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russrocks
08-25-2003, 07:58 PM
when calculating port air velocity, I understand that (by clicking the signal tab in the project window) you have to enter the drivers RMS value, but I dont understand why they ask for series resistance. Why would that affect port velocity? For instance, my sub is a D4, but Im going to wire it in parallel, should I enter 8 or should I enter 2? Also, do I keep the distance at 3.281 ft or should I change it to the distance between the drivers seat and sub box for best results?
When I was reading winISD's contents, it suggests to keep air velocity to under 17 meters/second. Are they for real? That seems really low, I would need a very big port to keep it that low. :banghead: I appreciate the help. Thanks!

russrocks
08-29-2003, 03:53 AM
I have one more question though..
in order to keep velocity under 30m/s, the port must be made bigger, thus longer. But shouldnt the port be as short as possible also? How do you compromise?
My box is going to be 4 cubes tuned to 34 hz. If I use 2 3*7 ports, velocity peaks at ~ 25m/s (1000 watts on the sub), but the ports will be ~20 inches long. Im worried that the ports will be a little too long and sound like crap. It ***** being a nOOb.

bigred78797
08-29-2003, 10:32 AM
If you make the ports correctly and not crappy then they won't sound like crap. I have had ports longer than 48" and as long as they were sturdy and sealed they sounded wonderful. Just sand down the interior edges of the port and that will take away alot more port noise. My current port is ~78cm ( ~31 inches ) and it there is hardly any audible port noise and the port is less than 2 feet away from me. I wouldn't worry too much about it... half the fun in building the boxes is learning what works and what doesn't.

russrocks
08-29-2003, 12:28 PM
thanks for the info red.
building the box is the easy part, at least Im good at that lol. I just dont want to put alot of hours into it just to throw it away because of a little 'chuffing.