Lets talk about box building.

vwguy3 · Post by **vwguy3** » Sun Mar 25, 2012 7:19 pm

I have an old school soundstream usa10 subwoofer that I would like to build a ported box for. I have built a few sealed boxes in my time and would like a little help with a ported. Here is the manual for the subwoofer http://www.soundstream.com/manuals/sbw/usa81025.pdf They recommend a 1.3 and 1.8 cubic foot boxes and don't know what would be better? Is it better to try and tune a sub to the lowest fq? Is it better to just build a box to the manufactures specs or should it try and input it into winISD? Also I know that you have to compensate for the port and subwoofer when building, but what about a port that is flared like this one? http://www.parts-express.com/pe/showdet ... mail042111 I am leaning towards putting that into the box.

Thanks
Justin

Virtue · Post by **Virtue** » Wed Mar 28, 2012 2:25 pm

Concerning the flared ports, they are great when trying to prevent port noise. This is caused when the sub moves a lot of air in and out of the box. Your sub does not have that much excursion, so, you really will not need it. As for a box design, well, looking at the BL spec of the sub, it is really designed for a sealed box, but, if you want some lower freqs, vented is the way to go. It will be sloppy though... if you really know your music. That is why the soundstream states: good for rock music... To help with the lows, go for the 1.5 cft box. Sometimes if you go too big, all the other freqs that your port is not tuned to, are non existent. So, you will hit the freq that your port is tuned to and it will be loud, but, if you play music that is outside that freq, there is almost no sound. And believe me, it will be disappointing! I've been there. Go by the Soundstream box suggestions, they are always spot on. And don't forget to take into consideration with how much volume the sub and port takes up. The port being a brick. These must be subtracted from the overall internal volume. So, the 10" will take up say .015 cft and the port say .27 cft. Therefore the box needs to be 1.8 cft inside to make a 1.5cft box...

And face the box towards the trunk/tail lights...

vwguy3 · Post by **vwguy3** » Wed Mar 28, 2012 4:30 pm

SO do you think that it would be better just to go with the sealed box? I have had good luck with sealed. I know it would suck if I spent all this time on a box and then it sounded like crap! What about bracing? Do you think I should put some in? I am going to have about 300 watts going to it. I'm either going to hook it up to a lil' wonder or the sub channel on a MC245. Anyone have any pics of some good bracing in a box?

Thanks
Justind

lukeman269 · Post by **lukeman269** » Sat Mar 31, 2012 8:19 pm

For bracing, you will want to offset it. I would cut a piece of 2x4 wood in half and cut it to whatever internal dimensions you will need. Then brace it similar to this.

Stryker · Post by **Stryker** » Sun Apr 01, 2012 7:03 am

lukeman269 wrote:For bracing, you will want to offset it. I would cut a piece of 2x4 wood in half and cut it to whatever internal dimensions you will need. Then brace it similar to this.

For a low power 10" that would be going in a small box that is total overkill, and almost unnecessary.....
Just sayin

lukeman269 · Post by **lukeman269** » Sun Apr 01, 2012 7:31 am

Stryker wrote:
lukeman269 wrote:For bracing, you will want to offset it. I would cut a piece of 2x4 wood in half and cut it to whatever internal dimensions you will need. Then brace it similar to this.
For a low power 10" that would be going in a small box that is total overkill, and almost unnecessary.....
Just sayin

Yeah, but it can't hurt!

vwguy3 · Post by **vwguy3** » Sun Apr 01, 2012 10:21 am

It probably wouldn't hurt, but it would be more of a PITA to do to. My thinking too was that it would be overkill. Its not like im going to have 2K watts going though it. Hey Luke where abouts are you in MN?

Later
Justind

Virtue · Post by **Virtue** » Mon Apr 02, 2012 8:55 pm

Go with the ported box. Bracing not needed. Just use 3/4inch, Ranger/MDF board. You will be impressed how it will pound with a ported box as compared with a seal box. I personally don't like sealed boxes. And it won't sound as bad as you might think.

00goobs · Post by **00goobs** » Mon Apr 02, 2012 10:39 pm

I saw a box lined with cement recently on an old car audio article. I've even seen someone double the walls with 3/4" birch, a heavy overbuilt box would be preferrable to one that is rattly. On some of the older sub manuals, they show almost a double in output using the manufacturer's recommendations for a ported box over their recommended sealed ones...

audiophyle_247 · Post by **audiophyle_247** » Wed Apr 11, 2012 6:56 pm

lukeman269 wrote:For bracing, you will want to offset it. I would cut a piece of 2x4 wood in half and cut it to whatever internal dimensions you will need. Then brace it similar to this.

Out of curiosity, why should the bracing be offset?

lukeman269 · Post by **lukeman269** » Wed Apr 11, 2012 8:11 pm

It is for structural purposes. Say if you had more than 2 braces, then you could do whatever layout you want. But when you don't want to take up a lot of space and use only 2 pieces of wood this is the strongest method for rigidity. If you centered the bracing, it can increase box vibration and make the problem worse.

audiophyle_247 · Post by **audiophyle_247** » Wed Apr 11, 2012 8:36 pm

lukeman269 wrote:It is for structural purposes. Say if you had more than 2 braces, then you could do whatever layout you want. But when you don't want to take up a lot of space and use only 2 pieces of wood this is the strongest method for rigidity. If you centered the bracing, it can increase box vibration and make the problem worse.

Do you have any proof of this? Links perhaps?
I have taken several structural design courses, and to me that sounds incorrect.

The bending moment of any span will be its highest at the very center, and naturally, bracing the weakest point offers the greatest benefit.
If the increased "box vibration" refers to the box actually moving around, then that should be proof enough that the enclosure is stronger when braced centrally, due to the fact that more kinetic energy from the speaker is being transferred through the box instead of being absorbed by the box as it flexes.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Wed Apr 11, 2012 8:43 pm

Dude just brace the shit out of the corners and you will be golden!!!

audiophyle_247 · Post by **audiophyle_247** » Wed Apr 11, 2012 9:21 pm

Assuming you've built the enclosure with tight clearances (ie accurate cuts & measurements), the corners/edges are already the strongest parts of the enclosure, but by all means "brace away".

Post by **ttocs** » Wed Apr 11, 2012 9:37 pm

this is all new to me.....

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Wed Apr 11, 2012 9:55 pm

ok you sarcastic bastards!!! I meant to say , that the more braceing the better, no matter how much power, the stronger the box the better the sub will sound! Brace the shit out of your box and you will be satisfied. the stronger the box the better the sound.!!!
Is that better smart asses!!??? jk!
One other thing ....it depends on how much power your feeding your sub aswell.
Long story short ........brace the shit out of your box and you will be happy!!

beers bitches

lukeman269 · Post by **lukeman269** » Thu Apr 12, 2012 11:52 am

Honestly I have only read some box building techniques and forums to learn about bracing. Bracing obviously makes it stronger. I am by no means an expert on box building. I read the vibration thing on this link here:

http://www.kicker.com/building_enclosures

Not sure if this is a credible source but it looked pretty good to me.

I don't really do much cross bracing and that picture I posted above was actually the only one I have done. I mainly only do corner bracing as I have had great results.

nutxo · Post by **nutxo** » Thu Apr 12, 2012 12:07 pm

why not use allthread then you dotn have to worry about the displacement?

lukeman269 · Post by **lukeman269** » Thu Apr 12, 2012 12:27 pm

What's allthread?

Post by **ttocs** » Thu Apr 12, 2012 4:40 pm

threaded rod is another term for it. Imagine a rod 12" long that is threaded from one end to the other. Drill a hole in either side, put the rod through and with a few nut/washers you now have a fairly sturdy brace with out taking up much airspace.

lukeman269 · Post by **lukeman269** » Thu Apr 12, 2012 7:04 pm

Ahhh I see! That would be a good brace.

audiophyle_247 · Post by **audiophyle_247** » Fri Apr 13, 2012 9:10 am

Threaded rod works great so long as you extend the rod through the box walls & tighten the bolts down to squeeze the box, flexing the walls inward. The rod NEEDS to be in tension, because it does nothing but bend in compression so the box will only be reinforced in one direction. The issues with this is you have to drill a hole in the panel, which actually weakens it. You also need to use as large of washers as you can to spread the footprint of the brace to distribute the load to a wider area. To do this you need to bolt down the rod from the exterior to flex the box inward as much as possible & follow up by counter tightening bolts from the inside to lock all the bolts in place to the panels.

Corner bracing does very little in adding strength to a box, the corners are already the strongest points so in reality the gains to bracing are minimal & a waste of interior airspace. (unless you are after massive SPL levels) This of course assumes your corners are good from the beginning and your edges are straight & flat. If your cuts suck or you measured shit badly, bracing would then be a logical decision.

Any bracing inside to support walls is always beneficial, offset or not, but the gains are smaller when offset and I have never heard of a box inducing more flex from any type of bracing. Bracing between walls is very tricky because you have to remember the box will be both stretching and smashing the brace, so it needs to be a very tight fit but also screwed into from the outside of the box.

Post by **ttocs** » Fri Apr 13, 2012 11:18 am

on my recent Ti9 door project I fiberglassed dowel rods between the top and bottom to help prevent flexing. The enclosure was only a few inches deep at most but very long/wide across teh front where I was concerned with flexing happening. If the dowel rods were any larger then a few inches I would be concerned with them flexing but with as short as they are it should help out.

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