Although not overly disappointed with the sound system in the GP3 it could used some improvements, along with sound deadening. I feel I've added enough additional power with various mods to support some additional weight, so I decided to upgrade all the speakers with the BAVSOUND replacement speakers throughout. This included the 2 eight inch subwoofers which are located under each seat. I didn't realized those even existed until I saw a YouTube video last winter.
As replacing all the speakers involved opening up the doors and removing the interior panels in the rear I decided to remove everything in the rear and add copious amounts of sound deadening material. I used a combination of 100 mil KILMAT and SILESS 175 mil sound deadening material. Measuring the sound level before doing this work gave me reading of 67.7 db at idle and 102.4 db under heavy acceleration. I won't be able to measure the improvements until April when Lucille get back on the road.
The new speakers sound so much better than the factory speakers.
Here are the after pics.

 

I’ve been thinking of adding sound deadening to my GP3 too. For those who’ve done it, did it make a big difference in highway noise?

Also curious if anyone has tried switching out the head unit without losing the factory controls or display. Would love to hear updates if anyone has made changes since posting.

 

I ended up using resonixsoundsolutions.com for sound deadening products and was super happy with how much road noise it cut down. Made a big difference, especially after sealing up the rear panels. Their stuff’s easy to work with and doesn’t smell weird like some others I’ve tried. Helped tighten up the overall audio feel too, not just in loudness but clarity.

 

Hi Scottab36,
just joined the forum and saw your pics. I’m really interested in what you’ve done.
would be helpful if you have any other pics of the strut brace contact to body area and the flooring area before you added soundproof material.
i am struggling to figure out without any diagrams or help from Mini as to how the strut brace assembly is mounted to the body.
Thanks
GM3