Here is an experiment with some old speaker drivers which delivers loooonng delay low frequency DIY reverb for almost no cost.
The reverb assembly consists of a 1 5/8 inch diameter Slinky Jr spring suspended on a four foot long frame, mechanically coupled to speaker drivers as transducers, and installed in a foam lined packing case.
The spring is mounted with tiny ball bearings to allow for free rotational movement. A four inch full range speaker drives one end of the spring while smaller speakers pick up the delayed vibrations at two other points further along the spring. A couple of pieces of foam rubber are inserted inside the spring to control a low rumbling bass resonance in the slinky.
The drive speaker has a round plate glued to the cone with silicone rubber, which is then coupled to a rocker arm with an “L” bracket and small bolts. All of these parts are made from plastic to prevent magnetic interference with the drive speaker. The other end of the rocker arm is clamped to the slinky near the end bearings. These bearings (BTW, most old VCR transport mechanisms have a few of these bearings buried inside) hold the rocker arm center of rotation at the center of the slinky’s diameter, for most efficient transfer of drive speaker linear vibration to slinky torsional motion.
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