The simple and can be cheap answer is to buy a speaker.. By doing this you are increasing in most cases the speaker by a huge amount offering a better output and being able to enjoy the instructions more.
When considering the speaker DON’T pick a bluetooth one, why ? By using bluetooth you will introduce a lag time between the music and what you are see on your phone.
This isn’t a problem when listening to your favourite music but, if you are streaming a fitness class and following steps the music needs to be the same with no lag…
By buying a speaker that will directly plug into your device you will spot any lag issues and enjoy the sound. You dont have to spend a lot and even budget 15.00 euro speakers will make a huge difference but obviously the more you spend the better the sound will be.
The important part is it must plug in