YEs, but is a building block to great sound productio.
To improve the sound drastically, you can start by increasing the tickness of the paper, change the plastic cup to fibre and add a vibration pivot which would enable bass sound production. i will give a tutorial on how to build a better one very soon.
yes, by increasing the weight of the cone, low frequency response improves but high frequency reduces. Further u hv to check the linearity of frequency response. To check frequency response requires acoustical room & test equipments.
Hope this clarifies what i mean.
Simply study the construction of midrange speaker & tweeter. U will understand a lot. The cone should be light & stiff/strong. This helps to get more high frequency response. Also the voice coil weight & spider stiffness plays a big role in frequency response & resonant frequency.
I hv tried to explain u in short & simple way.
There r books on this subject available with audio express.