estimating cubes for fiberglass enclosure

In my opinion it would be easier to build a regular box, with only the baffle board shaped to fit in the well. We are only talking about a box with about 2.5 cu.ft and you have tons more room down there.

Depth x height x width = cubic inches

Cubic inches divided by 1728 = cubic feet

 

We dont need to be that accurate. Those subs have a range that they will perform well in. Also there is not any real benefit in dividing the box. In fact loud and low is a function of Box Size. I would rather have four 10's in one four cubic ft box then I would four one cubic ft box.

Anyway the easiest way would be to constuct a simple cardboard box that is 12 x12 x 12 and use it to see how many times you can fill that space with Packing Peanuts. Its worked for me.

We can do this mathematically, not as simple as the peanuts. Give me a few minutes to figure this out.

 

To calculate volume of that area first calculate the cross sectional area as if it was a square or rectangle. Lenght x width = area

Now measure the lengths of each curve and add them together. The more precisely you measure these lenghts the more accurate this formula will get.
The lengths of all 4 curves added together will be S



Substitute the lengths of the curves in for S in the equation above.
Subtract that result from the area that you already calculated.

Now multiply by the depth of that space and you have the total volume.

Told you it wasn't difficult

I don't have time to post a portion of Vance Dickason's book The Loudspeaker Design Cookbook. If you can find it read chapter 1, there is a section on how sound couples and the properties of multipe woofers in a single enclousure.

The sections are titled Multiple Woofer Formats (1.90) and Standard Configuration (1.91)

 

little known fact, kicker solobarics work EXCELLENT as an infinite baffle sub!

Derate the power to about 200 watts from 40Hz on up, and they kicked some serious asshole!


Done a system using solo 10 inchers in the rear deck of (i think) a 89 cavalier, run them on a 280gx orion, lasted for years! sounded great. But they must be properly x-over and subsonic filters in use!

Just an FYI, thatas all

 

Old school. Yes

I did say infinite baffle, didnt i ?


Infinite baffle means they are mounted in the car like say, a 6x9 speaker. they use the trunk as an enclosure. No box invovled!

If you listen to "rap" and the likes, dont go with an IB!!!!!! put em in a box.


Ranger gave you some good advice on the box formulations, he is right.

Also, they DONT NEED to be in seperate enclosures to sound right or work right. BUT, putting them in seperate enclosures will enable one or two of the woofers to blow/launch/explode and not effect the other speakers tuning. thats about it.

 

I've got the old Kicker KITT maunal(the big red binder), next time I get to my storage unit I'll pull it out. It has the solobarics in it, not sure if they are the same gen.

But what I do know...... There shouldnt be any problems with running all in one chamber. In fact, if they are all running off the same amp, then they would be better in one chamber. When speakers are connected together they become electrically coupled(i know....duhhh), but in more ways than the obvious. They actually act as one speaker. Try this, hook them up together outside the box and push down on one cone, the other should go up. Its been a while since I did that trick, so I may have gotten some of it backwards, but you get the idea. If they are in different chambers then they can react differently(no two speakers are EXACTLY the same), and cause minor cancellations.

Plus...when you use one chamber you can reduce volume of the box. I would still build it over size though.....then add blocks/panels to the inside. That'll also help break up flat sides and reinforce the glass.

As for volume calcs....I prefer the sand method. Put a big(heavy) trash bag in the box fill it with sand, then take the sand out and measure its volume in a box or something else easier to calcualte the dimensions.

BTW...those Solos kick arse!!! What kind of system are you going for?

 

O.K. I'll simplify it even more (but then it won't look like I put any thought in it)



I don't get simpler.

 

Does that formula also work for multiple/different compound curves? I'm all for the most simple solution....

 

okay, how did you get so lucky as to score four good old school solobarics?

man I miss the old stillwater sh*t!

 

No. You must have a circle for this equation to work. I am assuming that the 4 rounded corners in shagdrums trunk would make one circle. In other words, I am assumming that each corner is 1/4 of a circle. Thats why I said in the directions to add up the lengths of the 4 curves.

To come up with the equation, I took the area of a square and subtracted the area of an inscribed circle. That remaining area would be equivelent to the area that would need to subtract from the rectangle area. I did it this way because I realized that the only thing you could physically measure would be the length of each individual curve, I used the formula for circle circumferance to come up with the areas that needed to be subtracted. You see, as long as the circle is inscribed in the square, the areas are proportional.

Can you apply this to other curves? Yes, but not with equation above. Only curves that are about the same and equal up to a circle will work with the equation above. A basic trigonometry formula says that the length of a curve = radius * theta where theta is the measure of the angle inscribed by the curve measured in radians. This fact allows us to compute areas of weird shaped polygons. With a little modification it can work for any area with any curve.

Thats enough trig and geometry for today

 

Well...... maybe enough trig and geometry.....but what about calculus? I believe that you *can* actually calculate the area(and therefore the volume) under a "non-linear curve" using derivatives, or anti derivatives(been a while since I took those classes). There was also a method of infinite segmentation(chords) between points that allowed for area calculations. I think thats the basis for y'. Granted most of these calcs require the formula to start, though you could probably model a simple parabola to get "close"...... and polyfil/block the rest.

If you have access, Autocad can do some pretty neat area and volume calcs too....

i still say a bucket of sand is easier...but yeah, the math is fun too

 

I suggested Packing Peanuts earlier. I really don't think we need to get that accurate. But if thats what shagdrum wants I'll supply him with the info.

And for area under a curve you what the intergral, but you need the equation that made the curve. Intergral is sometimes refered to as an anti-derivative but its been awhile since I've heard that term.

 

I knew I had a few brain cells left, just not enough....lol, integral.....thats the term I couldnt pull up. The only reason I remebered the anti-derivative was that I knew you had to "work backwards" from Y prime. Thanks for the refresher Ranger.......

 

Great memory and very logical thinking, maybe you should also study mathematics.
What do you remember about multi variable (vector ) calculus, I'm taking it this semester, my last elective (if i had any sense I would have taken Basket Weaving or Bowling as an elective lol)

 

Thanks for the compliment, yeah I was pretty good at math in school. Took AP Calc 2(college level) when I was a junior in HS...all the seniors hated me for it.....lol. Stupid me, didnt take the AP test.....ended up having to take it again in college. But that was as far as I got. I was a computer science major, but got tired of professors that couldnt speak english....lol. I shoulda stuck with it, but ended up with a degree in psych. Now I'm in grad school with a dual major in business and procurement managment. Funny how the road to "success" isnt always straight......or even paved somtimes....hehe

Sorry....the vector calc was only touched on in my last calc class.....it wasnt as hard as it sounds though....as long as you have a good foundation. Thats about all I remember....

oh....and sorry for threadjacking......