Most Headphones receive ‘grading’ based upon performance “out of the box”. Most reviews suggest EQ/PEQ, Capra band, pads etc.
Is there a list of ‘tuner’ headphones that might or might not already be ‘upper tier’ within their price ranges, but really come to the fore (within their price range or higher) with some tweaks?
[I’d owned a Mustang in the 90s in the UK. OK, it was quick, but otherwise frankly terrible on our roads. The best tuning was not the classic power upgrades but handling by a modest suspension upgrade, wheels and tyres. It was never better than a BMW M3, but a heck of a lot closer than others]
I don’t think the car mod analogy works well for headphones, as headphones involve relatively simple and straightforward technology.
Most tweaks address:
Comfort, such as adding new headband or Dekoni Nuggets to relieve pressure points.
Tone control and artifacts, such as swapping leather for fleece pads to reduce brightness or putting tissue paper in the cups to reduce harshness (e.g., Grado; Beyerdynamic).
Replacing the cables and/or converting to balanced to ~perhaps~ improve performance. Silver cables do sound a bit brighter to my ears, and balanced can sound a bit cleaner/blacker.
Some people go beyond this, such as switching out drivers, but then you get into questions of whether it’s the same product at all. There’s no basis for comparison any more.
When I think of headphone enthusiast tweaks, the entire chain and the Sennheiser 600/650 come to mind. These are considered “scalable,” and worth the effort of changing components. The discussion then often shifts to synergy and DACs and tube amps and fresh pads rather than headphone mods per se.
My Cadillac LYRIQ comes to mind. It has low background noise, and with the addition of an aftermarket sub and EQ via ROON ARC, it provides about 300 miles of driving and audio pleasure.