Post a photo of each part and the "assembled" part.
It's a delicate balance. A soft glue will dampen the high frequency vibrations needed for proper performance. A hard glue may shatter by the high frequency vibrations.
The recommended glues for normal speakers is a tacky white glue - the kind from the craft stores for gluing fabric. Keep the bond-line as thin as possible to prevent too much damping of the vibrations. Put a thin coat on both pieces before assembly to make sure the bond line is strong. Usually, when trying to glue with a minimum of glue, the second piece (uncoated piece) doesn't get good contact with the adhesive so put a thin coat on both and let the we edges meet up
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