Protege5

i had this in another thread but it was so off topic from what it started as, i thought id start a new 1

anyways, i want to build about a 2.0-2.5 cuft box with a port tuned to around 30hz. (just for info i have a 1001bd and S12L5). i just wanted to know what port size i should try with. i know your supposed to do trial and error but i dont even know what size to start with and how much to take off each time i do it and such. so if anyone can give me some help. thanks guys

WD21

Well if your going to use a round port u shouldnt use any thing smaller than 4" in diamater (inless its an aero port but i dont think they make them smaller then that)b/c u will get port noise. If you make a slot or square port, use a router on the start and end of the port, i found that that took alot of my port noise away. For length i belive that u talk off 1/4" at a time but im not sure. Any way i hope that helps a bit.

Protege5

how long should i start with like 12" 15" 18"?

seege

iTrader: (1)

If you are tuning a box to a given frequency, you do not have to use trial and error; there is a set of parameters that can calculate to within 1 Hz of the frequency the box is tuned to. Trial and error is only really useful for SPL applications where you cannot possibly take into consideration every variable affecting SPL. The formula on this page is what I use:
http://www.jlaudio.com/tutorials/ports/index.html
It is for 20 degrees celsius and 101 KPa, but can be easily manipulated to account for changes in temperature and pressure.
You can also download programs such as winisd that will do the calculations for you automatically.