MM104 Sub Cut-Out [Archive]

mtgcolwell

09-02-2003, 11:21 PM

Hey Polkies,

I am building this new box and have come to a certain aspect of the construction that has me stumped. For the Momo 10" how can I make (or more importantly, where can I find) the cut-out that is the model of where to cut the holes in the box for the woofers? The diameter of the sub is 10.5" and that means the radius is 5.25" ... I reduced the radius by 5/8 inch to make a radius of 4.625" which would generously allow space to bolt the sub to the box (I think). Next comes the hard part - I put a pin in the middle of my 10.5" diameter cut-out and connected a piece of rope that was 4.625" from the pin to a pencil. I then traced a new circle that came out looking accurate, but is not precise. I want this box to be a precise as possible so I figure my rigged version of the cut out is not doing the trick. Anyone have any suggestions?

Also, what is the formula for calculating cubic feet for a sub box? With this dual MM104 setup do I still try to get the .66 cubic/ft setup with 2 subs, or do I multiply that number by 2 (two subs, remember?) to get 1.32 cubic/ft?

One more question. What screws would someone use to bolt the subs to the box? The baltic birch plywood that I am using is 3/4" thick and I guess i dont want to have pointy ends sticking out of box on the inside.

PoweredByDodge

09-03-2003, 12:15 PM

re volume
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box volume = length x height x width...

for two 0.66 cube woofers you'll want one of hte following.

1- a box with one 1.32 cubic foot chamber.
2- a box with two 0.66 cubic foot chambers divided by a center wall of whatever u used to build the box with. (ie design for say 1.35 cubic feet and then figure with the wall in there that'll nick out the tiny difference.

re screws
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i dunno, i always use like 1 inch long pretty thick wood screws with flat heads on the back. whether it pokes through the inside of the box (if you are not going to see inside the chamber) is irrelevant is it not?

for heavy ass subs or subs that will be downfiring and thus need some form of suspension, i've been using carriage bolts or bolts/washers/lockwashers/nuts. which is a holy bitch because then you have to put the woofers in before you put the top or the back on the box (you have to be able to get to the inside to hold the other side of the bolt). but it works for my purposes well.

re subwoofer hole cutout
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dont use the bloody template... everytime iuse a template its off by a little... everytime i try to somehow figure it out myself -- its off.

use the given cutout diameter.

polk lists them on the website as... (THIS IS FOR ONLY THE 10" momo not the 12!!!!!!!!!!!!)

Driver Mounting Depth
..............Top Mount 5-1/4" (13.34cm)
..............Bottom Mount 5-5/8" (14.29cm)
Cut-out
..............Driver Cut-out Diameter 9-1/4" (23.50cm)

i've found the greatest success for the tightest, snuggest, yet still easy to get the speaker in and not have to dick around with it for 10 hours - manner of doing things to be...

measure from top the bottom on the panel you are mounting the sub... put a dot in the middle (top to bottom)

measure left to right, and put a dot in the middle that way... match the two dots to find the absolute center of the panel.

take HALF of the cutout diameter (9.25 / 2 = 4.625 i think - get a calculator that might be wrong)... and put a straight ruler on the panel you are gonna cut... put 4.625 on the ruler on the dot of absolute center... then make a hash mark at 0 inches and 9.25 inches.

do this in 3 or 4 spots around the panel... then get a compass, and make a perfect circle.

... double check it with the ruler after.

then jig saw... slowest speed with the shortest stroke of the blade.

should fit like a glove.

you'll know if you do it right... if u do, when you put the speaker in it wont move... it wont jiggle left to right or top to bottom (well it might just a hair, but it wont be moving enough to bother you)... and if you push the speaker to its extremem limit in one direction (on the panel - moving it in the hole if it can move at all), you will not see "space" behind any of hte screw holes -- just wood.