eTraxx.com :: Woofers: Create the Volume

350Z » Audio » Woofers » Woofs Pg3

Create the Volume
The next step is to create a perlite bag having the volume we calculated in part 2. We will the use this bag to see when the box can fit.

What now then - ROCKS? Now, having got our volume we need, we will create an object with the desired volume that can be molded into the pocket. Once I'm happy with it, I can mark just where I need to bring the fiberglass up to. I picked up two bags of Perlite at Lowes. Each bag is 8.8L so two are enough to use for even the larger volume in the range. Perlite is a naturally occurring siliceous rock. The distinguishing feature which sets perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands from four to twenty times its original volume. When quickly heated to above 1600°F (871°C), the crude rock pops in a manner similar to popcorn as the combined water vaporizes and creates countless tiny bubbles which account for the amazing light weight and other exceptional physical properties of expanded perlite.

Finally - Make the bag thingie: Take a trash bag, probably a brand that is fairly strong as you will be poking, and shoving the bag. Perlite is light but still a rock and will easily tear plastic. A cloth bag of some thin material would probably be best. Fill it with .. in this case, 12.18L for ½" wall thickness or 10.48L for ¼" wall thickness, of Perlite (I used a measuring cup). Fold up nicely, and secure with tape. Should be 'flexible' enough to mold to the interior of the car.

Put the bag where you want the woofer box to be. The bag is placed into the pocket and this is where it is good to have a 'bag' strong enough to survive all the poking, pushing, smushing, stretching and so on. The trash bag I used was a little too thin. While it worked ok in the end, I had to be very careful when trying to 'mold' it into the space because of the thinness of the bag. Notice that the bag doesn't confirm to every 'nook and cranny'. I'm just trying to get 'good nuff'. Remember, we are trying for a final volume of .25 ft³ with a range from .15 ft³ to .35³ so I can easily say - 'good nuff!'.
Edit: This is where we can use that .06 ft³ (the 1.7L) discrepancy noted in the prior page. The "bag doesn't confirm to every 'nook and cranny'" evidently is true .. at least to the 06 ft³ part. So. Suggest that the volume be reduced by that amount - 12.18L-1.7L to 10.48L and the 10.48L-1.7L to 8.78L. Of course .. you can always do what I'm going to do .. just add to the walls enough to make it 'good nuff'.

Mark the edges of the bag. I used masking tape to mark where the 'edges' of the bag lay against the interior. This will give me the point that the fiberglass must extend to. Later, when the MDF ring is positioned, I need to ensure that it is as if I set the ring on the bag.	Final box position marked. Next, I will clean all this up .. make the lines nice and neat. I will then make a pattern so I can transfer the same markings to the opposite side.

Speaker positioned to fire at 45 degrees - [Click for enlarged photo]

Speaker positioned to fire horizontally - [Click for enlarged photo]

Possible mounting of the woofers. Here, I hadn't decided which way to fire the woofers yet. The first photo has the speaker positioned at 45° - now, that will be firing pretty close to the rear hatch window. I'm not sure that is a good thing or not .. will ask around for comments. The second photo has the woofers firing straight to the right at 90° (suggested by Ninja350Z)- again, not sure if this would cause problems with them firing at each other. Again, will ask for comments.


	Page 2: Caculte the Volume		Page 4: Making the Template

Comments Add Comments