SOULMUSIC

iTrader: (8)

I'm doing a slight box rebuild .
I believe I read somewhere that the end (inside the box) of round ports should be no closer to a surface than the size of the port. ( ie 4" away from a wall for a 4" port)

What effect would putting the port at 3" or 2" from a surface have?
Would it diminish the airflow ability into/out of the ports by ALOT?

I ask because our ports are at about 3" from the bottom and I wonder if its worth the effort to add a couple baffles and raise them 1 1/2" ?

Father Yuli

iTrader: (17)

nice pics.

SOULMUSIC

iTrader: (8)

Ohhh. ok then Can't get away with lazy anymore huh...lol

Here's how close the ports are to the bottom and the port baffle that I would be adding onto to raise the ports without cutting them.

Dukk

Getting closer to a sidewall isn't so bad. If you get too close then the wall will start to 'shadow' the port and act as an extension, much like what happens with a slot vent that uses a wall for one side of the vent.

Closer to the bottom is a bigger deal. A full diameter or more is best but you can cheat down to half a diameter, ie 2" off the bottom for a 4" port, without much loss in performance.

SOULMUSIC

iTrader: (8)

Thanks Dukk. I'll probably only raise it 3/4", knowing now that it should be close enough to 4" that it shouldn't make much difference.

I really never had a clue or ever read about the "shadow" effect!
So it would change the tuning up or down just a bit to be close to a wall.
So being close to two walls(in a corner) would change the tuning even more !!...oooops

So even with the 4 ports the same lengths, the two double "shadowed" corner ports will be slightly off tune with the two center(not nearly as shadowed) ports?

Does it matter for any reason?

Father Yuli

iTrader: (17)

just put another peice of 3/4 mdf here...

SOULMUSIC

iTrader: (8)

Will do.

I'll come clean I guess..lol
This box was as perfect as I thought it would be, not perfect at all

First mistake was that I forgot about the 1 1/2"+ of the subs surround that stick out past the front baffle. So because of that, the two outside sub surrounds were coming within 1/2" of the rear plastic at higher excursion. Thats at about half power. a problem..

So far, I roughed in the new 3/4" recessed baffles and I'll be bracing, filling and applying resin to them later this week. That's my not so easy fix to give the subs a little more room to move.

Ohh yeah when I took the subs out, i noticed that the pressure had torn the alum. tape on one of the port collars and would have been falling of sometime REAL soon..
So THAT was the funny noise at higher volumes..
I'm gonna glue them this time or wrap alot more tape around them.

Father Yuli

iTrader: (17)

tape rips like that are common when using a crappy tape or not enough tape.

dont glue it, you will never be able to get it apart ever again. just use some good grade duct tape.

Dukk

Yes a corner will increase the effect - how much depends on how tight the port is into the corner. It's almost impossible to calculate and probably won't affect anything much anyway. If you were super bored you could test to see what each vent is tuned to and adjust the lengths but it would be work for likely no gain.

SOULMUSIC

iTrader: (8)

Got the port baffle cut and installed before the rain and snow came yesterday..
When I put the ports in I'll be sure to wrap the collars a few more times and skip the glue, thanks Yuli.

Dukk- The ports are at 3 3/4" off the bottom now , I'm really hoping that helps to bring down the tuning to closer to where I was expecting.
Since this box is for bassrace/daily I can see how checking the tuning of each port etc. etc. to gain a tenth or so would most likely not be worth it..thanks for saving me the time

a few pics