4-DD515, DD M1c, 2005 Denali

An octagon is actually pretty easy to make, if you have the right tools and a second set of hands.

The angles are 22.5deg, I use a Wixey digital angle gauge (best $40 you can ever spend for a table saw accessory).

This port is 196sq inches, 6.375" internal, 7" external cuts. With a good saw, just set the gate and make 8 cuts.

I hold the pieces one-by-one in place and have my co-worker Jay pop a brad 2" from the top and 2" from the bottom on each panel.

Then ratchet strap it together over night, its solid as a rock. The glue holds it, not the brads.

I'll post pics tomorrow showing that the sides are square.

Should have the box finished then.

 
The port is solidly square.







Port attached to the front panel and routered out.



Rear wall and baffle bracing. 2.5 x 1.5" baffle brace (connects to side wall) and 6" wedge for the back wall.



I ran out of paint for the port, but here is a nearly finished shot.



I will finish the paint and carpet the box in the morning.

 
Holy giant ports batman. How much area per cube?
I know this port looks HUGE, but it was actually 196sq inches of port area for at 14.5cuft (net) box.

So the port area per cubic foot was just 13.5sq/cuft.!!!

But, this is a 4-DD 515 build with only 1500wrms. Port noise will NEVER HAPPEN at that level of cone displacement.

The actual 'on paper' numbers for this build were ~14.5cuft @ 38hz. But 'in-cabin' tuning changes alot with big box builds, and I accounted for that change in my design (port firing into the back hatch and the distance to the listening position)

This box build is heavily braced...and I offered the owner the chance to replace the subs, add batts, alts, and a second DD M1c....to get louder.

I just have to say, the owner of this vehicle was stunned after hearing what he had purchased.

I wish I had taken a vid of his reaction....if the owner drops by soon, I will video his review for this install.

also...round ports are more efficient.

Slot-vents are ok, but a round vent is the most efficient vent (for tuning).

 
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