Notebook Audio

I have exactly the same problem as Esther 123  with my HP Pavilion Laptop 15-cw1xxx, the audio is flat and  there is no bass sound at all. The HP PC Hardware Diagnostics Window does a very simple test about the audio, and the diagnostic says there is no problem, because the sound is heard after all, but the quality of sound is bad. Please understand, this is a problem of quality of sound, related to the lack of  frequency of the sound. There is no bass frequency, the bass is not heard at all. And it appears to be in mono sound also, because of the flatness.
I am a musician, and I have other 3 computers (1 desk pc and 2 laptops). I have been recording audio in my Pavilion desktop PC since 1998, and it still works perfectly and records the sound as I hear it from the midi keyboard. I can say the same about the other lap tops (one Pavilion and one Toshiba), but not about the HP Pavilion Laptop 15-cw1xxx.
When I use Protools to reproduce midi files with virtual sound instruments, I hear them with the frequencies as it should. But after I record the session, the sound file lacks of low frequencies at all. It does not matter which program I use to record or play, the result is always the same. When I record from an external midi keybord, it also loose the low frequencies. And all this happens even if I use the computer speakers, or the earphones, or external speakers (through an audio out). I did all the tests I could during a month, and I just conclude the sound card does not work propperly, or even the audio driver.
I bought  the laptop in Best Buy, in Mexico 6 months ago, and the publicity says it was made specially for media creators, with loud and clear audio by B&O. That was why I chose this computer, but now I am dissapointed.
You considere that the problem is solved with the troubleshooter, but it is not. And I can send audio files for you to compare.
As I see in the case of Esther, I am not the only one with this problem. I saw other musician on the internet  in the same circumstances. So, please make the test on a computer of the same model and compare it. You will notice that this is not a matter of the user or software.
Thanks for your attention.
Dante