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View Full Version : 2 questions...one thread. Formula for Air space in fiberglass enclosures and....



Sideways17
04-05-2009, 06:41 PM
Questions:

1) How do I figure airspace in a crazy fiberglass enclosure?

2) How do I change port tuning on a slot ported box? Every box I've ever built has been by company recommendations for their subs.

thegreatestpenn
04-05-2009, 06:44 PM
1) area is always lxwxh or whatever for squares and triangles so if u need to break the box into sections and then calculate separate areas then combine for the total value do that.

2) u can change tuning by adding chambers to the slot port or extending it

squeak12
04-05-2009, 09:00 PM
I would fill trash bags with known volumes of packing peanuts, etc. See how many of the known value will fit into the box.

If everything else remains constant, which will not be the case unless you have external ports:

Longer Port = Lower Tuning
Less Port Area = Lower Tuning
Less Net Volume = Lower Tuning

Sideways17
04-05-2009, 09:56 PM
I would fill trash bags with known volumes of packing peanuts, etc. See how many of the known value will fit into the box.

If everything else remains constant, which will not be the case unless you have external ports:

Longer Port = Lower Tuning
Less Port Area = Lower Tuning
Less Net Volume = Lower Tuning

Thats pretty much what I used to do when I worked at the shop. I took cardboard box with a known internal airspace and filled it with packing peanuts. Then I filled in the box. But I didnt know if there was some formula anybody used since I dont have the packing peanuts readily available anymore...I could just get some from them I guess.

If I slotport that 13W6v2 what should it be tuned at for SQ? 30hz? JL's recommended slot ported box is tuned at 34.5hz. And I dont want to just make that box. I want a custom box Im kinda stuck. Anyone hear a 13W6v2 in a SQ slot ported box? How do I figure the box volume, port area and port length for that sub at 30hz?

ramos
04-06-2009, 04:30 PM
I like playground sand better than packing peanuts. It gives more accurate numbers :)

Sideways17
04-06-2009, 07:33 PM
I like playground sand better than packing peanuts. It gives more accurate numbers :)

Good call man! Never thought of using that. Thanks!

nineball
04-06-2009, 11:31 PM
i use a bean bag chair. they usually have the super small round styrofoam pellets which work better than peanuts, not as fine as sand but much easier to remove. when you are done measuring you just pour them back into the chair and wait til the next use or sew it back up and return it to the store.