Like many of you I wanted a higher quality of sound. After doing online research I decided to go with the BAV Sound upgrade. Installation was straight forward. There are written directions to installation and have a video on their web site which I watched about 5 times before I started. Total time was just over 2 hours. Went slow and took my time to do a quality job.
http://www.bavsound.com/Stage-One/Installation/
Cost was $497 and included free tool kit value $30. Used their no interest if paid in 12 mos. The sometimes have returned kits for under $300 if you like.
After is was finished the difference in sound quality was amazing. the sound is full and rich and no noticeable distortion which was there with OEM speakers.
Now at 3 weeks and with speakers broken in or breaking in the sound quality is even better.
I had the BMW professional head unit. The kit came with 4 subs and 4 tweeters. During install I realized the rear speaker on had only the subs. The kit was made for the HK system even though I selected the one for my head unit. The wiring harness was already set up for tweeters in the back. Plugged the in and the worked Called BAV and they said the Amp would handle the tweeters with no problem. When back and watched video again (they used a 2014 X1) I noticed the speaker grill in the video was oval shape was oval and mine were round. First thought was get the oval grills and replace them. Looked on line could only find the round ones. Went to dealer parts dept and parts guy let me come behind him and look with him. He finally found the oval ones on model with HK sound system. On those the grill is non replaceable. I wasn't going to pay $1,500 to buy ones with oval grills. next went on line and tried to find salvaged ones but none in beige color. So put that on hold and attached them next to grill with double stick tape until I came up with a solution.
Took my X1 in for LLumar window tint put Air-80 on front and CTX 30 all they way around. When I went back to pick it up he asked me about the rear tweeters being tapped. Told him the story and asked If I wanted the audio guy to look at it. I left one of the rear well cover not fully installed so I go back in easy as ideas developed. The audio guy explored the situation, tested the amp to ensure it handle the tweeters and said the load was fine and suggested I just drill them from the top and they will drop right in and sit on the lip. He measured the body being slightly larger than 1 5/8. the chrome and black really looks good and blends in with the trim in black no problem with looks. I asked him what he would charge to do it. He said plan on 2 hours @ $85 per hour. He said I know that a lot if you can just do it yourself which I did and took 30 min.
Used the 1 5/8 hole saw and drum sander bit to get a tight fit. Put clear silicone sealant on lip and tapped in place with piece of pvc, cleaned up sealant and C-clamped in place to for good seal. Let dry rest of day finished up after dinner and looks and sounds great.