How can I force my computer to always use my external speaker?

Question

I have an external speaker (USB2 device) on my Aspire 5 laptop, as the computer's laptop is so unloud and tinny-sounding.

It works fine when it works, but for some reason, the sound sometimes gets swapped back and forth to coming out of my external and internal speaker. It seems like it might be dependent on certain frequencies that will make it switch, or something in how the original audio was recorded, because often it will switch always at the same exact spots (not randomly).

Is there any way I can force the sound to always be played on the external speaker, and ignore the internal speaker altogether?

I implemented harrymc's suggestion, but it still (bizarrely) doesn't work. These are my settings:

UPDATE

I wrote too soon; the external speaker is going on random wildcat strikes still; since the internal speaker is disabled, it goes from external to silence rather than external to internal. So the problem is with the external speaker and/or the recordings. I say the latter because it's always in the same places in the recordings where the sound drops out.

Specifically, I'm playing along with recordings of songs (I'm playing along with the bass part with a different amplifier/not connected to my computer). So they are songs playing from websites (such as youtube and scottsbasslessons) that are "dropping out" in spots.

UPDATE 2

I replaced the external speaker with a pair of Logitech speakers. So far so good.

Answer 1

I think that you need to disable the internal and also set the USB as the default device. Try this.

1. Right-click on the "Speaker" icon in the system tray (bottom right corner of your screen) and select "Open Sound settings."
2. In the Sound settings window, locate the "Choose your output device" dropdown menu. Select your external USB speaker as the default output device. If you don't see the speaker listed, make sure it's connected and powered on.
3. To completely disable the internal speaker, right-click on the "Speaker" icon again and select "Sounds."
4. In the "Sounds" window, switch to the "Playback" tab. You will see a list of available playback devices.
5. Find the internal speaker (usually labeled as "Speakers" or "Realtek High Definition Audio" or similar). Right-click on it and select "Disable."
6. Click "OK" to save your changes and close the window.

Answer 2

If the sound is jumping from one device to another, it'd seem that the AUX-jack is disconnecting. You'd might want to try and replace the cable?

Windows won't move your sound otherwise. One other possibility is to set the application to always output from AUX - but again, it'll probably get disconnected and you will hear nothing, instead of the sound "jumping" to another output-device:

Go to control panel > sounds > "app volume and device preferences" ( at the bottom ). there you can control exactly where each application's sound should be played ( see attached picture )