones and see where the cone has the least amount of movement. That will be close to the actual tuning frequency.

When I test mine, I hook it up to my computer and use winisd as a tone generator and slowly slide it and watch for lowest amount of cone movement.

 

[Hintzyboy 5,000+ posts]

Is there any way I can save that sweep to a CD? If not, how do you hook up your sub to your computer?

 

[Immacomputer 10+ year member]

It's not used as a sweep but as a tone generator. You drag the crosshair to different frequencies and it plays them.

To hook it up, I use a small profile a200xl amp being powered by a computer power supply and I use an 1/8" to RCA cable to connect the computer to the amp. I use the gain as a volume knob since I'm only concerned with excursion.

Using test tones is accurate enough, especially if you use these tones which are in .5hz steps:

http://files.filefront.com/Toneszip/;6431032;;/fileinfo.html

 

[Hintzyboy 5,000+ posts]

Now if I substitute Lv for the L1 and L2 of the slant-ended port, do you think that will allow me to calculate a fairly accurate port tuning? I just don't want to end up building a bunch of boxes trying to find the right tuning.

 

[Immacomputer 10+ year member]

Just use winisd for port legth numbers. It's very accurate and saves a good amount of time.

 

[tommyk90 5,000+ posts]

Just use winisd for port legth numbers. It's very accurate and saves a good amount of time.

WinISD doesn't calculate for port displacement. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[Hintzyboy 5,000+ posts]

Any idea how much id would change my tuning if I had 2 4" aero ports that had like a 22" length on one side and a 26" length on the other side vs 2 4" ports with a solid 24" length?

 

[Hintzyboy 5,000+ posts]

Is there any disadvantage to using thin and long ports (talking about the face of the port, not the actual length)? Like would port noise increase with thinner, longe port, even though they have the same area?

 

[Volenti 10+ year member]

Is there any disadvantage to using thin and long ports (talking about the face of the port, not the actual length)? Like would port noise increase with thinner, longe port, even though they have the same area?

General rule of thumb is to not exceed a 10:1 ratio, width:height, the larger this ratio the more "lossy" the port becomes and output is reduced.

 

[Immacomputer 10+ year member]

WinISD doesn't calculate for port displacement. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

Correct. It doesn't build and design the enclosure for you but does tell you the length you need given the net volume you tell it.

 

[tommyk90 5,000+ posts]

Correct. It doesn't build and design the enclosure for you but does tell you the length you need given the net volume you tell it.

Yup.

Thats what I used to use it for. I would calculate the net box space I wanted, figured out with WinISD what the port size needed to be (and how much airspace it took up), added those two together and got the gross size I needed to make the box.

That is, until I made my own box program that does all that stuff for me. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[j3bus2k3 5,000+ posts]

Is there any way to measure the port tuning AFTER you build your box? I am asking this because I am looking to build a box that will have a port that is angled on the outer end. If I use the formula in the JL tutorials, do I just use (L1 +L2)/2 for the Lv?? I have no problem with the math, but I want to make sure I am substituting my values right.

Uh...if your using the formula off JL site just plug in the numbers and viola, it gives you your tuning...