8" Subwoofer Adapter Ring for Polk Audio DB 842 DVC on 10th Gen Civic Hatchback

Made specifically for Polk Audio DB 842 DVC, which has a 96.5 mm top mounting depth and a 196 mm diameter octagon screw pattern.

The Polk sub is a great step up from the factory subwoofer without amp upgrade (my Civic comes with a 540W amp built-in). It's the best bang-for-the-buck speaker I can find when writing this. It mostly fit in the factory subwoofer box besides the lack of a mounting/adapter ring.

The sub has a top mounting depth of 96.5mm on the manual. It's about 6.5mm thicker than the OEM sub. 

V1 mounted onto the factory box using the original speaker screw:

After putting on the ring and tighten the factory screws, drill some holes for the new screws (which comes with the speaker) with 3/32" drill bit. 

In the image above, I didn't model in notches for the speaker connectors. With the notches in the new version, notches were added. Align the connectors with the notch, and it should be easier to put the speaker into the box.

The connector pins are bent outward. I had to bend them back a bit to push the connectors in. Notches were added in the newer version, which should help.

There's also a couple cutoffs to compensate for the print space limitation of my MK3s.

Putting the speaker in the box…:

With the help from foam tape:

Just to be safe, mine was printed thinner than the 6.5mm required to compensate for the foam tape. However, I overdone it and left too wide a gap. So I added a layer of 1/8" weather tape along the foam ring comes with the speaker. 

Screws were tightened to the point where the foams were crushed by about ⅔ of its original thickness. There's only 3mm of plastic on the box for the screw to grab, so they can't be too tight.

Ready to go back in the car:

Added some more foam tape around the edge where the speaker grille will be pressed against. The grille does sit on the outer edge of the speaker (meaning that it's a little thicker than factory), but there's no visible bulging I can see.

Thanks for reading

If you plan to install the same subwoofer, hope this will help you along your journey.