Hi there

I installed a Pioneer SB300BT and two 100mm MTX TR 40C speakers inside the original grills. I adapted the equalizer and sound is good when the car is running at low speeds. But when I go on the highway and run it over 100km/h the sound becomes very thin and bad.

What options are there to improve this? Would a under seat subwoofer help? Or is this something that can't be really fixed as the Panda is just a loud car? What would you suggest?

adding sound deadening material under the carpet to reduce road noise would be a good start it shouldn't be a difficult job and it would go a Long way to help

I had 2 extra 2-way 13cm speakers in the rear trunk cover.
And a Subwoofer in the trunk with awesome sound as a result.

All of these things are true-

But it might be worth considering an amp; or more efficient speakers, to get a higher output, relative to the road noise...