box question (again)

[benz280se 0]

i have a box i was using for some other woofers in that i put to use in my trunk. here are the measurements 35x16x16 with divider and two four inch ports 8" long each i kinda wanna stay with this box for now because it fits perfectly. the problem is tuning what is this box tuned to and what should i change with the ports? the wood is 3/4 mdf. any suggestions? thanks oh yeah in case you didnt know 2 fi ssd12's copper option in the box.

[shizzzon 461]

If i calculated right, i'm getting 41.5hz tuning and looks to need the subsonic filter set right above 30hz if giving optimal power. Anything more and the filter needs to be set higher.

I got 1.99 cubes per sub, 0.14 displacement for the sub and 0.527 displacement for the port per chamber.

That comes out to be 1.8 cubes per chamber exactly.

That port seems VERY small for 800wrms. If you were to crank the volume, does it sound like it stops getting louder at a point that you think it should still be getting louder?

[BKOLFO4 29]

Definitely not much port if they are not flared.

As far as tuning, you can't change it much due to the depth of the box. You could try 4" ports x 11.25" long to see if it sounds any better. that puts the port 4" from the back wall and lowers the tuning to around 37 Hz. The drop in airspace with the additional length of the tube is not enough to matter.

You could also experiment with adding polyfill to the box. Add it away from the port, so it will not affect the airflow through the port.

Brian

[benz280se 0]

thanks for the info. the box does seem to have a nasty cutoff when i crank it. ill try playing with the ports and make em the 11.25" i have plenty of polyfill so thats going in there too. i dont have a subsonic filter so i cant do anything about that. the amp is the old school us amps400 no filters, no bass knobs, just power! and i have two batteries, running off the stock alt but vol drop isnt too bad. if i were to go bigger with the ports what should be the measurments for this box? i dont mind altering the box to do this cause this one is temp anyway but i know it can sound better. thanks folks

ps the ports arent flared just pvc pipe from lowes hardware lol

Edited February 22, 2008 by benz280se

[benz280se 0]

http://www.the12volt.com/caraudio/boxcalcs.asp#por did a search last night and found this which tells me what you guys just said, without the polyfill info. according to this i could make the port 14" and get 33hz tuning and i would just have part of the port protruding out of the box to give it some room on the inside. i'll try it today and and let you know wassup.

[BKOLFO4 29]

If you don't mind the ports sticking out, make them 14" long and push them into the box so they are no more than 4" from the back wall. . .

[benz280se 0]

i just finished putting the new ports in, almost exactly 4" from the back wall, what a big friggin difference! i played my favorite low song "moonstone" by bass mekanik and the benz emblem on my hood was actually shaking!! i cant wait to build a box to specs. thnks for your help i should have some new vids up tomorrow so you can see how yall's knowledge helped me out.