iMac volume problem

[SaltedsnakE]

Hello! how can I set my iMac's(late 2015 retina) volume, or sound, setting at its default? and by default I mean the state of when I first booted it. I posted a thread regarding reduced bass sound of the computer but no one has answered yet. I suspected an injection of few drops of windex into the speakers to be the cause of the problem but I don't think it is anymore. I think my mac's general level of volume is lowered since sometime past I didn't notice. Any suggestion for such issue? I would really really appreciate your help.

 

[DeltaMac]

You can immediately reset your Mac's system volume to default setting with a restart while resetting PRAM (NVRAM)
Very easy to do that. Restart while holding Command-Option-P and R. You will hear the boot chime sound.
Continue to hold the same 4 keys until you hear the boot chime two more times, then release the keys to allow your Mac to startup normally. You will likely hear a difference between the first and second boot chimes, indicating a reset to default levels.
That PRAM reset will also un-set your startup disk selection, so be sure to go into your System Preferences, then Startup Disk. You will need to unlock that pane by clicking the padlock, before you can set the Startup Disk for your preferred boot drive - usually whatever drive is the internal one.
Anyway, there's your volume reset to defaults.

note for the future: Try to avoid injecting foreign liquids into your iMac. It just doesn't need any form of fertilizer, and you certainly don't want to be spraying Windex directly on your iMac.
Here's what I use to clean the screen. One of those ultrasoft cleaning cloths, lightly sprayed with a vinegar-based glass cleaner (absolutely never ammonia-based). Slightly damp cloth (never wet) will usually clean that glass squeaky clean.
Oh, and try to learn not to touch the glass. Way less need to do much of anything to the screen when you don't ever touch it. (Maybe that's just me )

 

[SaltedsnakE]

You can immediately reset your Mac's system volume to default setting with a restart while resetting PRAM (NVRAM)
Very easy to do that. Restart while holding Command-Option-P and R. You will hear the boot chime sound.
Continue to hold the same 4 keys until you hear the boot chime two more times, then release the keys to allow your Mac to startup normally. You will likely hear a difference between the first and second boot chimes, indicating a reset to default levels.
That PRAM reset will also un-set your startup disk selection, so be sure to go into your System Preferences, then Startup Disk. You will need to unlock that pane by clicking the padlock, before you can set the Startup Disk for your preferred boot drive - usually whatever drive is the internal one.
Anyway, there's your volume reset to defaults.

note for the future: Try to avoid injecting foreign liquids into your iMac. It just doesn't need any form of fertilizer, and you certainly don't want to be spraying Windex directly on your iMac.
Here's what I use to clean the screen. One of those ultrasoft cleaning cloths, lightly sprayed with a vinegar-based glass cleaner (absolutely never ammonia-based). Slightly damp cloth (never wet) will usually clean that glass squeaky clean.
Oh, and try to learn not to touch the glass. Way less need to do much of anything to the screen when you don't ever touch it. (Maybe that's just me )

Thank you! and also thank you for the cleaning tip! I'm trying PRAM right now
*EDIT*
I tried the PRAM and I think volume is now adjusted as I intended thanks to you! but still the bass feels weak in the particular song I've been testing. I don't even know what to ask at this point...

 

[DeltaMac]

Then, just a suggestion:
If you feel that your speakers don't give you enough bass (and that may be completely normal, not indicating a faulty speaker), then use external speakers of your choice to give you a more solid sound.
You did not say which iMac you have - 21.5-inch, or 27-inch?
I _doubt_ that you actually damaged the speaker through liquid damage. I think it would take an unusual effort to do that.
So, if you think that your speakers (both of them) have defective cones, including the sub-woofer chambers inside, then take your iMac in to an Apple store to see what a "genius" can offer as an opinion. You still have the original 12-month warranty, so ask about that. You can choose not to volunteer your theory about liquid damage, that's really pretty unlikely with the angle that the speakers project sound (down!), and it would tend to unnecessarily "complicate" your discussion about warranty service.