Fiat Punto 100W 6.5" Subwoofer Upgrade Ground Zero

Here's my upgraded design for Fiat Punto original 100W subwoofer. With this you can fit most 6.5" subwoofers but it's designed for
Ground Zero GZHW 16SPL and Ground Zero GZRW 6XSPL:
Max diameter: 177 mm / 6.97“
Max mounting diameter: 153 mm / 6.02“
Max mounting depth: 110 mm / 4.33“

To fit these subwoofers you have to remove the rubber boot around the magnet for extra clearance. Measured spl gain with this subwoofer was 6 decibels which is easily hearable and the enclosures tuning frequency is about 5Hz lower than originally.

You need 11 screws to attach the adapter to enclosure and 8 for the subwoofer, diameter 3-4mm.

Here's some spl test footage:
https://youtu.be/1eLGnTAYKRI?si=NdEFaOFvWy2fs6V1&t=907

*Added 10mm spacer for subwoofer

**Added a 90 degree port extension to lower the tuning frequency, it was still a bit too high with max length straight port. The port length changed from 150mm to 300mm and tuning frequency from 50Hz to 40Hz. About 50mm has to be cut out from the original port to make room for the 90 degree bend.

***Added a coverplate if you want to use another amplifier, holes can be drilled as you wish. I measured 25W from the stock amplifier and it's too low for proper subwoofer. Instead I use SounDigital SD400.2 (2x200W at 2ohm, ~10x more power = 10dB louder, which means ~16dB louder than with original 5" subwoofer!) which is small enough to be installed inside the enclosure in the stock amp location. Hi/lo line out converter is also needed for easier install

See the pictures, use PETG or higher temp tolerance filament