Kicker KM8 Apache 2800 Spacer & Reinforcemnt Plate

This project contains an inner reinforcement plate and outer speaker spacer ring for attaching a Kicker KM8 speaker to an Apache 2800 rugged box.  These parts are each 10mm thick to provide a rigid foundation for the speaker on the flexible face of the box.

While polypropylene, as an LSE plastic, is very difficult bond to, successful use of these parts has been performed by using Lexel gel adhesive between the speaker and spacer and between the backing plate and the case lid and finally butyl tape between the spacer and the case face. Add the speaker gill to the outside of the speaker and bind this “sandwich” with 4 M4 hex cap screws (approx 50mm long), an M4 washer on the inside and a nylon lock M4 nut.  Gradually tightening all screws evenly in small increments, while crossing over X wise to provide an even compression of the speaker gasket and the butyl tape.  Clean excess Lexel with mineral spirits before it cures.  Scrap off excess butyl tap with a plastic tool to avoid scratching the face of the case or spacer and then clean the remaining residue with an adhessive remover such as “Goo-Gone”.  Slightly pre-heating the butyl with a heat gun before cleaning is helpful.  There is no rush to do the butyl as it remains pliable through its life.

The mechanical binding provided by the mounting screw/nut passed through the 4 screw holes along with these adhesives, provides a reasonable air-tight, water-resistant seal.  This has not been tested long-term.  There is also the option to add additional binding of the backing plate to the lid using heat set brass nuts in the stock screw bosses at the corners of the lid and fabricate a bracket to connect the backing plate to the screw boss.  This has not proven to be necessary in my testing so far.

Recommended print settings

- PETG filament - 6 wall loops for strength, particularly the screw holes - 45% Cubic infill for rigidness