Power Outage

Your MacBook Pro is unaffected by such things since it's battery powered. The worst that probably happened is that it got confused when your external HDD was no longer available, prompting an admonition to not disconnect it so rudely next time.

All my Macs have suffered from random power failures for years, the result of everything from lightning storms to hurricanes to toddlers pulling out power cords, with no apparent ill effect. Same for AirPort base stations.

Having said that it is a good idea to have a UPS for desktop Macs, if for no other reason than to prevent losing your work.

Don't know about the speakers.

So the disk is not damaged, hopefully?

Not damaged. You can be as certain as possible.

Hard disks have been designed for years to react to such events by parking their read/write heads in a safe "landing zone" within the first few milliseconds of an impending power failure. This minimizes the possibility of physically damaging the the hard disk due to a power interruption.

The Mac's file system also maintains file system integrity by "journaling":

Journaling is a technique that helps protect the integrity of the Mac OS Extended file systems on Mac OS X volumes. It both prevents a disk from getting into an inconsistent state and expedites disk repair if the server fails.

When you enable journaling on a disk, a continuous record of changes to files on the disk is maintained in the journal. If your computer stops because of a power failure or some other issue, the journal is used to restore the disk to a known-good state when the server restarts.

With journaling turned on, the file system logs transactions as they occur. If the server fails in the middle of an operation, the file system can "replay" the information in its log and complete the operation when the server restarts.

Although you may experience loss of user data that was buffered at the time of the failure, the file system is returned to a consistent state. In addition, restarting the computer is much faster. Always remember to back up your data as frequently as necessary.

If you had a Windows computer this might be a different story altogether, but you have a Mac. Rest easy.

As long as the electrical installation is within the norm, meaning adequate ground and properly polarized outlets, the power brick will be ok. If your area is prone to thunderstorms, adding surge protection to the outlets can be also a good preventive measure, as they will prevent any lighting-induced voltage/current spike from reaching the electronics.

skywalkerkenobi wrote:

Do you know if the hardware inside Computer speakers can be damaged by sudden lose of power?

None. Most electronics are not damaged by loss of power. (Some that may be damaged, eg, optical disc drives or hard drives, are actually electromechanical devices.) What can damage speakers (and other electronics) is the return of power. If there is a loss of power, make sure to switch the device off (switch it back on after power is restored), and, in the case of speakers, turn the volume to minimum. Turn it back to the desired level only after the power is restored and the speakers are switched on.

skywalkerkenobi wrote:

The device does not have a on off button

No, it does not have an "on off button"; however, it does have an electronic switch (see your user guide). As a rule, devices with electronic switches are automatically switched off when power is lost.

I can assume that they are not damaged?

You don't have to assume anything. With speakers, it's simple. You listen to them. If they are damaged, you'll hear it. If you don't hear any damage, they're not damaged.

skywalkerkenobi wrote:

So you are saying that the speakers would automatically shut down if it loses power?

The Bose Companion 20? Yes.

The speakers do not sound different after the outage.

So stop worrying and start being productive with your Mac.

skywalkerkenobi wrote:

The voltage changing box is producing a near unhearable hum.

What's a "voltage changing box"?

skywalkerkenobi wrote:

Bose names it switching power supply.

I have a vague suspicion that you'll find that it's not just Bose that calls it a 'switching power supply'.

Yes, it's normal.

You worry too much.