On the topic of sibilance, I think to truly eliminate other factors, source, headphones, etc. is to start with music that is rated as "Flawless" or "Non Sibilant." In searching the subject I have found and compiled the following list that (multiple) others including myself have confirmed are as stated. This should be a good starting point. Hopefully you have one of these songs to use as a test and use as a reference to test for sibilance.
There were 43 albums that were recommended (5) of more times and those albums are posted below.
TOP 43 Suggested FLAWLESS Albums:
Arcade Fire - Funeral (6)
Black Sabbath - Paranoid (5)
Brian Eno - Another Green World (5)
Charles Mingus: The Black Saint & The Sinner Lady (5)
Daft Punk - Discovery (12)
David Bowie - The Rise and Fall of Ziggy Stardust (5)
Depeche Mode - Violator (6)
Godspeed You Black Emperor - Lift Your Skinny Fists Like Antennas to Heaven (5)
Hanz Zimmer: Inception soundtrack (5)
Jethro Tull - Aqualung (5)
John Coltrane - A Love Supreme (6)
Joni Mitchell - Blue (5)
Joy Division - Unknown Pleasures (6)
Led Zeppelin - IV (6)
Mastodon - Crack the Skye (5)
Mastodon - Leviathan (5)
Megadeth - Rust in Peace (5)
Metallica - Master of Puppets (8)
Michael Jackson - Thriller (6)
Miles Davis - Kind of Blue (16)
Nick Drake - Pink Moon (6)
Pink Floyd - Wish You Were Here (15)
Pink Floyd - Animals (12)
Pink Floyd - Meddle (5)
Prince - Purple Rain (5)
Radiohead - OK Computer (14)
Radiohead - The Bends (7)
Rush - 2112 (5)
Rush - Moving Pictures (6)
Smashing Pumpkins - Siamese Dream (5)
Steely Dan - Aja (5)
Talking Heads - Remain in Light (8)
The Beach Boys - Pet Sounds (6)
The Beatles - Revolver (7)
The Beatles - Sgt. Peppers Lonely Hearts Club Band (11)
The Clash - London Calling (5)
The Who - Who's Next (7)
Tools - Laturalus (12)
U2 - The Joshua Tree (8)
V - Blood on the Tracks (8)
Van Halen - Van Halen (5)
Weezer - Blue album (7)
Yes - Close to the Edge (7)
Madonna - Lucky Star (The Immaculate Collection)
Madonna - I’ll Remember (Something to Remember)
Madonna - You’ll See (Something to Remember)
Sade: No Ordinary Love (remastered)
Michael Jackson - Speed Demon (Bad)
Michael Jackson - Thriller (Thriller SACD)
Michael Jackson - Billy Jean (Thriller SACD)
A Tribe Called Quest-Midnight Marauders
ABC - The Lexicon Of Love
A-ha - "Lifelines"
A-ha - Hunting High and Low
Bob Marley - One Love
Bob Marley and the Wailers: Exodus
Bob Marley: Legend (2)
Burning Spear - Marcus GARVEY (2)
Dennis Brown - The Crown Prince of Reggae: Singles (1972-1985)
Depeche Mode - 101
Depeche Mode - Violator (6)
Dr. Dre - 2001
Fleetwood Mac - Fleetwood Mac
Norah Jones-Come Away with Me (4)
Notorious B.I.G. - Born Again
Notorious B.I.G. - Life After Death
Prince - 1999 (2)
Prince - Come
Prince - Purple Rain (5)
Prince - Sign if the Times
Sade - Lovers rock
Sade - Stronger Than Pride
Snoop Dogg - Doggy Style
The Cure - Three Imaginary Boys
The Cure (10:15 Saturday Night)
The Cure: Disintegration (4)
The Smiths - Meat is Murder
The Smiths - The Queen is Dead (4)
Below is a link to a very large list of songs that are considered "Flawless" and maybe used as a reference to test for sibilance if you don't happen to have any of the songs listed above.
https://docs.google.com/spreadsheets/d/1y9V9-wiDUMirHFDGS4BDfykq8CyKtrA-WcUoehQr0VA/edit#gid=0
Hope that helps.