# how to find out what my box is tuned to when i bought it used



## locologan (Apr 1, 2011)

i bot a use fi bl 15' in a custom ported box i wanna know how to find out what the box was tuned to and how to find out what the sub has done to it like the upgrades thanks for you help


----------



## Sonically_Sound (May 26, 2011)

what are the dimensions of it?


----------



## locologan (Apr 1, 2011)

lenght is 36 3/4 inches
width is 16 1/2
and depth is 15 3/4 

2 sqaure ports that are 7x3


----------



## sqshoestring (Jun 19, 2007)

You can also play tones/sweep into it at a medium volume and when it unloads the air will blow out the ports. Above that the port will play hard and xmax of sub will be less that is tuning. Little higher frequency the sub will start to move more and stay the same on up.


----------



## locologan (Apr 1, 2011)

so what is it tuned to would you know and is the box for a lower bass?


----------



## papabearsc (Oct 2, 2010)

What is length of the ports?


----------



## locologan (Apr 1, 2011)

7 inchs by 3 inchs


----------



## jalba (Dec 20, 2010)

3/4" mdf? dimension of any internal braces or interior baffles? Dimensions of the port divider? What is the length of the ports? You gave us the width and height.

Also, is that port divider just on the face or is there a divider running through the entire length of the port(s)?


----------



## humandrummachine (May 17, 2010)

its probably tuned around 28-36 cycles/hertz because the dimensions probably dont allow for that long of a port


----------



## nick650 (Feb 7, 2011)

play test tones. 

SQ told what I needed to look for in this post. Never new that (just hearing air is unloading of a ported sub)! Just try 25, 30,32,35,38 test tones and see were you just hear air and not allot of BOOM.


----------



## jalba (Dec 20, 2010)

humandrummachine said:


> its probably tuned around 28-36 cycles/hertz because the dimensions probably dont allow for that long of a port


Uhh, most boxes like that have L ports. An L port in that box could be up to 50" long, though not likely.


----------



## jalba (Dec 20, 2010)

If you can't tell how long the ports are, just take a tape measure and measure the short length of the L port (from face to rear of port). Then extend the tape measure and feed it into the port and turn it sideways to measure the length of the long part of the L port (perpindicular to the face). Just extend the tape, hold it flat against the interior wall, and let it slide back until it hits the end of the internal port opening. Add measurement 1 to measurement 2 to get the total port length. And specify if the port divider is only on the face or if it runs the entire length. Internal volume and port dimensions (and tuning) will vary greatly depending on this. If it's just on the face, then you essentially have a 98 sq. in. port area with a brace on the face. If they're separated internally as well, you have 42 sq. in. port area. Huge difference, and that brace (port divider) is probably just going to create a restriction and port noise.

But as of right now, if the ports are separate, plugged into BassBox 6 Pro with a Kicker CVR 15 (no data on an Fi), that box would be 32.14hz if the ports are 21" long, 27.04hz at 40", 34.92hz at 16".


----------



## dogsbark26 (Feb 10, 2009)

Wow, impressive jalba! Can you do that with cylindrical ports and triangular enclosures?


----------



## Brian Steele (Jun 1, 2007)

Best way is to measure it rather than trying to calculate it. Use your PC to generate a few test tone signals (there are number of freeware utilities that can do this for you) starting @50 Hz and working down to 25Hz or so and record them to CD. Then play them back through the sub. At Fb, the driver's cone should be barely moving, compared to when it's playing the other frequencies.


----------



## dogsbark26 (Feb 10, 2009)

I'll have to wait till I install it then. Or at least till I power up the amp. Thanks for reply.


----------



## jalba (Dec 20, 2010)

dogsbark26 said:


> Wow, impressive jalba! Can you do that with cylindrical ports and triangular enclosures?


I sure can. Shoot me a PM if you need some help, or grab a copy of Bassbox 6 Pro, it's what I use. It can be had for free if you know where to look, not that I condone that kind of thing. :shifty:


----------



## humandrummachine (May 17, 2010)

jalba said:


> Uhh, most boxes like that have L ports. An L port in that box could be up to 50" long, though not likely.



yeah i still think a 50" long port will still only allow a tuning around 28


----------



## jalba (Dec 20, 2010)

humandrummachine said:


> yeah i still think a 50" long port will still only allow a tuning around 28


In my post above you'll see that, when plugging in his exact box dimensions and assuming the ports are separated, they would yield 27hz at 40" length.


----------



## humandrummachine (May 17, 2010)

jalba said:


> In my post above you'll see that, when plugging in his exact box dimensions and assuming the ports are separated, they would yield 27hz at 40" length.


yeah saw that


----------



## locologan (Apr 1, 2011)

yes the ports are divided but not all the way threw it stops at the back of the box


----------



## jalba (Dec 20, 2010)

locologan said:


> yes the ports are divided but not all the way threw it stops at the back of the box


So then the port divider is a 3/4"x3"x?" long piece of mdf? What is the length? And what is the length of the port after it makes a 90 degree turn? If you really want an exact tuning, you're going to need to supply all the info I asked for in the previous posts, or just tune it by ear.


----------

