I installed Cubase Pro 9.5 recently, and any sound that the program outputs is magnified to deafening proportions while everything else on my laptop is perfectly comfortable. Everything from instrument tracks to metronome clicks and imported audio files is too loud on headphones, and using external speakers is not an option in my current living situation. I’m not too familiar with DAW jargon, so please try to explain what you need to know from me simply and where I can find it as well.
Hi and welcome,
You can lower the red Stereo Out fader, you can find in the MixConsole. Or the Level Control fader, which is hidden in the Lower Transport Zone, if you expand the “Show Audio Activities & Levels” area (3 dots on the right side of the level meters).
While Martin is (of course) right that you can lower the level at the Stereo Out Fader, you shouldn’t really need to.
When you are playing back & it’s too loud is the meter on Stereo Out totally maxing out or does it jump around?
What audio interface are you using?
Thank you both for your replies. Please bear with me if I didn’t understand the questions you asked me. My knowledge of DAWs is quite simplistic, so I wouldn’t be surprised if I misunderstood anything you asked me. I’ll separate out my answers to your questions in order of when you posted.
I attempted that, but it only really helped with making instrument tracks seem less loud. I also think if the level control and such are changed, it affects the volume of a finished project when exported.
When I play even an empty project with only metronome sounds at their default volumes, the clicks are exceedingly loud. Nothing shows up on the meter unless I import something. I just finished testing out an import, and the levels look fine, but the playback itself in my headphones is extremely loud. Another thing I noticed about this problem is that the playback volume in my headphones doesn’t change when I try to change the master volume on my computer in either direction. This only happens when I’m using cubase, not when I’m listening to music some other way like on the internet or through iTunes.
I admit that I don’t know everything about my audio interface, but I’ll try my best. I’ve been experimenting with the generic low latency ASIO driver and ASIO4All v2 but the result hasn’t changed. I use regular headphones that plug into a headphone jack, not a USB port. When I looked at the playback devices on my computer, there are apparently separate devices for the built-in speaker output and headphone output. Let me know if I missed anything in the audio interface part because I personally don’t know where to find information about it.
Martin, I never knew about this control before 
But I found it a nasty little fader. After changing the level it was real difficult to set it back to zero. It doesn’t let you type a value into the field (?why?) so you have to drag the fader. Even holding shift to make fine changes it kept changing back & forth between 0.1 & -0.1 with no stop at 0.
If the meter on Stereo Out looks OK that implies that signal level leaving Cubase isn’t super loud. Make sure the Level Control fader Martin refers to above is set to 0. Under the Stereo Out fader it should tell you the peak level on that channel. What values are you seeing there? This is just to confirm that the levels out of Cubase are OK.
I’m guessing that something isn’t set right in ASIO4ALL. I don’t use that & am not familiar with its controls, but hopefully someone who knows will chime in. But poke around in it and see if you are somehow increasing the level there.
Oh, if your are changing values of controls you don’t really understand you might take some notes so you can set things back.
Okay, so I changed back to the generic low-latency ASIO driver and played with level control. Nothing seemed to happen. I was also getting no readout on the peak level for an empty project with just metronome clicks. With my tester import, it’s reading -3.1. I edited the stereo out volume and individual track volume to much more success than with the level control.
Are metronome clicks supposed to read on the output meter?
That depends on that your metronome clicks are and how you have the metronome set up. “Audio Clicks” will not show up.
It’s so loud because ASIO bypasses the normal Windows volume control. With an external audio interface you can adjust the volume, but on a laptop with ASIO4ALL that’s not an option…
It’s the same as the Level Control on the Transport Panel window.
Yes, unfortunately you are right. I’s impossible to reach 0.00 even by using Shift modifier, and you can’t type the value. 
But in fact it’s also the same value, as it is the red knob in the Control Room > Mix (Control Room Level). Here you can double-click, and type the exact value. See attached screenshot, please.
Oh, then I guess I’m using it all the time.
To the OP:
Since djw says you can’t adjust the level in ASIO4All then using this control is the best place to adjust the level out. If you think you’ll adjust this every so often you might want to enable Control Room so you can adjust it there with a big knob instead the tiny little control on the transport.
When you are exporting audio (i.e. generating a mp3 or wave file of your song) the level of the export is controlled by the Stereo Out level. However the Control Room Level will have no effect on the export file, it only controls the level of the signal going to your audio interface - which is your listening level.