vent velocity to high?

[hayes55987 0]

Hey guys, i recently built a box for my 18" BL and i realized it doesnt really have the low end that I am looking for. So, I'm looking at blocking up one of my ports to lower the tuning. my question about this is the vent velocity. currently, its tuned to around 37Hz. if i blocked up one of the ports, i'd lower it down to 31Hz.

Vent velocity is what worries me though:

at 37Hz, I have a peak of 15.7m/s VV @ 25Hz

at 31Hz, I'd have a peak of 22.9m/s VV @ 22Hz; i reach 15.7m/s of VV with the 31Hz tuning @ 34Hz

Is it worth it? or will the port noise be to much? the group delay also jumps a little bit, but i'm not to worried about that because it all happens in the 24Hz range and below.

Total port area @ 37Hz is...61 in^2

it'd be...@ 31Hz...42 in^2

[NDMstang65 403]

Try it and see what it sounds like, modeling things like that really are not that accurate to a real world in car scenario...

Thanks

-Nick

[DevilDriver 28]

Slot ports? Flares? What type of ports do you have?

[hayes55987 0]

I have slot ports. dimensions are:

22" Deep, 2" High, 30.5" Wide however, i have braces along them and think I am going to block up one of the braced areas. It would bring my dimensions too

22" Deep, 2" High, 21" Wide

I think what I'm going to do is just try it and see how it sounds. I will just cut out the MDF, throw it into the port to seal it up, and if it sounds fine, figure out a more permanent seal with silicone and what not. if its not so good, then i'll take it back out and figure out what to do from there.

as for the box programs not being that accurate. I'm aware of the SPL and cabin gain and all those things being way different. but shouldn't the vent velocity be the same? I didn't think that much would differ based on whether it was in an automotive enviroment or not.

[NDMstang65 403]

2" is wayyyyyyy too narrow.

Generally speaking you want to keep at least 3" for a slot port...anything below that and you will run into some serious noise issues...

Thats going to knock you down to 42sq inches of port as well..

How much volume do you have?

Thanks

-Nick

[hayes55987 0]

my box volume is 5 cubic feet now

if i seal off one of the ports, i will have 5.15 cu ft

as for the narrowness, i probably should have rethought it and went higher. I was worried about about the mounting depth of the BL because i think i am somewhere around 1.5 to 2 inches of clearnace right now above the port. However, i definetely hsould have thought of it before and I'm sure i could have gotten creative with it.