Have a couple stupid questions regarding vented box design.

[chad]

Time for new Rock In Roll subs (pro audio).

1) in WinISD what is Vent match? It will go red but what does the number represent? Mine is green and a VERY low number.

2) The vent will be a slot in the center of the baffle spanning the width of the cab 6"X20.5" do I need to take any special considerations since he sides of the cab will be forming 2 sides of the port? i thought I remembered something needed to be factored in, I coulda been high though.

3) Any plywood guru's here wanna tell me something cheaper than void-free Baltic Birch that is still fairly void free?

Chankya!

Chad

[big john]

Time for new Rock In Roll subs (pro audio).

1) in WinISD what is Vent match? It will go red but what does the number represent? Mine is green and a VERY low number.

2) The vent will be a slot in the center of the baffle spanning the width of the cab 6"X20.5" do I need to take any special considerations since he sides of the cab will be forming 2 sides of the port? i thought I remembered something needed to be factored in, I coulda been high though.

3) Any plywood guru's here wanna tell me something cheaper than void-free Baltic Birch that is still fairly void free?

Chankya!

Chad

1. I'm pretty sure it's vent Mach, and it's basically the speed the air is escaping from the tube. If it's red, you will have audible port noise, so having a low green is a good sign.

2. The depth of the vent?

3. idk!

[toolfan91]

1. Are you referring to vent mach(as in air velocity), or vent match?

2. You need to factor in end correction, go here for an easy tutorial on it - http://mobile.jlaudio.com/support_pages.php?page_id=165

3. I just use adequately braced MDF for all my projects, and it works great for me. Considering how many enclosures I build/test I can't justify dropping a good bit of money on relatively high grade baltic birch or the like...

[chad]

Awwww it IS vent Mach, stoopid me :blush:

Vent depth will be about 8" the factors aren't exact as I have not accounted for the vent, bracing, etc yet, just getting rough ideas.

Thankya for the tutorial, it will be well used!

MDF will not cut it on the road, it will get wet and heavily abused. Not to mention MDF is rather heavy, these will be big motha's! External dimensions are 22" X 31" X 50"
Ply is the defacto for pro cabs.

[lbridges]

...
3) Any plywood guru's here wanna tell me something cheaper than void-free Baltic Birch that is still fairly void free?
...

I doubt you can find it cheaper unless you have a friend in a cabinet shop, but there's always ApplePly. Here's a mini discussion I cut from a web page:

Baltic birch is probably the most common type of HDP, and uses birch as the substrate. This will come in 5' x 5' sheets. For a 1/2" sheet, there are typically 7 to 9 plies. Being birch, the surface does not finish as nicely as the maple counterpart, and there is a tendency for splintering at the edge of a machined cut.

Appleply is a manufacturer's name for high density maple plywood. From a fabrication stand point, it is similar to Baltic Birch, in that it carries about the same number of plies, except Appleply comes in standard 4'x8' sheets. Because the surface is maple, there will be slightly more grain pattern on the surface, and the surface will sand much smoother. There is less splintering of the machined edges, and those splinters which do appear will be shorter and less inclined to align with the edge.

[chad]

Thanks man! The cab will be finished in truck bed liner like stuff or carpet. We can get BB hare in 4X8 but it's VERY pricey!

I'm going shopping tonight (I hope)

Chad

[Whiterabbit]

bedliner will make the MDF waterproof. its already inherrently shockproof when built well.

I understand what you are saying about weight though :(

what is your problem with cheaper ply? what do you fear the voids are going to do to your bass response?

[chad]

The MDF will still chip/deform though even with bedliner on it.

I may just play around with darn good standard ply to see what I can do. One good thing about void free is the glue bond is better

[Whiterabbit]

I think you are thinking too hard about it.

i've tossed very large MDF boxes off long drops and watched them bounce off big rocks without catastrophic damage, much less a ply that I would think would have much greater impact resistance, weaker glue layer notwithstanding. And I'll bet you can build a box just as well as I can.

If you are that worried, you can always reinforce joints with additional material and further stiffen panneling with partial secondary layers, but when cost and weight are the concern of the day, I don't think you can beat picking a choosing (for flatness, naturally) construction ply. And if weight werent on that list, I'd be running MDF anyways.

After thick carpet and cabinet corners, I just dont see them getting absused via loading and travelling more than a 20 foot drop onto a boulder.