Casio CT-S1BK

I bought this for my wife who plays the piano as a second more portable option. Already having a decent digital piano about 4 times the price.
I watched tons of reviews online and had relatively high expectations.
My first impression when I turned it on was the weak sound. Low volume and lack of bass. It is not a disaster, but most reviewers say it sounds really good and loud enough through its own speakers which to my standards is not true.
Listening through headphones or a PA system is a different deal. The sounds are good and comparable to the more expensive piano we have.
The key action is very basic but this is expected for this class of product.
Overall I like it. It is built well, looks very stylish and has very good sound engine (especially for the price). But one needs headphones or external speakers in order to make it shine.