Audiophile slang
Fun tuning
Also called fun sound, consumer tuning, bass-boosted
A fun tuning is a deliberately non-neutral sound, usually with boosted bass and lively treble, chosen to be exciting rather than accurate. It is the reviewer’s polite word for a V-shape that works.
Fun is the honest alternative to "reference". A V-shaped or bass-heavy product can be a bad choice for judging a mix and a great one for electronic music on a train, and the label admits as much. Many wireless and gaming headphones are tuned this way on purpose.
The term is also a soft criticism: calling a product fun implies it is not Neutral, and listeners who prefer accuracy read it as a warning. The Harman target, with its bass lift, is where fun and research meet.