Many thanks to SWLing Post contributor, Steve Lebkuecher, who shares this video which compares the speaker audio of the PL-990 and PL-680:
https://youtu.be/anWfnsWNi_Q
Click here to view on YouTube.
I would love to hear a comparison with the PL-880 since the PL-880’s audio is also superior to that of the PL-680.
one more video on FM performance:
This is a good comparison of a small diameter speaker and one which is slightly larger. Neither give an indication of the sound quality available including stereo sound. Many people use headphones which will drastically improve the sound quality and you can hear the location of the sound source.
Also many such comparisons use a microphone from the camera. To provide the best sound it is better to plug into the headphone socket with a 3.5 mm plug an attenuator (couple of resistors to reduce the voltage to mic level) and then plug the other end into the camera will drastically improve sound quality.
It seems the PL-990 has a more bassy sound and lacks treble compared to the PL-680. I am not that enthusiastic about the PL-990, though. Yes, it is a brand new PLL dual conversion radio, but unexplicably lacks synchronous detection. Tecsun is missing a chance to improve this feature which I thinkg is already very good on the PL-660.