15" BTL Woofer Box Question(s)

[Hell-Razor 0]

A simple question, maybe not a simple answer though.

I am looking to (maybe) invert my 15" BTL when I get it. The whole reason why I want to do this is to give the woofer as much air as it wanted and to use the trunk as the entire box. Saving room would be a plus but isn't really needed. I know some subs simply cant be mounted this way. The more I think of it the more I actually think the BTL may not be able to. Dont think though that this will make or break me getting a sub, just an idea....

http://www.astinagt.com/forums/showthread.php?t=5601 (some guy posted a program to help with box cubic feet calculations)

[johnecon2001 82]

Why wouldn't you be able to invert mount the BTL? The only sub off the top of my head that would be difficult to invert would be the W7, but it could still be done.

[Hell-Razor 0]

Don't know. I was just reading on some other forums some should not be mounted upside down. Would mounting the woofer magnet out do anything to the sound?

[KU40 173]

I think you may be confused. Where the magnet is doesn't make that the box. So inverting the sub doesn't make the whole trunk the box.

Generally there is no difference in sound.

[Hell-Razor 0]

Oh I just thought thats where the air displacement comes from...

[johnecon2001 82]

Air displacement comes from the cone moving. You need a close space to resonate the air in.

[Hell-Razor 0]

Ah alright. So basically if I flip the sub upside down it will still need the same size box? (give or take a little from the sub itself)

[KU40 173]

It still needs the same size box in net volume. It's just that if you need 1.5 cubes, with the sub inverted you build the internal space to 1.5 cubes, but if you have the motor inside you build the box to 1.6 cubes or whatever. You just have to account for the space that the motor will take up so that after that displacement the sub still has the desired airspace.

Also, you have to remember that speakers move both in and out. They aren't single directional. So even though a sub appears to only move out when you look at it, it is in fact moving both directions equally. There is a wave coming off the front of the cone and a corresponding, equal wave coming off the back of the cone. In a sealed box one of the waves basically becomes trapped in the enclosure. It doesn't matter if it's the front wave or the back wave since they are equal.

[Hell-Razor 0]

Just a quick question.... I wonder what if I made a small box but with killer ports? Like make a brace for the sub and give it like 1/4 the box size but like 4x or 5x the port size?

(Just an idea that popped into my head. Probably wont do it...)

EDIT: I would keep the raitos the same. Somehow I would figure out well I need X space for Y port and then flip them so Y space for X port...

Edited June 8, 2009 by Hell-Razor

[KU40 173]

It doesn't work that way. There are enclosures that have massive ports and relatively small enclosure for the sub (like a horn), but they are definitely not smaller than a regular ported box.

Besides, if you build a small box and want a large port, the port will eat up a ton more room than you think. The smaller the box, the longer the port has to be with the same port area and tuning frequency, thus taking up more space. So that's a backwards solution.

Just go figure out what size box can fit in your trunk, or what you want to give up room for, and we'll go from there. Don't try to cut corners, it will turn out disappointing in the end.

[Hell-Razor 0]

It is possible to build a box with large port holes (for example, dont put on a cover or sides, just build a brace for the sub). But it sounds ilke its not doable so that idea is thrown out the window.

I am not trynig to cut corners, I was just curious. If I have to Ill fill my entire trunk, I dont care. My trunk is 40L, 40W, 20H.

Edited June 8, 2009 by Hell-Razor