My Custom Box (pictures)

[5.0YZF22]

Hey,
Just thought I would share my box that I just got done building for those who want some ideas . I dont think its too shabby being its a first for me. Im going to put a 12" Rockford fosgate in it which will be here monday. And I'm going to carpet it sometime today or tommorow. Ill post more pictures when its all done and installed in my car.

Bryan

 

[Longjohn119]

It looks very nice but I'd recommend two things ...

1st in the panel with the speaker cutout, I'd take a 1 1/2" -2" wide piece of scrap slightly shorter than the width of the panel and glue it on end half way between the Subwoofer cutout and the left side. This will brace the structurally weakened (because of the hole) panel and keep it from vibrating and creating an unwanted (and ugly sounding) resonance.

2nd I'd put some damping material on the back and ride side and probably the bottom too although that one isn't as important with the slanted side (non-parallel) opposing it ... what this does is stop any internal resonances caused by the parallel sides ... it will also increase the effective volume (5-10%) of the cabinet and cab size is nearly always compromised to the too small side.

Trust me, it would be 5 bucks and a little time very well spent .... you'll have a better sounding sub and something to be proud of.

Those of you making your own cabinets and speakers should take advantage of this FREE program .... http://www.speakerworkshop.com/ ... it takes some time to learn how to use it but the end results are definitely well worth it ....

 

[Nate1]

Definitely brace that ****! Its panels are big an will flex alot if you have a high displacement sub, so bracing is a veritable must.

 

[badazz89lx]

did you build the box according to specs for the sub(s)???

 

[5.0YZF22]

It looks very nice but I'd recommend two things ...

1st in the panel with the speaker cutout, I'd take a 1 1/2" -2" wide piece of scrap slightly shorter than the width of the panel and glue it on end half way between the Subwoofer cutout and the left side. This will brace the structurally weakened (because of the hole) panel and keep it from vibrating and creating an unwanted (and ugly sounding) resonance.

So do I want a piece running across the bottom like this:

Or from bottom to top like this:

Also what can I use for sound dampening? Pillow fluff ? Should home depot or a common crafts store carry it?

Thanks

Bryan

 

[5.0YZF22]

did you build the box according to specs for the sub(s)???

Yeah,
Fosgate says 1.25 cu-ft for a sealed enclosure with the P112S4.The cu-ft of my box is roughly 1.27 w/out the sub so it will be slightly under 1.25 with the sub.

 

[Nate1]

The second picture.

 

[Sams01XplrSprt]

it looks bad ass 5.0 I like it a lot

 

[cybercreeper]

 

[Longjohn119]

Neither ...

You want the brace across the front panel (The one with the hole only) from the bottom of the panel to top of the panel ... it doesn't need to go all the way across, just most of the way and you don't want it touching any other panel ... take your 1st drawing, make the board shorter and move it straight up onto the slanted panel ...

You can use polyester quilt batting, get it about 1/2" thick if possible or layer it so it is ... Sound bouncing between any two parallel surfaces with create a 'standing wave' and a resonance (boost) at a certain frequency, for instance 2 parallel surfaces 2 feet apart creates a standing wave resonance of about 500 hz ... there is a formula to predict it based on the speed of sound in free air but I don't know it offhand ....

How it makes the cabinet appear larger than it is, is also based on the speed of sound, the batting slows down the soundwaves so it takes longer for them to hit the cabinet sides and bounce back.

You can also use fiberglass as batting and audiophiles like Siegfried Linkwitz swear by good old fashioned wool ... in my studio reference Monitors I have two layers of shingles (which takes away some internal volume) and then poly batting on all sides except the face where the speakers are mounted but they are huge and most car audio people wouldn't like them because the are flat across the entire audio range and don't 'thump' at bass frequencies but they are true bass response .... it's also a fact of physics that you cannot get good low frequency response in a car, the cabin space is just way too small, the lower the frequency the longer the wave and the more space it needs to fully develop before it hits a surface and bounces back at itself but no one cares because 'thump' is considered 'good' bass ....

 

[5.0YZF22]

Okay,
I understand what your talking about now, its more like reinforcement, not exactly a brace running it from one side to the other.

The recommended cu-ft for my sub is 1.25 cu-ft and after making final measurements earlier im at 1.27 cu-ft with the sub. I've read adding polyfill makes your box seems larger, so is it really neccesary for me to add it being im .02 cu-ft over? Or should I not be worried about that?

 

[Nate1]

Actually, you want cross bracing.

But I'm going to drop this subject. Whatever.

 

[expo5.0]

the thing about the waves developing is physically incorrect

 

[Nate1]

Sound bouncing between any two parallel surfaces with create a 'standing wave' and a resonance (boost) at a certain frequency, for instance 2 parallel surfaces 2 feet apart creates a standing wave resonance of about 500 hz ... there is a formula to predict it based on the speed of sound in free air but I don't know it offhand ....

Yeah, I'm sorry, but no. This is not free air, this is an enclosed enviroment without a very small ability to radiate excess energy.

Standing waves will not develop with that angle he has going... the interference fields will be so violently chaotic that he will not notice anything. What he could potentially notice is the walls of his box flexing from the pressure difference.

If you drew a triangle and then from each corner drew a line to the center, and the made a peice of wood shaped like that to brace the angled front, back, and bottom... that would probably be pretty darn strong.

More bracing is more bracing... just dont throw your net volume off too much.

 

[5.0YZF22]

Yeah, I'm sorry, but no. This is not free air, this is an enclosed enviroment without a very small ability to radiate excess energy.

Standing waves will not develop with that angle he has going... the interference fields will be so violently chaotic that he will not notice anything. What he could potentially notice is the walls of his box flexing from the pressure difference.

Thats what i've been waiting for! That was the whole reason I designed the box like that so the sides would not be parrallel. I think im going to add maybe a 1/4 in of filler sorta behind the sub, but not much.

btw im only running a kenwood amp 320W max/150W RMS bridged , so I doubt I will pushing my box to its limits.

 

[Longjohn119]

You still have 2 parallel sides to take into consideration and they will create a standing wave also, a box has 3 parallel sides, front to back, side to side, top to bottom .... the brace is to strengthen you weakest panel, the one with a huge hole cut in it .... you may or may not need to brace the other sides, but most likely you'll be OK on the other side as MDF is pretty strong and doesn't flex (resonate) until you have a side longer than 3 feet assuming you are using 3/4" which it looks like

The inside of a cabinet is still considered being in 'free air' (as far as the speed of sound is concerned) until you include some batting material to slow down the soundwaves ... the pressure caused by the woofer movement doesn't change this enough to be relevent, the pressure created in a closed (non-ported) box is used to damp the speaker movement and make it more controlable and to set the resonant frequency and cutoff

I have a recording studio in my basement, a modified LEDE (Live End - Dead End) design and I splayed one of the longest (side) walls to break up the standing waves but I still had them front to back and ceiling to floor .... On the Dead End wall I have a tuned Helmholtz Resonator (bass trap) built into the wall to 'soak up' the standing wave and I also have a couple built into the drop-in ceiling to cut the floor to ceiling standing wave, plus another 'contraption' in the back 90 degree corner ... the slanted wall thing does work but you have to do it to ALL 3 sides to completely elininate the standing waves, which isn't very practical with wood .... this is why you are seeing more and more cabs made with composites which can be molded with curved surfaces like my little JBL Control 1 near field monitors, the first 'prebuilt' spoeakers I have bought in nearly 20 years ...