There are some rather rare / obscure collections included, that are barely known. I'm particularly fond of impulses that capture real indoor and outdoor locations, as well as classic analog hardware (eg plate reverbs)... work in progress! If you have any question simply forward an issue report
Please support the providers of these great gems by buying their commercial products! List compiled and curated by Isaak M. aka Synthiemental
Samplicity Free Impulse Responses Bricasti M7 and additional freebies
Beamsonic (archived) - includes IRs of microphones, a Studer tape machine, analog hardware and cabinets: https://web.archive.org/web/20120603060726/http://noox.sitesled.com/
MoreVox Free Pack 2020 - real spaces and analog devices captured http://www.morevox.com/web/freebbie.html
Echochamber (archived) - mostly IRs of analog and digital reverbs https://web.archive.org/web/20111130095313/http://www.memi.de/echochamber/responses/index.html
cksde.com Impulses - reverbs http://www.cksde.com/p_6_250.htm
Fokke van Saane impulses - real spaces, devices and reverbs https://fokkie.home.xs4all.nl/IR.htm , everything converted to wav here
PastToFuture Reverbs Freebies - (free IRs are shown together with free libraries, check their paid stuff - great and affordable!) https://gumroad.com/pasttofuturereverbs?maxPrice=0
Greg Hopkins / Hopkins Media Services free impulse collection - analog & digital reverb devices, real outdoor & indoor spaces https://www.dropbox.com/sh/vjf5bsi28hcrkli/AADNjt1AmES9TsEBblLrjUAaa?dl=0
Ikea Plate Reverb https://www.dropbox.com/sh/3h28jv0wapjrwdh/AACD5J5584yx8-Bh53tKJxira
Flo Audio x Spring Reverbs Demo https://floaudio.fr/product/flo-audio-x-spring-reverbs-demo/
Flo Audio x Electro-Harmonix Holy Grail https://floaudio.fr/product/flo-audio-x-electro%e2%80%8b-%e2%80%8bharmonix-holy-grail/
Flo Audio x Fender Vibro Champ Spring Reverb https://floaudio.fr/product/flo-audio-x-fender-vibro-champ-spring-reverb/
Flo Audio x Yamaha G5 Spring Reverb https://floaudio.fr/product/flo-audio-x-yamahag5/
Flo Audio x Park G10R Spring Reverb https://floaudio.fr/product/flo-audio-x-parkg10/
Fender Vibro Champ Amp & Spring Reverb Impulse Set https://floaudio.bandcamp.com/album/fender-vibro-champ-amp-spring-reverb-impulse-set
Classic King Tubby style Spring Reverbs by Dubbhism http://www.dubbhism.org/2008/10/free-download-60-classic-and-king-tubby.html
Henry Olonga Beautiful Room - Great room-type reverb sound created using hardware http://www.nebulapresets.com/?product=henry-olonga-beautiful-room-impulse-responses-192-khz
Studio Nord Bremen Analog Reverbs (EMT Plate & AKG Spring) http://www.grgr.de/IR/
Spring Reverb Impulse Responses (192kHz) by Qhohi https://qhohi.bandcamp.com/album/spring-reverb-impulse-responses-192khz
Yamaha SPX90 II by Jamie Skeen http://www.mediafire.com/file/oxgv0bniyyo/Yamaha+SPX90II.7z https://forum.cockos.com/showthread.php?t=18712
EdV3rb – LITE - industry & factory hall, staircase https://tovusound.com/shop/edv3rb-lite/
Fokke van Saane impulses - real spaces, devices and reverbs https://fokkie.home.xs4all.nl/IR.htm , everything converted to wav here
Isophonics Room Impulse Response Data Set - professionally captured real rooms and halls http://isophonics.net/content/room-impulse-response-data-set
Helsinki University of Technology (TKK) Concert Hall Impulse Responses - Pori, Finland http://legacy.spa.aalto.fi/projects/poririrs/
Greg Hopkins / Hopkins Media Services free impulse collection - analog & digital reverb devices, real outdoor & indoor spaces https://www.dropbox.com/sh/vjf5bsi28hcrkli/AADNjt1AmES9TsEBblLrjUAaa?dl=0
Echothief - outdoor places http://www.echothief.com/
Hainbach Pool Of The Black Star https://www.patreon.com/posts/28297187
Abandoned Audio - IRs of abandoned places in Berlin https://abandonedaudio.bandcamp.com/album/complete-bundle
University of Kent IRs: A Sonic Palimpsest: Revisiting Chatham Historic Dockyards https://research.kent.ac.uk/sonic-palimpsest/impulse-responses/
Allister Sandwich Impulse Response Collection - real indoor and outdoor spaces https://freesound.org/people/allistersandwich/packs/27118/
Openair Lib - outdoor places https://openairlib.net/
Hybrid Reverb 2 Room Impulse Responses Library - real spaces https://web.archive.org/web/20191028120033/http://www2.ika.rub.de:80/HybridReverb2/#download
Balancemastering Teufelsberg NSA tower https://x42-plugins.com/tmp/teufelsberg-ir.zip
EMES Virtual Rooms - based on articial room models, that are supposed to take away some of the artifacts of real room captures http://www.emes.de/pageseng/products/Impulsresponse/eimpulse.htm
Thatcher Ulrich DIY Room Impulse responses - real bedroom, dining room, bathroom captured http://tulrich.com/recording/ir_capture/#menu (scroll down to the bottom)
Clap Impulse Responses in Faraway Places by jonsept https://freesound.org/people/jonsept/packs/32542/
Balloon Impulse Responses in Cool Spots by jonsept https://freesound.org/people/jonsept/packs/32541/
MoreVox Free Pack 2020 - some real spaces and some analog devices captured http://www.morevox.com/web/freebbie.html
Reaperblog Kidsróom IRs https://www.dropbox.com/s/vshg2hnzt8ikdpu/REAPERBLOG_KIDSROOM_IRS.zip?dl=0
Studio Balkandji Spaces https://studiobalkandji.com/product-category/studiobalkandji/
Flo Audio x Rooms demo https://floaudio.fr/product/flo-audio-x-rooms-demo/
Professor Angelo Farina's public impulse responses of various theaters http://pcfarina.eng.unipr.it/Public/IMP-RESP/
Barefoot Recording Impulse Response Project https://www.cianriordan.com/barefoot
Henry Olonga Amps Bundle Community Edition http://www.nebulapresets.com/Henry_Olonga_ULTRA_HiRes_Amp_Models_VOL_1.zip
Studio Nord Bremen Amps http://www.grgr.de/IR/
TL806 and Basement 1960B Guitar Cab Impulse Responses by Zach Weeks https://zachweeks.bandcamp.com/album/tl806-and-basement-1960b-guitar-cab-impulse-responses