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View Full Version : accidentally got wrong size MDF. what should i do?



talon2nr7588
11-22-2006, 04:21 PM
i just got back from home depot. I bought two sheets of MDF for the box i will build for my 15 L7s. i was planning on using 3/4" MDF, but i accidentally got 5/8". what will be the difference? should i return it? i know it will be lighter but how much more will it flex? it is only a 1/8" difference but whould i worry?

mtdewelf
11-22-2006, 04:24 PM
how big is the box gonna be? just.....
use extra bracing.
If box small enough double all around.
double up biggest panels.

Honestly if anything just make sure to brace good. can't see it being much of a problem.

talon2nr7588
11-22-2006, 04:27 PM
the box will be 10.6 cu.ft gross.

iagrdshaka
11-22-2006, 04:35 PM
make a trip back to Home Depot and take it back (I would anyway :))

mtdewelf
11-22-2006, 04:37 PM
1" Ftw

Chevyaudio
11-22-2006, 04:38 PM
Yeah...5/8" wont cut it on a 10 cube box...go back and get the 3/4.

talon2nr7588
11-22-2006, 04:39 PM
what kind of bracing should i add? i don't think the 1/8" difference is much. i was thinking of adding a double baffle.

talon2nr7588
11-22-2006, 04:40 PM
Yeah...5/8" wont cut it on a 10 cube box...go back and get the 3/4.

****, i was wondering why it was cheaper.

GrnEydDvl
11-22-2006, 05:38 PM
what kind of bracing should i add? i don't think the 1/8" difference is much. i was thinking of adding a double baffle.

I would use internal bracing if possible via thread metal rod or wooden dowels. I use the dowels personally. A doubled baffle is not a bad idea if you don't mind the extra weight and size. Internal bracing is much more effective though. You could do both if you wish.

And use 3/4" MDF. A little bit thicker, a lot stronger.

Lakota
11-22-2006, 06:29 PM
Threaded rod ftw. I have pics if need an example.

baseballer1100
11-22-2006, 06:29 PM
Take it back.

talon2nr7588
11-22-2006, 10:31 PM
yeah i took it back and got the 3/4". lakota can you post pics?

Immacomputer
11-22-2006, 10:37 PM
yeah i took it back and got the 3/4". lakota can you post pics?

www.tinypic.com
www.imageshack.us
www.imgboxupload.net

Now you can post them yourself! All you have to do is locate them on your harddrive!

Calikid
11-22-2006, 10:39 PM
www.tinypic.com
www.imageshack.us
www.imgboxupload.net

Now you can post them yourself! All you have to do is locate them on your harddrive!


LOL

Calikid
11-22-2006, 10:40 PM
900 post :woot:

lilmaniac2
11-22-2006, 10:41 PM
wow ur gonna need more than 3/4 for a 10 cube box... the biggest panels should be doubled up and the box should have either 2x4's or threaded rod for bracing

Worlddre
11-22-2006, 10:48 PM
www.tinypic.com
www.imageshack.us
www.imgboxupload.net

Now you can post them yourself! All you have to do is locate them on your harddrive!

he was requesting to see pics of lakota's box featuring the threaded rod

smd4life
11-22-2006, 10:50 PM
owned......just....owned

matrxx dude
11-22-2006, 10:53 PM
i know on all my boxes i use 3/4 mdf and then double every part of it to,because teh flex is a bad thing.

Immacomputer
11-22-2006, 10:57 PM
he was requesting to see pics of lakota's box featuring the threaded rod

Haha, I misread that!

Worlddre
11-22-2006, 10:59 PM
;)

ssj2xxgotenxx
11-22-2006, 11:49 PM
i just got back from home depot. I bought two sheets of MDF for the box i will build for my 15 L7s. i was planning on using 3/4" MDF, but i accidentally got 5/8". what will be the difference? should i return it? i know it will be lighter but how much more will it flex? it is only a 1/8" difference but whould i worry?

How many drivers are you using specifically? 10.9 cubes is alot of airspace.


900 post :woot:

2,000 posts :woot:

talon2nr7588
11-23-2006, 01:01 AM
for 2 15L7s. thats 10.6 cu. ft. gross.

talon2nr7588
11-23-2006, 01:03 AM
yeah i was also asking lokata to post pics of his brace.

PV Audio
11-23-2006, 01:04 AM
You're going to need at least 3/4" MDF. Remember, you say that 5/8 is just 1/8 smaller than 3/4, but it's also just 1/8 larger than .5". You should really look into 1" with that size enclosure, or just double up the critical panels (the baffles really), and brace the rest if you decide to just use 3/4. 5/8" just will not suffice for anything of this magnitude, you'll see more flexing than Muscle Beach.

jmanpc
11-23-2006, 01:06 AM
5/8 ought to be okay. just be careful with your cuts. get everything straight, use plenty of glue and make some bracing. it'll be fine

talon2nr7588
11-23-2006, 01:13 AM
well i returned it to get the 3/4". but i've never really looked into bracing, but i am gonna double baffle this ****. will to much flexing hurt my subs or make the box explode?

talon2nr7588
11-23-2006, 01:14 AM
jman who the fu(k is that in your avavtar?

PV Audio
11-23-2006, 01:19 AM
5/8 ought to be okay. just be careful with your cuts. get everything straight, use plenty of glue and make some bracing. it'll be fine
That isn't true in the least. Straight cuts and using lots of glue are not going to cut down on panel flexing. He needs thicker wood and more bracing.

PV Audio
11-23-2006, 01:21 AM
well i returned it to get the 3/4". but i've never really looked into bracing, but i am gonna double baffle this ****. will to much flexing hurt my subs or make the box explode?
It won't hurt your subs, but if you don't build it properly, then it could potentially explode. Remember, a ported box at Fb can have higher pressure internally than a sealed box. You're going to want to brace it up well. If nothing else, you'll get some panel resonance which is one of the nastiest sounds in all of box building right behind port chuffling/port noise. It can also take away from your sound output (not always), so bracing is almost always to your benefit.

talon2nr7588
11-23-2006, 01:29 AM
what wil panel resonance sound like? ok so double baffle whcih will make it a 1.5" baffle, but if i add a metal rod or 2"x4" on the inside will it affect the sound?

PV Audio
11-23-2006, 12:19 PM
I cannot really explain what it sounds like, but you'll definitely know it when you hear it. It's just an overly loud vibration noise. When you open your trunk, you shouldn't really hear anything at all besides the subwoofer working. There's usually only two other things you would hear: port noise and panel vibration. You don't want either, but port noise is livable.

http://realmofexcursion.com/videos/Audiobahn/immortal15.8.wmv <-- that's an example of panel vibration. The box moves around in the trunk because it isn't internally braced properly. If it were, you wouldn't hear that rattling sound on some notes.

talon2nr7588
11-23-2006, 07:05 PM
OH! you were talking about bracing the box as in bolting it down so it doesn't move correct? yeah i plan on doing that so that it doesn't move around while driving/ playing. i thought you meant bracing the box internally. or that too? is there a way to eliminate port noise?

PV Audio
11-23-2006, 09:36 PM
No, that isn't what I meant. I meant bracing it internally. If it's properly braced, then the panels won't be absorbing the sound waves from the back of the speaker which causes the box to slide around (think about putting a vibrating cellphone on a wooden table, the vibrations through the exterior of the phone cause it to move).

talon2nr7588
11-23-2006, 09:56 PM
will adding a 1 1/2" dowel going up and down in each chamber with the double baffle be enough?

talon2nr7588
11-23-2006, 09:57 PM
also will the dowels affect the sound of the box at all? i dont want it to sound like ****.

PV Audio
11-23-2006, 09:59 PM
It will make the tuning go up, yes. You probably won't even notice it with a box that large though. However, a 1.5" dowel most likely will not be sufficient for a box that size. I'd look into multiple 2" dowels, or as was previously suggested, threaded rod.

talon2nr7588
11-23-2006, 11:16 PM
ok would double baffle and 2 2" dowels per chamber be enough? i wanna make sure because ima redesign the port to tune it lower to make up for the dowels.

PV Audio
11-23-2006, 11:32 PM
If you're running 10 cubes, some dowels will not change your tuning by very much, at least not noticeably. That should be fine for bracing though.

baseballer1100
11-23-2006, 11:33 PM
pV where you been?

PV Audio
11-23-2006, 11:35 PM
pV where you been?
Been gone! Made a thread about 5 weeks ago. Took some time off caraudio.com to focus more on school rather than Eugenics' constant quick remarks :laugh:

baseballer1100
11-24-2006, 12:00 AM
I wish i could do that where you looking at going?

PV Audio
11-24-2006, 12:23 AM
I wish i could do that where you looking at going?
Accepted into Purdue's mechanical engr. school, and that was my first choice....:woot:

baseballer1100
11-24-2006, 12:37 AM
**** congrats.

talon2nr7588
11-24-2006, 10:30 AM
If you're running 10 cubes, some dowels will not change your tuning by very much, at least not noticeably. That should be fine for bracing though.


cool. look for a build log sometime soon

GrnEydDvl
11-24-2006, 03:27 PM
Me and Saywhat? played this game during the design of my first box. The rods take up very little volume relative to net vol of the box. I know everyone understands and assumes this but lemme show you some real numbers.

Let's assume you have a 35w x 15t x 15l net internal box. So that is 7875 cu inches or ~4.56 cu ft.

If you use two 1.5 inch dowels to support the box (one up and down, one front to back) that will take up (.75^2)x(3.14) x (15) = 26.5 cu inches of space for each. Or 53 cu inches or .03 cu ft for both. For you less than mathematically inclined folks, that is 3 hundredths of a cubic foot to increase the structural integrity of your box considerably.

And this is using 1.5 inch rods, which I think are pretty excessive but I haven't dealt with anything larger than about 4.5 cubic feet net. Bigger boxes may require larger supports but I normally use 1/2 - 3/4 inch dowels. In our example, if we used 3/4 inch rods they would take up 6.6 cubic inches each, or ~13 cubic inches / .0038 cu ft for both. Considerably less volume than 1.5 inch rods but I doubt either will affect tuning noticeably. Maybe someone with a calculator can let us know how it changes tuning.

Another tip is to cross internal rods so they touch each other and bind them together. This further strengthens the support they provide. You can bind them with wood glue or twine or a zip-tie.

talon2nr7588
11-24-2006, 03:42 PM
i redesigned my box to accomadate the dowels i will be using.

PowerNaudio
11-25-2006, 05:51 PM
here is an example of how i like to brace the enclosure to add strength to the wall but still keep air turbulence to a minimum. and raise the resonant frequency of the walls. double baffle is great for spl enclosures, but for daily enclosures that have power levels below 2kwrms. and youre conserned with doubling the weight of the enclosure. i think this is a great way to brace.

http://img1.putfile.com/thumb/11/32816135541.jpg (http://www.putfile.com/pic.php?img=4088569)

talon2nr7588
11-25-2006, 06:07 PM
thats a good design... but the ports for my box are gonna be one on each side. are the rails made of MDF too?

PowerNaudio
11-25-2006, 08:31 PM
yes everything is mdf, i just used that as an example.