Okay since I can't leave stuff alone when its working fine I moved my subs from a perfectly good box in my Civic to a box built to fit in between the tire wells in the back of the wifes 4runner. The old box was built to the specs for the woofers, the new box is built to fit in the back of the 4runner. I tried to get the air space close to the right size for the woofers, but i think the box is too big. The subs used to be connect to the 5th channel of a 5 channel amp, now they are hooked up to a 4 channel amp, one sub bridged to channel 1&2, and the other sub bridged to channel 3&4. Well in the 4runner the box sound like crap, the one 10" that was in there before sounds better then the two in there now. Sometimes i wonder if the subs are working at all.

If the box is too big what does that do to speaker output? How can i calculate the volume of a wedge box?

Thanks
Matt

 

ok disregard this info if its wrong, i failed math.

to calculate the volume of a wedge box (or any wierd-shape) you must decompose it into shapes you actually can calculate. in your case into a 3d rectangle and a 3d triangle (french school = french math terms, ill leave it to this) like this: (i hope the pic gets uploaded)
you have to calculate the colume of the section A and then add it to the volume of the section B
the terms i will use are:
vA = volume of srction A
vB = the volume of section B
L = lenght
H = height
W = width

vA = LxHxW / 2

vB = LxHxW

vA+vB=Total volume

edit: don't forget, most subwoofer manufacturers include the driver's size into the box, therefore if it calls for 1 sq. foot of air that includes the sub's size in the box so you do not need to deduct it from the size.

 

Actually, using your diagram there is a much easier way to calculate the volume of a trapezoidial cross-sectioned enclosure. Your math is correct, but to calculate volume:

I will look at your diagram and label it this way, the Length I will call the longer dimension, the one going away from us in the pic; the height is of course the the height; and there are two "widths", I will label these UW for "upper width" and LW for "lower width".

Because the angle is constant, we can get the average internal width of the enclosure by taking the internal UW, and adding the internal LW, and dividing by two.

~W = (UW + LW)/2

Then we can simply use a normal volume formula:

V = L x W x H

Simple! This works because imagine if you cut your drawing halfway between your red line and the tip, this will give you a smaller triangulated volume which would be cut off at the average width point. Then, if you were to take this piece and spin it, it would fit right on top of the other slope, giving you a full rectangulated box.

It's hard to imagine, and if I had a good pics host I would edit your diagram to show you... hope that helps!

 

just simply add the lower section to the upper section to have equal length, for example the width of the lower section is 12" so the upper section will be 8" so if u subtract 2" on the lower section & add or put the 2" on the upper section of the box, the total width is 10". got it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by KamoteMan &raquo;</TD></TR><TR><TD CLASS="quote">just simply add the lower section to the upper section to have equal length, for example the width of the lower section is 12" so the upper section will be 8" so if u subtract 2" on the lower section & add or put the 2" on the upper section of the box, the total width is 10". got it? </TD></TR></TABLE>

now THATS why i failed math...too lazy to try to understand so i skim over it and decide i dont feel like thinking

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 4doorex &raquo;</TD></TR><TR><TD CLASS="quote">Okay since I can't leave stuff alone when its working fine I moved my subs from a perfectly good box in my Civic to a box built to fit in between the tire wells in the back of the wifes 4runner. The old box was built to the specs for the woofers, the new box is built to fit in the back of the 4runner. I tried to get the air space close to the right size for the woofers, but i think the box is too big. The subs used to be connect to the 5th channel of a 5 channel amp, now they are hooked up to a 4 channel amp, one sub bridged to channel 1&2, and the other sub bridged to channel 3&4. Well in the 4runner the box sound like crap, the one 10" that was in there before sounds better then the two in there now. Sometimes i wonder if the subs are working at all.

If the box is too big what does that do to speaker output? How can i calculate the volume of a wedge box?

Thanks
Matt</TD></TR></TABLE> If the box is too big it will have a neg. effect on output, also a problem you run into when 2 subs share the same airspace and are run off 2 amps or 2 ch. of the same amp, is cancellation, you will have a very hard time getting the two amps or 2 ch. to have the same output, it can be done, but its very hard

As for calculating volume, go with what Phat_Jax said its easy and accurate....

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Phat_Jax &raquo;</TD></TR><TR><TD CLASS="quote">Actually, using your diagram there is a much easier way to calculate the volume of a trapezoidial cross-sectioned enclosure. Your math is correct, but to calculate volume:

I will look at your diagram and label it this way, the Length I will call the longer dimension, the one going away from us in the pic; the height is of course the the height; and there are two "widths", I will label these UW for "upper width" and LW for "lower width".

Because the angle is constant, we can get the average internal width of the enclosure by taking the internal UW, and adding the internal LW, and dividing by two.

~W = (UW + LW)/2

Then we can simply use a normal volume formula:

V = L x W x H

Simple! This works because imagine if you cut your drawing halfway between your red line and the tip, this will give you a smaller triangulated volume which would be cut off at the average width point. Then, if you were to take this piece and spin it, it would fit right on top of the other slope, giving you a full rectangulated box.

It's hard to imagine, and if I had a good pics host I would edit your diagram to show you... hope that helps!</TD></TR></TABLE> 94

PS....you can always make a box that's too big, smaller, just use up unwanted volume with bracing, [bracing helps the box anyway]

 

Thanks!

Oh there is a divider wall in the box, so the subs are in their own enclosure, but what you are saying about cancelation makes sense. Maybe I'll just put my 5 channel in her car and run the subs like they used to be...

Time to go shopping for new stuff for me!

Matt