-Left speaker actually working
-Root Explorer or similar file manager (recommended method)
--ADB if you don't use Root Explorer
--Text editing program (Notepad++ is recommended and free) if you decide to use ADB
Let's start with the recommended method, Root Explorer.
Step 1: Open Root Explorer and navigate to /system/data.
Step 2: Tap on the "Mount R/W" button.
Step 3: Tap and hold on the file "srs_processing.cfg" and once the menu comes up, select the "Open in Text Editor" option.
Step 4: Scroll down to:
//BLOCK: ( srs_spk_int : ) TruEQ - Internal Speaker Tuning
Here's where things can get kind of annoying, because you will have to change values, save & exit, then reboot and test your results. Anyway, there are 4 values you will want to focus on, and those are:
srs_spk_int:trueq_lband0 = 900.000000,-9.000000,0.700000 // TruEQ Left Band 0 Tuning (CF Gain Q) -
srs_spk_int:trueq_lband1 = 11000.000000,6.000000,0.500000 // TruEQ Left Band 1 Tuning -
srs_spk_int:trueq_lband2 = 400.000000,3.000000,0.7000000 // TruEQ Left Band 2 Tuning -
srs_spk_int:trueq_lband3 = 2500.000000,-9.000000,0.700000 // TruEQ Left Band 3 Tuning -
The values in bold are the only ones I've messed with so far with very good results. The beginning values have a maximum of around 16000, and 17000 results in your left speaker not working, something above 16000 but below 17000 may work but I haven't tried it. The two middle ones, I don't know the maximum because It wasn't necessary to up them that much. For example, mine look like this:
srs_spk_int:trueq_lband0 = 1400.000000,-9.000000,0.700000 // TruEQ Left Band 0 Tuning (CF Gain Q) -
srs_spk_int:trueq_lband1 = 16000.000000,10.000000,0.500000 // TruEQ Left Band 1 Tuning -
srs_spk_int:trueq_lband2 = 900.000000,7.000000,0.7000000 // TruEQ Left Band 2 Tuning -
srs_spk_int:trueq_lband3 = 7500.000000,-9.000000,0.700000 // TruEQ Left Band 3 Tuning -
For me, this works out wonderfully! However, results may vary.
Once you've changed those values, save & exit, then restart your TF and examine results. Repeat steps if necessary.
Method 2: ADB. NOTE: Make sure USB debugging is enabled.
Step 1: Connect TF to computer.
Step 2: In a command prompt/terminal navigate to where your Android SDK is and type adb devices to make sure your TF is recognized, if so, type adb remount. If it succeeds, proceed to step 3, otherwise you may need to either enable USB debugging, or install drivers.
Step 3: Type "adb pull /system/data/srs_processing.cfg" It will save the file in the same directory as adb.
NOTE: Do not close command prompt/terminal.
Step 4: Open "srs_processing.cfg" in Notepad++ or whatever qualified text editor you use. NOTE: Due to the nature of how Windows reads files, Notepad might not save the file correctly and definitely will not open it looking pretty. Wordpad might be the same. Basically, the file needs to be saved in UNIX format.
Step 5: Scroll up to Step 4 of the Root Explorer method and proceed.
Step 6: Save the file with Notepad++ or whatever qualified text editor you use.
Step 7: Back in command prompt/terminal, with the file saved over the original type "adb push srs_processing.cfg /system/data/"
Step 8: Reboot your TF as you normally would, or with adb method "adb reboot"
Examine results and repeat steps if necessary.
Attached below are the default srs_processing.cfg and my edited one.
Feel free to post back your own values, because they may be more refined than mine or may work for someone else better as well. ENJOY!
Update: Thanks to seshmaru, a typo was discovered. ASUS added an extra zero to the bold part in line: srs_spk_int:trueq_lband2 = 400.000000,3.000000,0.7000000 // TruEQ Left Band 2 Tuning - I've updated the default file as well as my edited one to remove this extra 0. While this did boost volume in the left speaker for me, it still was not on par with the right one.
Update 2: verkion suggests "turn off the Hard Limiting in the Internal Speaker Boosted section by setting:
hlimit_skip to 0 instead of 1. This gave me a little more "headroom" before distortion became unbearable. A hard limiter is a CLIPPING filter...it just "snips the sound" when it goes over a preset value instead of trying to "scale down the volume.""