What is the most FUN pair of speakers you've ever had and why?

Keg 104AB’s.  My first foray into the then perceived “high end”. Followed closely by the Quad 63’s with an Entec Subwoofer

The most fun speakers were my first ones.  I bought a DIY speaker building book.  Designed my own ported cabinets, around 12" three way Jensen speakers.  Did this fifty years ago when I was sixteen years old.  Then I bought an Eico amplifier kit.  Spent a couple weeks building it.  Bought a Garrard turntable, and we had music!  Mid 60's rock and roll, at its finest!  Were these the best?  Heavens no.  But they were good sound and loud.  What more could a kid want?  They went to college with me, blasting Ina Gada Davida, for the whole dorm to hear.  Sold them and the amp when I got married and moved up to Sansui separates.  Those were the days.

Back in the mid-70s I had a set of double Advents, stacked vertically, on custom stands, tweeters together. Powered by an HK Citation 16 and Soundcraftsman preamp with octave EQ, Thorens TD-160 and an Ortofon MC cart. It combined the Advents neutrality and bass, doubled up for the wall of sound bigness and the dynamics of a whole bunch of power, with the kinda peaky Ortofon making up for the Advents soft upper treble.  That system rocked. With 4X10" woofers it could play the subterranean synth bassline on Stevie Wonder's "I Believe (When I Fall In Love)" from Talking Book like few others. The Eagles "Hotel California", Linda Ronstadt, they all sounded fabulous, as did Keith Jarrett's "Koln Concerts" Al di Meola "Mediterranean Sundance". 

While I’m in love while in in love w my Energy RC-70s’ currently, they sound amazing.

 My most fun pair (which I still own)

CERWIN VEGA D9s’—- Great sound and thump.

 Honorable mention - CERWIN VEGA AT-15s’- a more crunchier midrange than the D9s’, but less bass.
 For a few years I had both pairs stacked w D9s’ on bottom and AT-15s’ upside down on top. That was some of the best music I’ve ever heard,, I eventually ended up melting the binding posts on the back of my Onkyo m-504 amp.
 Have since learned about the work OHM LOAD,...and why it’s IMPORTANT when choosing an amplifier for driving an amp at a basically 0 ohm load.

:))

I enjoy my Pique restored Quad 57s and 63s. Also loved my DQ 10s for a number of decades.