Damping details

Cross-sectional view of "Buddy sub" showing location of damping materials

The main resonances of concern were:

Side to side half-wave resonance between opposite extension pods - 167hz

Driver to extension pod quarter-wave - 167hz

Of slightly less concern:

Enclosure top to bottom half wave - 274hz

Driver to top or bottom quarter-wave - 274

Damping foam was glued to the endcaps of the extension pods and to the top and bottom of the enclosure.

I was initially going to staple accoustic wool to the centre brace to soften the side to side resonance. This however would not have helped with the driver to side resonance. Moving the wool to the extrance to the extension pods, covers both these problems in one go. Because I did not want to restrict the airflow to the ports in any way, I did not cover the pods containing the port inlets.

According to some Speaker Stuffing experiments I did a few projects ago, this treatment should cut the problem by around 6 - 7dB

Some more foam was added to the top and bottom of the enclosure to moderate the 274hz standing wave. Probably overkill, but it will help with harmonics.

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