Wall Design 4 15's. To small port? Need length help for tune

[WOT]

2 sheets is more than enough, already worked it out, thats why I chose 24" depth

Just need port length help

Never ran all 4 of these together with much success due to amp failure, so Id like to try. Like I said itll probly only be in for a bit until I sell all 4 of them and pick up an RD heavyweight

 

[01 S 10 10+ year member]

you need to work with a NET measurement to figure out how long the port needs to be... so how many cf net do you want/need? and what dimension can vary if needed to?

 

[01 S 10 10+ year member]

just with the 1/2" MDF (not including bracing or double baffle) that is right about 15cf GROSS.

you have about 12.8cf net after sub and port displacement (still not including a double baffle or bracing)

your port is 31" tall, 6" wide, 12.86" long for 38hz. (port takes up about 1.44cf)

i estimated about .7cf for sub displacements

so 186sq. inches of port is plenty enough for 12.8cf net (~14.5sq in per cf)

 

[WOT]

Thanks man I appreciate it alot, I was plugging numbers in WInisd trying to figure out how to use it

Yeah sub displacement is .15 each, . 6 total, small 45's in the corners and the braces really dont take up much room. Just to comensate for the 45's and the bracing, trying to keep it as close to 38hz as possible, would I make the port a little longer or a littler shorter

 

[01 S 10 10+ year member]

Thanks man I appreciate it alot, I was plugging numbers in WInisd trying to figure out how to use it
Yeah sub displacement is .15 each, . 6 total, small 45's in the corners and the braces really dont take up much room. Just to comensate for the 45's and the bracing, trying to keep it as close to 38hz as possible, would I make the port a little longer or a littler shorter

a little longer

but not much longer, only like 1/4" on the port for every 0.1cf smaller inside volume.

 

[01 S 10 10+ year member]

btw, by adding a double baffle, you'll only lose another .322cf, bringing you down to 12.468 cf net. port will now be 13.58" long

 

[WOT]

I may double baffle to flush mount the subs, but I would just put it on the outside as to not change my box specs.

I'll probably go 13.25" long, 3 lenghts of threaded rod and 2 1" wooden dowels for braces

Should be solid

Thanks again

 

[pioneerpimp 5,000+ posts]

not even gonna come close to solid. do you have any idea how bad of an idea, if youre not going to double baffle it, 1/2 inch wood to mount 4 15s in is going to be? the flex will be unreal. i just want to assure you that when this is all said and done, everything everyone says will hold true.

I built my wall out of 3/4s wood, and an 8 layered thick DB, and it still flexed.

 

[WOT]

Well heres a pic of my last atempt @ 4 15's before my amp low volted. Was over 18 cubes I think

Didnt flex at all, what was it made of? 1/2"

I make skeleton braces, and threaded rod ontop of that Im pretty confident I can control this box. Im also not worried about very little flew as this is just a daily street beater with a bored owner lol, would never see a show or competition.

 

[audioholic 5,000+ posts]

The amount of bracing it would require to really make that 1/2" mdf rigid enough, would be substantial enough that it would leave most people with the simple decision to up-size to 3/4" and forget about it.

No offense, but you saying it didnt flex doesn't mean it didnt flex. There's a reason the entire industry uses 3/4" as its standard, because 1/2" is insufficient for many large and/or high powered installs. Yours will be both.

Either way, good luck to you. Im trying to be helpful, not just critical. Keep us posted.

 

[audioarsonal 10+ year member]

Sub displacement for a 15 is about .35cuft usually.

 

[WOT]

The amount of bracing it would require to really make that 1/2" mdf rigid enough, would be substantial enough that it would leave most people with the simple decision to up-size to 3/4" and forget about it.
No offense, but you saying it didnt flex doesn't mean it didnt flex. There's a reason the entire industry uses 3/4" as its standard, because 1/2" is insufficient for many large and/or high powered installs. Yours will be both.

Either way, good luck to you. Im trying to be helpful, not just critical. Keep us posted.

Well like I said, I change boxes bimonthly lol, so FREE wood is a nice word to me. My word is good on that box pictured not flexing, even though it only saw 2000rms, you can see 2 of 6 1/2 threaded rods I used to do so, to me bracing and fiberglass makes more of a difference than thickness. And for this build I struggled with a design for a basic square that still gave me enough room behind it for a case of beer between it and the back hatch lol

As for sub displacement, I got .15 directly from DJ himself

 

[Towncar 10+ year member]

Not the best idea ive heard today..

 

[Xprime4 10+ year member]

i'm pretty sure you loose some dbs with mdf so thin. box flex ain't good //content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

 

[mlstrass 5,000+ posts]

I did 4 15" HDC's in a temp wall last year in 12 cubes and it was less then stellar in an enclosure that small. It's your time and $$$, but I wouldn't bother as it'll look cool, but won't back it up...