These are Rectify Series drop-in speaker systems for Atlas Master ALP-45DP locomotives. More than just a box, the enclosures feature Diapasonic Tuning™, which allows the lower frequencies to accurately develop and resonate, clears the midrange of excess resonance and tunes the upper-mid/high response. The speaker use a strap of tape to mount and no modifications are needed to replace 
the factory speaker.
 
Two speakers are available:
 
The ALMA-ALPF-RC1 is a front-mount speaker sitting behind the cab. If choosing only one speaker, this would be my preference. I do not recomend leaving the stock speaker wired with this front-mount speaker.
 
The ALMA-ALPR-RC1 is a rear-mount speaker that replaces the stock speaker.
 
The speakers come fully assembled and tested.
 
If you experience shell-rattle, you can use some thin bubble wrap, thin foam, maybe even folded paper over the top of the speakers. There should be enough material to create a gentle compression fit of the shell but not make the shell impossible to snap fully down.
 
Dimensions are:
ALMA-ALPF: 19mmH x 30mmW x 18mmL
ALMA-ALPR: 14mmH x 30mmW x 18mmL 
 
VIDEO: https://youtu.be/UNig7I6j1SA