Relatively neutral is a very dodgy term, you either want neutral or natural
Natural will mean a smoother top end, neutral a stronger one, since neutral would mean something that wouldn't color the sound either way, so music would come as recorded, so large differences between records and masters. Audeze LCD-MX4 is a great example of this, they really let the master shine through.
Neutral - Say something like FiiO F9Pro is good, but has a little stronger top end than it should, ETY ER4-XR, but has a little too little bass and too little treble to be actuall neutraly, so too smooth and not really enough bass,
Natural - Say HD600 from Sennheiser, and Dunu DK-3001, Simgot EN700 series, there are more.