Hi I am working on a project where I am mounting a set of speakers into steel spheres as enclosures. I have holes cut in the spheres to accept the speaker body, which fit nicely, but the mounting bracket of the speaker sticks out on either side due to the curvature of the sphere.

What would be a good method for filling or eliminating this gap? The steel sphere is 8" diameter, the speaker is 6.14" outside diameter (edge of the mounting bracket), and the cutout in the sphere for the speaker body is 5.25". Here are some pictures of my setup for reference:

enter image description here [enter image description here enter image description here

Three strategies came to mind:

  1. Getting a rubber gasket that could sit between the speaker bracket and the surface of the sphere. This is easy install wise, but seems hard to find the correctly sized part and might end up with the same problem, just with a gap between the bottom of the gasket and the sphere.

  2. Dremeling notches into the edges of the cutout of a pre-calculated depth and spacing, then hammering the notched sections flat. Pretty labor intensive and potentially imprecise, but would probably lead to the closest mount.

  3. Hammering the edges of the speaker mount to sit flush with the sphere. Probably would look busted, but it's on the table.

Any of these or other methods that seem like they would be the best approach?

Here are my steel sphere and speaker components for reference. Thanks!



  • How are you intending to secure the speaker to the housing? Commented Apr 27, 2023 at 21:04
  • @AndrewMorton M4 screws, connecting the speaker's mounting bracket to tapped drills into the sphere Commented Apr 27, 2023 at 21:44

2 Answers 2


One option you have would be to find a local makerspace or solicit a creation via Reddit for someone to design and print on a 3D printer the precise shape you require.

It's a simple matter to generate a cylinder of the diameter of the flange and of sufficient height to intersect the sphere. As you have already the diameters of both, various parametric modeling programs can accept those values and provide for a plastic "collar" which would meld the two shapes together in a semi-organic fashion.

sphere and collar

I threw together the above image in OpenSCAD but didn't bother to run the math necessary to allow for the speaker, other than the outside diameter. The code to create this image is four lines and would be more for the entire project, but it's representative of one method to create a starting point.

One can choose the material and color to match the desired sound characteristics. PLA is a hard inexpensive plastic while TPU can be found in varying flexibility ratings which may damp some frequencies.

Additionally, printing something of this type of design can be done with the flat side on the print bed, removing the need for support material and the attendant post-processing.


Silicone or polyurethane caulk

You will need to practice a bit on how to apply it neatly, but it will fill a gap of this size well.

If you want the speaker to be removable, wax the sphere before applying the caulk.

  • Expanding on your answer, one could construct a pour form into which casting silicone could be poured in a similar manner. Mold release applied to the components (including the suggested wax) also is useful, but molding/casting silicone releases rather nicely without it.
    – fred_dot_u
    Commented Apr 27, 2023 at 16:07

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