It is very clear what the difference is between a Full HD screen and an HD screen, and between a 13 camera and a 20 megapixel camera, but it is not so clear what the difference is in terms of sound output, since why is this difference. One of the keys is the DAC that the mobile has.
What is the DAC?
Headphones, or speakers, require an analog signal. However, mobiles have a digital system. Therefore, it is necessary to convert the signal from digital to analog. While a digital signal is made up of two values, 1 and 0, an analog signal is made up of electromagnetic pulses. How to go from a signal of the first type to a signal of the second type? With a DAC, which stands for "Digital-to-Analog Converter," or digital-to-analog conversion.
Quality DAC?
All mobiles and computers with a jack socket have a built-in DAC. Your mobile also has a DAC. However, there are good quality DACs and more standard DACs. What mobiles have a quality DAC? In general, high-end mobiles have quality DACs, although this might not be the case for all mobiles. For example, the iPhone 6s Plus does not have a Hi-Res compatible DAC, while the high-end Samsung Galaxy do. Other mobiles that have high-level DACs are the Meizu Pro, both the Meizu MX4 Pro and the new Meizu Pro 5, precisely because Meizu had high-quality sound equipment.
Better sound?
Now, do these mobiles, like the ones already mentioned, really have a better sound? Yes and no. Your speakers don't sound better. It is possible that the speaker of the Meizu Pro 5 is worse than that of the iPhone 6s Plus, for example. But it is that the great relevance of the DAC is when we use a sound equipment to which we send the signal from the DAC. When we use headphones, or when we connect speakers, the sound quality of a Meizu Pro 5 will be better than that of an iPhone 6s Plus. Thus, the DAC is one of the most relevant elements when determining the sound quality of our smartphone with a computer or with headphones.