No offense intended, but the stereo in the photos is obviously of very low quality.  I seriously doubt it is capable of producing tight, clean bass let alone quality sound in any of the other frequencies. No doubt, when you use the Bass Boost button, it only makes things worse.

As I suspected, your recorded voice is being distorted by intermodulation distortion.  In other words, the bad, over-blown distorted bass is adversely affecting the reproduction of the higher frequencies by the speakers.

That's why higher quality speaker systems generally employ two or more drivers (speakers) with crossover circuits to distribute the different frequencies to the appropriate driver.

There's nothing you can do about it other than to acquire a high quality audio system.