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View Full Version : Is this tuning frequency correct..



bholtmeier
01-11-2007, 09:55 PM
I believe i found what i want to do with my new box, this should work great, i just needa know if this tuning frequency is about right.

internal volume of 3.39
port area of 39.75 sqin
port dimensions of
H:26.5" x W:1.5" x L:21"
tuning freq:~32hz

some reason i just re did it and i got 34hz about...someone check it for me.

bholtmeier
01-11-2007, 10:02 PM
Oh and also, they say to use 1:8 ration of HxW, i'm using like a 1:17 ratio, will i expect problems from that?

berserker
01-11-2007, 10:13 PM
I get 34.72 so 35 hz if that is your true net volume of 3.39 I didnt take away for port displacement I am assuming you did to get that volume and your length to width ratio of your vent is a too high with 17.7:1 you shouldnt go above 9:1 max

bholtmeier
01-12-2007, 12:17 AM
internal volume of 3.39
port area of 39.75 sqin
port dimensions of
H:18" x W:2.25" x L:21"
tuning freq:~32hz

those are my new ones, but i'm going to have to find some way to limit how tall it is to achieve the 1:8 ratio, if you remember how my box looks you may know what i'm talking about on how the height is kind of standard at 26.5" .....(box is 28" tall)

anyone have any suggestions?

http://i25.photobucket.com/albums/c77/slikrider20/photobucket.jpg

matt_martin87
01-12-2007, 01:40 AM
Is it possible to put 2 dividers throughout the port to shrink the ratio? I'm going to be helping with this build and I've almost given up hope on this box. If the internal dimensions of the port are 26.5" now, you take away 1.5 inches of mdf, and divide by three...that equals 8 1/3". Now you would have 3 ports each 1.5"x 8 1/3". This would satisfy the 1:8 port ratio. You would end up with a little less port area of course, but would this even work?

If you keep the net volume the same and do what's listed above, tuning comes out to be ~33.8hz according to my calculations.

berserker
01-12-2007, 02:02 AM
internal volume of 3.39
port area of 39.75 sqin
port dimensions of
H:18" x W:2.25" x L:21"
tuning freq:~32hz

Well with you new tweak and I believe you mean you have 40.5 in2 for port area and still assuming that is the true net at 3.39 cubes (although the Vb should’ve changed as you adjusted your plan and then in turn affecting your Fb), I get 35.01 so 35 Hz.

Also I would personally give that SI Mag, if that is what you are using from your signature, a little more port area. Use 12 – 15 square inches per cubic foot for a good rule of thumb, you are close but still below the minimum, remember port noise *****.

rpfuror
01-12-2007, 09:04 AM
I have never had problems going above the 8:1 ratio>> ANyone have any reading on this?

I have design and tested many boxes recently with the ratio over this and not heard any type of issue at full excursion.

bholtmeier
01-12-2007, 10:49 AM
Hmm....no port noise or anything with over a 8:1 ratio?

Some how we have to split this port into 2 or 3, to make the ratio more even, but i'm not even sure if thats really possible...

rpfuror
01-12-2007, 11:45 AM
I'm kinda confused about the whole thing.. are you doing a slot port running along the width of the box and trying to maintain the 8:1 ratio??? That pic is a little confusing... tell me wha tyou trying to do and I'll see if I can help.

bholtmeier
01-12-2007, 12:13 PM
Its confusing me too..initially i was going to try to do the port along the whole width of the box, but it would be impossible to stay at 9:1 or less doing that, so some how i have to create multiple openings for the port by puting dividers in there, or something. I dont know how it would work if it could though