Im no audiophile, but I consider the acoustics of a 911 cab. I never expected concert hall sound in these cars but a modern radio and speakers will likely be sufficient to achieve satisfactory sound.
You’re playing cassettes and not ‘as ancient’ CDs, so a lot clarity is lost there. Remember “Is it live or is it Memorex”. Not use if that reference was reel-to-reel or cassette quality, anyway
a set of speakers matched to modern head unit and perhaps some strategic sound deadening material helps.
I had a Blaupt CR4096 w/2 oem door speakers, my PO replaced w/an ugly Pioneer. I ditched the cassette and went with a Continental TR7412 and kept the 48 yr old door speakers. I’m pleased with the media type features of this modern stereo but found no noticeable improvements with the sound, nor do I care (to replace door speakers). Plus radio looks good and bland, almost stock.
I once bought and installed a used double din stereo radio cassette that had a stacked equalizer (Nissan), with the mix of music genre and FM, fiddling with the equalizer each time was troublesome, even occasionally knocking the sliders out of sync. Nice radio worked well with stock 4 speakers but couldn’t really define the usefulness of the equalizer over just the stereo. Noisy car, sound bouncing around, etc. wasn’t worth the 2 DIN cut out effort.
I’m hard of hearing now, so Balance and Fade is my equalizer.
On new radios….do they even make single Din cassette players anymore, those with built-in equalizer modes (rock,jazz,talk) ?
Added enlightenment:
https://www.hagerty.com/media/tags/obsolete-car-audio/