Hi Eduardo,
The overall sound of the SX900 depends, among other things, on the Master EQ and Master Compressor settings.
These settings apply to the internal speakers as well as if you play through an external PA system or headphones. Under certain circumstances, you may have to change (switch) the Master EQ / Master Compressor settings, for example if you switch between internal speakers and headphones. (There are 30 user slots on the SX900 for your custom compressor and EQ settings.)
A good pair of headphones should already sound good with the "EQ > Flat" + "Compressor > Natural" (or Compressor switched OFF) setting. The sound through the internal speakers also depends to a certain extent on the room or the POSITION in the room in which the SX900 is set up. For example, if it is placed directly on a wall or in a corner of the room, you will hear more BASS or low frequencies than if the keyboard is a little further away from the wall.
I recommend that you first read through the relevant chapters in the manuals:
- SX900 Owner's Manual, page 96: "Adjusting the Sound at the Final Output (Master Compressor, Master EQ)"
- SX900 Reference Manual, pages 103/104: "Editing EQ Parameters"> Master EQ
- SX900 Reference Manual, pages 108/109: "Editing Master Compressor Settings"
Please open the display "Mixer > tab Master" to see which settings are active there for "Compressor" and "EQ".
For a neutral sound, you could try the following settings:
- Compressor ON, Preset "Natural" (or Compressor switched OFF)
- EQ: Preset "Flat"
Also try the other preset EQ types ("Powerful", "Mellow" and "Bright") to hear the differences. It is best to play different Preset Styles (and their OTS) with these settings.
Note: With the preset EQ type "With Subwoofer" the low-frequency bands are reduced. (Intended for operation with an additional, external subwoofer.) This preset may also be suitable for you without a subwoofer.
If you basically like a certain EQ preset (e.g. "Flat"), only the low frequencies are too much, first turn the gain control for the frequency 80Hz (far left) a little counter-clockwise (e.g. from 0dB to say -3dB).
If that's not enough, you can also use the next Gain control to the right. A center frequency of 250Hz is set for this frequency band in the "Flat" preset. If necessary, you can also change this frequency (tap on the value) so that this Gain knob controls e.g. at 200 Hz.
The Q-Factor determines the so-called "bandwidth" for each individual EQ frequency band. Q=0.7 (= standard setting) corresponds to the largest possible bandwidth. With this attitude, you can least "go wrong". However, if you want to lower a certain (disruptive) frequency (e.g. because of room resonance), I recommend setting a narrower bandwidth, e.g. Q=1.5. Then you can lower the frequency set for this frequency band with the gain control in a narrow band, i.e. without strongly influencing the frequencies below and above.
Hope this helps!
Best regards,
Chris