I've been using a sub & box combo that I picked up at a local car audio store a few years ago to get me by and have recently begun thinking about upgrading. So I've been reading up and just trying to educate myself on the matter and tonight I went out to try and calculate the box volume and tune of the ports. Just wondered if I figured this out right. I used a calculator here (the vent length calculator at the bottom). I had the vent length so I swapped frequencies in and out until I got one to match.

Here's what I know. The box contains 2 10s. It's 30.5" wide, 13" tall, 9.5" deep at the top and 12" deep at the bottom (so I used an average depth of 10.75"). When I calculate those and divide by 1728 I get a volume of 2.47 cu.ft. which is probably close but not completely accurate because the measurements are from the outside and do not include the divider. The ports are 2.25" wide and about 4" deep.

By using that calculator I figured the tune to be about 39Hz. Does that sound about right? It didn't account for the size of the driver. Does that matter?

I've been using a sub & box combo that I picked up at a local car audio store a few years ago to get me by and have recently begun thinking about upgrading. So I've been reading up and just trying to educate myself on the matter and tonight I went out to try and calculate the box volume and tune of the ports. Just wondered if I figured this out right. I used a calculator here (the vent length calculator at the bottom). I had the vent length so I swapped frequencies in and out until I got one to match.

Here's what I know. The box contains 2 10s. It's 30.5" wide, 13" tall, 9.5" deep at the top and 12" deep at the bottom (so I used an average depth of 10.75"). When I calculate those and divide by 1728 I get a volume of 2.47 cu.ft. which is probably close but not completely accurate because the measurements are from the outside and do not include the divider. The ports are 2.25" wide and about 4" deep.

By using that calculator I figured the tune to be about 39Hz. Does that sound about right? It didn't account for the size of the driver. Does that matter?

how thick is the wood used in the box? to figure NET, all you need to do is subtract the wood thickness all the way around.

how many ports are there?

and if it's a prefab box, that tuning is going to be close. as you lose volume, and yep, sub and port displacement matter, tuning goes up. and most prefabs are in the 40-45hz area.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

how thick is the wood used in the box? to figure NET, all you need to do is subtract the wood thickness all the way around.

how many ports are there?

and if it's a prefab box, that tuning is going to be close. as you lose volume, and yep, sub and port displacement matter, tuning goes up. and most prefabs are in the 40-45hz area.

I'm not sure about the thickness because it was raining out there yesterday when I took the measurements and didn't want to stand in it while I removed all the screws holding the sub in to check. Yes it's a prefab so probably not more than .5 inch? Assuming so, that would make it 29" wide (subtracting the chamber divider), 12" tall and 9.75" avg depth for a total of 1.96 cu.ft net volume. There are 2 ports, one for each chamber.

Playing with the calculator again puts me around 44hz.

Thanks for your help

no problem.

some prefabs use 5/8th as well.

in anycase, that calculator is pretty close, and being prefab, i'd say that yoru tuning is indeed in that area.

yep, i'm agreeing with myself!

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee