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@123toid Something I started doing with my designs is use of dadoes and grooves in the design step to help tie elements together more, as well as doing a modified D vertical brace (how some companies run a vertical brace with a rounded cut out to make way for the drivers and to not fully cut off the two sides of the box from each other, often accompanied with horizontal bracing at points), but instead, since I glue two sheets of the material together to make the brace (so 1.406″ for plywood, 1.5″ MDF), you can then cut a part and inverse each of the two that get glued together to then put the horizontal brace inside the opening of the vertical brace, then have where it is a halved-jointed along the spine and front part of the brace that in the middle runs from the top to the bottom, while gluing the part cut back in place afterwords.
An example may make what my thoughts are easier to understand. Take this brace here (being considered for the tower subwoofer chamber):
Now, since you make two of these to glue together, you can cut one at the top, then one at the bottom around where the red lines are. You then move the horizontal braces to the inside space, then glue the two vertical pieces together to make the 1.5″ thick brace, with the mirror part being whole acting as a support for the piece that was cut to allow the horizontal braces to fit inside. Then, the horizontal braces, without the need for the shape at the bottom to hold the vent shelf, just slide into the cut positions to create the halves-joint between all the bracing. This reinforces the position and prevents flex of the bracing as the horizontal reinforces the vertical bracing and vice versa.
To take it further, either a dado set or your CNC can cut grooves and dadoes in the vent shelf and the walls and top and bottom, similar to some kits you have used, although the corners may need cleaned up with a chisel, to help really connect the elements together. But, do not do this to the front, generally, due to concerns that if you glue that last separately, minor deviations or swelling due to glue application may make it not fit in those grooves. Plus the baffle can be reinforced by doing a double baffle to stiffen it, which with an MTM design and not having many contact opportunities with the bracing of the rest of the cabinet kind of makes that a way to stiffen the front without much additional work, while allowing a canvas to use your CNC to shape the baffle, such as having a slope away from the center tweeter like pyramid walls, reducing down to around 0.75″ at the connecting edge (so after a flush mount, give like a quarter to half inch buffer on the sides, then slope from that point to the edge of the baffle), while with the larger drivers doing a more rounded part to the baffle edge (doesn’t recess as much). I will have to figure out how to draw what I see in my head, but the idea is that since you have the CNC, start playing with some design elements in the baffle, which the double baffle gives ample room to be creative with.
Although the bracing equations are wrong for me now including a vertical brace to hold the vent (which can also act as the spacer, along with the grooves for the vent in the sides, to help the vent be held at the perfect distance), but throwing it in my spreadsheet, it approximates a box, using a vertical and two horizontal braces of MDF, to be around 7″x20″x12.88″ (just use 12 7/8″) internal dimensions, with a front facing vent, the vent is calculated as 2 vents of 2.75″ (7″ internal width minus 1.5″ for the bracing thickness which separates it into two vents, then divided by 2) which gives a 1.5″x2.75″x21.07 vent length. I would wrap the rest up the back and create the slot in the sheet goods going upward, but no dado or groove in that part of the vent, only a half-joint at the top the thickness of the amount for the vent material (1.5″) so that you slip that part in, slide it up, then when you slide in the part for the vent from the baffle toward the back, it locks in underneath that part holding it up into the half joint. That would create a pocket for where the bracing is if using a dado in the bottom piece, but I suppose the second part of the vent could have a little piece glued onto it once in place, followed by the second part being slid into place. I know, this is sounding more like a 3D jigsaw puzzle with the bracing the more I speak about it. LOL.
Box volume is 0.594 ft^3. I might try calculating it using the 0.75 ft^3 and the other factors you used to drop down the F3 to 35Hz later.
I did not model for any damping material in my calculations yet as I am trying to figure out if I can come up with a better way than creating a specific formula for each design I create moving forward (although I am not going to hold my breath on that).
But just where my thoughts are going with techniques for bracing and building. Let’s hope sheet goods pricing start dropping soon. Lumber futures are already down to $458.60 as of today and we are fast approaching the end of construction season, meaning hopefully soon demand on sheet goods will drop off.
BTW, my bracing is still simplistic when compared to something like this Polk internals: