When installing a sound decoder we often must fit a loose speaker into a way-too-small sealed enclosure. Bass response always suffers. Standard speakers want to be in enclosures far larger than we can fit in our models.
A small Taiwanese company, Tang Band, has been producing a line of very high quality, small multimedia speakers, including some already in small sealed enclosures with passive radiators. In each the passive radiator, essentially a weighted speaker cone without a voice coil, is tuned to resonate at a frequency lower than the active driver. Set up this way, it extends bass response by about an octave.
The 1925S and 2008S modules are more expensive than the typical model railroad speakers, but at the moment they are the best sounding I’ve installed, putting out much stronger bass and cleaner sound. The 2008S will distort at high volume, but is still plenty loud. It is rated at 1/2 watt, and the Loksound V4L decoder has a 3 watt amplifier. With this pair you do want to program the volume considerably lower than factory default.
Here’s a recycled photo of the two modules side-by-side. The larger one easily fits in Alco and EMD hood units such as an RS11 or GP30. The smaller speaker is not as tall and fits inside Atlas SWs, under the radiator cutout.
I overlaid the data sheet frequency response curves of both modules for comparison purposes. The larger module has an extended bass response below 200 Hz.
A good friend has speaker characterization equipment and measured a 1925 module. He confirmed the surprisingly-strong low bass response.
These speakers are also available without an enclosure. Unfortunately, the passive radiators are not.
Do note that these are 4 ohm units. Some brands of sound decoders require 8 ohm speakers.
Sound samples can be heard in the Loksound Full Throttle thread.