Bose on Mazda a tad better then no brand 6 speakers on the 2017 Elantra Sport.
This is just strictly objective sound quality, clarity, distortion, noise, base 2 distinctive beats isolation, not muffle together.
Not the subjective more/less base/treble, warn/cold, etc that related personal preference.
Harman Kardon on the Volvo is so much better than Bose, like 100x better, there is no second doubt.
Again this is on objective sound quality alone.
The instruments vs vocal separation, and separation among different instruments are next level. You'll notice a lot not dominant instruments playing, that wasn't aware before.
The whole soundstage also appear wider, sounds appears to come from further distance beyond the car 4 walls.
To an extend, it made me question how Mercedes justify the hefty price tag of Bang & Olufsen, the quality is not at the same level as HK in Volvo.
And I own B&O devices, I know how good is B&O quality. Sometime it is the chassis, interior, rather then speakers themselves.
Bowers & Wilkins on Volvo again next level from the HK. Base, mid about the same.
Treble is clearer, vocal from artist come out "CLEAN", and contains more "DETAILS".
Especially when the female vocalist do a very subtle transpose at the end of highest pitch, the HK can completely loss that details.
Actually same for most major brands soundbars, headphones that I experienced, they loss this kind of details. Don't talk about B&W 803 level of madness.
An audiophile, that super tall guy at mid-valley told me sound wave bounce off glass make huge difference. But I seriously can't recognize the impact objectively, scientifically.
Interested to test Mark Levinson in Lexus next...
I don't have experience with high-end sound systems in expensive upmarket cars such as Volvo, Mercedes etc. but share the same experience that the Bose sound system in the Mazda is slightly or noticeably (not significantly) better than most bread and butter Japanese models or any other vehicle in the price range of RM100k+/- or higher. I have owned Bose lifestyle systems since my student days and B&W N805 more than 20 years ago. Bose is known as a lifestyle product rather than outright sound quality. People who predominantly look for sound quality don't really look at the Bose.
I usually don't listen to music in the car when the sound system is crap. The stereo will be switched off completely silent if I don't enjoy music due to the subpar quality of the sound system. I somehow miss the Sony sound system in the Ford Focus but anyway music in the car is not important to me as I can drive without any music on.