Guitar amp for bass?

Not in any useful way.

 

Guitar amps aren't designed to handle the low end that a bass has so while yeah you will get a sound out of it, it will likely damage the amp and could break it.

 

Most combo amps have open back cabinets. A proper (for bass) cabinet wil be closed back and either sealed or ported. These will control the excursion of the speakers. An open back cabinet will offer no excursion control and damage is easy.

Also, the sound coming off the back of the speakers is out of phase with the sound from the front. Any sound from the back that mixes with the sound from the front will cancel out. Since low frequencies are non-directional the lows are what will cancel the most. This usually causes the player to turn the bass up which increases excursion and speaker damage is likely.

Speakers for bass are designed for higher excursion to more readily produce lows and move more air at low freq's. Guitar speakers usually have much lower excursion limits and can't handle the low freq's of bass.

There is no problem using a guitar AMP for bass. The speakers and design of the cabinet are the problems. You can use that amp for low volume practice but if you hear any speaker breakup, farting or distortion, turn down.

Bass giant, Carol Kaye often recorded with an old Fender Concert guitar amp. It was open back with four low power, 10" guitar speakers. Phase problems weren't an issue as the amp was mic'd from the front. She did not push the amp or speakers into distortion.

If the combo is a tube amp, don't even think about closing the back.

 

What combo amp are you questioning about?

 

You'd likely not get enough volume out of it to endanger the speaker. It's only a 5 watt amp. it would work for low volume home practicing.