Wireless speakers are usually thought to be second-rate speakers when it comes to sound quality. In the past that assessment has usually been true due in part to the poor speaker construction and also due to the poor wireless connection. However, a lot of the technology has changed and speaker vendors have invested a lot of money into research and development with the aim of improving upon the bad sound quality.
First of all, the wireless transmission that was used by the majority of wireless speakers in the past would degrade the audio signal a fair amount. In particular most models would exhibit noise or hissing and also crackling whenever other wireless devices would start transmitting. However, newer models such as cordless speakers from Amphony have incorporated much more sophisticated audio transmission. In particular digital audio transmission is able to achieve very high fidelity which is comparable to the audio quality of a music CD.
Aside from the wireless transmission, vendors have also worked hard to improve the sound quality of the built-in audio amplifiers. Previous models would have fairly high audio distortion. New types of audio amplifiers not only have high efficiency and thus eliminate large heat sinks but also very low audio distortion.